Pollination is the transfer of pollen from the male part of a plant(anther) to the female part of the plant(stigma) leading to fertilization and production of seeds.
Also referred to as male gametes, Pollen grains are microscopic single cell bodies which contain the male reproductive cell of a plant. This is the process of reproduction in plants.
Pollination occurs when these pollen grains move from the male part of the plant to the female part of the flower
After the pollen lands on the stigma a pollen tube is formed through the length of a style (a style connects the stigma to the ovary of the flower) where the male gametes pass through to the ovary. Where the male and female cells fertilize to form a seed. Later the seed is detached from the parent plant and it grows into a new plant and pollination goes on.
Types of pollination.
There are two types of pollination in plants; self and cross pollination.
Occurs when pollen is transferred from the anthers of a flower to the stigma of the same flower. This form of pollination is common in hermaphrodite or dioecious plants which contain both male and female sexual parts on the same flower.
Self – pollination can be further divided into two types:
- Autogamy– In this type of self-pollination, the pollen is transferred from the anthers of one flower to the stigma of the same flower.
- Geitonogamy– In this type of self- pollination, the anthers are transferred from the anthers of one flower to the stigma of another flower but on the same plant.
Advantages of self- pollination.
- Self- pollination ensures that recessive characters are eliminated.
- The wastage of the pollen grain is very less compared to cross-pollination
- No diversity in the genes
- In self- pollination, there is no involvement of external factors like wind, water, and other pollinating agents.
- Self-pollination ensures that even a smaller quantity of produced pollen grains from plants have a good success rate in pollination.
Disadvantages of self-Pollination
- The major disadvantage of Self- pollination is there is no mixing up of genes. Due to which:
- The vigour and vitality of the race are reduced
- The immunity to diseases is reduced in the resultant offspring’s.
- Cross pollination
Occurs when the pollen is transferred from the anthers of one flower to the stigma of another flower which are genetically different from each other. Cross-pollination depends on external agents like birds, animals, water, wind, and insects.to facilitate the transfer of pollen.
Types of cross -pollinations include;
- Hydrophilous Flowers-These flowers are pollinated by water means because they are often very small and inconspicuous to other agents. They do not have any scent or color on their petals. Their pollen is adapted to be able to float in water.
- Zoophilous flowers – In this case, the flowers depend on pollinating agents like human beings, bats, birds etc. because they have pollen that is designed to stick on to the body of the animal so that they can be easily carried from one flower to another.
- Anemophilous flowers– Pollination is facilitated by wind. Similar to Zoophilous flowers, these ones are also small and inconspicuous. Their pollen grains are very light, non-sticky and sometimes winged.
- Entomophilic flowers– These flowers are pollinated by insects, and they have bright petals and are fragrant to attract the insects. They often have broad stigmas or anthers to allow the insect to perch on it. Theses flowers also secrete nectar which attracts bees, butterflies or other similar insects to the flowers. The pollen grains in these flowers have extensions that help them to stick on to the body of the insects for pollination.
Advantages of cross- pollination
- The produced seeds are good in vigour and vitality.
- All unisexual plants can reproduce through the process of Cross-pollination.
- The recessive characters in the lineage are eliminated as a result of genetic recombination.
- This process improves the immunity of the offspring towards the diseases and other environmental factors.
- Cross-pollination introduces new genes into a sequence of species and this is mainly due to the fertilization between genetically different gametes.
Disadvantages of cross -pollination.
- In this process, there is a great wastage of pollen grains.
- Due to genetic recombination during meiosis, there are chances of eliminations of good qualities and additions of unwanted characteristics in offspring