Anatomy Of Flowering Plants - Class 11 Medical Biology - Extra Questions

Discuss the internal structure of monocot roots.

Character Monocot Root
Pericycle Gives rise to lateral root.
Vascular bundles Present more than 6 in number (polyarch condition)
Cambium Absent
PithAbundant and fully developed.
Secondary growthDoes not take place
Cortex and endodermisCortex is wide.
Casparian strips are visible in young roots.
Later on, endodermal cells become highly thickened.


How open vascular bundles differ from closed vascular bundles?

Open vascular bundlesClosed vascular bundles
It contains cambium in between phloem and xylem.
Intra-fascicular cambium is absent.
Phloem and xylem are not in direct contact with each other.
Phloem and xylem are in direct contact with each other.
These are found in dicot and gymnosperm stems.These are found in leaves and monocot stems.
These can be collateral and bi-collateral.These can be collateral or concentric.


Mention two differences in the vascular bundles of sunflower and maize stems.

 Sunflower stem (dicot stem) Maize  stem (monocot stem)
1) Hypodermis is made up of chollenchyma. 1)Hypodermis is made up of sclerencyma.
 2)Vascular bundles are arranged in a ring. 2)Vascular bundles are scattered in ground tissue.


What is the difference between fibers and sclereids in plant histology? Give one example of each.

FibersSclereids
These are elongated.These are broad.
They have tapering end walls.They have blunt end walls.
They are unbranched.They may be branched or unbranched.
They originate from meristematic cells.They are formed by the thickening of parenchyma cells.
For example- wood fibers, bast fibers.For example- macrosclereids, osteosclereids.


A T.S. of a trunk of a tree shows concentric rings which are known as growth rings. How are these rings formed?

  • In the spring season, cambium is very active and produce a large number of xylary elements having vessels with wider cavities and are called spring or early wood and is lighter in color.
  • In winter season the activity of cambium reduces and it forms xylary elements having vessels with narrow cavities and is considered as autumn or latewood and is dark in color.
These both rings appeared as alternate concentric rings and constitute an annual ring which is used to estimate the age of a tree.



What are medullary rays and what are their functions?

  • Medullary rays are strips of parenchyma present between vascular bundles of dicot stem. They separate xylem and phloem bundles. 
  • They serve as a link between pith and cortex. They are also known as pith rays and vascular rays. 
  • They perform various functions like food storage, storage of tannins, transport of food and water, gaseous exchange, etc.


Answer the following with reference to the anatomy of dicot root.
Which type of cells constitute the cortex?

Cortex region of dicot root is made up of circular or polygonal parenchyma cells. These lack chloroplast but contains leucoplast to store starch and large vacuoles to store water.



Give any four differences between tracheids and vessels.

TracheidVessel
They have comparatively narrow diameter.They have comparatively wide diameter.
They have very few large pits.They have numerous small pits. 
They are imperforated cells.They are perforated cells.
Walls are more thickened with narrow lumen.Walls are less thickened with wide lumen.
They are conducting element of pteridophytes and gymnosperms. They are conducting element of angiosperms.


How does the cork act as a protective tissue?

  • Cork is a protective tissue with dead suberin rich cells that forms thick and waterproof covering of older stem and root. 
  • Suberin is a waterproofing waxy substance which restricts water movement.
  •  Presence of suberin in dead cells of cork and absence of intercellular spaces makes the cells impermeable to water and gases thereby protecting the underlying tissues from desiccation, mechanical injury and pathogenic infection.  


Which plant tissues are responsible for giving a plant strength and support?

    • Plants possess supporting tissues that give them definite shape, strength, rigidity and resistance against external forces such as wind and water to which they are continuously subjected. 
    • Sclerenchyma tissue present in plants provides the main structural support to a plant.
    • Sclerenchyma is dead, long, narrow cells with thick and lignified cell walls having a few or numerous pits. They provide mechanical support and are economically important. These are commonly found in the fruit walls of nuts, the husk of the coconut,  jute etc.


    What is eustele?

    In dicot stem, the vascular bundles are arranged in the form of a ring around the pith. This type of stele is known as eustele. In addition to being found in stems, the eustele appears in the roots of monocot flowering plants. 


    Define meristems.

    Meristems are tissues that contains undifferentiated or meristematic cells. These are found in the plant part like stem and root tip where growth takes place.


    What is an annual ring?

    Annual ring is a ring of wood found in the cross section of the stem or root of a temperate plant. It represents one year's growth of a plant.


    Name the different components of xylem and draw the living component of it.

    The different components of the xylem are xylem parenchyma, xylem sclerenchyma (fibres), vessels, and tracheids.
    Out of the four components, the xylem parenchyma is living, while the rest of the components are dead and lignified.

