Chapter 2: Sexual Reproduction in Flowering Plants Class 12 Biology NCERT Solutions

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

Question 1. Name the parts of an angiosperm flower in which development of male and female gametophyte takes place.

Male gametophyte develops inside the pollen grain, which is formed within the microsporangium of the anther.
Female gametophyte develops within the embryo sac, which forms inside the ovule located in the ovary.

Question 2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events?

Characteristic	Microsporogenesis	Megasporogenesis
Occurs in	Anthers (microsporangia)	Ovules (megasporangia)
Gives rise to	Microspores (pollen grains)	Megaspores (usually one survives)
Initial cell involved	Microspore mother cell (MMC)	Megaspore mother cell (MMC)
Type of division	Meiosis	Meiosis

Note: Both processes involve meiotic division, resulting in haploid spores.

Question 3. Arrange the following terms in the correct developmental sequence:

Terms: Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes

Correct sequence: Sporogenous tissue → Pollen mother cell → Microspore tetrad → Pollen grain → Male gametes

Question 4. With a neat, labelled diagram, describe the parts of a mature angiosperm embryo sac.

The embryo sac (female gametophyte) is a 7-celled, 8-nucleate structure. Key components are:

• Three antipodal cells at the chalazal end
• Two synergids and one egg cell at the micropylar end (forming the egg apparatus)
• One central cell with two polar nuclei in the center

(Insert labelled diagram of embryo sac here)

Question 5. What are the possible types of pollinations in a chasmogamous flower? Give examples.

A chasmogamous flower is open at maturity, allowing:

• Autogamy: Self-pollination within the same flower (e.g., Sunflower)
• Geitonogamy: Pollination between different flowers on the same plant (e.g., Maize)
• Xenogamy: Cross-pollination between flowers of different plants (e.g., Apple, Papaya)

Question 6. Cleistogamous flowers are invariably autogamous. But why do they not need pollinators?

Cleistogamous flowers remain closed throughout their life cycle, so self-pollination happens internally without any external agent. Hence, they do not require pollinators, ensuring guaranteed seed formation even in the absence of pollinators.

Question 7. Mention two strategies evolved to prevent self-pollination in flowers.

• Dichogamy: Anthers and stigma mature at different times (e.g., Sunflower)
• Herkogamy: Physical separation of anthers and stigma within the same flower (e.g., Gloriosa)

Question 8. What is self-incompatibility? Why does it develop?

Self-incompatibility is a genetic mechanism in some flowering plants that prevents self-fertilization despite viable pollen and ovules. It ensures cross-pollination and promotes genetic diversity. This is governed by specific S-genes that inhibit pollen germination or pollen tube growth on the same plant.

Question 9. What is bagging technique? How is it useful in a plant breeding programme?

Bagging is the process of covering emasculated flowers (removal of anthers) with a bag or cover to prevent unwanted pollination.
Use: It allows controlled pollination with desired pollen in artificial hybridization programmes, preventing contamination by foreign pollen.

Question 10. What is triple fusion? Where and how does it take place? Name the nuclei involved.

Triple fusion is a fertilization event where one male gamete fuses with two polar nuclei in the central cell of the embryo sac, forming the triploid (3n) primary endosperm nucleus.
Nuclei involved: One male gamete (n) + Two polar nuclei (n + n)

Question 11. Why do you think the zygote is dormant for some time in a fertilized ovule?

The zygote remains dormant temporarily to allow:

• Endosperm formation first, which provides nutrition
• Proper preparation of ovule tissues to support embryo growth

Question 12. Differentiate between:

(a) Hypocotyl and Epicotyl

Feature	Hypocotyl	Epicotyl
Position	Between radicle and cotyledons	Between cotyledons and plumule
Develops into	Root system	Shoot system

(b) Coleoptile and Coleorhiza

Feature	Coleoptile	Coleorhiza
Function	Covers and protects the shoot tip	Covers and protects the root tip
Found in	Monocot embryos	Monocot embryos

(c) Integument and Testa

Feature	Integument	Testa
Definition	Protective layer of ovule	Outer hard seed coat
Origin	Part of ovule before fertilization	Derived from integuments post-fertilization

(d) Perisperm and Pericarp

Feature	Perisperm	Pericarp
Definition	Remnant of nucellus in seed	Wall of fruit developed from ovary
Function	May or may not store food	Protects the seed and aids dispersal

Question 13. Why is apple called a false fruit? Which part of the flower forms the fruit?

Apple is called a false fruit because its edible part develops from the thalamus rather than the ovary. In apples, the ovary remains small while the thalamus becomes fleshy and forms the main fruit body.

Question 14. What is meant by emasculation? When and why is it done?

Emasculation is the removal of anthers from a bisexual flower before the release of pollen.
It is done to prevent self-pollination and is essential in artificial hybridization to ensure that only desired pollen fertilizes the flower.

Question 15. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?

Fruits selected: Banana, grapes, oranges.
Reason: These fruits are commercially important, and seedless varieties are preferred by consumers. Parthenocarpy helps in developing seedless fruits by using growth hormones like auxins.

Question 16. Explain the role of tapetum in the formation of pollen grain wall.

The tapetum is the innermost nutritive layer in the anther and plays a crucial role in:

• Providing nutrients and enzymes for microspore development
• Producing sporopollenin precursors for forming the exine (outer wall) of pollen grains
• Secreting proteins essential for pollen viability and recognition during fertilization