in which polination and variation are produced
Answers
Answer:
Pollination is the transfer of pollen grains from the anther of one flower to the stigma of the same or another flower. It is said to be the first process of sexual fertilization in flowering plants. Pollen grains contain the male gamete and are present in the anthers of the flower.
Explanation:
Types of Pollination
Pollination can be of two types:
Self- Pollination
When the pollen is transferred from the anthers of a flower to the stigma of the same flower, it is called as self- pollination. This form of pollination is common in hermaphrodite or dioecious plants which contain both male and female sexual parts on the same flower.
In self-pollinating plants, there is less dependence on the external factors to cause pollination. These plants depend on wind or other smaller insects that visit the flower regularly. In self- pollinating flowers, the anthers, and stigma are of similar lengths to facilitate the transfer of pollen. 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.
Cross-Pollination
In this type of pollination, the pollen is transferred from the anthers of one flower to the stigma of another flower. In this case, the two flowers are genetically different from each other. Cross-pollination is always dependant on another agent to cause the transfer of pollen. The agents of pollination include birds, animals, water, wind, and insects. Based on the agent of pollination, cross-pollination can be of different types:
Hydrophilous Flowers-These flowers are pollinated by water means. The flowers are often very small and inconspicuous to other agents. They do not have any fragrance or too much color on their petals. The pollen is adapted to be able to float in water.
Pollination
Zoophilous flowers– In this type of pollination, the pollinating agents are animals like human beings, bats, birds etc. The zoophilous flowers 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– These flowers are pollinated by the agency of wind. These flowers, like zoophilous flowers, are small and inconspicuous. Another important feature of flowers that are wind pollinated is that they are very light so that they are easily carried by the wind. The pollen grains are very light, non-sticky and sometimes winged.
Entomophilic flowers– These flowers are pollinated by insects. These flowers are often attractive to look at with bright petals and are fragrant to attract the insect visitors to them. They often have broad stigmas or anthers to allow the insect to perch on it. Many of the insect-pollinated flowers also secrete nectar which attracts bees, butterflies or other similar insects to the flowers. The pollen grains in these flowers are often spiny or have extensions that help them to stick on to the body of the insects.
Ornithophilous flowers– These flowers are pollinated by birds. Very few flowers and birds show this form of pollination.
Explanation:
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