Sexual Reproduction In Flowering Plants - Class 12 Medical Biology - Extra Questions

(a) Name the part marked. 'A' in the diagram.
(b) How does 'A' reaches part 'B'?
(c) State the importance of the part 'C'.
(d) What happens to the part marked 'D' after fertilisation is over?

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(a) (b) Letter "A" represents pollen grain that reaches stigma (B) through the process of pollination. Germination of pollen grain forms pollen tube that reaches egg cell through ''D''
(c) Pollen grain germination is attachment of pollen to stigma of flower and formation of pollen tube. Letter "C" refers to pollen tube that carries male gametes to ovule for fertilization.
(d) Event of double fertilization and subsequent growth and development results in development of ovule into seed. Each seed contains a young plant embryo (developed from zygote) and nutritive tissue (the endosperm), both of which are surrounded by a protective seed coat (derived from integument). During development of seed from an ovule following fertilization, the ovary wall surrounding it enlarges and develops into a fruit wall while ovary makes fruit. 


What is a false fruit? Cite an example.

A false fruit is derived from the floral parts other than ovary. It is also called pseudocarp or accessory fruit or spurious fruit. Example peduncle in cashew nut.


Why is the apple referred to as a false fruit?

After fertilization in plants, ovaries and are converted into fruits and ovules into seeds. Fruits are of 2 types: true and False fruits. True fruits develop from ovaries. False fruits develop from any other part of the plant except ovary. Parts of fruit include exocarp, mesocarp, and endocarp. As Apple does not grow from the ovary, it is a false fruit.


Define Geitonogamy.

Geitonogamy is a mode of pollination. In this type, there is fertilization of a flower by the pollen grains of the same or genetically identical flower. It is a type of self-pollination. It comes from a Latin word, geiton = neighbor and gamy means marriage.


Pollination of flowers by birds.

Pollination of flowers by birds - Ornithophily 


How is pollination different from fertilisation?

 Pollination Fertilisation
 Seen only in plants Seen in both plants and animals.
 Pollination is the process in which the male gamete in the form of pollen is transferred to the stigma of a flowering plant.  Fertilisation is the process of fusion of the male gamete and the female gamete for the production of the zygote. In plants, it occurs after pollination when the pollen grain reaches through the style to the ovary where it fuses with the egg.


Name the part of the flower which the tassels of the corn-cob represent.

The tassels of flower is male flower, present at the top of the corn stalk. It produces pollens which is carried by the wind to female flowers for fertilization.


State one advantage and one disadvantage of cleistogamy.

Cleistogamy is self-pollination. It is well known in plants like peanuts, beans, and beans. The advantage is no pollinator is required as it can propagate by using non-opening, self-pollinating flowers. The absence of variation is the biggest disadvantage.


How does 'A' reaches part 'B'?
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In the diagram the pollen grain labelled 'A' reaches part 'B' the stigma through self pollination or through agents like insects, wind, water etc.


(a) Explain the different ways apomictic seeds can develop. Give an example of each.
(b) Mention one advantage of apomictic seeds to farmers.
(c) Draw a labelled mature stage of a dicotyledonous embryo.

a) There are two ways by which apomictic seeds can be produced:
  • Agamospermy: In this method, seeds are produced from diploid cells without meiosis and fertilization e.g., apple.
  • Adventive embryony: In this method, nucellus and integuments extend into the embryo sac and develops an embryo. In this method, the formation of more than one embryo takes place and this condition is called as polyembryony e.g., citrus fruit.
b) The main advantage of apomictic seeds to farmers is that, this method is of low cost and gives high yield production.
c) Mature stage of dicotyledonous embryo:




Why is apple called a false fruit? Which part(s) of the flower forms the fruit?

False fruits develop from any other part of the plant except the ovary. As an apple does not grow from the ovary, it is a false fruit.


(a) Plan an experiment and prepare a flow chart of the steps that you would follow to ensure that the seeds are formed only from the desired sets of pollen grains. Name the type of experiment that you carried out.
(b) Write the importance of such experiments.

(a) Steps to be followed to ensure the seeds are formed only from the desired sets of pollen grains:
Selection of flowers from desired plants $$\to$$ emasculation $$\to$$ bagging $$\to$$ dusting of the pollens on the stigma of the flowers that were bagged $$\to$$ flower rebagged $$\to$$ fruit formed
This experiment carried out is artificial hybridization.

(b) Artificial hybridization leads to the production of superior / improved varieties of plants.


State what is apomixis. Comment on its significance. How can it be commercially used?

Reproduction by special sporophytic or gametophytic generative tissues without fertilization (fusion of male and female gamete) is known as apomixis. It is a mode of asexual reproduction in flowering plants and hence produce clones, not variations. Apomictic seed production in hybrid plants allows commercial use of hybrid seeds without conducting hybridization again and again. 


Geitonogamous flowering plants are genetically autogamous but functionally cross-pollinated. Justify.

Geitonogamous flowers are those where the pollen grain comes from the same plant. The pollen is transferred to the stigma of another flower of the same plant. So it is functionally cross-pollination by involving pollinating agent but genetically it is autogamy (as the plant is same).


What is bagging technique? How is it useful in a plant breeding programme?

Emasculation i.e. removal of anthers from the bisexual flowers is followed by covering the stigma with poly covers/butter paper to ensure pollination of stigma with pollen from desired plant only and to prevent self-pollination. Covering the stigma with bags is called the as bagging technique which helps to prevent contamination of stigma with undesired pollens as well as ensure pollination with pollens from desired male parent during breeding programme.


What is apomixis and what is its importance?

  • Reproduction by special sporophytic or gametophytic generative tissues without fertilization (fusion of male and female gamete) is known as apomixis. 
  • It is a mode of asexual reproduction in flowering plants and hence produce clones, not variations. 
  • Apomictic seed production in hybrid plants allows commercial use of hybrid seeds without conducting hybridization again and again.


Mention the most significant function of each of the following.
(i) Tapetum cells
(ii) Serotonin
(iii) Lenticels
(iv) Cerebrospinal fluid
(v) Islets of Langerhans
(vi) Bundle sheath

(i) Tapetum cell is the fourth and innermost layer of the microsporangium which provides nutrition to the developing pollen grains. 
(ii) Serotonin is a neurotransmitter which is acetylated and then methylated within the pineal gland to produce melatonin. 
(iii) Lenticel is a porous tissue which provides a direct pathway between the internal tissues and atmosphere through the bark, but impermeable to gases.
(iv) Cerebrospinal fluid acts as the cushion for the brain and acts as the shock absorber for the central nervous system.
(v) Islets of Langerhans is also called pancreatic islets contain many cells including the beta cells, that secreted insulin.
(vi) Bundle sheath is the layer of compact cells surrounding the vascular bundle (in a plant) that regulates the movement of substances between the vascular tissue and the parenchyma and in leaves protect the vascular tissue from exposure to air. 


How bisexual and unisexual conditions in plants are denoted?

Bisexual flowers are the flowers which has both the essential whorls, i.e., androecium and gynoecium, including stamens , carpels and an ovary. This kind of flowers can undergo self-pollination. A dioecious or unisexual flower bears either male or female sex organs. The plant could be either male or female. When only stamens are present, it is called as staminate flower. When only carpels are present, it is called as pistillate flower. 
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Redraw the diagram and label the following parts.
(a) Exine
(b) Tube nucleus
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The exine and the tube nucleus in the pollen have been represented in the diagram. 
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Why do pollen grains remain preserved for long time ?

The pollen grains have a tough outer wall. The wall is made up of cellulose and sporopollenin. Sporopollenin is a substance which is very tough and resistant. This provides protection to the pollen grains from adverse conditions like high temperature, pH, etc. This helps to preserve the pollen grain and prevents from getting denatured for a long period of time. 


Draw the given diagram and label the following parts:
(i) Exine (ii) Tube nucleus
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R.E.F image
Pollen - Male Gametophyte

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What is emasculation?

Explanation:

  • Removal of anthers from the flower is called emasculation.
  • It is done before dehiscence to prevent contamination of stigma with any undesired pollen and to ensure cross-pollination by desired pollens. 
  • Emasculation is useful in artificial hybridization to pollinate stigma with selected emasculated pollens only. 


Briefly explain the structure of pollen grains.

The androecium is the male reproductive whorl of the flower which produces male gametes. The stamen is the androecium composed of anther and filament. The anther contains pollen sacs which produce pollen grains.The pollen grain is the male gametophyte which contains the male gametes. The pollen grain is surrounded by two layers as exine which forms the outer layer and intine which forms the inner layer. The generative cell divides to form the two male gametes. The vegetative cell is responsible for the providing nutrition. The intine layer comes out of the germ pore to form the pollen tube.
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Explain the process of pollination in Vallisneria. How is it different in water-lily, which is also an aquatic plant?

The pollination in the Vallisneria is achieved with the help of water. In Vallisneria, the female flowers are submerged in the water. They reach the surface of water by the long stalk on reaching maturity. At this time, the male flowers are released onto the surface of water. With the help of the water, the pollens come in contact with the female flowers and the pollination is achieved. 
In the case of water lily, the female flowers remain submerged in water. The pollen grains are released inside the water. The pollen grains are long, thread-like and are carried with the water and reach the stigma and achieve pollination.


Pollen grains in wheat are shed at "3-celled stage while in peas they are shed at 2-celled stage." Explain. Where are germ pores in a pollen grain?

In plants like peas, the microspores have two cells vegetative and generative. The vegetative cell has abundant reserve food material and a large nucleus which is irregular in shape while the generative stage is a spindle-shaped and are shed at the two-celled stage while in plants like wheat the generative cell divides mitotically and give rise to two male gametes before pollen grains are shed at the three-celled stage.


Pollination takes place by the agency of bird is known as 

Pollination takes place by the agency of bird is called ornithophily. It is is a type of pollination of flowers that takes place by the agency of birds. The flowers pollinated in this manner are usually large, colourful, often tubular and secrete copious nectar. Birds with long beaks such as hummingbirds show this type of pollination. 


What is pollination? List out biotic and aboitic factors which are involved in pollination?

Pollination is the transfer of pollen grains from the stamen to the stigma present in the carpel. Pollination is done by birds, insects, animals, wind, water, it’s accidental. To be pollinated, pollen must be moved from a stamen to the stigma.
Various types of pollination have also been identified based on the vectors of pollen grains or agents of pollination. These pollinators are described under two main classifications:
 (1) nonliving pollinators which are also called as abiotic, 
 (2) living pollinators which are also called as biotic. 
Abiotic pollinators such as wind, water, rain and biotic pollinators such as birds, insects, flies, animals.


Albuminous seeds store food materials in ___________.

Endosperm is the nutritive tissue which provides nourishment to the embryo in the seed plant. Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development (e.g., wheat, maize, barley, castor, sunflower, etc.). 
Hence the answer is $$endosperm$$.


Distinguish between apocarpous and syncarpous ovary.

