RBSE Solutions for Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

Rajasthan Board RBSE Solutions for Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants Textbook Exercise Questions and Answers.

RBSE Class 12 Biology Solutions Chapter 2 Sexual Reproduction in Flowering Plants

RBSE Class 12 Biology Sexual Reproduction in Flowering Plants Textbook Questions and Answers

Question 1. 
Name the parts of an angiosperm in which the development of male and female gametophyte take place.
Answer:
In an angiosperm, the male gametophyte is developed inside the anther. And the female gametophyte is developed inside the ovary.

Question 2. 
Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structure formed at the end of these two events.
Answer:
Difference between Microsporogenesis and Megasporogenesis:

Meiotic cell division occurs during megasporogenesis and microsporogenesis. It is also called reduction division that leads to the production of haploid gametes. The structures formed at the end of these events are: 
Microsporogenesis: Pollen grains.
Megasporogenesis: Embryo sac.

Question 3. 
Arrange the following terms in correct development sequences:
Pollen grain, sporogenous tissue, Microspore tetrad, Pollen mother cell, Male gametes.
Answer:
Following is the correct developmental sequence: 
Sporogenous tissue → Pollen mother cell → Microspore tetrad → Pollen grain → Male gamete.

Question 4. 
With a neat, labelled diagram, describe the part of a typical angiosperm ovule.
Answer:
An ovule is a female megasporangium where the formation of megaspores takes place.

Various parts of ovule are as follows:

1. Funiculus: It is a stalk - like structure which represent the point of attachment of the ovule to the placenta of the ovary.
2. Hilum: It is the point where the body of the ovule is attached to the funiculus.
3. Integuments: They are the outer layers surrounding the ovule that provide protection to the developing embryo.
4. Micropyle: It is a narrow pore formed by the projection of integuments. It marks the point where the pollen tube enters the ovule at the time of fertilization.
5. Nucellus: It is a mass of the parenchymatous tissue surrounded by the integuments from the outside. The nucellus provides nutrition to the developing embryo. The embryo sac is located inside the nucellus.
6. Chalaza: It is the basal swollen part of the nucellus from where the integuments originate.

Question 5. 
What is meant by monosporic development of female gametophyte?
Answer:
Monosporic development is the development of female gametophyte from one functional megaspore. In angiosperms, a single diploid megaspore mother cell undergoes meiotic division to form four megaspores (haploid). Out of the four, only one megaspore is functional that form a female gametophyte, while the rest of the three degenerate.

Question 6. 
With a neat diagram explain the 7 - celled, 8 - nucleate nature of the female gametophyte.
Answer:
Female gametophyte or embryo sac is a small oval structure that contain a 3 - celled egg apparatus, 3 antipodals cells and one binucleate central cell hence, it is 7 - celled and 8 - nucleate structure.

• Egg apparatus: It consists of two synergids and an egg cell towards the micropylar end. The cells of egg apparatus are uninucleate. Synergids have cellular thickening called filiform apparatus that helps in guiding pollen tube into the synergids.
• Antipodal cells: Chalazal end of embryo sac contains three cells of various shapes and sizes called antipodal cells.
• Central cell: It is the single and largest cell which is bounded by a membrane of embryo sac. It contains two polar nuclei which later fuse to form diploid secondary nucleus. After fertilization the central cell gets converted into triploid primary endosperm cell which forms endosperm.

Question 7. 
What are chasmogamous flowers? Can cross - pollination occur in cleistogamous flowers? Give reason for your answer.
Answer:
Chasmogamous flowers are the flowers that have open petals such that the reproductive organs are exposed to allow cross - pollination.
Cleistogamous flowers are small, closed flowers with unexposed reproductive organs. Therefore, they cannot undergo cross - pollination. However, they undergo self pollination since the stigma and anther are present near each other.

Question 8. 
Mention two strategies evolved to prevent self - pollination in flowers.
Answer:
Two strategies evolved to prevent self - pollination in flowers are:

1. Dichogamy: It refers to the production of male and female reproductive organs at different times in order to prevent self - pollination.
2. Self - incompatibility: It is a genetically controlled mechanism in which pollen grains of a flower are unable to completely grow on the stigma of the same flower.

Question 9. 
What is self incompatibility? Why does self - pollination not lead to seed formation in self - incompatible species?
Answer:
Self - incompatibility refers to a genetically controlled mechanism that prevents self - pollination and promotes cross - pollination in flowers. Self - pollination cannot lead to the formation of seeds in a self - incompatible species. This happens because the pollens are unable to fertilize the ovule that would develop into an embryo and hence from seeds.

Question 10. 
What is bagging technique? How it is helpful in a plant breeding programme?
Answer:
Bagging technique is the covering of female plant with polythene or butter paper to avoid their contamination from foreign pollen grains during breeding programme. The bagging technique is helpful in the plant breeding programme. In this, only desired pollen grains are made to fertilize the stigma in order to produce plants with desired characters.    .

Question 11. 
What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion?    
Answer:
Triple fusion is fusion of one male gamete and two polar nuclei (or secondary nucleus; if the two have already fused) in the central cell of embryo sac to form primary endosperm nucleus. Triple fusion takes place in the central cell of an embryo sac. Three nuclei are involved in triple fusion, i.e., one male nucleus and two polar nuclei in the central cell.

Question 12. 
What do you think the zygote is dormant for sometime in a fertilized ovule?
Answer:
The zygote remains inactive until the endosperm is formed as a result of triple fusion. The endosperm provides nutrition to the developing embryo and is formed from the primary endosperm cell that results from triple fusion.

Question 13. 
Differentiate between:
(a) Hypocotyl and epicotyl,
(b) Coleoptile and Coleorrhiza,
(c) Integument and Testa, 
(d) Perisperm and Pericarp.
Answer:
(a) Difference between hypocotyl and epicotyl:

(b) Difference between Coleoptyle and Coleorrhiza.

(c) Difference between Integument and Testa:

(d) Difference between Perisperm and Pericarp

Question 14. 
Why is apple called a false fruit? Which part(s) of the flower forms the fruit?
Answer:
The fruit which is derived from ovary is known as true fruit. A false fruit is the one that is derived from secondary parts and not from ovary. Apple is derived from the thalamus and hence called false fruit.

Question 15. 
What is meant by emasculation? When and why does a plant breeder employ this technique? 
Answer:
Emasculation is a practice of removal of stamens / anthers before the anther dehisces from bisexual flowers. A plant breeder employs this technique in the bud condition before the anthers begin to differentiate. It is required to prevent self - pollination.

Question 16. 
If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?
Answer:
Parthenocarpy refers to the development of fruits without fertilization. The varieties of fruits such as watermelon, muskmelon, guava devoid of seeds are in great demand. Therefore, these varieties will be developed by parthenocarpy.

Question 17. 
Explain the role of tapetum in the formation of pollen - grain wall.
Answer:
Tapetum is the internal layer of microsporangium and plays an important role in the formation of pollengrain wall. It provides nutrition to the maturing pollen grains. Various amino acids, enzymes and hormones are produced by tapetum cells that are essential for the maturation of pollen grains. Tapetum also forms the exine layer of pollen grains.

Question 18. 
What is apomixis and what is its importance? 
Answer:
Apomixis: It is the process of seed formation without the occurrence of fertilization. It plays a vital role in the production of hybrid seeds. Apomixis inhibits the loss of desired characters in a hybrid. Also the process of production of hybrid seeds through cultivation is an expensive process. Therefore, apomixies is used for the production of hybrid seeds.