Self-pollination can be found in legumes such as orchids, sunflowers, peas, peanuts, oats, peaches, potatoes, wheat, and others.
Self-pollination occurs in several fundamentally different ways, which can be described as the "modes" of self-pollination.
Presence of male and female organs in the same flower is known as bisexuality. The presence of bisexual flowers is a must for self-pollination. All the self-pollinated plants have hermaphrodite flowers.
The pollination within the same flower is called autogamy. In general, unfavourable pollination conditions are likely to increase the amount of autogamy, both because self-pollen then competes less with cross-pollen.
In some plants, several flowers are connected to the same stem. In these flowers, pollen grains of the different flowers pollinate flowers in the same stem. This is called geitonogamy. The carpels and stamens are of the same length, grouped together in flowers, which use geitonogamy. The distinctive nature of geitonogamy has led to its being the only mode of chasmogamous selfing that was distinguished traditionally.
Some flowers are self-pollinated even before the opening. This is called cleistogamy. It occurs in closed flowers that are structurally specialized for self-fertilization and do not
outcross. Cleistogamy differs from all other modes of selfing in several respects. It is the only mode that occurs in morphologically distinct flowers.
It ensures self-pollination and prevents cross pollination. Cleistogamy has been reported in some varieties of wheat, barley, oats and several other grass species.
Opening of flowers only after the completion of pollination is known as chasmogamy. This also promotes self-pollination and is found in crops like wheat, barley, rice and oats.
The advantage of self-pollination is that plants are capable of reproducing while even there are no external pollinating agents to assist the pollination. It also helps to keep this trait stable in the species.
The disadvantage of self-pollination is that it reduces the genetic diversity of plants in the same species. Self-pollination