    1718608_79029_ans_d9a502f7c9954edf9aa6e8ee2c1eaec3.png


    Draw illustrations to bring out the anatomical difference between
    (a) Monocot root and dicot root 
    (b) Monocot stem and dicot stem 



    (a)Monocot root and dicot root
    Monocot root and dicot root
    (b)Monocot stem and dicot stem
    Monocot stem and dicot stem


    Why are xylem and phloem classified as complex tissues? Describe the structure of phloem.

    Xylem and phloem are called as complex tissues because they are formed of more than one type of cells. Xylem is composed of tracheids, tracheae, xylem parenchyma and xylem fibres.
    Phloem is made up of four types of cells:
    (i) Sieve elements
    (ii) Companion cells
    (iii) Phloem parenchyma
    (iv) Phloem fibres
    (i) Sieve elements: In lower vascular plants sieve cells are present while the Angiosperms have the sieve tube members. They are tubular channels. They are formed of elongated living cells without nucleus and arranged in vertical rows. The end walls of the individual sieve tubes are perforated by number of pits. The end walls of sieve cells are known as sieve plates. These plates connect the adjacent sieve cells to form a continuous long distance channel for the transport of food materials.
    (ii) Companion cells: Sieve tube, members of the Angiosperms are accompanied by highly specialised parenchyma cells termed as companion cells. They are strongly attached to th sieve tube members by thin walls and perforation. Companion cells have nucleus, richly granular cytoplasm and vacuoles. They do not have starch.
    (iii) Phloem parenchyma: Like the xylem parenchyma cells, the phloem parenchyma cells are the most simple and delicate ones. They contain starch, tannins and crystals. These cells perform the function of storage and lateral translocation of food substances.
    (iv) Phloem fibres: The phloem fibres of sclerenchyma cells are the components of phloem. The fibres may be septate or nonseptate and may be dead or non-living at maturity. They support the plant body and sometime functions as storage tissue.


    What are passage cells?

    In the roots, there are certain endodermal cells which are modified to allow the transport of water. These are the cells which are opposite to the protoxylem elements. These cells have a thin wall and there is no deposition of suberin-like the Casparian strips. These cells are known as passage cells due to its function to transport water and minerals salts from the cortex to the xylem elements.


    Write any three functions of epidermal tissue system.

    Functions of epidermal tissue system are as follows.
    • This tissue system in the shoot checks ecessive loss of water due to the presence of cuticle.
    • Epidermis protects the transpiration and gaseous exchange.
    • Stomata involve in transpiration and gaseous exchange.
    • Trichomes are also helpful in the dispersal of seeds and fruits.
    • Root hairs absorb water and mineral salts from the soil.


    Give three anatomical differences between a monocot root and a dicot root.

     Monocot root Dicot root
     (i) There are numerous xylem and phloem, that is 8 - many. The xylem and phloem are limited, that is 2 to 8.
    (ii) Pith is large and well developed.  Pith is absent or very small.
     (iii) No secondary growth occurs in it. Secondary growth occurs in it.
     (iv) The conjunctive tissue is most sclerenchyma.Conjunctive tissue is parenchyma. 


    Describe the primary structure of monocot root.

    Primary structure of monocot root: The monocot root is circular in outline. The arrangement of tissues is as follows.
    1. Rhizodermis of epiblema: The outermost layer is the Rhizodermis. It is made up tubular living cells. Some of the epidermal cells are protruded out in the form of root hairs. These root hairs are useful in the absorption of water. The epiblema gives protection to the roots.
    2. Cortex: The cortex is broad and consists of parenchyma cells with large intercellular spaces. The cells are living and possess leucoplasts. Their function is storage. The last layer of the cortex is endodermis. The endodermal cells contain bands like structure made of suberin in their radial and transverse walls. These band-like structures are known as Casparian strips. Those endodermal cells in front of protoxylem are thin walled and known as passage cells. These passage cells conduct water from the cortex to xylem.
    Stele: Stele in dicot root is differentiated into pericycle and vascular system.
    Pericycle: Pericycle is a single layer of thin-walled parenchyma cells forming the outermost layer of the stele. Lateral roots arise endogenously from pericycle.
    Vascular system: The primary xylem and phloem are arranged in alternate radii. Xylem and phloem are separated by the conjunctive tissue. Such a vascular bundle is said to be radial vascular bundles. Xylem occurs in the form of a solid core with a ridge like projections extending towards the pericycle. The number of protoxylem points is four. Hence the xylem is called tetrarch. As the first-formed xylem is pointing towards the periphery the xylem of roots is exarch. Phloem consists of sieve tubes, companion cells and phloem parenchyma. Pith is usually absent.

