Kinds of Pollination - Self Pollination (Autogamy)

Self-pollination or Autogamy:

• Greek Auto = self, gamos = marriage
• According to a majority of Botanists, the transfer of pollen on the stigma of the same flower is called self-pollination or Autogamy.
• Self-pollination is possible only in those plants which bear bisexual flowers. In order to promote self-pollination, the flowers of the plants have several adaptations or mechanisms. They are:

1. Cleistogamy: In cleistogamy (Greek Kleisto = closed. Gamos = marriage) flowers never open and expose the reproductive organs and thus the pollination is carried out within the closed flower. Commelina, Viola, and Oxalis are some examples of cleistogamous flowers. In Commelina benghalensis, two types of flowers are produced chasmogamous and Cleistogamous flowers.
   (i) Chasmogamous flowers: Chasmogamous flowers are aerial flowers, brightly coloured, chasmogamous and insect-pollinated. Chasmogamous flowers are similar to flowers of other species with exposed anthers and stigma.
   (ii) Cleistogamous flowers: Cleistogamous flowers are underground flowers borne on the subterranean branches of the rhizome that are dull. In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to effect pollination. Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma. Cleistogamous flowers produce assured seed-set even in the absence of pollinators.
   

   Commelina with Cleistogamous and Chasmogamous flowers

2. Homogamy: When the stamens and stigma of a flower mature at the same time it is said to be homogamy. It favours self-pollination to occur. Example: Mirabilis jalapa, Catharanthus roseus
   
   
3. Incomplete dichogamy: In dichogamous flowers the stamen and stigma of a flower mature at different times. Sometimes, the time of maturation of these essential organs overlaps so that it becomes favourable for self-pollination.

Advantages of Self-pollination:  

1. The purity of the race is maintained.
2. Plants don't need to produce a large number of pollen grains.
3. Ensures seed production.
4. Eliminates bad recessive characters.  

Disadvantages of Self-pollination:  

1. Variable and hence adaptability to changed environment reduced.
2. Vitality decreases and ultimately leads to degeneration.