Pollination

Ways of pollination Geitonogamy Autogamy Allogamy Self Pollination Cross Pollination Pollination between flowers of the same plant Pollination between flowers of different plants Geito – neighbour Allo – other Auto – self When can self pollination occur? Gamy - marriage Geitonogamy Same plant but a different flower Autogamy Same flower Allogamy

Self pollination Cross pollination Autogamy 1.Allogamy No agent required 2. Agent is required Male & female parts 3. Male & female parts mature at the same time mature at different times 4. Can occur even if the 4. Can occur only when flower is closed flower is open 5. Offspring can become 5. Offspring healthier Weak 6. New variety not possible 6. New variety possible 7. Preserves parental 7. Does not preserve Characters parental characters Build advantages and disadvantages of self and cross pollination from this.

Self pollination Advantages Disadvantages Pollination is sure 1. Offspring gets weaker Parental characters 2. New variety not are preserved possible 3. Fewer pollen grains 3. Weaker strains cannot are needed eliminated 4. Flowers are not large / showy/scented / have nectar

Cross pollination Advantages Disadvantages Healthier offspring 1. Pollination is not always sure 2. New varieties can be 2. Lot of pollen is produced produced & wasted 3. Seeds are abundant 3. Flowers may have and good quality to be large, showy, scented, have nectar Nature favours cross pollination

Conditions which favour Cross pollination Unisexuality – Dioecious plants Dichogamy – different maturation of androecium and gynoecium - Sunflower i) anthers mature earlier – protandry e.g. Maize ii) Stigma matures earlier – protogyny e.g. bajra

Self sterility – Even if the stigma receives pollen form the anthers of the same flower, pollen does not undergo further growth. E.g. Ray florets of sun Flower

Mechanical or structural barriers – Herkogamy There may be a hood covering the stigma which can be broken only by agents like the insects e.g. Pansy, Calotropis

Anther Stigma Anther Stigma Heterostyly – Anthers and stigma grow at different heights which does not permit self pollination – Primrose

To watch video of insect pollination http://www.youtube.com/watch?v=ge3EM8AERV0

Interesting Fact One anther on a maize flower produces 3000 pollen grains. This means that all the anthers on one plant produce a total of around 18 million pollen grains! To watch video of Wind pollination in Pine trees http://www.youtube.com/watch?v=V_9palHvAIc

Water Pollination

Insect Pollinated Entomophilous Wind pollinated Anemophilous Water Pollinated Hydrophilous Flower Large Coloured, Scented Has nectar Small Not coloured Not scented No nectar Pollen Not in large numbers Sticky or spiny Large numbers Dry and light Loosely attached Float below the surface of water Vallisneria pollen float till they meet female flowers Stigma Sticky Does not hang out of the flower Feathery Hang out of the flowers Dioecious

Ornithophilous – Bird Pollinated e.g. Begonia, Canna Elephophilous – Elephant pollinated e.g. Rafflesia