Apocarpous ovary consist of free carpels. 
It forms aggregate of fruits
Example: custard apple, strawberry, Magnoliaceae

Syncarpous ovary consists of fused carpels.
It forms a single fruit with one or many seeds
Example: Coconut, Guava, Mango etc


A farmer has two fields A and B. He cultivates peas (Pisum sativum) in both the fields. Field A is covered with nets to keep out birds and insects. Field B is left uncovered.
(i) Name the type of pollination that would occur in field 'A' and field 'B'.
(ii) Which of these fields will give a higher yield?
(iii) To raise the next crop, from which field should the seeds be chosen by the farmer. Give reasons to support your answer.

(i) Field A - Self pollination would have taken place since insects were not able to effect pollination. The field was covered with nets. In field B self and cross pollination could have occurred since insects could visit the flowers.
(ii) Field B will give higher yield since cross pollination will result in production of more fruits and seeds. But due to visit of birds there may be fluctuations in yield, if proper care is not taken. In field A the production of seeds may be less due to self poll ination, but no wastage due to birds / insects will be recorded.
(iii) To raise the next crop, the 'seeds should be chosen by the farmer from field B because new varieties of plants can be obtained. Cross pollination favours development of new varieties of plants


Describe the outbreeding devices that prevent the autogamy.

Outbreeding defines the process in which the mating of the animals is performed which belongs to the different breed. This technique helps in preventing self-pollination and inbreeding depression. The devices which are used to prevent autogamy are:
  • The male and the female reproductive organs in the flower do not get matured at the same time (protandry and protogyny). 
  • The male and the female flowers are present on the different plants (monoecious).
  • The stigma of the female flower does not recognise the pollen from the anther of the flower on same plant (self-incompatibility) 


Sunflower is pollinated by insects while rice is pollinated by wind. Plants can be self or cross-pollinated. Write any two mechanisms existing in nature to promote cross- pollination.

Cross pollination can be favored-
1. Unisexual plant- In this situation, the male and female reproductive whorls are present on different flowers. This leads to transfer of pollens from the anther of one flower to the stigma of another flower.
2. Maturation of anther and stigma in the same flower at different time period favors cross pollination.


Three different flowers are given to you in the practical class.
(i) Maize
(ii) Vallisneria
(iii) Rose
You are asked to group them based on pollinating agents. Describe the adaptions of each flower related with the agents of pollination.

i) Pollination in maize is brought about by the wind and this method is called anemophily. Maize plant has both male and female flowers on each plant. The tassel is the male flower and the ear is the female flower of the plant. Tassel and ear are separated by a distance on an individual plant.
ii) Pollination in vallisneria is through water. In vallisneria, the female flowers are submerged in water. They reach the surface of water by the long stalks on reaching maturity. During this period the male flowers are released onto the water surface. The pollens from male flowers come in contact with the female flowers and the pollination is achieved. 
iii) Roses are pollinated by insects and this method is called entomophily. The flower is brightly colored and produces nectar. This attracts the insect. When the insect visits the flower pollens stick on its body. When the same insect visits another flower it dusts the pollens on its stigma resulting in pollination.


Sunflower is pollinated by insects while rice is pollinated by the wind. How are these plants adapted to their respective type of pollination method?

Sunflowers show entomophily that is pollination by insects. The flower is brightly coloured that easily catches the eyes of insects. The flower produces yellow coloured sticky pollens rich in nectar. When insects such as bees visit the flower for nectar the pollen sticks on their body. When the same insect visits another flower, the pollen is deposited on the stigma of another flower resulting in pollination.
Rice is pollinated by wind and the process is called anemophily. The rice plant produces large quantities of light and dry pollens that can be carried on the wind. The stigma are long and feathery to capture the pollens resulting in pollination.  


Why are petals colorful?

The transfer of pollen grains from the anther of one flower to the stigma of a pistil of the same or another flower is termed as pollination. Majority of plants (70%)  use animals for pollination. Bees, butterflies, beetles, wasps, ants, moths, birds and bats are common pollinating agents. The colorful petals of flowers attract insects for pollination.


How do insects, butterflies, honeybees, and birds help Angiosperms?

  • Pollination is the transfer of pollen grains from the anther to stigma.
  •  Pollination takes place by both biotic and abiotic (wind and water) agents.
  •  Pollination is done with the help of biotic agents like butterflies, honeybees, and birds which help to transfer pollen grains from one flower to another flower, and thus result in fertilization. 


Define the term epipetalous stamen.

Epipetalous stamen is a stamen that is borne over a petal instead of being inserted directly over the thalamus. For example, Solanum.


Describe the various modes of fixation of anther over filament.

Fixation is the mode of attachment of filament to anther. These are of different type and are as follows:-
A)Basifixed fixation in which the filament is attached to the base and is seen in Brassica.
B)Adnate fixation in which filament run throughout the length and become continuous with the connective as see in Mangolina, Ranaculus.
C)Dorsifixed fixation in which filament is attaches to the dorsal side of anther as seen in Citrus.
D)Versatile fixation in which filament attaches in the middle of the connective in such a way that the anther can swing freely as seen in grasses.

Image result for Describe the various modes of fixation of anther over filament.


What is parthenogamy ?

Parthenogamy is a type of apomixis where asexual reproduction mimics sexual reproduction. The formation of new individuals is through asexual reproduction without involving fusion of compatible gametes. Parthenogamy is the union of two incompatible gametes i.e. fusion of two female gametes. Examples are banana, apples as they can grow without fertilization.


Sketch and label a pollen grain of angiosperms.

A pollen grain of angiosperms contains two-layered cell wall: outer exine and inner intine. Exine has one or more pores called germ pores through which pollen tubes come out on germination. It has a vegetative cell and a generative cell. The generative cell divides further to form two male gametes.
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Write the male part of flower.

The male reproductive part of a flower is called Stamen. It has two parts: the long and slender stalk called a filament, and the terminal generally bilobed structure called the anther. The anther is four side structure that consists of four microsporangia located in each lobe. The microsporangia develop further and become pollen sacs.


Give a reason for the following.
Pollen grains of wind pollinated flowers are produced in large quantities.

Pollen grains of wind-pollinated flowers are produced in large quantities to make sure that at least some pollen grains reach the stigmas of other flowers and successful pollination takes place as many pollen grains are wasted. These pollen grains are light and hence are easily transferred to other flowers. A wind-pollinated flower is known as anemophilous.


Write a short note on polyembryony.

A seed is formed after fertilization of ovule. Generally, each seed bears an embryo but sometimes more than one embryo is found in a single seed. This occurrence of more than one embryo (from a single fertilized egg) in a seed is called polyembryony and it was first observed in orange seeds by Antony von Leeuwenhoek in 1917. 
  • There are two types of polyembryony:
1. Gametophytic Polyembryony -  
It arises from the haploid cell i.e. gametophytic cell of the embryo sac without fertilization or after fertilization.
2. Sporophytic Polyembryony - 
Here, embryos arise from the diploid cell or sporophytic cell of the embryo sac i.e. from cells of pre-embryo or nucellar cells or integumentary cells.
  • Significance of polyembryony:
1.  Seedlings develop a better root system and show better yield.
2. Seedlings are free from diseases.
3. For large scale production of uniform plants, induced polyembryony is very suitable.
4. Artificial seeds can be formed by somatic embryos which are also suitable for field planting.


Given alongside is a diagrammatic sketch of the sectional view of a plant part relating to reproduction.
(a) Identify the plant part as a whole.
(b) Name the structural parts numbered 1-5.
(c) Where would it be found as a stage as shown?
(d) What is the function of part 4?
(e) What immediately next happens to the part 5?
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a) The given diagram shows generating pollen.
b) 1-Exine
    2-Intine
    3-Pollen Tube
    4-Vegetative nucleus
    5-Generative nucleus
c) The stage is found when the pollen reaches a stigma of a flower and the chemical reaction stimulate the tube elongation and subsequent fertilisation.
d) The vegetative nucleus synthesizes the pollen tube.
e) The Generative nucleus bifurcates into two male gametes out of which one fuses with the polar nuclei in triple fusion to form endosperm and the other male nuclei fuse with the egg cell to form the zygote and subsequent embryo. 


State the name of the chief pollinating agent against the corresponding plant by choosing from those given in brackets
Maize_______(Bees, locusts, rain, wind).

 The stamens of the maize flower produce a light, fluffy pollen which is borne on the wind to the female flowers (silks) of other maize plants.
So, the correct option is 'wind'.



Give any two examples each of endospermic (albuminous) seeds and non-endospermic (exalbuminous) seeds.

Correct Answer: 
Endospermic seeds:  It is that type of seed in which the embryo does not consume complete endosperm. some portion of endosperm may be left. It is also known as an albuminous seed.
Example - Maize, wheat, etc.
Non-endospermic seeds: It is that type of seed in which an embryo consumes complete endosperm during its development. It is also known as exalbuminous seed or non-albuminous seed.
Example- Pea, groundnut, etc.


State the name of the chief pollinating agent against the corresponding plant by choosing from those given in brackets.
Vallisneria____(Wind, water, ants, rabbits).

In Vallisneria pollination is through hydrophilic ie through the water. In Vallisneria, the female flower appears on the surface of the water as it has a long stalk. The pollen grains released by the male flower reaches to female flower for fertilization through water currents.
So, the correct option is 'water'.


Give the technical terms for the following :
Pollination of flowers by insects.

Pollination of flowers by insects is known as Entomophily.


Explain the following term : Artificial pollination

Artificial pollination occurs when humans intervene in the natural pollination process.They carry pollen, or plant sperm, from one flower to another, allowing the pollen to fertilize the ovaries and create seeds that will develop into fruits and new plants.


Germinated grams are considered highly nutritive. What is the reason for this belief?

Explanation: 
Germinated grams are known to be rich in nutrients because the seed cotyledons absorb the nutrients during the period of germination from the endosperm, due to this sprouting of grams is observed, which makes the gram nutritious. 
Hence, Germinated grams are considered highly nutritive.


Write two ways in which pollination may occur in plants.

The two ways in which pollination occurs is the 
1.Self-pollination- It is the transfer of pollen grains from anthers of a flower to the stigma of the same flower or to another flower of the same plant.
2. Cross pollination-It is the transfer of pollen grains from the anthers of the flower to the stigmas of another flower in another plant of the same kind.


Explain the following term : Elephophily.

  • Pollination that is carried out by elephants is called Elephophily.
  • It is found in Rafflesia whose flowers are very large and are found at ground level. 
  • The pollen grains of one flower get attached to the feet of elephants and may be carried to the stigma of another flower.


Fill in the blanks with appropriate words.

The formation of more than one embryo from the zygote is called..........

Polyembryony


What is pollination? Describe the pollination brought through the agency of insects and explain with suitable examples the adaptations of plants for this type of pollination.

Pollination is when pollen grains from an anther, the male portion of a flower, are transferred to a female part in the flower, known as the stigma. Although all flowering plants rely on pollination for reproduction, there is a variation in how plants pollinate. Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns (honeyguides) leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromone. Plants like Jatropha, Daisy, Orchids, spider lily, etc. are pollinated through insect pollination.


