Pollination
Ways of pollination
Self Pollination Cross Pollination
AutogamySame flower
GeitonogamySame plant but a different flower
Pollination between flowers of the same plant
Pollination between flowers of different plants
Allogamy
Self pollination Cross pollination1. Autogamy 1.Allogamy2. No agent required 2. Agent is required3. Male & female parts 3. Male & female partsmature at the same time mature at different
times4. Can occur even if the 4. Can occur only when flower is closed flower is open5. Offspring can become 5. Offspring healthierWeak6. New variety not possible 6. New variety possible7. Preserves parental 7. Does not preserve Characters parental characters
Advantages Disadvantages1. Pollination is sure 1. Offspring gets weaker2. Parental characters 2. New variety notare preserved possible3. Fewer pollen grains 3. Weaker strains cannot are needed eliminated4. Flowers are not large / showy/scented /have nectar
Self pollination
Cross pollination
Advantages Disadvantages1. Healthier offspring 1. Pollination is not
always sure2. New varieties can be 2. Lot of pollen is
produced produced & wasted3. Seeds are abundant 3. Flowers may have and good quality to be large, showy,
scented, have nectar
Conditions which favour Cross pollination• Unisexuality – Dioecious plants• Dichogamy – different maturation of
androecium and gynoecium - Sunflower i) anthers mature earlier – protandry e.g. Maizeii) 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
There may be a hood covering the stigma which can be broken only by agents like the insects e.g. Pansy, Calotropis
Mechanical or structural barriers – Herkogamy
Stigma
Anther Stigma
Anther
• 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=ge3EM8A
ERV0
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 PollinatedEntomophilous
Wind pollinatedAnemophilous
Water PollinatedHydrophilous
Flower LargeColoured, ScentedHas nectar
SmallNot colouredNot scentedNo nectar
Small
Pollen Not in large numbersSticky or spiny
Large numbersDry and light
Loosely attached
Large numbersFloat below the surface of waterVallisneria pollen float till they meet female flowers
Stigma StickyDoes not hang out of the flower
FeatheryHang out of the flowers
Dioecious
Ornithophilous – Bird Pollinated e.g. Begonia, Canna
Elephophilous – Elephant pollinated e.g. Rafflesia
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