    634939_607808_ans.jpg


    Observe the given picture.
    a) Which portion forms clear cytoplasm and prominent nucleus?
    b) Which functional portion is performing the function of conductivity?
    c) Which portion is considered dead tissue?
    d) Which portion stores starch and fats?
    619874_70ca51c990b948c0b6da62e8a9c66595.png

    The given figure is that of a phloem that transports food material to the plant and is made up of:-
    (a)Companion cells - the portion that forms clear cytoplasm and nucleus.
    (b)Sieve tubes - help in conductivity.
    (c)Phloem fibers or bast fibers - considered to be dead tissues.
    (d)Phloem parenchyma - stores starch and fats.


    Answer the following questions in short.
    1. Which ground tissue are you eating when you eat mashed potatoes?
    2. Which ground tissue makes the shell of a groundnut hard?

    1. The ground tissue we eat when we eat a potato is parenchyma as it is modified to store food in the stem.
    2. Sclerenchyma is mainly responsible for the formation of the protective layer of a seed. Hence, it makes the shell of a groundnut.


    Draw and label brachysclereids.


    633808_607922_ans_40193cd6b8b9430d85b0c7ed040bb09a.png


    Write any three anatomical differences between monocot root and dicot root

      Dicot roots  Monocot roots
    Xylem is usually tetrarch.
    		Xylem is polyarch.
    Pith is usually absent.Pith is usually large at the centre.
    Metaxylem vessels are generally polygonal in cross section.Metaxylem vessels are generally circular in cross section.
     Secondary growth is present. There is no secondary growth.


    Answer the questions with respect to the given figure.
    i) Copy the diagram and name the parts marked(a) to (c).
    ii) Which part is responsible for elongation of the stem?
    iii) Which part is responsible for secondary growth?
    iv) Name the part which is responsible for elongation of internodes.
    619877_c1efe6d1361b4e96b472ed318abe2fea.png


    ii) The apical meristem (A) is responsible for the elongation of a stem.
    iii)The lateral meristempart (C) is responsible for the secondary growth.
    iv)The intercalary meristem (B) is responsible for the elongation of internodes.


    981413_619877_ans_66a68fa53d2441fcbedb3e9a0ee40771.png


    Which meristem does produce growth in length?

    The length of the plant is increased by the primary meristems present from the early life of the plant. Apical meristems that are present at the tip of the shoot and sub-terminal region of root mainly helps in the increase in the length of the plant by adding more cells as they show periclinal division. Periclinal division adds length.


    Why is cambium considered to be a lateral meristem?

    Cambium is considered to be a lateral meristem because it is present along the lateral sides of stem and roots. For example, interstellar cambium ring formed by intrafasicular and interfascicular cambium.


    Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is monocot stem or dicot stem. Give reasons.

    One can ascertain whether the transverse section of young stem is of monocot or dicot by observing the vascular bundles. In monocot stem, vascular bundles are scattered whereas in dicot stem, they are arranged in a ring.
    746336_680188_ans_4bf3af03dc574d43ae72c545087ea835.jpg


    Differentiate fusiform initials and ray initials.

    Fusiform initialsRay initials
    1. These are elongated spindle shaped cells arranged as bricks.They are arranged horizontally in vascular cambium.
    2. They aid in secondary xylem elements and secondary phloem elements production in the vascular cambium.
    		They aid in production of phloem and xylem rays.


    Name the most durable wood.

    Teak wood obtained from Tectona grandis is the most durable wood because of its high tensile strength and fibre density. The high content of oil in teak makes it resistant to termites and other insects. 


    There are two unlabelled microscopic slides showing transverse sections of root and stem of a dicot plant. How will you differentiate between the two on the basis of the arrangement of the conducting tissue?

    Dicot stem is recognized by the endarch condition that is the presence of protoxylem towards center and metaxylem towards the periphery.Dicot root is recognized by 
    the presence of exarch condition that is the presence of metaxylem at center and protoxylem at the periphery.


    Define collateral vascular bundle.

    In the collateral vascular bundle, xylem and phloem are arranged side by side in the same radius. Usually, xylem is towards the inner side whereas phloem is towards the outer side. There are two types of the collateral vascular bundle, open and closed.


    Distinguish between Tracheid and vessel.

    TracheidVessel
    1. They have the comparatively narrow diameter.They have comparatively wide diameter.
    2. They have very few large pits.They have numerous small pits. 
    3. They are imperforated cells.They are perforated cells.
    4. Walls are more thickened with narrow lumen.Walls are less thickened with wide lumen.
    5. They are conducting element of pteridophytes and gymnosperms. They are conducting element of angiosperms.


    Define bicollateral vascular bundle.

    Bicollateral vascular bundles are those which have phloem on both the sides of the xylem. In this, all of them lie within the same radius. Apart from phloem, vascular cambium is also present on both the sides of the xylem.