Differentiate between wind and insect-pollinated flowers.

  • Wind-pollinated flowers are usually inconspicuous, with versatile anthers. The pollen grains are usually smooth walled, relatively light, small and dry so that they can be easily blown away by wind. The pollen grains are produced in large quantities. The stigmas are comparatively large and protruding, sometimes branched and often feathery.
  • On the other hand, insect-pollinated flowers undergo several adaptations to attract insects. They develop large and brightly coloured petals, scent or nectar. The pollen grains are sticky or have spinous outgrowths on the exine ; their stigmas are also sticky.


Why is necessary to emasculate a bisexual flower in a plant breeding programme? Mention the condition under which emasculation is not necessary.

  • Emasculation is the process of removing anthers from bisexual flowers without affecting the female reproductive part (pistil), which is used in various plant hybridization techniques.
  • Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. To remove the anthers, the flowers are covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.
  • Emasculation is not performed in unisexual flowers and those plants which exhibit self-compatibility.


In what ways does the study of pollination enrich our understanding of biology and enable us to apply it for increasing crop productivity?

Pollination is when pollen grains from an anther, the male portion of a flower, are transferred to a female part in the flower, known as the stigma enabling later fertilisation and the production of seeds. The study of pollination brings together many disciplines, such as botany, horticulture, entomology, and ecology. The pollination process as an interaction between flower and pollen vector. The productivity of many crops benefits from the presence of pollinating insects. Animal-mediated pollination contributes to the sexual reproduction of over 90 % of the approximately 2,50,000 species of modern angiosperms. The diversity of crops that depend on animal pollination provides still more impressive estimates.


Differentiate between.
Autogamy and geitonogamy.

Autogamy is the pollination of a flower by its own pollens, whereas geitonogamy is the pollination of a flower by pollen grains of another flower present on the same plant.


Differentiate between.
True and false fruit

When a fruit develops exclusively from the ovary, it is called a true fruit But, when in addition to the ovary, some other floral parts like tepals, bracts or thalamus also participate in the formation of the fruit, then it is known as false fruit .


Explain why emasculation and bagging are practised during artificial hybridisation prorgamme involving plants bearing bisexual flowers.

  • Emasculation is the process of removing anthers from bisexual flowers without affecting the female reproductive part (pistil), which is used in various plant hybridization techniques.
  • Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. To remove the anthers, the flowers are covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.


Describe apomixis and it's significance in plants.

Apomixis is the type of asexual reproduction. It is a method of production of seed without meiosis and syngamy. It is a cheaper and cost effective method of producing hybrid seeds. It is easy to maintain hybrid characters intact as characters segregate during meiosis. It prevents the loss of specific characters in the hybrid. It also helps in producing individuals with desired qualities in more numbers. The offsprings produced are exact replica of mother plant.


Normally one embryo develops in one seed but when an orange seed is squeezed many embryos of different shapes and sizes are seen. Mention how it has happened.

Orange shows the phenomenon of polyembryony.
It is the phenomenon of two or more embryos developing from a single fertilized egg. Due to embryos resulting from the same egg, the embryos are identical to one another but are genetically diverse from the parents.
In botany, it is used to describe the process of seedlings emerging from one embryo.


Wind-pollinated flowers are not visited by honey bees. Give two reasons.

Wind-pollinated plants do not have the properties required to attract pollinating insects. They are not showy, do not have nectar and also do not produce scent. They produce large quantities of light, dry pollen from small, plain flowers that can be carried by the wind.
Therefore these flowers are negligibly visited by honeybees.


What is pollination? Mention any four features of wind pollinated flowers.

Transfer of pollen grains from male part to the female part of the plant is called as pollination. The pollen are transfer to the stigma of pistil.
Features of wind pollinated flowers include:
(i) Pollen grains are light and non-sticky.
(ii) Well exposed stamens for easy dispersal by wind.
(iii) The stigma is sticky, large and feathery to trap pollen grains in the air.
(iv) Numerous flowers are packed together to form inflorescence.


Mention the pollinating agent of an inflorescence of small dull-coloured flowers with well-exposed stamens and large feathery stigma. Give any one characteristic of pollen grains produced by such flowers.

Wind-pollinated plants have small, dull-coloured flowers with well-exposed stamens and large feathery stigmas.
These plants have light, dry and non-sticky pollens so that they can be easily carried away by the air currents. Pollens are produced in large quantities as well.
The large stigma then easily catches these pollen grains.


Define anemophily.

Wind pollination is also called anemophily. Almost all gymnosperms are anemophilous including grasses, sedges, and rushes. Other examples include oaks, chestnuts, alders, etc.
Wind-pollinated plants lack scent production, lack showy floral parts, reduced production of nectar, and production of pollen grains in large quantities. Pollen grains are light and non-sticky so that they can be easily transported by air currents. They possess well-exposed stamens and feathery stigma.


Why is tender coconut considered a healthy source of nutrition?

Endosperm is the nutritive tissue for the developing embryo and also the seedling. In angiosperm, the endosperm develops from triploid primary endosperm nucleus which is formed as a result of vegetative fertilization, a triple fusion of a male gamete with the secondary nucleus of the central cell. On the basis of development of endosperm, there are three types and the free nuclear is a type of endosperm development, where the primary endosperm nucleus divide by repeated mitotic free nuclear division without the formation of walls. Results in the formation of a large number of the free nucleus in the central cell of the embryo sac. A big central vacuole develops in the embryo sac in all the nucleus periphery cytoplasm. Finally, cell wall formation takes place from the periphery of the embryo sac towards the centre leading to the formation of cellular endosperm tissue. In coconut endosperm is multicellular in the outer part and free nuclear in the centre.


Why does endosperm development precede embryo development in angiosperm seeds? State the role of endosperm in mature albuminous seeds.

Endosperm work as a capacity house. It stores sustenance for the developing fetus in developing seeds. At the point when seeds develop they require nutrition, in albuminous seeds they get it from the endosperm. 


Describe endosperm development in coconut.

Endosperm is the nutritive tissue for the developing embryo and also the seedling. In angiosperm, the endosperm develops from triploid primary endosperm nucleus which is formed as a result of vegetative fertilization, a triple fusion of a male gamete with the secondary nucleus of the central cell. On the basis of development of endosperm, there are three types and the free nuclear is a type of endosperm development, where the primary endosperm nucleus divide by repeated mitotic free nuclear division without the formation of walls. Results in the formation of a large number of the free nucleus in the central cell of the embryo sac. A big central vacuole develops in the embryo sac in all the nucleus periphery cytoplasm. Finally, cell wall formation takes place from the periphery of the embryo sac towards the centre leading to the formation of cellular endosperm tissue. In coconut, the endosperm is multicellular in the outer part and free nuclear in the centre.


Two mark Questions:
Banana is a parthenocarpic fruit whereas oranges show polyembryony.How are they different from each other with respect to seeds?

The banana is a parthenocarpic organic product as it creates without treatment, while in oranges, an incipient organism grows straightforwardly from a diploid cell other than egg like nucellus and integument. In banana, the ovary may form into the natural product without preparation. Likewise, the parthenocarpic organic products never contain seeds though oranges have seeds, so along these lines, they contrast with one another concerning seeds. The banana natural product is shaped without Fertilization The organic product is in this manner seedless. In Oranges, an occurrence of more than one fetus in a seed is alluded to as Polyembryony. A portion of the atomic cells encompassing the incipient organism sac begins isolating and protrude into the fetus sac and form into the developing lives. In this way, every ovule contains numerous incipient organism.


Two mark Questions:
Suggest two advantages to a farmer for using apomictic seeds of hybrid varieties.

The preferred standpoint of apomictic seeds to agriculturists that they would radically lessen the expense of crossover creation so plant raisers deliver new assortments of seed all the more week by week and all the more economically. 


Answer in brief:
Why does a pollen grain possess two male gametes?

Pollen sacs contain pollen grains. A pollen grain contains two male gametes. One of the male gametes fuses with female gamete to frame zygote and the other one breakers with the polar cores to shape the essential endosperm core.


A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds. Answer the following questions giving reasons :
What is the minimum number of pollen grains that must have been involved in the pollination of its pistil?

The number of suitable seeds delivered by the tomato plant through sexual proliferation = 240 
(a) The base number of dust grains that more likely than not been associated with the fertilization of its pistil are 240 in light of the fact that every dust grain contains two male gametes. Out of postulations two gametes, one circuit with polar cores and structures endosperm, while, the other male gamete wires with the egg cell to frame the zygote that in the long run offer ascent to seeds. Along these lines, so as to acquire 240 seeds, the number of dust grains required would be 240. 


Differentiate between albuminous and nonalbuminous seed, giving one example of each.

Albuminous seeds refer to those seeds that retain or restores some part of the endosperm during embryonic development. Examples include maize, barley, castor, and sunflower.
Non-albuminous seeds refer to those seeds that consume the entire endosperm during the embryonic development. Examples include peas and groundnut.


Why is geitonogamy also referred to as genetical autogamy?

Autogamy is a kind of pollination in which the pollen from the anther of a flower is transferred to the stigma of the same flower.
Geitonogamy is the type of pollination where the flower is pollinated by another flower of the same plant. As the genetic material is the same therefore there is no cross-pollination and this is also known as genetic autonomy. This results in inbreeding depression because there is no variation.


Pistil of a flower does not accept pollen from any plant other than from its own kind. How does it happen?

This procedure is called Self-fertilization. In self-fertilization, blossoms trade dust with same bloom or another bloom on a similar plant. Any remote dust that lands on a blossom from an alternate bloom are rejected. Self fertilization does not generally guarantee hereditary variety since hereditary material between same plants  is traded.


Explain the following terms : polyembryony 

Polyembryony is a condition in which a single egg develops into two or more embryos. In such a condition the single egg produces two or more genetically identical offsprings. It is seen in both plants and animals (including humans, where it results in the birth of identical twins). 


List the different types of pollination depending upon the source of the pollen grain.

Pollination can be classified into three different types based on the source of pollen grains. They are:

i) Autogamy: It is defined as the transfer of pollen grains from the anther to the stigma of the same flower in the same plant.

ii) Geitonogamy: It is defined as the transfer of pollen grains from the anther of one flower to the stigma of another flower on the same plant.

iii) Xenogamy: This type of pollination brings genetically different types of pollen grains to the stigma of the flower.




What is polyembryony?

When two or more embryos develop from a single fertilized egg, the condition is known as polyembryony. In the case of humans, it results in forming two identical twins. This phenomenon is found commonly in plants and animals. 


Mention the ploidy levels of the cells of different parts of an albuminous seed.

The diverse kinds of cells in the female gametophyte emerges because of rehashed mitotic division of the practical megaspore. This utilitarian megaspore is thusly created by the meiotic division of megaspore mother cell, therefore haploid in nature. Along these lines, every one of the cells present in the female gametophyte is haploid in nature. However, the focal cell consists of two haploid cores, which may wire to offer ascent to a solitary diploid core. In this way, Ploidy dimension of a focal cell might be diploid. 


