Pollination is the process of transfer of pollen the male gametes from anther to stigma a female part in the flower of plants.
This is a part of sexual reproduction in plants. There are different methods of pollination in plants.
But this process is facilitated through different agents of pollination.
The pollination agents in general include wind, water, insects, birds, cattle and even humans (manual or assisted pollination in farms)
The flowers of a plant in general have a single female organ consisting of stigma, ovary and ovule.
While the male part has one or more of stamens which bear the male gametes namely pollen’s in the anthers.
Plants have two types of flowers in this regard. Those having both male and female gametes in same flower. Those plants having either only male or female flowers. These flowers have only one type of organs either male or female.
Types of pollination.
- Self pollination. (Autogamy)
- Cross pollination.
Self pollination: Here transfer of pollen occur within the same flower. Hence the name autogamy (Auto= self, gamy= pollination). The pollen grains from male anthers settle on the stigma of the same flower. This type of pollination requires closed flowers and also the the anthers and stigma should lie close to each other in the flower.
Cross pollination: Here transfer of pollen occur in between flowers. Pollen from one flower fall on the stigma of other flower.
Based the flower in the same and different plants, this is of two types.
a. Geitonogamy: Here the pollination occurs in between two flowers of same plant. That is pollen from one flower reaches stigma of another flower on the same plant.
b. Xenogamy: Here the pollination occurs in between flowers of two plants. That is the pollen from one flower reaches stigma of a flower on another plant.
Agents involved in cross pollination: based on the agents involved in cross pollination, we have following two types as
I) Abiotic: Without involvement of animals the transfer occurs.
II) Biotic: Due to animals involvement pollen transfer occurs.
Abiotic Pollination involves transfer of pollen by air and water.
- Anemophily:The agents aiding pollination here is the wind. Pollen grain released into air are carried over to distant plant flowers. Hence we can notice allergy of respiratory system during cropping season if one stays close to farms. Ex: Pinus plant
- Hydrophily: Here pollen grains are transferred by flowing water currents as seen in rivers. The pollen in some species travel on water surface while in other submerged in water i.e. below water surface. Ex:Hydrilla, vallisneria.
Biotic Pollination: This is the most common and also efficient methods of pollination.
Many animals are involved in pollen transfer
- Zoophily: Here the pollen grains are transferred from one plant to another by the help of vertebrate animals, bats, birds etc.This occurs due to dependence of animals on plants for food. The transfer happens mostly by limbs and other body parts which come in contact with flowers.
- Ornithophily: Here pollen grains are shifted from one flower to another due to birds. These plant secrete nectar to attract birds.
- Entomophily: Here the pollen transfer happens due to insects. Honey bees, beetles are common pollinators.
Even in agriculture, manual cross pollination is done by farmers to enhance yield.