    What makes the apical meristem of the root sub-terminal?

    As the tip of the root is covered by the root cap for the protection. The apical meristem present in the region of meristematic activity lies at the subterminal position. It lies just above the root cap.


    What forms the cambial ring in a dicot stem during the secondary growth?

    Fascicular and intrafascicular strips of meristem form the cambial ring in a dicot stem during the secondary growth.


    Differentiate between root apex and shoot apex.

     Shoot apex Root apex
     It is terminal. It is sub-terminal
     Longer than root apex and spread up to 1 cm. Quite short, less than 1 mm in length.
     No protection is present. It is protected by root cap.
     Nodes and internodes are present. Nodes and internodes are not formed.
     Branches develop exogenously. Branches develop endogenously.


    Where is pericycle located in dicot root?

    Pericycle is only present in dicot stem is a single or multilayered thin or thick walled cells present between the endodermis and vascular bundles. It provides support, structure, and protection to the plant. 


    How are the xylem vessels arranged in dicot root?

    Protoxylem is the primary xylem in which narrow vessels are formed while metaxylem is the mature xylem with wider vessels. In the root, the narrow vessels are present towards the periphery while the mature vessels are present at the center and are called exarch condition.


    Name and define the different types of vascular bundles.

    When phloem and xylem arranged in a pattern and forms four different types of vascular bundles. They are:-
    1. Collateral Vascular Bundles:- When the strand of phloem is present external to the strand of xylem on the same radius side by side is known as a collateral bundle.
    2. Bicollateral Vascular Bundle: -A vascular bundle with phloem situated on the peripheral and inner side of xylem is known as a bicollateral bundle.
    3. Concentric Vascular Bundles:- A vascular bundle in which one type of vascular tissue surrounds the other is known as a concentric bundle.
    4. Radial Vascular Bundles: -A vascular bundle, in which the primary xylem and primary phloem strands are separated from each other by nonvascular tissues and they are situated on alternate radii of an axis, is known as a radial vascular bundle or radial bundle.


    Describe the structure and organisation of stem apex.

    Shoot apex is the terminal part of the shoot with leaf primordium.
    Various theories are given to explain its structure and organization but the most accepted theory is corpus tunica theory given by Schmidt in 1924.
    Structure and organization of shoot apex-
    1. It is convex in shape or slightly elongated at the base.
    2. It is divided into four regions-tunica, corpus, flank meristem, and rib meristem.
    3. Tunica is divided into two single layers outer and inner tunica that divide from anticlinal division and forms epidermis.
    4. Corpus layer is 3 to 5 layer thick and divides at any plane to provide volume growth to the plant.
    5. Cells of flank meristem are small, narrow and radially elongated.
    6. Rib meristem is present below corpus.
    7. Leaf is generally grown by periclinal division in an inner corpus.


    Briefly describe the anatomy of primary dicot root.

    1. The epiblema is the outermost layer of root made of thin-walled, slightly elongated parenchymatous cells. Root hair present on its surface helps in water and mineral absorption.
    2. Cortex is narrow.
    3. Endodermis is less thickened and Casparian strips are more prominent that maintains the transportation of water.
    4. Pericycle gives rise to secondary xylem and lateral meristem.
    5. Vascular bundles are 2 to 6 in numbers that are diarch to hexarch with exarch condition.
    6. Cambium develops at the time of secondary growth.
    7. Pith is absent or poorly developed.
    Image result for anatomy of primary dicot root.


    Differentiate between.
    Collateral vascular bundle and concentric vascular bundle.

    In a collateral vascular bundle xylem and phloem are present on the same radius and the phloem is. located on the outer side of the xylem. Whereas in concentric vascular bundle one type of vascular tissue (xylem or phloem) is surrounded by the other. A collateral bundle may be open or closed type whereas a concentric bundle is always closed.


    Short / Long answer type questions.
    Give a brief account of complex tissue present in plants.

     Xylem and phloem are the complex tissues which constitute the component parts of the vascular bundle. They are also called vascular tissues.
    • Xylem:
    It is primarily ins­trumental for conduction of water and solutes, and also for mechanical support. Primary xylem originates from the procambium of apical meristem, and secondary xylem from the vascular cambium. As a complex tissue, it consists of different types of cells and elements, living and non-living.
    • Phloem:
    The other specialized complex tissue forming a part of the vascular bundle is phloem It is composed of sieve elements, companion cells, parenchyma, and some fibres. Sclerotic cells may also be present. Phloem is chiefly instrumental for transloca­tion of organic solutes—the elaborated food materials in solution. The elements of phloem originate from the procambium of apical meristem or the vascular cambium.