What is apomixis? Mention its significance.

Apomixis is the mechanism of seed production without fertilization. It is a kind of asexual reproduction which mimics sexual reproduction, where the female gametophyte or the ovule in the flower directly develops into an embryo skipping meiosis and syngamy. Thus apomixis produces a clonal progeny with a maternal genotype.

Apomixis is of high importance as;
  • It produces seed progeny which are exactly the same as the mother plant. Thus apomixis helps in the preservation of good characters over generations for crop plants.
  • It helps in the production of hybrid seeds with a combination of desirable characters. It also prevents the loss of specific characters from a hybrid.
  • It helps in the cost-effective and time-efficient production of seeds.


Suggest some advantages and disadvantages of self-pollination to a species of plant.

Advantages:

Self-pollination helps to maintain parental characters or purity of the species. 

The plant does not need to depend on the pollinating agents. 

No need of producing a large number of pollen grains. 

Flowers do not need to develop devices for attracting insect pollinators. 

It ensures seed production. Rather it is used as a fail-safe device for cross-pollinated flowers. 

It eliminates some bad recessive characters. 

Disadvantages:

Self-pollination does not allow new adaptions according to the change in the environments. 

It can lead to the reduced health of the species, due to the breeding of related specimens.  

Immunity to diseases decreases. 




Give the property of stigma due to which it receives the pollen grains 

$$\textbf{Solution}$$

$$\bullet$$Stigma is the part of the female reproductive system of plant. The surface of the stigma is sticky which helps the pollen to attach to it.

$$\bullet$$ Pollinating agents such as bees helps in the transfer of the pollen from one state to another.
$$\bullet$$ Stigma is one of the most essential part of the ovary because it helps in the germination of the Pollen. It is also a very important part for the reproduction process.
$$\bullet$$ Stigma is sticky and adapted to catch pollens with various flaps, hair and sticky surfaces.




Which type of pollination takes place in self-incompatible flowers?

In self-incompatible flowers, viable pollen are not able to germinate on the stigma of the same flower. Hence, in such flowers, cross pollination takes place in which pollen from one flower is transferred to the stigma of the another flower of the same plant (Geitonogamy) or of another plant (Xenogamy).


Describe the technique of emasculation.

  • Removal of anthers from the bisexual flower bud before the anther dehisces is referred to as emasculation.
  • Emasculated flower buds are generally, further covered by a bag of a suitable size generally made of butter paper, to prevent contamination of stigma with unwanted pollen. This step is referred to as bagging. These two steps are performed in order to obtain F$$_1$$ hybrids. 
  • As the stigma of the flower bud attains receptivity mature pollens are collected from anthers of the desired male parent are dusted on the stigma and flowers are rebagged then fruits are allowed to develop.


Based on the type and location of storage materials, how many types of seeds are there? What are they? Give examples.

The storage material in a seed is endosperm. Based on the presence or absence of endosperm, seeds have been classified into following two types:
  • Albuminous or endospermous seeds: In this type of seeds, the endosperm is not consumed by the developing embryo. For example, Wheat and Maize.
  • Ex-albuminous or non-endospermous seeds: In this type of seeds, the endosperm is fully consumed by the developing embryo. For example, Pea and Groundnut.


Differentiate between Albuminous and non albuminous.

Albuminous SeedNon-Albuminous Seed
The seed which retains some part of endosperm not completely used up during embryo development.The seed which does not retain any endosperm as it is completely used up during embryo development.
The examples are wheat, barley etc.The examples are the pea, groundnut etc.


Give one example of endospermic dicot seed and non-endospermic seed.

Seeds having endosperm is called as endospermic seed. Seeds without endosperm is called as non-endospermic seed. Example of plant having endospermic dicot seed is Ricinus communis (Castor). Example of plant having non-endospermic dicot seed is Pisum sativum (Pea).


What is oogamy?

Oogamy is the type of sexual reproduction in which male gamete is small and vigorously motile while female gamete is large and either non-motile or movement is less. This is found in all the higher plants as well as animals.


Define apomixes. Mention two ways in which apomictic seed develop.

Formation of seeds from ovules without fertilization is called Apomixis. It mimics the sexual reproduction. The organisms reproducing through apomixis is called apomictic. It is controlled by genes. Apomictic seeds are developed by Agamospermy, Parthenogenesis, Apogamy, Polyembryony.


Distinguish between dicotyledonae and monocotyledonae.

DICOTYLEDONAE                                                                                 MONOCOTYLEDONAE
$$1)$$ $$2$$ cotyledons in the Embryo                                                         $$1)$$ $$1$$ cotyledon in the Embryo
$$2)$$ Tap root system                                                                            $$2)$$ Adventitious root system
$$3)$$ Stem is profusely branched                                                         $$3)$$ Stem is unbranched
$$4)$$ Reticulate Venation                                                                      $$4)$$ Parallel Venation
$$5)$$ Flowers show tetramerous or pentamerous symmetry             $$5)$$ Flowers show trimerous symmetry
$$6)$$ Vascular Bundle is Conjoint, Collateral and open                     $$6)$$ Vascular Bundle is Conjoint, Collateral and closed
$$7)$$ Secondary growth is found                                                         $$7)$$ Secondary growth is absent


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Define emasculation.

The removal of the anthers of a flower in order to prevent self-pollination or the undesirable pollination of neighbouring plants.
1171665_1147333_ans_37c89f3092bf4ff6b536bc7b3833182c.jpg


A farmer maintained beehives in his Brassica field during its flowering season.How will he be benefitted?

  • Bee-keeping is not labour intensive. Keeping beehives in crop fields increases pollination efficiency during the flowering season. 
  • Hence, it becomes beneficial from both point of views; increased crop yield and honey yield.


Why should a bisexual flower be emasculated and then bagged prior to artificial pollination in hybridization programs?

Artificial pollination implies when fertilization is finished by fake strategies. Androgynous bloom is weakened to avert self-fertilization. Emasculation implies expulsion of stamens. At that point, undermined blossoms are stowed to stay away from fertilization by undesirable dust grains.


Define autogamy.

Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual within the same flower.  


(a) Identify the figure.
(b) Name the initial cell from which this structure has developed
(c) Draw the next mature stage and label the parts.
1152941_40851c0c0ab44394ad33219b8a4e1c17.PNG

a)The given figure is identified as Dicot proembryo.

b)Zygote

c)diagram 
1173906_1152941_ans_616595c53a7e4bd68a6e0fad09aaf6b5.jpg


Name the seeds where remnants of nucellus can be found in the seeds ?

The remnants of nucellus which are found in seeds are called perisperm. These perisperms are found in black pepper, cotton castor etc


What is the pollen basket?

The pollen basket is a pollen-collecting apparatus present in some species of honeybees. It is present in the region of the tibia of the hind legs and is surrounded by stiff hairs. Honeybees move to several flowers in a day and the pollen they collect in their journey is stored in these pollen baskets.


The exine of pollen grain is hard and resistance to enzyme action. Give reason.

Pollen, a mass of microspores in a seed plant appearing usually as a fine dust. Each pollen grain is a minute body, of varying shape and structure, formed in the male structures of seed-bearing plants and transported by various means (wind, water, insects, etc.) to the female structures, where fertilization occurs. Pollen consists of one or more vegetative cells and a reproductive cell. A pollen grain itself is not the male gamete. Most pollen grains consist of three distinct parts. The central cytoplasmic part is the source of nuclei responsible for fertilization. The other parts constituting the wall of the grain are an inner layer, the intine, and an outer layer, the exine. The intine consists, at least in part, of cellulose or hemicellulose. The outer and most durable layer, the exine, is very resistant to disintegration; treatment with intense heat, strong acids, or strong bases has little effect upon it. The constituents of the exine have been termed sporopollenins.
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How is artificial pollination useful to plant breeders? Discuss briefly.

  • Artificial pollination is the process in which pollination does not occur naturally but is rather influenced by humans, where they carry the pollen of the flowers to another flower and allow them to fertilize the flowers. 
  • In this method, the pollen grains of the desired flower is deposited on the stigma of an emasculated flower i.e a flower whose anther has been removed. Natural pollination is dependent on a large number of different factors such as the vector population (natural pollinators that help in pollination such as bees) and the climatic conditions. 
  • If the climatic conditions are adverse, it can negatively affect the production and transport of pollen. Pollen transport by vectors can also be negatively affected by a large number of different factors like diseases and pesticide treatment. 
  • Artificial pollination helps plant breeders overcome such problems. It also helps them produce a new and better variety of crops with the desired features by helping them to cross breed and pollinate.


What is called filiform apparatus?

  • Synergid cells are two specialized cells that lie adjacent to the egg cell in the female gametophyte of angiosperms and play an essential role in pollen tube guidance and function. 
  • The term synergid comes from the Greek “synergos,” which means “working together”. 
  • After a pollen grain germinates on the surface of the stigma, it forms a pollen tube that grows through the style and is guided through the micropyle (a minute opening at one end of the ovule). 
  • The pollen tube grows toward and into one of the synergid cells, which begins to degenerate as the pollen tube enters it (or shortly before). 
  • The pollen tube then ceases growth, ruptures, and releases its two sperm cells, which migrate to the egg and central cell, fertilization of which gives rise to the embryo and endosperm, respectively.
  • The synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end, consisting of numerous finger-like projections into the synergid cytoplasm. 
  • This structure greatly increases the surface area of the plasma membrane in this region, which is also associated with an elaborated endoplasmic reticulum. 


What are the sexual parts in the flower?

The flower is the main structure of a plant that involves in the reproduction of the plant. The sexual parts of the flowers are Pistil and Stamens.
A) Pistil: The pistil is the female reproductive parts of the flower. It contains 3 parts
1. Stigma - To catch the pollen grains and can stick to stigma.
2. Style - It is the stalk like thing and holds up the stigma.
3. Ovary- It holds ovules or eggs. It produces sexual cells.

B) Stamens: Stamens are the male reproductive parts of the flower. It contains 2 parts - Anther and filament.
The filament is a stalk-like structure that attaches to the base of the flower and supports the anther, which is the structure that produces pollen.


In case of polyembryony an embryo A develops from the synergids and the embryo B develops from the nucellus. State the ploidy of embryo A and B

The synergids are haploid in nature and the nucellus is located within the integumentary region and has abundant reserve food materials. It is diploid in nature. So, embryo A that develops from the synergids will have a ploidy of n and embryo B that develops from the nucellus will have a ploidy of 2n.


Name the male and female reproductive parts in plants.

1) The male reproductive part in a plant is called stamen.
  • It consists of anther and filament.
  • The anther is a lobed structure which produces pollen grains.
  • The filament is a slender stalk-like structure.
2) The female reproductive part in a plant is called the pistil.
  • It consists of three parts- stigma, style and ovary.
  • The sticky part at the top called a stigma.
  • A thin tube passing down is called a style.
  • A swollen sac-like structure at the bottom is called an ovary. 
  • The pollen grains are transferred onto the stigma which then travels down the style into the ovary, where it meets with the ovules and fertilization takes place.


