Sexual Reproduction in Flowering Plants
Pollination - types, agencies and examples
- Pollination refers to the process of transfer of pollen grains on to the stigma of the flower, which is a pre-requisite for fertilization.
- Self-pollination is transfer of pollen grains from the anther of a flower to the stigma of either the same (or) genetically similar flower.
- Self-pollination is of 2 types (i) autogamy [Transfer of pollen grains from the anther to a stigma of the same flower]. (ii) Geitonogamy [Pollination between genetically similar plants.]
- Cleistogamy (Closed flowers – Pisum, Lathyrus, Commelina) and chasmogamy are the contrivances for self-pollination.
- Self-pollination maintains pure lines and the parental characters and ensures seed production by eliminating some bad recessive characters.
- The major disadvantage of self-pollination is the reduction of immunity, variability and adaptability.
- Cross pollination refers to the deposition of pollen grains from anther of a lower to the stigma of a different flower that happens only through an agent.
- Anemophily is an abiotic means of pollination by wind, where the pollen grains are light, small, dry but non-sticky and convertible.
- Examples: Maize, grass, Amaranthus, palm, Cannabis, Mulberry.
- Pollination by water is called Hydrophily that is of 2 types (i) Epihydrophily (surface pollination) Eg. Vallisneria (ii) Hypohydrophily (inside water) Eg. Najas, Zostera, Ceratophyllum.
- Wind and water pollinated flowers are not colourful and they do not produce any nectar.
- The most common pollinators are insects (eg. Wasp, bees, beetles) that pollinate the flowers of Asteraceae and Labiatae family.
- Most insect pollinated flowers have a landing plant platform, special markings on petals to guide insects.
- Edible pollens are produced by Rosa, Clematis and Magnolia etc.
- Zoophily is a type of pollination carried out by animals which is divided into many kinds based on the type of animal.
- Malacophily – tropics, birds
- Ophiophily – Snake
- Ornithophily – birds
- Chiropterophily – bats.
- Myrmecophily – ants Eg: some members of Rubiaceae.
- Cross pollination develops immunity, variation and adaptation is a newly formed progeny but some undesirable characters may creep in the race.
Part-1: Watch this video for the topic from 1:13 to 48:08
Part-2: Watch this video for the topic from 0:44 to 55:38
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