Question

Discuss about self-pollination and cross-pollination?

Answer 1

Pollination is the process of transfer of pollen grains from the male anther of a flower to the female stigma. The objective of any living organism is to produce offspring for the next generation.

Complete answer: Pollination is the transfer from the anther, which is the male part of the flower, of pollen grains to the stigma that is on the female part. Normally, this step precedes fertilisation. It is an important mechanism in the reproduction of plants, without which there would be no sexual reproduction. Two forms of pollination occur, namely, cross-pollination and self-pollination.
Pollen grains are moved from anther to sigma of another plant during cross-pollination. Cross-pollination contributes to the development of offspring with heterosis or hybrid vigour when accompanied by fertilisation. Nature has invented a way of ensuring the effectiveness of cross-pollination and avoiding self-pollination. Some are dioecious plants. In dioecious plants, female flowers are produced by male plants and female flowers are produced by women. This varies from monoecious plants, where both male (staminate) and female (pistillate) or bisexual flowers are produced by plants. Evidently, since one plant produces either male or female flowers, self-pollination does not take place in dioecious plants. Mechanisms such as dichogamy, heterostyly, and self-incompatibility require the prevention of self-pollination in monoecious plants.
On the other hand, self-pollination is the transition from an anther to a stigma of the same flower or plant of the pollen grains. This also results in inbreeding depression, where the offspring exhibits undesirable recessive characteristics. In species where pollination agents are rare and in closed flowers where the pollination agents have restricted access to the flower 's sexual structures, self-pollination occurs. In species with cleistogamous flowers, and in plants where pollinators are rare, self-pollination occurs. In cleistogamous flowers, the petals that form a keel enclose the sexual structures (androecium and gynoecium). The stamens and pistils inside the keel cannot be accessed by pollination agents. Self-pollination also happens in plants that are monoecious.

Note: Pollination is typically the unintended effect of the action of an animal on a flower. Because of its protein and other nutritional characteristics, the pollinator also consumes or absorbs pollen, and pollen grains bind to the body of the animal and fall off the stigma of the flower and can contribute to good flower reproduction.