Bihar Board - Class 12 Biology - Chapter 2: Sexual Reproduction in Flowering Plants Short Answer Question

Class 12th Bihar Board chapter Sexual Reproduction in Flowering Plants explain the process of gamete formation, pollination, and fertilization in angiosperms. Vidyakul offers detailed notes and short-questions-answers to simplify concepts and assist in exam preparation.

Short Answer type

Q.1. What are the component cells of the egg apparatus in an embryo sac?

Ans.  An egg apparatus consists of:

1. One egg cell

2. Two synergids

Q.2. What is common in the function performed by nucellus and cotyledon?

A.2. The cotyledons and nucellus both store reserve food material and do the work of providing nourishment- nucellus (embryo sac), cotyledons (embryo).

Q.3. Which regions of pistil form fruits and seeds?

A.3. The ovary develops into a fruit. The ovule develops into the seed.

Q.4. During polyembryony, if one embryo is formed from synergids and the other from nucellus, state the one that is haploid and the one that is diploid.

A.4. Embryo developed from the synergid- haploid Embryo developed from the nucellus- diploid.

Q.5. Is it possible that an unfertilized apomictic embryo sac gives rise to a diploid embryo? Give a reason in support of your answer.

A.5. Yes, an unfertilized apomictic embryo sac can give rise to a diploid embryo. If the megaspore develops into an embryo sac without mitotic division, it will give rise to a diploid embryo.

Q.6. When a pollen grain is shed at the 3-celled stage, which three cells are found?

A.6. The following three cells are found at the three-celled stage:

1. One vegetative cell

2. Two male gametes

Q.7. Define self-incompatibility. How do self-incompatible plants pollinate?

A.7. Self-incompatibility is a genetic mechanism in which the growth of the pollen tube in the pistil is inhibited which prevents self pollen from fertilizing the ovules. The self-incompatible plants pollinate by cross-pollination.

Q.8. Which is a triploid tissue? How is the condition achieved in a fertilized ovule?

A.8. The endosperm is a triploid tissue in a fertilized ovule. Triple fusion, leading to the fusion of one male gamete and two haploid polar nuclei form the triploid tissue.

Q.9. Does apomixis require fertilization and pollination? Give reasons in support of your answer.

A.9. No, apomixis does not require pollination and fertilization. This is because apomixis is a form of asexual reproduction in which the female reproductive apparatus is used. The embryos can develop directly from the nucellus or synergids.

Q.10. How do aquatic plants undergo pollination?

A.10. A few aquatic plants have their flowers growing in the air. They are pollinated by insects. Other plants that have their flowers submerged in water release their pollen in the water that drifts in the water and are caught by the feathery stigma of female flowers.

Q.11. Each pollen grain in the flowering plants produces male gametes. State the function of the male gametes.

A.11. One male gamete fuses with the nucleus of the egg cell, while the other male gamete moves towards the two polar nuclei present in the central cell and fuses with it to form a triploid primary endosperm nucleus.

Q. 12. What is polyembryony? 

A.12. When more than one embryo occurs in a seed, it is referred to as polyembryony. This can be seen in a few citrus fruits and mango varieties. Polyembryony plays a significant part in plant breeding and horticulture. These embryos give rise to virus-free plantlets and are healthy. Hybrid varieties of such plants and vegetables are being grown extensively. These varieties thus obtained are highly productive.

Q.13. Apomixis and parthenocarpy explain the benefits of each.

A.13. parthenocarpy is different from apomixis. In parthenocarpy, the fruit is produced without the fertilization of the female gamete. It is used for the production of fruits without seeds such as bananas and grapes for commercial purposes. Apomixis is the process in which the seeds are produced without fertilization but the process occurs in the female reproductive tract of the plant. In this, the megaspore mother cell does not undergo meiosis. It is used for the commercial production of hybrid varieties and in the production of virus-free varieties.

Q.14. Why is it that the generative cell of 2-celled pollen divides in a pollen tube and not of 3-celled pollen?

A. The generative cell divides to form two male gametes. In three-celled pollen, the generative cell divides into two gametes, therefore, no further division takes place in the pollen tube. However, in two-celled pollen, the generative cell moves down the pollen tube and divides to form two male gametes.

Q.15. The zygote divides only after the division of the primary endosperm cell. Give reasons in support of the statement.

A. Zygote requires nourishment for its growth and division. This nourishment is provided by the primary endosperm cell. That is why the zygote divides only after the growth, food storage and division of the primary endosperm cell.

Q.16. State the role of endothecium.

A. The endothecium protects the microsporangium and helps in the dehiscence of anther for the release of pollen grains.

Q.17. Define Morphogenesis.

A.Morphogenesis is defined as a biological process which controls the growth, development in size, shape and structure and distribution of cells during the embryonic development of an organism.

Q.18. What are the main layers of a flower?

A. There are different types of flowers in a plant kingdom. A few among them vary in color, structure, shape, etc. However, all flowers have unique layers. The four main layers of a flower:

1.  Calyx 

2. Corolla

3. Androecium

4. Gynoecium

Q.22.Define double fertilization.

A.In plants, double fertilization refers to the fusion of one female gametophyte with two male gametophytes. It is a complex process in all flowering plants.

Q.23. What is cross-pollination?

A.Cross-Pollination is the complex type of pollination during which the pollen grains are transferred from the anther of one flower into the stigma of another flower. This type of pollination makes use of both biotic and abiotic agents like wind, water, insects, birds, animals, and other agents as pollinators.

Q.24 What are the male and female reproductive parts of a flower?

A.A flower plays a vital role in the reproduction process of a plant. Therefore, it is called the reproductive organ of plants.  The male reproductive parts of the flower include the stamen, the filament and the anther, which are collectively termed the androecium. The female reproductive parts of the flower include carpels, pistils, stigma, style and an ovary, which are collectively termed the gynoecium.

Q. 25. What are the stages of post-fertilization in plants?

A.In all flowering plants, the post-fertilization is a critical stage which occurs after the double fertilization and includes the series of steps:

1. Endosperm development.

2. Embryo improvement.

3. Development of ovule into a seed.

4. Development of ovary into a fruit.