Pollination, self-pollination, cross pollination

1. BY
DIVYASHREE.B.R

2. POLLINATION
The term pollination refers to the transfer and deposition of pollen
on the stigma of the flower.
It is of two types:
 Natural pollination: which occurs naturally in plants.
 Induced pollination: which is carried out by artificial means.
Natural pollination is of two types:
 Self-pollination
 Cross pollination

3. SELF-POLLINATION
It involves the transfer of pollen grains from the anther to the stigma of
the same flower(Autogamy) or another flower of the same plant
(Geitonogamy).
Examples:
Ground Nut BarleyPea plant

4. Self-pollination is promoted by certain floral adaptation.
Mirabilis jalapa Vinca rosea
 Cleistogamy: It is a
phenomenon in which the
flowers do not open at the
time of fertilization.
Violaceae
 Homogamy: It refers to the
maturation of sex organs at
same time.
balsaminaceae

5. ADVANTAGES OF SELF-POLLINATION
i. Parental charecters are preserved indefinitely.
ii. The flowers need not to be large.
iii. Fragrance and nectar production is not required, which saves
considerable nutrient material of plants.
DISADVANTAGES OF SELF-POLLINATION
i. Continued self-pollination may lead to weakening of the off-springs.
ii. Seeds produced will be poor in quality.
iii. The defective character of plants cannot be eliminated.

6. CROSS POLLINATION
It involves the transfer of pollen grains from the anther of a flower to
the stigma of another flower of different plant(Allogamy).
Pollination between flowers of different genetic constitution is known as
xenogamy.
Examples: Sunflower, date palm, maize etc.
Cross pollination is favoured by certain adaptations.
• Dicliny: plants bearing unisexual flowers posses only one kind of sex
organs(male or female).
Example:
Papaya Mulberry

7.  Dichogamy: It refers to maturation of
sex organs at different time period.
It shows two conditions
1. Protandrous: here anthers mature
before stigma.
Example: Rubiaceae, Malvaceae, Labiatae.
2. Protogynous: here stigma
matures before the anthers.
Example: Mangolia, Michalia, Adhatoda.

8.  Heterogamy: The phenomenon of bearing two types of morphological
dissimilar flowers. Ex: Primrose.
It bears two types of flowers.
 Long-styled or Pin eyed: Flowers bearing long style and short stamens.
 Short-styled or thrum eyed: Flowers bearing short style and long stamen.

9.  Herkogamy: In certain flowers, morphological barriers develop which
makes self pollination impossible.
Example:
Calatropis Zeuxine
 Self-Sterility: Flowers in which pollens are incapable of causing
fertilization. Example: Maize.

10. AGENTS OF CROSS POLLINATION
In angiosperms, pollens are immotile and thus, have to be carried to the
stigma by external pollinating agents.
Depending upon their nature the agents may be
1. Biotic agents: Insects, Birds, Snails etc.
2. Abiotic agents; wind, water.
BIOTIC AGENTS
i. Entomophily: It refers to the
pollination brought about by
insects.
Examples: Salvia, Yucca, Ficus.

11. ii. Ornithophily: It refers to the pollination brought about by birds.
Examples: Salmalia, Erythrina, Callistemon.
iii. Cheiropterophily: It refers to the pollination brought about by bats.
Examples: Adansonia, Eperua falcata.

12. iv. Malacophily: It refers to the pollination brought about by snails & slugs.
Examples: Alocasia, Lemna, Colocasia.
v. Myrmecophily: It refers to the pollination brought about by ants.
Examples: Medicago sativa, Melitotus officinalis.

13. vi. zoophily: It refers to the pollination brought about by animals.
Examples: Arctium, Galium aparine.
ABIOTIC AGENTS
i. Anemophily: It refers to the
pollination brought about by
winds.
Examples: Wheat, maize, coconut.

14. ii. Hydrophily: It refers to the pollination brought about by water.
It is of two types;
1. Ephydrophily: Pollination occuring
on the water surface.
Examples: Elodes, Hydrilla.
2. Hyphydrophily: Pollination
occuring beneath the water surface.
Examples: Najas, Ceratophyllum.

15. ADVANTAGES OF CROSS-POLLINATION
i. Off-springs are healthier.
ii. New varities may be produced.
iii. Helps in increase seed production in cereals.
DISADVANTAGES OF CROSS-POLLINATION
i. The pollination is not always certain.
ii. A large number of pollens are to be produced to ensure chances of
pollination.
iii. If in a crossing, a diseased plant gets involved, it will give weak
off-springs.