Draw the diagram of microsporangium of an Angiosperm and label any four parts. State the function of its innermost wall layer.

 A typical microsporangium appears near circular in the outline in its transverse section It is made up of four layers namely:
Epidermis. 
Endothecium
Middle layers
Tapetum

Epidermis, endothecium and middle layers are protective in function and help in dehiscence of another. The innermost layer is tapetum which nourishes the developing pollen grain. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus. Tapetal cells can also become binucleate or multinucleate by undergoing endomitosis. In endomitosis, nucleus divides within the nuclear membrane but cytokinesis does not occur.


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Why should a bisexual flower be emasculated and then bagged prior to artificial pollination in hybridisation programmes?

Emasculation of the flower is the removal of anthers from the plant. It is done by the use of a sterilized pair of forceps and then it is covered by polythene or any kind of bag which is known as bagging. This process is very necessary for the hybridisation as it stops the fall or different pollen of species..


Emasculation is not required when flowers are?

  • Emasculation can be defined as the process of removal of stamens or anthers or killing the pollen of a flower with the female reproductive organ being untouched.
  • Emasculation is not required in unisexual flowers. 
  • Emasculation is done to prevent self-pollination and since unisexual have only one type of flowers, therefore only one gamete is produced so emasculation is not required here to prevent self-pollination. 


Both wind and water pollinated flowers are not very colourful and do not produce nectar. What would be the reason for this ?

  • Pollination is the process of transfer of pollen grains to the stigma of the flower that results into fertilization. The pollen grains are carried out by different means like wind, water, insects etc.
  • Wind and water pollinated flowers are light in weight as air and water cannot carry heavy pollens. They are neither colorful nor nectar producing as these are the characters for the insect-pollinated flowers. Insects get attracted towards the nectar and flower color but this does not occur in the case of wind and water. So, wind pollinated flowers do not produce nectar or essential oils/fragrance.



Viability means

The viability of a fetus outside the womb has increased dramatically with the advent of new technologies and procedures. the capacity to operate or be sustained. The viability of the company was guaranteed by the success of its new product.


What is pollination? State its significance.
1289631_6a72f7a8188b4f968507a8fb30f6388a.png

Pollination refers to the transfer of pollen grains from the anther of a flower to the stigma of the same or a different flower. Pollination is a significant process as it helps in fertilisation by bringing the male gamete (male pronucleus) closer to the female (egg) and allowing their fusion. It, therefore, helps in the production of seeds and fruits and thereby help in reproduction as the seeds formed helps in generation of new offsprings. Cross-pollination (in which the pollen grains of one flower are transferred to the stigma of a different flower) helps in the introduction of new variations in plants.


Name the parts labelled as A, B, C and D in the diagram given.
1289629_38b6a747cc84418ca5c8a789ef34a886.png

Solution:

  • Given diagram shows longitudinal section of  flower after pollination. Here we can observe that pollination has occurred and pollen tube has started to extend towards egg apparatus.
  • Here A represents pollen grain. B is pollen tube carrying male nuclei, C is ovary and D represent the end of pollen tube that moves through the micropyle (in the ovule).



What is pollination?

$$\textbf{Solution:}$$

Pollination is the process of pollen grains being transferred from the male anther of a flower to the stigma of a female flower.
There are two forms of pollination:-
$$\bullet$$Pollen grains are transmitted from the stamen of one flower to the stigma of a flower on another plant of the same species in cross-pollination. 
Different pollinating factors, like as wind, water, and insects, are used to achieve cross-pollination.
$$\bullet$$Self-pollination occurs when pollen grains from one flower's anthers are transferred to the stigma of another flower.


Some angiosperm seeds are said to be 'albuminous', whereas few others are said to have a perisperm, Explain each with the help of an example.

Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development e.g., wheat, barley, castor, sunflower. When remnants of nucellus are persistent it is said to have a perisperm. 
Example: black pepper, beat.


What is meant by emasculation ? How is it useful in plant breeding programme?

Emasculation is the process of removing anthers from bisexual flowers without affecting the female reproductive part (pistil), which is used in various plant hybridization techniques.

Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. To remove the anthers, the flowers are covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.


Some species of plants are self-pollinated. Discuss the long-term effect of self-pollination on the evolution of these plants.

The effect of self-pollination are:-

1. There is no mixing up of genes, there are no new characters or features that are introduced into the lineage of the offsprings.
2. Self- pollination is said to reduce the vigor and vitality of the race as there are no new features introduced.



Define apomixis.

A few flowering plants such as some species of Asteraceae and grasses, have evolved especial mechanism, to produce seeds without fertilisation, called apomixis.
Apomixis is a form of asexual reproduction that mimics sexual reproduction. There are several ways of development of apomictic seeds. In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation.


What does pollen tube carry?

Pollen tubes act as conduits to transport the male gamete cells from the pollen grain—either from the stigma (in flowering plants) to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms.


Why do we use sucrose as the medium for pollen germination?

Sucrose is use for pollen germination as it helps in formation of pollen tubes, in vitro. various criteria is essential for pollen germination which is fullfilled by sucrose such as providing preferable osmotic pressure and substrate for the metabolism(by providing energy during growth) of pollen.


State the function of plumule and cotyledon of embryo of a dicot seed.

Answer :
Function of Plumule :
i) Plumule is the part of the embryo above the cotyledons, from which develops the shoot proper, consisting of stem, leaves, and flowers.
Function of  Cotyledons :
i) Cotyledons are the embryonic part of the seeds of flowering plant which upon germination forms the first green leaf and help in the photosynthesis. 
ii) Cotyledon is an important part of the seed and helps in its germination. 
iii) These are the first leaves produced by plants but are not true leaves.



It is said apomixis is a type of asexual reproduction. Justify.

Apomixis involves the production of seeds without the function of gametes means avoiding the processes of meiosis and fertilization, leading to embryo development. so apomixis is a form of asexual reproduction.


List the parts of a typical dicot embryo.

Parts of typical dicot embryo includes- Plumule, cotyledons, hypocotyl, radical and root cap.
  • A typical dicotyledonous embryo, consists of an embryonal axis and two cotyledons.
  • The portion of embryonal axis above the level of cotyledons is the epicotyl, which terminates with the plumule or stem tip.
  • The cylindrical portion below the level of cotyledons is hypocotyl that terminates at its lower end in the radical or root tip.
  • The root tip is covered with a root cap.

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Define pollination. Explain the different types of pollination. List two agents of pollination? How does suitable pollination lead to fertilization?

Pollination: Is defined as the deposition of pollen grains on the stigma of a flower from anthers belonging to the same flower, same plant or a different plant.
Pollination is of two types 
Self pollination - Stigma receiving pollen grains from the same flower 
Cross pollination - Stigma receiving pollen grains from a flower on the same plant or a different plant
Wind and insects are two agents of pollination, called as Anemoplily and Entomophily respectively
Example of wind pollination - Grasses, Gymnosperms etc
Example of insect pollination - Rose, Euphorbia sps etc
Pollination and fertilization - Suitable pollination leads to compatible pollen grains being deposited on the stigma, leading to pollen tube development and fertilization.



Complete the following chart and rewrite :
Sr. No.AgenciesType of Pollination
1.Water......
2....Entomophily
3.Bat.....
4......Omithophily

1. Hydrophily
2. Insect pollination
3. Chiropterophily
4. Bird pollination


Stamen has two parts called ______ and ______.

Stamen has two parts called filament and anther.
The filament is the stalk of the anther. Pollen grains are produced in the anther.


State the appropriate terms for the following:
Plants which bear seeds with two cotyledons.

 Plants which bear seeds with two cotyledons are called Dicotyledons.
Angiosperms are divided into two classes monocotyledons (one cotyledon) and dicotyledons (two cotyledons).
Example of dicotyledonous plants are Mango, pea, groundnut etc


i) What is meant by pollination?
ii) what are its two types?
iii) what are the agents which help in pollination?

The transfer of pollen grains from the anther of a stamen to the stigma of a pistil or carpel is called pollination. 
Pollination is of two types:
Self-pollination: Occurs when the pollen grains of a flower are transferred to the stigma of the same flower or another flower of same plant.
Cross-pollination:Occurs when the pollen grains from the anther of a flower are transferred to the stigma of the  flower on another plant of the same species.
Agents of pollination: are those which aid in cross pollination
Air or wind - pollination type- Anemophily (Cycas)
water  - pollination type - hydrophily (Vallisneria)
Insects -pollination type - entemophily - (Hibiscus) 
Birds - pollination type - ornithophily - (Butea)

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What do you mean by true fruit and false fruit?

If only ovary of the flower takes part in formation of fruit then it is called true such as Mango, other than the ovary, if petals, thallamus of the flower take part in formation of fruit, then it is called false such as Apple.


Briefly explain pollination?

Pollination is the process of transfer of pollen grains from the anther and their deposition on to the stigmatic surface of the flower. 
It Is mainly of two types: 
(a) Self Pollination 
(b) Cross-Pollination 

(a) Self-pollination is between the flowers of the same plant. It is of two types: autogamy, in the same flower, and geitonogamy. in the different flowers of the same plant. 

(b) Cross-pollination is between the flowers of different plants. 
It takes place in various ways: 
Wind Pollination - Anemophily
Insect Pollination  - Entomoshily
Water Pollination  - Hydrophily
Bird Pollination - Ornithophily
Bat Pollination - Chiropterophily


Very Short Answer.
Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant : embryogenesis, fertilisation, gametogenesis, pollination

The sequence of events in sexual reproduction are as follows;
Gametogenesis $$\rightarrow$$ Pollination $$\rightarrow$$ Fertilisation $$\rightarrow$$ Embryogensis


a) Distinguish between pollination and fertilisation. 
b) Mention the site and product of fertilisation in a flower. 
c) Draw a neat, labeled diagram of a pistil showing pollen tube growth and its entry into the ovule. 

PollinationFertilisation
Pollen grains are transferred from another to stigma.Fusion of male and female gametes takes place.
Happens outside the ovary. Happens Inside the ovary.
It happens before fertilization.It is the next step after pollination. 
Site of fertilization: Ovary 
Product of fertilization: Zygote 

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"Identify if the statement is right, if not, correct it."
Anther is a part of the pistil.

The given statement is wrong.
Anther is not the part of the pistil but the stamen and forms the pollen grains.


Differentiate between Pollen and Pollinium.

The male gamete containing structure in a flower is called pollen. A mass of pollen grains from the same flower is called pollenium. In a pollenium, the pollen grains are held together by a sticky substance and all the pollen grains are thus transferred together, as is Calotropis


Are pollination and fertilisation necessary in apomixis? Give reasons.

Apomixis is a condition in which embryo develops without fertilization. Hence, pollination and fertilization are not necessary for apomixis.


Identify the type of carpel with the help of diagrams given below:
1851558_3d24b6749dbe4186b15105710f7898f0.png

Figure 'A' shows multicarpellary syncarpous condition and figure 'B' shows multicarpellary apocarpous condition.
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Can an unfertilised, apomictic embryo sac give rise to a diploid embryo? If yes, then how?