    Short / Long answer type questions.
    Answer the following with reference to the anatomy of dicot stem:
    (i) Where exactly are the cambial cells located in the vascular bundles?,  (ii) What is the name given to such a bundle,  (iii) How are the xylem vessels arranged ?,  (iv) What type of cells constitute the pith ?

    (i) The cambial cells are located between the xylem and phloem. They consist of meristematic cells. The division of these meristematic cells adds to the phloem towards the periphery and xylem towards the centre during the secondary growth.
    (ii) Such a bundle is conjoint, open, and with an endarch arrangement.
    (iii) Xylem is situated towards the inner side of each vascular bundle. It is endarch type i.e. protoxylem lies towards the pith and metaxylem towards the periphery.
    (iv) The central portion of the stem is occupied by a large number of parenchymatous cells which comprise the pith. These cells are rounded in shape and have large intercellular spaces.


    Short / Long answer type questions .
    Give the anatomical (internal structure) differences between a dicot stem and a monocot stem.

     Character Dicot stem Monocot stem
     Ground tissue Differentiated in cortex and pith. No such differentiation.
     Hypodermis Collenchymatous cells found Sclerenchymatous cells found.
     Endodermis Single layered Absent
     Pericycle Parenchymatous or sclerenchymatous cells found Absent.
     Vascular bundle Uniform size

    Arranged in ring form
    Conjoint and open.    		 Larger towards centre
    Scattered
    Conjoint and closed
     Pith Situated in the centreAbsent 
     Medullary rays Found in between vascular bundles Absent
     Stele Conjoint, collateral, open Conjoint, collateral, closed


    Very short answer type.
    What is an open type of vascular bundle?

    The vascular bundle which has cambium in between the xylem and phloem is known as open type.


    State the location and function of collenchyma and sclerenchyma.

      Collenchyma
        Location: Present in leaf stalks below the epidermis.
          Function: Provides mechanical support to plants.
            Sclerenchyma
              Location: Present in stems, around vascular bundles, veins of leaves and the hard covering of seeds and nuts.
                Function: Provides strength to the plant parts.




                Draw a labelled diagram of the transverse section of a dicot root.

                Transverse section section of dicot root
                968024_1039193_ans_fdb81a3c3c8c48aeb47166c2989453fb.png


                Explain the process of secondary growth in the stelar region of a dicot stem.

                • The growth that results from cell division in the cambia or lateral meristems which causes the stems and roots to thicken is called secondary growth
                • This type of growth occurs due to the activity of the two lateral meristems- the cork cambium and vascular cambium. 
                • Secondary growth in dicots:- 
                1) Formation of cambium ring:
                • The cambium of vascualr bundles becomes meristematic.
                • Some of the medullary ray cells lying at the level of cambium also become meristematic.
                •  It forms a strip of interfasciular cambium together with intrafasciular cambium to form a circular ring called cambium ring.
                • This cambium ring forms secondary tissues in the stellar region.
                • The vascular cambium consists of two types of cells-  fusiform initials and ray initials. 
                • The fusiform initials are vertically oriented which divide to form the elements of xylem and phloem.
                2) Formation of secondary vascular tissues: 
                • The cambium ring cuts off new cells, both on outer and inner sides,
                • The new cells formed on the outer side modify into the elements of secondary phloem.
                • The cells formed on the inner side modify into the secondary xylem.
                3) Vascular rays: 
                • Ray initials of the cambium ring form narrow bands of parenchymatous cells.
                • These cells extend radially from the pith to the phloem. 
                • These are called secondary medullary rays or vascular rays. 



                Which tissue makes up the husk of coconut?

                Explanation:

                • Sclerenchymatous tissue makes up the husks of coconuts. It is also called as the plant’s supporting tissues as it provides mechanical strength and hardness to the plant.
                • It is considered as dead, simple-permanent ground tissue because of its dead, degenerated and functionless inner protoplast.
                • During the early growth cycle of the plants, the sclerenchyma cells persist as the living cells and re-assemble spiral or ring like patterns. 
                • All physical traits like cell-wall type, rigidity, shape, size etc., of sclerenchyma will vary according to different plant types.



                Select the odd one. 
                Apical, Lateral, Intercalary, Epidermis

                Epidermis is odd one- The epidermis is the outermost layer of the skin. 
                Apical, lateral and intercalary meristem are the types of plant meristematic tissue.



                What are meristmatic and permanent tissue?

                Meristematic tissues are the tissues which are capable to divide. They are active cells which are undifferentiated cells. They have abundant cytoplasm and a clear nucleus. They add cells and contributes in the growth. For example, apical meristematic tissue.
                Permanent tissues are the tissues which are specialized and have lost the capacity to divide. They are differentiated cells which has specific function. They have less cytoplasm as compared to meristematic tissues. For example, parenchyma cells.


