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In this article we will discuss about the dispersal of fruits and seeds:- 1. Dispersal by Wind 2. Dispersal by Animals 3. Dispersal by Explosive Mechanism 4. Dispersal by Water.
Dispersal by Wind (Fig. 113):
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Some fruits rind seeds are so small and light that they may be easily carried by wind. Many of them develop crowns of hairy outgrowths and winged expansions often acting like parachutes, which help them in distribution. Hairy outgrowths are present on the seeds of cotton, Calotropis (B. Akanda), Nerium (B. Karabi).
Many small fruits of sunflower family have modified hairy sepals. Persistent hairy styles are found in Naravelia (B. Chagalbati). Winged expansions on the seeds are common in Moringa (B. Sajina), mahogany Fruits of Hiplage. (B. Madhabilata). Dipterocarpus (B. Garjan) have winged outgrowths for the same purpose.
Dispersal by Animals:
Many fruits and seeds are provided with spiny projections or sticky glands to adhere to the animal bodies, and are thus scattered. Andropogon (B. Chore Kanta), Achyranthes (B. Apang) have stiff hairs on the pericarp; curved hooks and barbs are present in Martynia (B. Bagnak. Fig. 114); Xanthium (B. Okra), Plumbago (B. Chita) have glands by which they stick to the animal bodies.
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Fleshy fruits like tomato, figs, develop beautiful colours to attract animals like birds, squirrels and bats. The small seeds are carried by those animals from place to place. Some of the fruits are eaten up by animals and seeds remain uninjured even when they pass through their alimentary canals. The excreta of the animals rather forms a more congenial soil for the germination of the seeds.
That explains the occurrence of the seedlings on the roof-tops and cornices of big buildings. Ants, mice and other rodents, store small fruits and thus become responsible for their dispersal.
Even human beings are instrumental in the dispersal of many seeds and fruits of economic interest and ornamental value. Plants like water hyacinth, papaw, pine-apple which grow abundantly all over India today have come from foreign countries through human agency.
Dispersal by Explosive Mechanism:
Certain fruits burst with a bit of force to scatter the seeds away from the mother plant. Familiar examples are Balsam (B. Dopati), Oxalis (B. Amrul), castor. Fruits of Rvellia (B. Chatpati), Andrographis (B. Kalomegh), burst suddenly when they come into contact with moisture. Legumes of Clitoria (B. Aparajita), dehisce by both the sutures and the two halves twist just to scatter the seeds.
Dispersal by Water:
Aquatic plants and plants growing on river banks and sea-shore have fruits and seeds which are dispersed through water. They have usually fibrous tissue for floating on water surface, and protective devices so that the embryo may not be damaged.
Fruits of cocoanut, Nipa (B. Golpata) are common examples. Lotus fruits remain embedded in the spongy thalamus. The seeds of water-lily contain air-spaces in the testa for ready dispersal by water.