Apomixis is formation of seed without meiosis and fertilization. Here, the embryo sac develops from a diploid megaspore with all its components like the egg cell, synergids the antipodals to be diploid. If any one or all of these cells undergo embryonic development, the embryo sac will give rise to diploid embryos.


What is self-incompatibility?

When the pollen grains from the same plants are prevented from germinating on its stigma, this phenomenon is known as self-incompatibility.


Given below are the events that are observed in an artificial hybridization programme. Arrange them in the correct sequential order in which they are followed in the hybridization programme.
(a) Re-bagging
(b) Selection of parents
(c) Bagging
(d) Dusting the pollen on stigma
(e) Emasculation
(f) Collection of pollen from male parent

Following is the correct sequence of steps being followed in hybridization:

Selection of parents $$\rightarrow$$ Emasculation $$\rightarrow$$ Bagging  $$\rightarrow$$ Collection of pollen from male parent $$\rightarrow$$ dusting the pollen grain on stigma  $$\rightarrow$$  Re-bagging.


Name the part of gynoecium that determines the compatible nature of pollen grain.

Stigma of the pistil determines the compatibility of the pollen grains.



Which are the three cells found in a pollen grain when it is shed at the three celled stage?

When a pollen grain is shed at the three celled stage, it contains a vegetative cell and two male gametes. The generative cell divides into two male gametes.


In case of polyembryony, if an embryo develops from the synergid and another from the nucellus which is haploid and which is diploid?

The embryo developing from synergid will be haploid and the embryo developing from nucellus will be diploid.


List three strategies that a bisexual chasmogamous flower can evolve to prevent self-pollination (autogamy).

Following are the three strategies that a bisexual chasmogamous flower can evolve to prevent self-pollination (autogamy):
  1. In many flowers, pollen release and stigma receptivity are not synchronized. Either the pollen is released much before the maturity of stigma or stigma matures much before the release of pollen.
  2. In some flowers, anthers and stigma are placed at different places so that pollen grains from the same flower cannot reach the stigma.
  3. Some flowers follow self-incompatibility between pollen and stigma. This is a genetically mediated process which prevents autogamy in these flowers.


What are the possible types of pollinations in chasmogamous flowers. Give reasons.

Chasmogamous flowers: These are open flowers in which stigma and anthers are exposed and flowers are similar to other species. Possible types of pollinations in chasmogamous flowers are as follows:

(a) Geitonogamy: The situation in which pollen grains from the same plant but different flower reaches the stigma is called geitonogamy. This is similar to autogamy because the zygote gets the gene pool from the same plant.

(b) Xenogamy: The situation in which pollen grains from a different plant reaches the stigma is called xenogamy. This can be termed as the true cross-pollination because the zygote gets the gene pool from two different plants.

Most of the plants produce hermaphrodite flowers and thus self-pollination is a clear cut eventuality. But continuous self-pollination can result in inbreeding depression. Variation will not be possible in case of self-pollination. Hence, plants have evolved various ways and means to facilitate cross pollination even in bisexual flowers. One of the strategies followed by plants is loss of synchronization between pollen release and stigma maturity. Another strategy is self-incompatibility between pollens and stigma of the same flower. A third strategy is the positional difference between anthers and stigma so that pollens from the same flower are unable to reach the stigma.


What is a ‘false fruit’? Give one example.

False fruit is a fruit in which some of the flesh is not derived from the ovary, but from some adjacent tissue exterior to the carpel. Examples of false fruits include apple, pineapple, strawberry, pears, etc.


Name the three agents of pollination.

The three agents of pollination are:
(a) Insect
(b) Wind
(c) Water


Embryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.

The development of an embryo sac apomictically can occur due to Diplospory or Apospory.
In Diplospory type, the embryo sac is formed from an unreduced  (with out undergoing meiotic division) Megaspore. Hence, all the component cells of the embryo sac are diploid. The egg cell develops into a diploid embryo without fertilization.
In Apospory type, the development of the embryo sac takes place by mitotic divisions in one of the cells of the nucellus. Hence, all the cells within the embryo sac are diploid including the egg cell. Here also, the egg cell develops into an diploid embryo without undergoing fertilization.
The above forms of apomictic embryo sac development is also known as gametophytic apomixes.


Draw a diagram of longitudinal section through a monocot seed


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Are parthenocarpy and apomixis different phenomena? Discuss their benefits.

Yes, they are different. Parthenocarpy is the condition in which fruits are developed without fertilization, while apomixis is a condition in which seeds are developed without fertilization. Fertilization is absent in both the case but seeds are present only in apomixis. Parthenocarpic fruits are seedless.
Apomixis produces genetically indentified mother cells whereas parthenocarpy produces genetically identified offsprings.

Benefits of Parthenocarpy: Seedless fruits are easier to consume; especially those fruits which naturally contain too many seeds, e.g. papaya, watermelon and banana.

Benefits of Apomixis: Apomixis can be used to produce apomicts hybrid seeds so that farmers  not need to buy hybrid seeds every year. This will help in drastically cutting the cost for farmers.
Apomictic seeds produce clones of the parent plant, so a plant with desired characteristics can be grown apomictically than, through sexual reproduction.


What is emasculation? Why and when is it done?

Removal of anthers in a flower is called emasculation. This is done by cutting off the anthers by scissors or any other suitable tool.


Does self-incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.

$$\textbf{Explanation:}$$

$$\bullet$$ Self-incompatibility is a genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

$$\bullet$$ Thus, self-incompatibility imposes complete restriction on autogamy. 

$$\bullet$$ This evolution might have occurred in order to prevent too much inbreeding because continuous inbreeding prevent variations.

$$\bullet$$ In such plants, cross-pollination or artificial hybridization can be adopted for pollination which ensures accumulation of gene pools from two different plants.


What is polyembryony and how can it be commercially exploited?

Answer:
Polyembryony is a condition in which two or more embryos develop from a single fertilized egg, forming what in humans is known as identical twins. A common phenomenon in many plant and animal species, polyembryony occurs regularly in the nine-banded armadillo, which usually gives birth to four identical young.
Polyembryony can be commercially exploited by producing seeds of hybrid varieties at lower cost. In case of hybrid plants, a farmer needs to buy seeds every year because plants from hybrid seeds fail to produce hybrid seeds due to laws of inheritance. Buying fresh seeds in every season is very costly.


Distinguish between the following pairs: Polyandrous and Polyadephous androecium

Polyandrous androeciumPolyadelphous androecium
The filaments of the stamens are freeThe filaments of the stamens are united in multiple groups 


Pollination is the process of transfer of _________

Pollination is the process of transfer of Pollen grains to the stigma.


Name the different types of androecium found in flowers.

Answer:
The different types of androecium found in flowers are-
  • Polyandrous – When a flower's stamens are free, the state is known as polyandrous.
  • Monadelphous - Monadelphous refers to a state in which the filaments of anthers in a flower are merged into a single group.
  • Diadelphous: Diadelphous is when the filaments of anthers in a flower are united into two groups.
  • Polyadelphous: Polyadelphous is a phenomenon in which the filaments of an anther of a flower are united into more than two groups.

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Explain the terms Monadelphous, Diadelphous and Polyadelphous. In each case name a flower possessing such an androecium. 

Type of AndroeciumFlower PossessingExample 
Monadelphous  filaments are fused in a flower to form one groupHibiscus 
Diadelphous  filaments are fused in a flower to form two groupsPea 
Polyadelphous  filaments are fused in a flower to form more than two groupsBombax 


Different timings for maturation of gynoecium and androecium, is called _______.

Different timings for maturation of gynoecium and androecium, is called Dichogamy.


Why are the following describes as stated:
(a) The androecium of pea flower is diadelphous
(b) Ray florets of sunflower as neuters
(c) In  Salvia sepals as petaloid 

$$\textbf{Solution:}$$


$$\textbf{a)}$$

$$\bullet$$ Diadelphous means united filaments of stamens clubbed together in 2 bundles.

$$\bullet$$ In pea flower, the stamens are united to form two bundles and therefore, the androecium is called diadelphous.


$$\textbf{b)}$$

$$\bullet$$ Neuters are non-fertile. It indicates absence of male and female reproductive organs.

$$\bullet$$ Ray florets of sunflower are neuters.

$$\bullet$$ They do not contain any male or female parts.


$$\textbf{c)}$$

$$\bullet$$ Petaloid means petal-like.

$$\bullet$$ In Salvia, the sepals are petaloid as 3 sepals are red in color and united as petals. 

$$\bullet$$ They are not differentiated from the petals. 



Give any two examples each of endospermic (albuminous) seed, and non-endospermic (exalbuminous) seeds.

Listed below are the examples for each: 
Endospermic (albuminous) seed - Maize, Castor, Poppy 
Non-endospermic (exalbuminous) seed - Gram, pea, bean 


When pollen grains of a flower reach the stigma of the same flower 

When pollen grains of a flower reach the stigma of the same flower - Autogamy/self-pollination.


Name the type of androecium found in
(a) China rose
(b) Bombax
(c) Pea

The type of androecium found in the following structures are: 
(a) China rose - This plant displays Monadelphous androecium. wherein the stamen is united in one group by their filaments and anthers are free. 
(b) Bombax - This plant displays Polyadelphous androecium, wherein filaments are united in a few groups. 
(c) Pea - This plant displays Diadelphous androecium, wherein filaments are united in two bundles. Nine out of ten filaments form the stamina tube and the tenth is left free. 


Transfer of pollen grains from anthers to stigma of the same flower is called ______.

Transfer of pollen grains from anthers to stigma of the same flower is called Autogamy .


Pollination of flowers by insects

Pollination of flowers by insects - Entomophily 


From where does developing embryo gets nutrition?

 During development the embryo derives nourishment from the endosperm.


Write in detail, the structure of pollen grain.

Pollen grains in Angiosperms are two celled structures. Each pollen grain contains two haploid cells, the generative cell and the vegetative cell.It is non-motile and normally round structure. It is protected by a two-layered wall. The outer layer is thick, stiff and protective and is called exine. The inner layer is thin and elastic and is made up of cellulose and pectin. There are a few thin areas in the exine called germ pores. 


What are Ubisch bodies?

The fatty substances deposited on the wall of pollen by the secretions of tapetal cells are termed as Ubisch bodies. 


Why pollen grains are conserved for a long time? 

The wall of the pollen grain has deposition of a complex compound known as sporopollenin. This substance is waterproof, resistant to microbial decay. and is very stiff. This hardshell ensures that the tender cells inside has a strong chance of survival.


Amit visited an orchard where he found some flowers were covered with butter paper bags. He was about to remove the bags, but the gardener did not allow him. Can you say why?

Emasculation is the process of removing anthers from bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. Anthers are removed and the flowers are covered with a bag to avoid pollination with unwanted pollen. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.


