CBSE Questions for Class 12 Medical Biology Sexual Reproduction In Flowering Plants Quiz 12 - MCQExams.com

• Apomixis is the formation of new individuals of seeds with embryo growing directly from diploid cells of nucellus or integument (as in Mango and Orange), diploid egg or some other gametophytic cell (as in Apple, Rubus, etc.).

Hence, Apomixis is none of the given options.

1. The pollen grain is the male gametophyte that produces two mature male gametes vegetative and generative cell.
2. Embryo sac is the female gametophyte that contains a thin sac within the nucellus that contains egg which is female gamete.

$$\textbf{Correct option:C}$$  

$$\textbf{Solution:}$$

$$\bullet$$ The wall that protects the pollen grain is known as sporoderm which is divided into two layers outer exine and inner intine.Intine is pectocellulosic in nature.

$$\bullet$$ Exine is made of a highly resistant fatty substance called sporopollenin which does not degrade even with the exposure of hydrolytic enzymes , temperature,strong fluids such as acids or bases. These can be preserved as fossils or later use due to the presence of sporopollenin.

$$\bullet$$ At place exine is incomplete those spaces are known as germ pores which lacks any covering and from these pores the pollen tube comes out at the time of fertilisation.

$$\bullet$$ In entemophily flowers ,the pollen grains are convered by a yellowish sticky oily layer known as pollenkit(made of lipids and carotenoids).

$$\textbf{Hence, the correct option is (C)}$$

• About 80 percent of all plant pollination is biotic i.e it is carried out by insects such as bees, wasps, and birds.
• The remaining 20 percent of abiotically pollinated species, 98 percent is by wind pollination and 2 percent by water pollination.
  

1. Pollination occurs between the two flowers of the different plant is known as cross-pollination also known as xenogamy. 
2. Plants use various methods of pollination like air (anemophily), water (hydrophily) and animals (zoophily).
3. Pollen grains land on stigma if it is compatible the pollen tube grows through style.
4. Cross-pollination is better than self-pollination as it provides variation.

• Pollen wall contains a pair of principal layers the inner inline and outer exine. The inline is pectocellulosic in nature. 
• A special feature of intine is that the supply of beads, ribbons, or plates of catalyst proteins is considerably within the vicinity of germ pores. The exine contains sporopollenin that originates from carotenoids by an aerobic chemical process. 
• It's immune to physical and biological decomposition. Due to this, spore walls are typically preserved for long periods in fossil deposits. Hence, the spore(pollen wall) has cavities containing proteins is the incorrect statement among all.

• Stamen is the unit of androecium. Stamens collectively form the androecium.
• Microsporophyll bears microsporangia which contains numerous pollen grains. Microsporophyll is modified into stamens. Hence, stamen is also known as microsporophyll.
  
• The stamen consists of a stalk called filament and an anther which bears microsporangia.
• Stamens are the male sex organ of the flower because it transfers pollen grains from anther to pistil of the flower.

• Autogamy is the transfer of pollen grains from the anther to the stigma of the same flower. Geitonogamy is the transfer of pollen grains from the anther to the stigma of another flower of the same plant.
  
• Date palm is the dioecious plant, as it bears exclusively either male flowers or female flowers
• Hence, autogamy and geitonogamy are not possible in dioecious date palm plant because it bears either male or female flowers but not both.

Hybridisation is an offspring of two animals or plants of different breeds, varieties, species or genera.

Heterosis is the increase in growth, size, fecundity, function, yield or other characters in hybrids over those of the parents

Test cross is a genetic cross between a homozygous recessive individual and a corresponding suspected heterozygote to determine the genotype of the latter.

Back cross is the cross (a hybrid) with one of its parents or an organism with the same genetic characteristics as one of the parents. 

Thus, the correct answer is option A.