Long Answer TypeDevelopment of female gametophyte
1. The functional megaspore is the first cell of female gametophyte of angiosperms.
2. It enlarges to form the female gametophyte, also called embryo sac.
3. Its nucleus undergoes a mitotic division and the two nuclei move to the opposite poles, forming the 2-nucleate embryo sac.
4. Two successive mitotic divisions in each of these two nuclei result in the formation of an 8-nucleate embryo sac.
5. Cell wall formation starts at the eight-nucleate stage, resulting in the formation of a typical female gametophyte.
6. Three cells are grouped together at the micropylar end to form the egg apparatus, consisting of two synergids and a female gamete/egg cell.
7. Three cells are grouped together at the chalazal end; they are called antipodal cells.
8. The remaining two nuclei are called polar nuclei; they move to the centre of the embryo sac (now called central cell) and fuse to form a diploid secondary nucleus.
9. Thus, a typical angiosperm embryo sac is 8-nucleate and 7-celled.
Development of embryosac.
Short Answer TypeName the parts of an angiosperm flower in which development of male and female gametophyte take place.
Draw a sectional view of human ovary and label the different follicular stages, ovum and Corpus luteum.
Long Answer Type(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.Short Answer TypeMention the unique flowering phenomenon exhibited by Strobilanthus kunthiana (neelakuranaji).
Where is sporopollenin present in plants? State its significance with reference to its chemical nature.
Differentiate between albuminous and non-albuminous seeds, giving one example of each.
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