Pick up the correct match
A) A-1, B-2, C-3,D-4
B) A-2,B-3,C-4,D-1
C) A-3,B-2,C-4,D-1
D)A-3,B-4,C-1,D-2

The stamen is the reproductive organ of a flower that produces pollens.
 Monodelphous stamens are when all the filaments are fused into a single with the anthers remaining free. for e.g., China rose
Polydelphous stamens - when the filaments are fused into two or more bundles with the anthers remaining free. e.g., Castor
Synandrous stamens - when the anthers are connate ( that is they are joined in the same whorl) i.e. when the anthers and the filaments of the stamens are joined together to the whole length.e.g., Cucurbits and Colocosia.
Syngenesious stamens - When the anthers are united but the filaments are free e.g., Sunflower.



What is pollination? State its types.

261526_14b099e4994343109dba1ed522183259.png

In the given figure, A represents the pollen grain, B represents the pollen tube, C represents the ovary and D represents the female germ cell.
The transfer of pollen grains from the anther to the stigma of a flower is known as pollination.
It is of two types:
(i) Self-pollination: It is the transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant.
(ii) Cross-pollination: It is the transfer of pollen grains from the anther to the stigma of the flower present on two different plants.
Significance of pollination:
(i) It is a significant event, because it precedes fertilisation.
(ii) It brings the male and female gametes closer for the process of fertilisation.
(iii) Cross-pollination introduces variations in plants because of the mixing of different genes. These variations further increase the adaptability of plants towards the environment or surroundings.


(a) Why does endosperm development precede embryo development in angiosperm seeds? State the role of endosperm in mature albuminous seeds.
(b) Describe with the help of three labelled diagrams the different embryonic stages that include mature embryo of dicot plants.

a) Endosperm provides nourishment to the developing embryo thus, embryo development starts after an endosperm is formed. The main role of endosperm is to provide food for growing embryo.
b) The labelled diagram of the different embryonic stages in dicot plants is given below:




Two mark Questions:
Name the organic materials the exine and intine of an angiosperm pollen grains are made up of. Explain the role of exine.

The exine layer is made up of sporopollenin, which is one of the most resistant substances found in nature. The intine layer is made up of cellulose and pectin materials.
Exine plays an important role in:
(1) It protects gametophytes in harsh environments and serves as a barrier against various physical and chemical factors and biological pathogens.
(2) It helps in pollen dispersal and cross-pollination in some species.
(3) It enables stigma cells to capture the most appropriate pollen grains by providing species-specific factors for pollen-stigma recognition and adhesion.


Where is sporopollenin present in plants? State its significances with reference to its chemical nature.

$$\textbf{Solution:}$$

$$\bullet$$ Sporopollenin is present in the outer layer of pollen grains, called exine.

$$\bullet$$ Sporopollenin is the hard and one of the most resistant organic materials known.

$$\bullet$$ Significance of sporopollenin: Due to the presence of this sporopollenin, the microscopic pollen grains of the past are obtained as fossils.



Explain the function of each of the following.
(a) Coleorhiza (b) Umbilical cord (c) Germ pores

The function of coleorhiza, umbilical cord and germ pores are as follows:
(a) The coleorhiza portects the radicle in some plants that is penetrated by the root in germination. 
(b) Umbilical cord serves a s blood source for the foetus and as a means of transferring nutrients, proteins, vitamins, etc to the foetus. It also aids taking away waste produces and deoxygenated blood from the foetus.
(c) The germ pore is aperture in the exine layer of the pollen grain where the sporopollenin is absent. The germ pore helps in the formation of the pollen tube and release of male gametes during fertilization.


Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).
(a) Ovary
(b) Anther
(c) Egg
(d) Pollen
(e) Male gamete
(f) Zygote

(a) Ovary - It is the female part of the plant which has ovules. It is a diploid (2n) structure.
(b) Anther - It is the male part of the flower and contains pollen grain. It is a  diploid structure (2n).
(c) Egg - Ovules are known as egg. It is female gamete present  in the ovary. It is a haploid structure (n).
(d) Pollen - Pollens are male gamete. It is a haploid (n) gamete.
(e) Male gamete - Pollens are male gamete. It is a haploid (n) gamete.
(f) Zygote - It is formed by the fusion of male and female gamete. It is a diploid structure (2n).


What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?

Self-incompatibility is a condition where pollen is not able to fertilize the same flower or other flowers on the same plant due to inhibition of the growth of the pollen tube in the stigma and style, thereby preventing delivery of male gametes to the ovules. The absence of fusion of male and female gamete leads to no seed formation in these plants. 


(a) Name the organic material of the exine of the pollen grain. How is this material advantageous to pollen grain?
(b) Still, it is observed that it does not form a continuous layer around the pollen grain. Give reason.
(c) How are 'pollen banks' useful?

a) The exine of the pollen grain is made up of a resistant substance called sporopollenin. It helps the pollen grains to resist high temperatures and action of strong acids and alkalis. Since it cannot be easily degraded by enzymes, it can be preserved as fossils. 
b) Sporopollenin is not continuous. At places and in regions where it is absent, it forms germ pores from where pollen tube formation takes place when pollen grain germinates on stigma. 
c) Pollen banks are used to store pollen grains under viable conditions for longer periods of time so that they can be used later on for crop breeding programmes or in other biochemical or physiochemical studies. 


(a) How does cleistogamy ensure autogamy?
(b) State one advantage and one disadvantage of cleistogamy to the plant.

(a) Cleistogamy is a type of self-pollination of certain flowers that can propagate by using non-opening, self-pollinating flowers. Cleistogamy ensures autogamy as cleistogamous flowers do not open at all and hence there is no chance of cross-pollination as there is no chance of cross-pollen landing on the stigma.

(b) Advantage: Cleistogamous flowers produce assured seed set even in the absence of pollinators.
Disadvantage: As there is no cross-pollination, there is no variation in the progeny.


Write the difference between chasmogamous and cleistogamous flowers.

Chasmogamous flowersCleistogamous flowers
Chasmogamous flowers open at maturity. Cleistogamous flowers do not open and remain in the bud state. 
Chasmogamous flowers are usually cross-pollinated (and sometimes self-pollinated). Cleistogamous flowers can only carry out self-pollination.
In chasmogamous flowers, reproductive structures are often larger and more pollen needs to be produced. In cleistogamous flowers, reproductive structures are often smaller and less pollen needs to be produced. 
Chasmogamous flowers are showy and highly conspicuous.Cleistogamous flowers are non-showy and inconspicuous. 
Chasmogamous flowers are usually dichogamous.Cleistogamous flowers are homogamous.
Chasmogamous flowers are dependent on pollinating agents since they are usually cross-pollinated.Cleistogamous flowers do not need any agents for pollination. 


Why does white flowers bloom at night?

Night time flowering plants are typically white but have pleasing smell, as insects don't see in night time but get attracted to their smell. White is a good reflector of light and is a shade better seen at night by a variety of pollinators. Hence, white flowers bloom at night.


Describe pollen-pistil interaction in detail.

Pollination refers to the falling of the pollen on the stigam and germination of the pollen grain to form a pollen tube. The arrival of a pollen grain on the stigma does not assure there will be fertilization. Interspecific incompatibility means there is failure of pollen from one species to germinate on the stigma of another species. Intraspecific incompatibility occurs within a species. Self-incompatibility is the incompatibility between the pollen and the stigma of the same individual. If the pollen and the stigma are compatible, the pollen absorbs the water (hydrates) from the stigma and the pollen tube emerges. The pollen tube grows down the style of the carpel toward the micropyle. This is necessary for the migration of the male gametes to the egg cell.  
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Imagine you have a garden with the plants listed below. A swarm of bees visited your garden, do you think the bees will visit all the flowers? Name the flowers which you think the bees will be attracted to. Give reasons to substantiate your answer.
(Jasmine, Nerium, Gulmohar, Rose, Lotus, Corn, Sugarcane, Bamboo, Chrysanthemum, Dahlia, Grass, Coconut, and Peas)

Swarm of bees will visit the following flowers

 1. Jasmine

2. Nerium

3. Gulmohar

4. Rose

5. Lotus

6. Chrysanthemum

7. Dahlia and

8. Peas

Reason: These flowers are entomophily and have the following adaptations for pollination by insects

 1. They have bright petals.

2. These flowers are large in size

3. They have a sweet smell and

 4. These flowers produce nectar



What is meant by emasculation? When and why does a plant breeder employ this technique?

Answer:

The process of removal of anthers from the flower is called as emasculation. It is done before dehiscence to prevent contamination of stigma with any undesired pollen and to ensure cross-pollination by desired pollens. Emasculation is useful in artificial hybridization to pollinate stigma with selected emasculated pollens only. 


With the help of diagrams, describe emasculation and bagging.

Emasculation: The process of removal of stamens or anthers before they dehisce or destroy the pollen grains of a flower without affecting the female reproductive organs is called emasculation. By emasculation the female flower can be artificially pollinated by the desired pollen grains. This is a process used during artificial hybridisation.
Bagging : The emasculated flower is enclosed in a bag to avoid pollination by any unwanted pollen. This is called bagging. 

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Name the agents of pollination in the following cases 
(i) Bright coloured flowers with scent and nectar glands.
(ii) No colour/scent/nectar but pollen grains are dry, light weight and powdery. Stigma is feathery.
Also mention the plants in cases (i) and (ii)

(i) Insects act as a pollinator in the flowers with bright colored flowers with scent and nectar glands. Ex: cucumber, watermelon, squash.
(ii)Wind pollination occurs in the flowers with No color/scent/nectar but pollen grains are dry, lightweight and powdery. Stigma is feathery.
Ex: wheat, rice, corn, rye, barley, and oats.


Explain the difference between self-pollination and cross-pollination

Self PollinationCross Pollination


Transfer of pollen grains from the anther to the stigma of the same flower
Transfer of pollen grains from the anther to stigma of another flower
Occurs in bisexual flowers having anther and stigma maturing at same time
Occurs in bisexual flowers having anther and stigma maturing at different times
External medium is not required
External medium is required
Examples- wheat, peas etc.
Examples- lady finger, tomato, brinjal etc.


(unisexual, fertilisation, fruit, stamen, anther, bisexual, pollination, seed, ovary)
Transfer of pollen grains from the anther to the stigma is known as .........

Unisexual- An organism involving only one sex i.e, either male or the female.
Fertilisation- It is the process of fusion of male and female gametes to produce a zygote.
Fruit- It is the seed-bearing structure of plants found in most angiosperms.
Stamen- It is the male reproductive organ of the plant which produces pollen.
Anther- It is a part of stamen which contains pollen.
Bisexual- A flower that bears both male and female parts of a plant.
Seed- It is an embryonic plant closed in a covering.
Ovary-  It is the female reproductive part of the plant.
'Transfer of pollen grains from the anther to the stigma is known as POLLINATION'


Differentiate between.
Geitonogamy and allogamy

When pollens of a flower pollinate any other flower present on the same plant, it is said to be  geitonogamy. Whereas transfer of pollen grains from the anther of a flower from one plant to the stigma of the flower on another plant is called .allogamy.


Name the three agents of pollination.

