What is Cross Pollination? – Definition
Pollination in which pollens are transferred from anthers of one flower to the stigma of flower from another plant with the help of some kind of agency like wind, insects, water.
Mechanisms promoting Cross Pollination
There are various mechanisms which facilitates cross pollination and resist self pollination. Those are as follows.
- Dicliny or Unisexuality
- Monoecy
- Dioecy
- Dichogamy
- Protogyny
- Protandary
- Herkogamy
- Heterostyly
- Combinations
- Self-incompatibility
- Male-sterility
Dicliny or Unisexuality
Flowers are either male (staminate) or female (pistillate). It can be of two types
- Monoecy
- Dioecy
Monoecy
Male and female flowers occur on the same plant, either in the same inflorescence (mango, banana,castor) or in separate one (maize).
Examples – strawberries, rubber, cucurbits, grapes etc.
Dioecy
The male and female flowers are present on different plants i.e. plants in such species are either male or female.
Examples – papaya, spinach, date, asparagus,
Dichogamy
Flowers have both stamens and pistils i.e. male and female reproductive organs but they attain maturity at different times. It can be of two types
- Protogyny
- Protandary
Protogyny
Pistils mature first, then stamens.
Example – bajara
Protandary
Stamens mature first, then pistils.
Example – maize, sugar beet
Self-incompatibility
Details are given on the page Self-incompatibility.
Male-sterility
Details are given on the page Male-sterility.
Herkogamy
It’s a physical barrier. In some crops like lucern and alfalfa stigmas are covered with a waxy film. For pollination to occur this film should be broken, this is achieved with the help of some agencies like insects.
Combination
Various combinations of above mechanisms facilitate cross pollination.
Genetic Consequences of Cross-pollination
Leads to heterozygosity, incorporates variation. Exhibit considerable heterosis and mild or some more inbreeding depression.