NEET-XII-Biology
02: Sexual Reproduction in Flowering Plants
- #1Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
Ans : The male gametophyte or the pollen grain develops inside the pollen chamber of the anther, whereas the female gametophyte (also known as the embryo sac) develops inside the nucellus of the ovule from the functional megaspore.
- #2With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
Ans : An ovule is a female megasporangium where the formation of megaspores takes place.
The various parts of an ovule are -
(1) Funiculus - It is a stalk-like structure which represents 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) Chalazal - It is the based swollen part of the nucellus from where the integuments originate.
- #3What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
Ans : Self-incompatibility is a genetic mechanism in angiosperms that prevents self-pollination. It develops genetic incompatibility between individuals of the same species or between individuals of different species.
The plants which exhibit this phenomenon have the ability to prevent germination of pollen grains and thus, prevent the growth of the pollen tube on the stigma of the flower. This prevents the fusion of the gametes along with the development of the embryo. As a result, no seed formation takes place.