Agents
of Cross Pollination
In order to bring about
cross pollination, it is necessary that the pollen should be carried from one
flower to another of a different plant. This takes place through the agency of
animals, insects, wind and water.
The pollination with the
help of wind is called anemophily. The anemophilous flowers produce
enormous amount of pollen grains. The pollen grains are small, smooth, dry and
light in weight. Pollen of such plants are blown off at a distance of more than
1,000 km. The stigmas are comparatively large, protruding and sometimes hairy
to trap the pollen grains. e.g. Grasses and some cacti.
Pollination with the
help of insects like honey bees, flies are called entomophily. To attract
insects these flowers are brightly coloured, have smell and nectar. The pollen
grains are larger in size, the exine is pitted, spiny etc., so they can be
adhered firmly on the sticky stigma. Approximately, 80% of the pollination done
by the insects is carried by honey bees.
The pollination with the
help of water is called hydrophily.This takes place in aquatic plants.
(i) Pollen grains are produced in large numbers.
(ii) Pollen grains float
on surface of water till they land on the stigma of female flowers e.g. Hydrilla,
Vallisneria.
When pollination takes
place with the help of animals, it is called Zoophily. Flowers of such
plants attract animals by their bright color, size, scent etc. e.g. sun bird
pollinates flowers of Canna, Gladioli etc., Squirrels pollinate flowers
of silk cotton tree.
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