Question

What is autogamy and allogamy?

Answer 1

Hint: Pollination is a process similar to that of reproduction as both occur to form new progenies. Pollination is the process of transfer of pollen grains from anther to the stigma of the flower. It occurs in various ways in various flowers.

Complete answer:
We have already discussed pollination. Now pollination as a process occurs in two different ways in different flowers and those different processes are known as autogamy and allogamy. Now let us discuss further to get into more details –
Autogamy- this is also known as self-pollination as the transfer of pollen grains takes place from the anther to the stigma of the same flower. Now it can occur in three circumstances-
Chasmogamy: in this pollination occurs when the flower opens and exposes the reproductive organs e.g.- Mirabilis
Cleistogamy: in this the flowers do not open so that only self-pollination can occur for e.g. in Commelina benghalensis.
Bud pollination: in some plants, self-pollination occurs in the bud condition before the flowers open for e.g. wheat, rice etc.
Allogamy- this is also known as cross-pollination as the transfer of pollen grains takes place from anther to the stigma of another flower of another plant. There are various arrangements that favor this process-
Unisexuality: in unisexual flowers only allogamy is favored.
Self-sterility: the pollen of the flower does not have any effect on the stigma of the same flower.
Dichogamy: male and female organs mature at different times.
Heterostyly: in some plants flowers are of two to three forms with anthers and stigma at different levels.
Herkogamy- male and female flowers are placed such that they are not able to reach the stigma of the same flower.

Note:
In a situation when the pollen grain is transferred from anther of a flower to the stigma of another flower of the same plant then this process is known as geitonogamy, it comes across as a special case in autogamy. Xenogamy is another name for allogamy.