Pollination – Biology Notes
Pollination – Biology general knowledge notes help you to prepare for any kind of government examinations such as Railway, Banking, IAS, UPSC, Defence, SSC, CGL, MTS, Police, Army, Group D, etc.
Before knowing pollination in biology one should know the structure of the flower. Therefore we need to know what is pollen and grains.
Pollen: In a flower of a plant the Anthers of stamens produce a powdery material called pollen.
Grains: The tiny particles of pollen are called grains.
Inside the pollen grains, a nucleus is present which is responsible for the reproduction of plants.
- Autogamy: Autogamy is a process of plant reproduction by which the pollen of the same flower may fall on its stigma by itself.
- Geitonogamy: In geitonogamy, the pollen of other flowers from the same tree falls on the stigma.
- Allogamy: In allogamy, the pollen of other trees may fall on the stigma. Obviously the pollen should be from the same kind of tree.
What is Pollination?
Pollination is a process by which the pollen grains transfer from anther to the stigma.
The pollen grains may receive by stigma through the blow of wind, insects or butterflies.
Types of Pollination
Mainly, there are two types of pollination occurs, one is Self-Pollination and another is Cross-Pollination. For this, the flowers must be mature at that time.
Self-Pollination occurs in bisexual and unisexual flowers where both male and female organs or flowers exist.
Advantages of self-pollination:
- In a bisexual flower, the stamens and carpels mature at the same time.
- Parental characters are preserved indefinitely.
- Very small or no wastage of pollen grains occurs.
- A small quantity of pollen is sufficient for fertilization.
- It is not necessary to be large and showy of the flowers.
- Also, it is not necessary to produce Scent and Nectar in flowers.
Disadvantages of Self-Pollination:
- Self-pollination may lead to a weakening of the variety of generations or the species.
- The seeds produced may be poor in quality.
- The defective characteristics may not be eliminated.
Cross-Pollination occurs for different plants where the pollen of one plant transfers to the stigma of another plant of the same kind.
Advantages of Cross-pollination:
- There are healthier offspring.
- Abundant and viable seeds produced.
- It yields new varieties.
Disadvantages of Cross-Pollination:
- The pollination may not always be certain as the pollination agent may not be available at the proper time.
- There is more wastage of pollen.
- Flowers must have to be large and showy to attract pollinating agents like bees, butterflies, etc. That’s why this is uneconomical for the plant.
Conditions of Cross-Pollination
Unisexuality: For a unisexual flower cross-pollination is the only possibility for fertilizing. Examples: Palms, papaya, cucumber, etc.
Dichogamy: If the time of maturation of androecium and gynoecium is different than it is called dichogamy. In this case, cross-pollination is the only possibility. Some examples are Sweet pea, salvia, sunflower, apple, peepal, etc.
Self-sterility: When stigma receives pollen from the anther but it fails to grow then from another plant pollen is received and complete the further process to make a seed.
Herkogamy: Here, the pollen is unable to reach the stigma of the same kind of flower and a hood act as a mechanical barrier. Example: Pansy flower.
Heterostyly: In a flower, the anthers and stigma do not grow the same height and unable self-pollination. Example: Pri rose.
Ther are mainly four agents for cross-pollination, Insect-pollinated, Wind-pollinated, water-pollinated, and artificial pollination.
For the occurrence of insect-pollination, the following characteristics are prime.
- The flower should be large enough.
- The flower should be colorful.
- There should exist a scent to attract insects.
- Must be produced nectar for insect’s food.
- The pollen grains and stigma should be sticky.
The main features of wind-pollination are-
- The size of the flowers is small.
- Flowers may not be bright.
- Flowers do not possess scent.
- The stamens are generally tall.
- The anthers are not tightly attached and are usually large.
- A large quantity of pollen is produced.
- Pollen grains are not too heavy and necessarily dry.
Water-pollination has the following features.
- Huge pollen grains are produced.
- Pollen grains must remain floating below the surface of the water.
- In the case of Vallisneria, the pollen grains float on the surface of the water.
Artificial pollination has the following characteristics.
- When the pollen transfer to stigma by an artificial process like by men, it is called artificial pollination.
- It is also called artificial crossing.
An example of sweet pollination is the sweet pea. Maize is an example of wind-pollination.
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