The agents of pollination are wind, water, and animals. Pollination by wind is called the anemophily,  by water is called the hydrophily and by animals is called the zoophily.


What is meant by pollination? Explain the structure of germinating pollen grain with the help of a labelled diagram.

Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma. It is a very important part of a plant's life cycle. Pollination is of two types Self-pollination and Cross-pollination. Self-pollination is the basic type because it involves the bisexual flower. Cross-pollination is when one plant pollinates a plant of other varieties. Pollen grains are the microscopic structures which carry the male reproductive structures of the plants.  Germinating pollen contains Exine, Intine, pollen tube Germ pore, Tube nucleus, Germinating nucleus.
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Differentiate between .
Heartwood and sapwood

In most trees the outer light coloured region of the wood is distinct from the inner dark coloured region. The former is known as sapwood and the latter heartwood. The sapwood consists of living cells, whereas the heartwood is composed of dead cells which become impregnated with resins, gummy or tannin like substances.


Differentiate between.
Mesogamy and porogamy 

When pollen tube enters the ovule through integument, the condition is described as mesogamy. 
Inporogamy, the pollen tube enters the ovule through the micropyle.


Differentiate between Hypocotyl and epicotyl.

 Hypocotyl Epicotyl
The portion of the embryonal axis which lies below the cotyledon in a dicot embryo is known as the hypocotyl.The portion of the embryonal axis which lies above the cotyledon in a dicot embryo is known as the epicotyl.
 It terminates with the radicle.  It terminates with the plumule.


What is malacophily?

Pollination can occur through various agents including wind, water, birds, animals, bats, molluscs, etc.
Malacophily refers to when pollination of plants occurs through snails.


Draw a labelled diagram of the structure of mature dicot embryo.

Image result for labelled diagram of the structure of mature dicot embryo.


Describe the structure of pollen grain of angiosperms.

Structure of pollen grains: Pollen grains represents the male gametophyte.
1. The pollen grain are surrounded by prominent two layered wall.
2. The hard outer thick layer is called exine and is made up of sporopollenin, which can withstand against high temperature, enzymes and strong acids and alkali.
3. It has prominent aperture called germ pore where sporopollenin is absent.
4. The inner thin wall of the pollen grain is called intine. It is made up of cellulose and pectin.
5. The cytoplasm of pollen grain is surrounded by plasma membrane.
6. Pollen grain consists of two cells, the vegetative cell and generative cell on maturity.
7. The vegetative cell is larger in size with large amount of reserve food material and a large irregularly shaped nucleus. 
8. The generative cell is smaller in size and floats inside the cytoplasm of vegetative cell.
9. Internally, each pollen grain posses two type of nucleus called generative nucleus and tube nucleus.
10. The generative nucleus divides and forms two male gametes nucleus and develops pollen tube after pollination.
11. In majority of angiosperms, pollen grains are shed at two celled (vegetative cell and generative cell) and in few, three celled stage (vegetative cell and two male gametes).
12. In some plant species, pollen grains externally posse sharp teeth like projection help in adhering of pollen grains to the stigmatic surface.


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Differentiate between Coleoptile and coleorhiza

 Coleoptile Coleorhiza 
 It is a conical protective sheath that encloses the plumule in a monocot seed. It is an undifferentiated sheath that encloses the radicle and the root cap in a monocot seed.


Draw a labelled long sectional view of an albuminous seed.

Image result for labelled longisectional view of an albuminous seed.


Fertilization is essential for the production of seeds but in some angiospermic seeds develop without fertilization.
Give an example of angiosperm that produces seeds without fertilization. Name the process.

$$\textbf{Solution:}$$

$$\bullet$$Although fertilisation is required for seed formation, certain angiosperm seeds develop without it. 
$$\bullet$$Apomixis is the term for this procedure. 
$$\bullet$$The diploid egg cell is generated without reduced division in some animals and grows into the embryo without being fertilized.
$$\bullet$$For example.Mango with citrus,


Draw a neatly labelled sketch of L.S. of an endospermous monocot seed.

Image result for labelled sketch of L.S. of an endospermous monocot seed.


Starting with the zygote, draw the diagrams of the different stages of embryo development in a dicot.

diagram of different stages of embryo development in a dicot.
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Why is fossilization of pollen possible?

Pollen grains have a prominent two-layered wall. The hard outer layer called the exine is made up of sporopollenin. Sporopollenin is the major component of exine of spores and pollen. It is the most extraordinarily resistant material known in the organic world. It is extremely resistant to non-oxidative chemicals, enzymes and strong chemical reagents. It is chemically stable and remains unchanged in pollen grains that are 500 million years old.
Sporopollenin remains unchanged when extant pollen grains are heated to 300°C or treated with concentrated acids and bases. 
Due to sporopollenin pollen gets preserved during fossilization.


A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds. Answer the following question giving reasons :
How many megaspore mother cells were involved?

From one megaspore mother cell, 4 megaspores are formed.
Out of these 4 megaspores, 3 of them degenerate and only one remains functional. In the production of 240 seeds, 240 megaspore mother cells are involved.



Describe with the help of three labelled diagrams the different embryonic stages that include mature embryo of dicot plants.

Image result for three labelled diagram the different embryonic stages that include mature embryo of dicot plants.


Draw a labelled diagram of L.S. of an embryo of the grass.

Image result for labelled diagram of L.S. of an embryo of the grass


Shreya was walking along with her young brother Srijjan in the garden. Suddenly Srijjans attention was drawn towards a butterfly that was visiting one flower after another. He asked Shreya what was the butterfly doing. Shreya told her younger brother about honey collection and pollination by a butterfly. What values were highlighted by Shreya?

Butterfly visits the flowers for collecting honey which is its food. In the process, it picks up pollen from anthers of one flower and deposits them over the stigma of another flower. The phenomenon is called cross-pollination (entomophily).
(i) It shows that both the plants and the butterflies are benefitted by their mutual cooperation butterfly getting food and the plants getting pollinated,
(ii) Shreya gives instances of this cooperative behaviour in day to day working in the family. She helps her mother in many jobs while the mother takes care of her tiffin, clothes and other requirements,
(iii) Our society is based on cooperative working of its members, some are looking after electricity, water supply, communications, transport, education, health, removal of trash, supply of food stuffs, etc for payment made by everybody.


Explain how some plants are adapted for achieving pollination through wind. How sea - grasses and Vallisneria achieve pollination ?

Pollination achieved by wind is known as anemophily. Wind-pollinated plants do not invest in resources that attract pollinating organisms, such as nectar and scent. Instead, they produce dry and very small sized pollen grains and are in very large quantities so that they can be carried by the wind easily. Female structures on wind-pollinated plants are adapted to capture the passing pollen from the air. In Vallisneria pollination is achieved through hydrophily. In sea-grasses, the female flowers are submerged in water and the pollen grains are released inside the water. 



What is staminode?

A staminode is an often rudimentary, sterile or abortive stamen, which means that it does not produce pollen.


Describe the structure of androecium/stamen.

The stamen (plural stamina or stamens) is the pollen-producing reproductive organ of a flower. Collectively the stamens from the androecium.
Stamen in a flower consists of two parts, the long narrow stalk-like filament, and upper broader knob-like bi-lobed anther.
The proximal end of the filament is attached to the thalamus or petal of the flower. The number and length of stamens vary in different species.
A normal dithecous or dithecous anther is made up of two anther lobes, which are connected by a strip of the sterile part called connective.
Young anther, while it is still in flower bud in T.S., reveals the presence of outermost epidermis. The outermost wall layer lying just below the epidermis is called endothecium or fibrous layer because wall (two radial and inner) develop fibrous thickenings on them except at the junctions of two pollen sacs. Below the endothecium, there are 1-3 middle layers of parenchyma cells.
The cells of the innermost wall layer are radially elongated and rich in protoplasmic contents. This layer is called tapetum. The tapetum forms the nutritive tissue nourishing the developing microspores. The tapetal cells provide nourishment to young microspore mother cells either by forming a plasmodium (amoeboid or invasive type) or through diffusion (parietal or secretory type).


A flower of tomato plant following the process of sexual reproduction produces $$240$$ viable seeds. Answer the following question giving reasons.

What is the minimum number of pollen grains that must have been involved in the pollination of its pistil?

The minimum number of pollen grains that must have been involved are 240, as 240 viable seeds are formed. This is because each pollen grain contains 2 male gametes, out of which one fuses with egg forming zygote that gives rise to seeds.


Define pollinations. Explain wind and water pollination with example.

The process of transfer of the pollen from the anther to the stigma is known as pollination. Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order poales, including grasses, sedges and rushes. Other common anemophilous plants are oaks, sweet chestnuts, alders and members of the family Juglandaceae (hickory or walnut family).
1. Have brightly coloured petals to attract insects
2. Have a strong smell to attract insects
3. Usually contain nectar to attract insects
Water pollination is also termed as hydrophily and mode of pollination is water. It is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons.
Example: Vallisneria, Hydrilla


Describe the structure of a pollen grain.

Answer:
  • The androecium is the male reproductive whorl of the flower which produces male gametes.
  • The stamen is the androecium composed of anther and filament.
  • The anther contains pollen sacs which produce pollen grains.
  • The pollen grain is the male gametophyte which contains the male gametes. 
  • The pollen grain is surrounded by two layers as exine which forms the outer layer and intine which forms the inner layer. 
  • The generative cell divides to form the two male gametes. 
  • The vegetative cell is responsible for providing nutrition.

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Draw a well labelled diagram of the embryo of a dicot seed. Also write the role of cotyledons. 


Cotyledon is the part of the seed. It helps in the germination. They are photosynthetic and function as leaves.
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The exine of pollen grain is hard and resistant to enzyme action. Give reasons.

Exine has outer layer that is made up of sporopollenin. It is the most resistant organic compound and tolerate high temprature, strong acid and alkalis. It cannot be degraded with the help of any enzyme. Therfore, it protects the pollegrain from degradation.


a) Explain two ways by which apomictic seeds get develop.
b) List one advantage and one disadvantage of a apomictic crop.
c) Why do farmers find production of hybrid seeds costly?

a) Two ways by which apomictic seeds can be produced:
Agamospermy: In this method, seeds are produced from diploid cells without meiosis and fertilization e.g., apple.
Adventive embryony: In this method, nucellus and integuments extend into the embryo sac and develops an embryo. In this method, the formation of more than one embryo takes place and this condition is called as polyembryony e.g., citrus fruit.
b) Apomictic seeds reduce the cost of production of hybrid breeding and apomictic seeds can be replant year after year. Disadvantage of apomictic crop is that thegenetic diversity is not observed due to lack of variations.
c) Production of hybrid seeds involve the process of artificial hybridization that comes along with various steps. Moreover, hybrid seeds can not be used in the next year, seeds lose their hybrid characteristics in the progeny. Thus, the hybrid seeds have to be produced year after year, this increases the cost of production.


Draw a diagram showing various parts of an embryo of a dicot seeds.


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Class 12 Medical Biology Extra Questions