What is Self-pollination? – Definition
Self pollination is the phenomenon in which pollen grains are transferred from anthers to stigma of the same flower or another flower of same plant (geitonogamy).
The another terms used for self-pollination are autogamy or self pollenizing.The basic requirement for this type of pollination is a flower should has both stamen and stigma, and should be able to contact each other for actual self-pollination. There are various mechanisms to promote self pollination. Generally these mechanisms are more efficient than those, which promote cross pollination.
Mechanisms facilitating self pollination
- Hidden Stamen and Stigma
- Anther position
In this case flowers never open. This prevents foreign pollens to reach the stigma of flower with cleistogamy mechanism. Hence, facilitates self-pollination.
Examples – Some varieties of wheat, barley and oat, some grasses etc. have cleistogamy.
In Chasmogamy, flowers remain close still self-pollination occurs, once it over, they open. No doubt, this opening could allow some cross-pollination too.
Examples – rice, wheat, barley, oat etc.
Hidden Stamen and Stigma
In this mechanism, some kind of the floral organs ( as keel in case of legumes) do the job to hide or cover the reproductive organs (stamens and stigmas), to avoid cross-pollination.
Examples – legumes like pea, gram, black gram, soybean etc.
Here, stigmas remain densely and closely surrounded by anthers. This much close position of anthers promotes self pollination, though cross pollination may occur too as flowers are open.
Examples – tomato, brinjal etc.
In this kind of mechanism, anthers and stigma of a flower mature at the same time. It is very important for occurrence of self pollination.
In some species, stigmas become receptive and elongate through staminal columns.
It means presence of male and female reproductive organs in the same flower. A hermaphrodite flower is a characteristic feature of self pollinated plants.
Genetic consequences of Self Pollination
Self pollination causes rapid increase in homozygosity, there is no incorporation of variation. Inbreeding depression is not observed in case of self pollinated species, but they may exhibit considerable heterosis.
Examples of Self Pollinated Crops
|Legumes||Pea, gram, groundnut, cowpea, soybean, black gram, green gram, lentil, khesari, rajma, sunhemp, guar|
|Cereals and millets||Wheat, rice, barley, oat, ragi|
|Vegetables||Potato, tomato, brinjal, chillies, okra, lettuce|
|Forage crops||Wheat grass, burr clover, subterranean clover, velvet bean|
|Fruit trees||Apricot, peach, citrus|
|Fiber crops||Jute (often cross pollinated)|