Question

Name the different factors responsible for cross-pollination.

Answer 1

Cross-pollination:

1. Cross-pollination is a type of outbreeding in which the pollen grains are transferred from the anther to the stigma of a flower of a different plant.
2. It is a good process as compared to self-pollination.
3. There are specific mechanisms present in the plants due to which self-pollination is not favored. These are called outbreeding devices.
4. Outbreeding devices occur in certain plants to ensure cross-pollination. These devices ensure that cross-pollination takes place.

Different types of outbreeding devices:

1. Dicliny (Unisexuality): In unisexual flowers, self-pollination is impossible, so they invariably undergo cross-pollination.
2. Dichogamy: Anther and stigma mature at different times in certain plants. If anthers mature first and release the pollen grains, the stigma is not mature/receptive. This condition is called protandry. But, if the stigma matures first and the pollen grains are not released, then the stigma might receive pollen grains from some other flower; this condition is called protogyny.
3. Self sterility: In certain plants, the pollen cannot germinate on the stigma of the same flower; this is a genetic device called self-incompatibility.
4. Heterostyly: In some plants, there are two or three types of flowers with different lengths of styles and stamens. Pollination occurs between anthers and stigma of the same height.