Page 4 - LN-CH-2[2]

Xenogamy:

 Transfer of pollen grains from the anther to the stigma of different plant.
 It is commonly called as cross-pollination.
 It brings genetically different types of pollen grains to the stigma.

Agents of pollination:

 Plant use two abiotic agent i.e. wind and water for pollination.
 One biotic agent for pollination such as animals.
 Majority of plant use biotic agent for pollination.
 Few plant use abiotic pollinating agent.

Anemophily:

 Pollinating agent is wind.
 Plants produces enormous amount of pollen when compared to the number of ovules available for
pollination to compensate the uncertainties of pollination.
 Flowers with well exposed stamens.
 Large feathery stigma to trap air-borne pollen grains.
 Most wind pollinated flower contains single ovule in one ovary and numerous flower packed into an
inflorescence e.g. corn cob.
 Pollen grains are light and non-sticky.

Hydrophily:

 Pollination by abiotic agent like water.
 This type of pollination is very rare, about 30 genera, mostly monocot.
 Vallisneria, Hydrilla and Zostera are the common example for Hydrophily.
 All aquatic plants are not Hydrophily.
 Pollen grains released into the surface of water and carried to the stigma by air current as in Vallisneria.
 In sea grass the flowers remained submerged.
 Pollen grains are long, ribbon like and carried passively inside the water
 Pollen grains are protected from wetting by mucilaginous covering.

Pollination by biotic agent:

 Majority of flowering plants use a range of animals as pollinating agents.
 Among the animal, insect particularly bees are the dominant biotic agents for pollination.
 Insect pollinating flowers are very large, colorful, fragrant and rich in nectar.
 Small flowers present in cluster to make them conspicuous.
 Flower pollinated by flies and beetles secrete foul odours.
 Nectar and pollen grains are the usual floral rewards for insects.
 In some species floral rewards are in providing safe places to lay eggs: e.g. Amorphophallus.
 A species of moth and Yucca plant cannot complete their life cycle without each other. The moth deposits
its eggs in the locule of the ovary and the flower in turn get pollinated by the moth.