Question 1.
Name the parts of an angiosperm flower in which the development of male and female gametophyte take place.
Answer:
The male gametophyte or pollen grain develops inside the pollen chamber of the anther, whereas the female gametophyte (embryo sac) develops inside the nucellus of the ovule from the functional megaspore.
Question 2.
Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events.
Answer:
| Microsporogenesis | Megasporogenesis | |
|---|---|---|
| 1 | Formation of microspore tetrads from microspore mother cell by meiosis. | Formation of four megaspores from megaspore mother cell by meiosis. |
| 2 | Occurs inside pollen sac of anther. | Occurs inside ovule. |
(c) Microsporogenesis forms haploid microspores, whereas megasporogenesis forms haploid megaspores.
Question 3.
Arrange the following terms in correct developmental sequence.
Answer:
Sporogenous tissue → Pollen mother cell → Microspore tetrad → Pollen grain → Male gametes
Question 4.
With a neat labelled diagram, describe the parts of a typical angiosperm ovule.
Answer:
An ovule is the female megasporangium where megaspores are formed.
- Funiculus: Stalk attaching ovule to placenta.
- Hilum: Point of attachment of ovule to funiculus.
- Integuments: Protective outer layers.
- Micropyle: Opening for pollen tube entry.
- Nucellus: Nutritive tissue containing embryo sac.
- Chalaza: Basal swollen part of nucellus.
Question 5.
What is meant by monosporic development of female gametophyte?
Answer:
Development of embryo sac from a single functional megaspore is called monosporic development.
Question 6.
Explain the 7-celled, 8-nucleate nature of female gametophyte.
Answer:
The embryo sac develops from a single functional megaspore by three mitotic divisions producing 8 nuclei. These organise into 7 cells – egg apparatus (3), antipodals (3) and one central cell with two polar nuclei.
Question 7.
What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers?
Answer:
Chasmogamous flowers have exposed anthers and stigma.
Cross-pollination does not occur in cleistogamous flowers because they never open and only self-pollination is possible.
Question 8.
Mention two strategies to prevent self-pollination.
Answer:
- Self-incompatibility: Genetic mechanism preventing pollen germination.
- Protandry / Protogyny: Different maturation time of androecium and gynoecium.
Question 9.
What is self-incompatibility?
Answer:
It is a genetic mechanism that prevents self-pollination by inhibiting pollen germination and pollen tube growth, hence preventing seed formation.
Question 10.
What is bagging technique? How is it useful?
Answer:
Bagging is the covering of emasculated flowers to prevent unwanted pollination. It ensures controlled fertilisation in plant breeding programmes.
Question 11.
What is triple fusion?
Answer:
Fusion of one male gamete with two polar nuclei inside embryo sac forming triploid endosperm nucleus is called triple fusion.
Question 12.
Why does the zygote remain dormant?
Answer:
Zygote remains dormant until endosperm formation which provides nourishment for embryo development.
Question 13.
Differentiate between hypocotyl & epicotyl, coleoptile & coleorrhiza, integument & testa, perisperm & pericarp.
Answer:
Question 14.
Why is apple a false fruit?
Answer:
Apple develops from ovary along with thalamus. Since edible part is derived from floral parts other than ovary, it is a false fruit.
Question 15.
What is meant by emasculation? When and why does a plant breeder employ this technique?
Answer:
Emasculation is the process of removing anthers from bisexual flowers ! without affecting the female reproductive part (pistil), which is used in various plant hybridisation techniques.
Emasculation is performed by plant breeders in bisexual flowers to obtain the desired variety of a plant by crossing a particular plant with the desired pollen grain. To remove the anthers, the flowers are f covered with a bag before they open. This ensures that the flower is pollinated by pollen grains obtained from desirable varieties only. Later, the mature, viable, and stored pollen grains are dusted on the bagged stigma by breeders to allow artificial pollination to take place and obtain the desired plant variety.
