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POLLINATION
It refers to the transfer of pollen from the anther to the stigma of the same flower, or to the different flower on the same plant or to the different flower on the different plant but of the same species. It is an important initial step of the sexual reproduction which leads to fertilization, zygote formation, embryo development and seed formation.
KINDS OF POLLINATION
Basing upon the sources of pollen, it can be of varied types:
1. Autogamy: The transfer of pollen from anther to stigma of the same flower marks autogamy. For it, pollen release and stigma receptivity for it should be synchronous or at the same time to undergo self-pollination.
Eg: Oxalis, Commelina, Viola possess two types of flowers. One is chasmogamous flowers which possess exposed pollen and stigma. Another is, cleistogamous, which do not open at all. So, cleistogamous flowers have to necessarily undergo autogamy because their pollen and stigma are hidden in the corolla (collection of petals).
2. Geitonogamy: It refers to the transfer of pollen from anther to stigma of another flower on the same plant. Genetically, it is similar to autogamy as fertilsation will take place flowers of the same plant.
3. Xenogamy: It refers to the transfer of pollen from anther to the stigma of another flower on different plant of the same species. It results in bringing genetically different types of pollen grains to the stigma. It is also known as allogamy. Functionally, geitonogamy is also a form of allogamy.
AGENTS OF POLLINATION
The agents of pollination can be of 2 types:
1. Biotic: These are the living agents that help in pollination. It includes:
a. ENTOMOPHILY: Pollination by insects is known as entomophily. Eg. Hibiscus, Sunflower, orchids.
b. CHEIROPTEROPHILY: Pollination by bats is known as chiropterophily. Eg. Kigellia, Bauhinia, Adansonia.
c. ORNITHOPHILY: Pollination by birds is known as ornithophily. Eg-Salvia.
d. MYRMECOPHILY: Pollination by ants is known as myrmecophily. Eg. plants of the family Leguminosae, Euphorbiaceae, Orchidaceae
e. MELITTOPHILY: Pollination by bee is known as melittophily. Eg. Pea and Foxglove.
f. CANTHAROPHILY: Pollination by beetle is known as cantharophily. Eg. certain grasslands of South Africa.
2. Abiotic: These are the non-living agents that help in bringing pollination. It includes:
a. ANEMOPHILY: Pollination by wind is known as anemophily. Common examples are: maize and some grasses. The essentialities for wind pollination are:
• Pollen grains should be light and non-sticky.
• Feathery stigma.
• Well exposed anther.
• Presence of numerous flowers in an inflorescence.
b. HYDROPHILY: Pollination by water is known as hydrophily. Examples are: Zostera, Hydrills, Vallisneria etc. Water pollinated flowers show-
• Mucilagenous covering around pollen grains to prevent over wetting of the pollen grains.
• Ribbon like pollen grains, so that they can swim with the water current and reach their destination (stigma).
• Sometimes, flowers come out of the water surface so that they can be easily pollinated by various biotic agents and wind.
QUESTIONS:
1. Which plant shows chiropterophily?
a. Salvia
b. Zostera
c. Kigellia
d. Hibiscus
Ans.c
2. Water pollination is shown by:
a. Hydrilla
b. Vallisneria
c. Both
d. None
Ans. c
3. Ornithophily refers to pollination by:
a. Ant
b. Bat
c. Beetle
d. Bird
Ans. d
4. Chiropterophily refers to pollination by:
a. Ant
b. Bat
c. Beetle
d. Bird
Ans. b
5. Entomophily refers to pollination by:
a. Beetle
b. Bat
c. Insect
d. Ant
Ans. c
6. Geitonogamy refers to:
a. Pollination within the same flower
b. Pollination between 2 flowers of the same plant
c. Pollination between 2 flowers of the different plant but of the same species
d. Pollination between 2 flowers of the different plant but of the different species
Ans.b
7. Allogamy is:
a. Pollination between 2 flowers of the different plant but of the same species
b. Pollination between 2 flowers of the same plant
c. Pollination within the same flower
d. Pollination between 2 flowers of the different plant but of the different species
Ans.a
8. Anemophily refers to pollination by:
a. Wind
b. Bat
c. Insect
d. Water
Ans. a
9. Cleistogamous flowers:
a. Normal flowers
b. Never open
c. Water pollinated
d. Bat pollinated
Ans.b
10. Wind pollinated show:
a. Sticky pollen
b. Sticky stigma
c. Single flower
d. Minute pollen
Ans. b
