Explain the Agents of cross-pollination.

Explanation

Cross pollination takes place through the agency of animals, insects, wind and water.
(a) Pollination by wind: The pollination with the help of wind is called Anemophily. The Anemophilous flowers produce enormous amount of pollen grains, which are small, smooth, dry and light in weight. This kind of pollen can blown off at a distance of more than 1,000 km. The stigmas are large, protruding and hairy to trap the pollen grains. eg. Grasses and some Cacti.
(b) Pollination by insects: Pollination with the help of insects like honey bees, flies are called entomophily. These flowers are brightly coloured, have smell and have nectar, to attract insects. The pollen grains are larger in size, and the exine is pitted and spiny, so it can easily adhere firmly on the sticky stigma. About 80% of the pollination by insects is carried by honey bees.
(c) Pollination by water: The pollination with the help of water is called hydrophily. This takes place in aquatic plants. Pollen grains are produced in large numbers. Pollen grains float on surface of water till they land on the stigma of female flowers. eg. Hydrilla, Vallisneria.
(d) Pollination by Animals: When pollination takes place with the help of animals, it is called Zoophily. The flowers have bright colour, size and scent to attract animals. eg. Sun bird pollinates flowers of Canna, Gladioli etc., Squirrels pollinate flowers of silk cotton tree.