Name the pollinating agent of flowers like maize and cannabie. Give any two characteristics features of these flowers favouring this kind of pollination
Anemophily (Gk. anemos- wind, philein- to love; Wind Pollination; Fig. 2.19):
It is a mode of cross pollination or transfer of pollen grains from a mature anther to the stigma of a pistil which is accomplished through the agency of wind, e.g., Coconut Palm, Date Palm, Maize, many grasses, Cannabis.
(i) Flowers are small and inconspicuous.
(ii) Non-essential parts are either absent or reduced.
(iii) The flowers are colourless, odourless and nectarless.
(iv) In case of unisexual flowers, the male flowers are more abundant. In bisexual flowers, the stamens are generally numerous. Pistil are generally uniovuled.
(v) Flowers are produced above the foliage, before the appearance of new foliage or placed in hanging position.
(vi) Both the stigmas and anthers are exserted.
(vii) Anthers are versatile (Fig. 2.20).
(viii) In some cases like Urtica, the anthers burst suddenly to throw the pollen grains (gun-powder mechanism).
(ix) Pollen grains are light, small and winged or dusty. They can be blown by wind to distances of up to 1300 km. Winged pollen grains of Pinus are found hundreds of kilometres away from the parent plants.
(x) Pollen grains are dry smooth, nonsticky and unwettable.
(xi) Stigma is hairy, feathery (Fig. 2.19) or branched to catch the wind-borne pollen grains.
The large thread-like stigmas and styles of cob of Maize hang in air to catch wind borne pollens.
(xii) Anemophily is highly wasteful as it is nondirectional.
(xiii) Pollen grains are produced in very large number. For example, a single flower of Cannabis produces 5,00,000 pollen grains, a tassel of Maize gives rise to 20-25 million pollen grains while a plant of Mercurialis annua produces 135 million pollen grains.
Consequently, the pollen grains spread over large tracts so that even isolated plants get pollinated. But the large number of the pollen grains causes bronchial allergy or depression in many human beings. The phenomenon is also called hay fever.