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Pollination and Fertilization

Pollination is the transfer of pollen grains from the anther to the stigma, and there are three types: autogamy, geitnogamy, and allogamy. Self-pollination occurs within or between flowers on the same plant and has the advantages of preserving parental traits and not wasting pollen, but it can lead to inbreeding. Cross-pollination occurs between plants and has the advantages of producing healthier offspring and new varieties, but depends on pollinators and has more pollen waste. Conditions like unisexual flowers, dichogamy, self-sterility, herkogamy, and heterostyly favor cross-pollination over self-pollination

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60 views2 pages

Pollination and Fertilization

Pollination is the transfer of pollen grains from the anther to the stigma, and there are three types: autogamy, geitnogamy, and allogamy. Self-pollination occurs within or between flowers on the same plant and has the advantages of preserving parental traits and not wasting pollen, but it can lead to inbreeding. Cross-pollination occurs between plants and has the advantages of producing healthier offspring and new varieties, but depends on pollinators and has more pollen waste. Conditions like unisexual flowers, dichogamy, self-sterility, herkogamy, and heterostyly favor cross-pollination over self-pollination

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Pollination and fertilization:

 Pollination is the process of transfer of pollen grains from anther to the stigma of the flower.
 There are three types of pollination :
1. Autogamy
2. Geitnogamy
3. Allogamy
 Only the pollen of the same species will survive and grow further to continue the process of
reproduction.
 Self pollination is the process of transfer of pollen grains from anther to the stigma of the same
flower or to another flower of the same plant.
 Some bisexual flowers do not open even at maturity so their reproductive structures lie hidden
in the plant close to each other thereby facilitating self pollination.
 Self pollination can occur in bisexual flowers or in unisexual flowers when the male and the
female flower both lie on the same plant.
 To ensure self pollination the anther and the stigma must be mature at the same time.
ADVANTAGES DISADVANTAGES
1.Parental characteristics are preserved . 1.Continues self po. May lead to weakening of
the variety .
2.There is no wastage of pollen grain. 2. The defective characters of the variety cannot
be eliminated.
3.Scent and nectar need not be produces by the 3.It does not yield new varieties.Thus chance of
flower. improvement is not much.

 Cross pollination is the process of transfer of pollen grains from anther of one plant to the stigma
of another plant of the same species.
ADVANTAGES DISAVANTAGES
1.The offsprings are healthier. 1.The pollination is not always certain as it
depends on a pollinating agent.
2.The seeds produced are viable. 2.There is a lot of wastage of pollen.
3.New varieties may be produced. 3.The process is very uneconomical.

 Some of the conditions that favour cross pollination are :


1. Unisexual-The male and the female flowers may be borne on different flowers so cross pollination
is the only way for reproduction in such flowers.
2. Dichogamy-In many bisexual flowers the anther and the pistil may not be mature at the same
time.
3. Self-Sterlity-It is a condition that even if the stigma receives pollen from the anther of the same
plant the pollen fails to grow.In such cases a pollen from another plant of the same species can
effectively complete the process of setting of the seeds.
4. Herkogamy-In some self pollinating flowers the pollen is not able to reach the stigma.
5. Herterstyly-In some self pollinating flowers the stigma and anther are at different heights thus it
does not favour self pollination.There this condition favours cross pollination.

 Certain agents are needed to make cross pollination possible:


Insect pollinated-
1. The flowers are large.
2. They are bright coloured and scented
3. They produce nectar which is food for insects.
4. The polllen grains are sticky.
5. The stigma is sticky and does not hang out of the flower.
6. These flowers tend to be in clusters.

Wind pollinated-
1. These flowers are small.
2. They are usaully not bringhtly coloured and are dull green .
3. They do not produce scent or nectar.
4. The stamens are long and hang out of the flower.
5. Pollens are produce in very large quantities.
6. Pollens are light dry and smooth.

Water pollinated:
1. Pollen grains are produced in large numbers.
2. The pollen grains have a specific gravity almost equal to that of water to remain floating below the
surface of water.
3. In some cases the male flowers float in the water until they meet the female flowers.

Pollination by birds-Ornithology
Pollination by elephants-Elephophlily
Pollination by humans -Artificial pollination

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