Structure of mature female gametophyte
1. The female gametophyte is formed from the contents of megaspore. However, it always remains embedded within the membrane of the megaspore.
2. The mature female gametophyte is 7-celled (An egg, two synergids, three antipodals and a central cell).
3. Out of 7 cells of mature female gametophyte, the egg cell fuses with male gamete to form zygote, one synergid degenerates and the other synergid directs the pollen tube entry, the central cell fuses with the male gamete to form triploid primary endosperm nucleus and the three antipodals degenerate before or after fertilization.
4. They sometimes act as antipodal haustoria.
(a) hypocotyl and epicotyl
(b) Coleoptile and coleorhiza
(c) Integument and testa
(d) Perisperm and pericarp.
With a neat labelled diagram, describe the parts of a typical angiosperm ovule.
What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?
Name the parts of an angiosperm flower in which development of male and female gametophyte take place.
(a) Draw a diagrammatic sectional view of a mature anatropous ovule and label the following parts in it:
(i) that develops into seed coat.
(ii) that develops into an embryo after fertilization.
(iii) that develops into an endosperm in an albuminous seed.
(iv) through which the pollen tube grains entry into the embryo sac.
(v) that attaches the ovule to the placenta.
(b) Describe the characteristic features of wind pollinated flowers.(a) Explain the different ways apomictic seeds can develop. Give an example of each.
(b) Mention one advantage of apomictic seeds to farmers.
(c) Draw a labelled mature stage of a dicotyledonous embryo.(a) Explain the post-pollination events leading to seed production in angiosperms.
(b) List the different types of pollination depending upon the source of pollen grains.