pollination. ways of pollination self pollinationcross pollination autogamy same flower geitonogamy...

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