Question

Why is cross-pollination considered to be superior than self-pollination?

Answer 1

Hint:-Pollination is a process which involves the transfer of pollen from the anther (male reproductive organ) to the stigma (female reproductive organ) of the same flower or another flower. In nature, pollination is brought about by help of agents such as insects, animals, water and wind.

Complete step-by-step solution:-Pollination is categorized into two main types - self-pollination and cross pollination.
Self-pollination occurs when the pollen grains from the stamen of a flower are transferred to the stigma of the same or another flower on the same plant, e.g. Wheat, Peas, etc. However, when the pollen from the stamen of one flower is transferred to the stigma of another flower on a different plant of the same species, it is called cross-pollination, e.g. Papaya, Calotropis, etc.
Continued self-pollination often results in inbreeding depression in plants. There are several advantages which explain cross pollination is a better mechanism than self-pollination.
- Cross pollination promotes the production of healthier offspring.
- These offspring have great vigour.
- Seed production is abundant and they are more viable and possess high germinating capacity.
- Cross pollination allows the inclusion of variations and hence varieties are formed. It helps to maintain the crop yield.
- Cross pollination eliminates undesirable characters of the plant.
- Cross pollination allows combination of genetic information and this brings about diversity in the species.
- Cross pollination helps in evolution.
- Cross pollinated species are more adapted to survive in different climatic conditions.

Note:- Flowering plants have developed many devices to discourage self- pollination and to encourage cross-pollination. In Protandrous flowers, anthers and stigma mature at different times and the pollen is released before the stigma matures, e.g. Rose. In Herkogamy condition, the anther and stigma are placed at different heights due to which pollen does not fall on the stigma thus, preventing self-pollination, e.g. Hibiscus. In dioecious plants, male and female flowers are borne separately on different plants, e.g. Papaya.
Artificial pollination is also done by hand to produce offspring with desired traits, such as quality, colour or pest resistance.