Define geitonogamy and xenogamy. Give advantages of self-pollination and cross-pollination. Explain how dichogamy favours cross pollination?

Geitonogamy: The transfer of pollen grains from the anther of a flower to the stigma of another flower borne by the same plant.

Xenogamy: Transfer of pollen grains from the anther of a flower to the stigma of another flower borne on a different plant but belonging to the same species.

Advantages of self-pollination:

a) This is a sure method of pollination

b) No dependence on external agents.

c) More economical and do not have to develop large, attractive flowers, nectar and honey.

d) Least wastage of pollen.

e) Genetic stability is maintained.

f) Pure line plants can be preserved.

g) Improved varieties of plants can be multiplied by preserving their characters.

Advantages of cross-pollination:

a) Offsprings are strong, disease resistant, better adapted.

b) Variations possible through recombination.

c) Improved varieties of plants developed by hybridization.

d) Desirable characters can be introduced and undesirable characters may be eliminated.

e) Plants produced by cross-pollination show more vigour and vitality. Maturation of anther and stigma at different times is called dichogamy. It favors cross-pollination as it stands as a barrier to self-pollination.