                The tissues derived directly from the meristem of a embryo is called as ............

                • The tissues derived directly from the meristem of an embryo is called as meristematic tissues.
                • It consists of undifferentiated cells or meristematic cells.
                • It helps in increasing the length of growing tips of root and stem and even increase the girth of the stem. 


                How many types of ground tissues are there? What are they? Write about parenchyma.

                • Ground tissue, also known as fundamental tissue system, forms the main bulk of the plant body. All tissues except the epidermis and vascular bundles are included underground tissue. There are three types of ground tissue:
                1. CORTEX: It is the main zone that lies between the epidermis and pericycle. The thickness of this zone varies from few layers to many layers and is made up of primary tissues. In monocot stems and roots, the cortex is parenchymatous while in dicot stems, the cortex is differentiated into three sub-zones which are hypodermis, general cortex, and endodermis. The cortex serves as a protective zone and also stores food material in stems and roots. It also helps in absorption and translocation of water.
                2. PERICYCLE: It is found just within the endodermis. Endodermis is the innermost layer of cortex having Casparian strips in roots.
                3. MEDULLA OR PITH: It is the central part of the ground tissue which is mostly parenchymatous. Intercellular spaces may or may not be present. The pith forms the central part or core of the roots and stems. The pith of dicot stems is large and distinct whereas pith of dicot roots is very small. It serves as the storage organ for excretory substances of plants such as tannins, phenols, etc. and also for reserved food material.

                • Parenchyma is the most abundant and commonly found tissue in plants. It is made up of thin-walled living cells having a distinct nucleus. The cells of parenchyma have intercellular spaces and are morphologically as well as physiologically unspecialized. The cells are typically isodiametric and may also be spherical, oval, rectangular etc.


                Distinguish between the following with suitable diagram:
                 Exarch and endarch 

                Exarch is the arrangement in which the protoxylem is directed towards the periphery and metaxylem towards the center. The development of the xylem in this arrangement follows the centripetal pattern. It is the characteristics of roots.
                Endarch is the arrangement in which the protoxylem is directed towards the center and metaxylem elements towards the periphery. The development of the xylems in this arrangement follows the centrifugal pattern. It is the characteristics of the stem of flowering plants.


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                Phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells. Why?

                When the girth of the plant increases the layers need to be replaced by new protective layers. To fulfill this need, a meristematic tissue develops in the cortex region. This meristematic tissue is called cork cambium or phellogen. The phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem. The inner cells differentiate into secondary cortex or phelloderm. As the cork cambium is impervious to water due to suberin deposition in the cell wall. The cells of the secondary cortex are parenchymatous are pushed towards the periphery and after some time the cells die due to the pressure towards them.


                Give three ways in which phloem tubes differs from the xylem vessels.

                 PHLOEM TUBESXYLEM VESSELS 
                 It is a part of phloem tissue.
                		 It is a part of xylem tissue.
                 It is a long distance channel made up of living cells and vacuolated cytoplasm.
                		 It is a long distance channel made up of a number of dead cells with a hollow lumen.
                 It conducts food or organic nutrients.
                		 It conducts water and mineral salts.
                 The wall is unlignified and thin.
                		 The wall is lignified and thick.
                The end walls are perforated to form sieve plates.
                		 The end walls are dissolved completely.
                 It does not provide any mechanical strength.
                		 It provides mechanical strength.


                cells which can secret substances at the epithelial tissue folds inward

                The inward folding of epithelium leads to the formation of a multicellular gland. Columnar (goblet cells) and cuboidal epithelial cells often become specialised as it provides mechanical support and folds inwards. 


                What are the various protective tissues present in plants? Explain with the help of examples.


                1337864_1393120_ans_8d4deb800f864168bf14ebc5680bc9f4.jpg


                Arrested flower development.

                Arrested flower development is the means in which flower development is stopped. This is used as a method of artificial selection in plants and farmers use this method to obtain broccoli.


                Give reasons.
                Intercellular spaces are absent in sclerenchymatous tissue.

                Intercellular spaces are absent in sclerenchymatous tissues because they have a cementing substance (known as lignin) around their cell membrane which makes them stiff and hard.


                Name the tissue found in the husk of a coconut. List two characteristics of the tissue.

                Sclerenchyma tissue is found in the husk of a coconut. Some of the characteristics of this tissue are:
                1) It is composed of dead cells. 
                2) The cells of this tissue have thick lignified cell walls.


                The stomatal pore is guarded by two bean-shaped guard cells. Are there other types of cells that are part of the stomatal complex? How is their presence in the vicinity of guard cells functionally effective?

