Self Pollination vs Cross Pollination
Pollination is the transfer of pollen grains to the stigma of a flower or two flowers belonging to the same species. There are two types of pollination; they are cross pollination and self pollination.
It is the deposition of pollen of a flower on the stigma of the same flower. Most annual plants show self pollination.
It is the deposition of the pollen of a flower on the stigma of a different flower of the same plant or a different plant of the same species. Most plants are adapted for cross pollination.
Colour, smell is normally produced in cross pollinated flowers. These adaptations are mainly to attract insects. Some plants show special types of adaptations for cross pollination. One adaptation is the unisexuality, which is the presence of different male and female plants. Dichogamy is another adaptation. That is, maturity of the gynoecium, and the androecium of the same flower takes place at 2 different times. Stamens or gynoecium may mature first.
Dimorphism is another adaptation. That is some flowers possess short styles and the stamens at the mouth of the corolla tube. Other flowers have long styles and the anthers are attached to the corolla tube below the mouth. Insects with long mouth parts pollinate flowers with short styles taken from pollen from the anthers attached to the corolla tube below the mouth. Insects with short mouth parts pollinate flowers with long styles taken from pollen from the anthers at the mouth of the corolla tube.
Another adaptation is the herkogamy. This can be of different ways. When the stamens are erect, the style bends away from the stamens and, when the style is erect, the stamens bend away. Sometimes the anthers are above the stigma. The stigma is like a drumstick, and its respective surface is the lower surface. Pollen falling on the upper surface will not grow. In some plants, anthers are always below the stigma. In some plants, the pollens are sterile if they fall on the stigma of the same flower.
Wind pollinated flowers also show some adaptations to enhance cross pollination. The flowers are small, not coloured, not scented and no nectar. Stigma is large and feathery. It is normally elevated above other parts. Pollen grains are small, light and produced in large numbers. They are dry with smooth extine. The flowers are simple. They are born on long stalks so that they are elevated above the other parts of the plant. The anthers are versatile.
Insect pollinated flowers also show some adaptations to enhance cross pollination. They are large, brightly coloured, scented flowers with nectar. Stigma is small and sticky. The anthers need not be versatile. Pollen grains are large and heavy with a rough extine. The flowers show a complex structure. Cross pollination results in cross fertilization. Cross fertilization allows gene flow within a species to produce new genetic combinations.
What is the difference between Self Pollination and Cross Pollination?
• Self pollination is the deposition of pollen of a flower on the stigma of the same flower whereas cross pollination is the deposition of the pollen of a flower on the stigma of a different flower of the same plant or a different plant of the same species.