                • Stomata are minute openings found in the epidermis of plant organs. It helps in exchange of gases. It is guarded by two bean-shaped cells called guard cells.
                • Other than guard cells, specialized subsidiary cells are also a part of the stomatal complex. These cells are formed from a few epidermal cells, in the vicinity of the guard cells. They provide support to the guard cells by offering a mechanical advantage and facilitate guard cell movements and also act as a reservoir for water and ions.

                2145855_1606349_ans_f36cbd8d3daf49f988c793f958ef4514.jpg


                Write the name of the following tissue. 

                Tissue responsible for increasing the height of plants. 

                Tissue responsible for increasing height of plants - Apical meristem.


                Explain the structure and functions of xylem? 

                Xylem is a complex permanent tissue which conducts water and mineral salts upward from roots to leaves.
                Structural elements of xylem: 
                $$\to$$ Tracheids are elongated, dead cells with large cavities and possess highly lignified, thick walls. Depending upon the kind of thickening, tracheids may be annular, spiral, reticulate, scalariform and pitted.
                $$\to$$ Vessels are broader as compared to the tracheids. These are composed of many cells, joined end to end with their walls perforated to give it a tube-like appearance. They also show thickening like the tracheids.
                $$\to$$ Xylem Fibres (= Wood fibres): They represent sclerenchyma fibres present in xylem. The fibres are mechanical in function. 

                Functions of each of the elements are: 
                $$\to$$ Tracheids: They transport water and minerals vertically.
                $$\to$$ Vessels: They also transport water and minerals vertically.
                $$\to$$ Xylem parenchyma: It stores food and helps in sideways conduction of water.
                $$\to$$ Xylem fibres: They are mostly supportive in function.
                Only the xylem parenchyma cells are living cells. 
                2035931_1838333_ans_0c442ba3324247bd9746afd8b050218b.png


                Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?

                $$\textbf{Explanation:}$$

                $$\bullet$$  The first formed primary xylem elements are called protoxylem and the later formed primary xylem is called metaxylem.

                $$\bullet$$  In the stems, the protoxylem lies towards the centre and metaxylem lies towards the periphery. This type of primary xylem is called as Endarch.

                $$\bullet$$ In the roots, the protoxylem lies towards the periphery and next to phloem while the metaxylem lies towards the centre. It represents Exarch condition of primary xylem.


                2123877_1841818_ans_06271f7f17d64d589c39068c884e249f.png


                Name the chief mechanical supporting tissue in plants. 

                The chief mechanical supporting tissue in plants is Sclerenchyma. 


                 The cross-section of a plant material showed the following features when viewed under the microscope. 
                (a) The vascular bundles were radially arranged.
                (b) Four xylem strands with exarch condition of protoxylem.
                To which organ should it be assigned?

                $$\textbf{Explanation:}$$

                $$\bullet$$ The radial vascular bundle represents the arrangement of xylem and phloem side by side on different radii. It is the characteristic of monocot and dicot root.

                $$\bullet$$ But the four xylem strands with exarch condition of protoxylem is the characteristic of the dicot root.

                $$\bullet$$ Hence, the cross section is of dicot root as it shows the presence of radial vascular bundles and four xylem strands with exarch condition of protoxylem.


                What part of the plant would show the following: 
                (a) Radial vascular bundle
                (b) Polyarch xylem
                (c) Well developed pith


                $$\textbf{Explanation:}$$

                a) Radial vascular bundle is found in roots.

                $$\bullet$$ In radial vascular bundles, xylem and phloem are arranged in an alternate manner on different radii.

                b) Polyarch xylem is characteristic of monocot root.

                $$\bullet$$ Polyarch xylem shows the presence of more than six xylem elements.

                c) Well developed pith is present in Dicot stem and monocot root

                $$\bullet$$ Parenchymatous pith occupies the central part of the dicot stem and monocot root. 



                Distinguish between open and closed vascular bundles.

                A vascular bundle which is not capable of secondary growth is called a closed vascular bundle. Cambium is absent in closed vascular bundle, example, monocot stem. A vascular bundle which is capable of secondary growth is called an open vascular bundle. Cambium is present in open vascular bundle, example, Dicot stem.


                State the location and function of different types of meristematic tissues in plants.

                Meristems are specialised regions of plant growth. The meristems mark the regions where active cell division and rapid division of cells take place. Meristems are of three types depending on their location.
                Apical meristem:
                It is present at the root apex and the shoot apex. The shoot apical meristem is present at the tip of the shoots and its active division results in the elongation of the stem and formation of new leaves. The root apical meristem helps in root elongation.
                Intercalary meristem:
                The intercalary meristems are located at the internodes or the base of the leaves. The intercalary meristems help in increasing the length of the internode. This is usually seen in monocotyledonous plants.
                Lateral meristem:
                The lateral meristems are present on the lateral side of the stem and root of a plant. These meristems help in increasing the thickness of the plants. 

                387634_424383_ans_44f0a1a00e5c4e2f8f66c54956e0bcc9.jpg


                What is a periderm? How does periderm formation take place in the dicot stems?

                Periderm is composed of the phellogen, phellem and phelloderm.
                During secondary growth, the outer epidermal layer and the cortical layer are broken because of the cambium. To replace them, the cells of the cortex turn meristematic, giving rise to cork cambium or phellogen. It is composed of thin-walled, narrow and rectangular cells.
                Phellogen cuts off cells on its either side. The cells cut off toward the outside give rise to the phellem or cork. The suberin deposits in its cell wall make it impervious to water. The inner cells give rise to the secondary cortex or phelloderm. The secondary cortex is parenchymatous.


                Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.

                When secondary growth occurs in the dicot stem and root, the epidermal layer gets broken. There is a need to replace the outer epidermal cells for providing protection to the stem and root from infections. Therefore, the cork cambium develops from the cortical region. It is also known as phellogen and is composed of thin-walled rectangular cells. It cuts off cells toward both sides. The cells on the outer side get differentiated into the cork or phellem, while the cells on the inside give rise to the secondary cortex or phelloderm. The cork is impervious to water but allows gaseous exchange through the lenticels. Phellogen, phellem, and phelloderm together constitute the periderm.


                Draw and label the diagram of the T.S. of stem.

                The diagram of the T.S. of stem

                2147387_569256_ans_6da43f717e47462994434b521c09d740.png


                Distinguish between Phellem and phelloderm.

                PhellemPhelloderm
                It is a tissue formed on the outer side of phellogen or cork cambium.It is a tissue formed on the inner side of phellogen.
                It is made of dead cells.It is made of living cells.
                It is protective in function.It is involved in the storage of food.
                Suberisation is present.
                		Suberisation is absent.
                Tannins are present.Tannins are absent.


                Distingusih between Fascicular cambium and interfascicular cambium.

                Fascicular cambiumInterfascicular cambium
                It is present between xylem and phloem of the vascular bundle.It is present in vascular bundles.
                It is derived from pro-meristem.It is derived from the permanent tissue.
                It is primary meristem.It is secondary meristem.
                It can produce both primary and secondary vascular components.It can produce only secondary vascular components.


                Distinguish between Softwood and hardwood.

                SoftwoodHardwood
                It is originated from evergreen trees. It is originated from Deciduous trees.
                These are light in colour.These are dark in colour.
                They have poor fire resistance. They have good fire resistance.
                For example,  Pine, Spruce, Fir.For example, Oak, Teak.


                Draw a labelled diagram of T.S. of dicot root. Give four differences between internal structure of dicot and monocot root.

                Image result for structure of t s of dicot root
                 Character Dicot rootMonocot root 
                 Pericycle   Gives rise to secondary roots and lateral meristem and is single layered. Gives rise to lateral root only and is two to three layered thick.
                  Vascular bundles Present 2 to 6 in numbers.(Diarch to hexarch condition) Present more than 6
                 in number (polyarch condition)
                  Pith Absent or poorly developed.  Abundant and fully developed.
                 Secondary growth Takes place. Does not takes place.


                Differentiate between .
                Open bundle and closed bundle

                In open bundles cambium is present in between the xylem and phloem, whereas closed bundles are without cambium.


                Differentiate between.
                Amphicribal vascular bundle and amphivasal vascular bundle

                Both amphicribal and amphivasal vascular bundles are of concentric type. In amphicribal vascular bundle, xylem is surrounded all around by phloem, whereas, in amphivasal vascular bundle, phloem is surrounded all around by xylem.


                Very short answer type :
                What is a bicollateral vascular bundle ?

                A vascular bundle with both external and internal phloem is said to be bicollateral vascular bundle.


                Very short answer type :
                Why is propagation through grafting not successful in monocots ?

                Since in monocots, vascular bundles are scattered, and moreover secondary growth is wanting due to the absence of cambium the union of xylem and phloem in grafting is not possible. Hence propagation through grafting is not successful in monocots.


                Define fascicular cambium and interfascicular cambium.

                In the stelar region, secondary growth occurs by the activity of vascular cambium. A strip of cambium that originates from the procambiun is present between the xylem and phloem of the vascular bundle. This cambial strip is called fascicular cambium. At the onset of secondary growth additional strips of cambium are formed from the interfascicular parenchyma between the vascular bundles. These later formed strips of cambium is known as interfascicular cambium. These strips join with fascicular cambium and form a complete ring of cambium.


                Class 11 Medical Biology Extra Questions