SEED AND FRUIT FORMATION

Ovule after fertilization forms seeds. Zygote forms the embryo by mitosis. This consist of tiny radical, a plumule with one or two short special leaves called cotyledons. Cotyledons store the food of endosperm in some seeds and become thick e.g. bean seed. The outer integument of ovule forms the testa and the inner integument forms legmen. Testa and legmen constitute seed coat. Seed provide protection and nourishment to the embryo.

        After the formation of seeds and ovary wall become fleshy or scaly and forms fruit wall. The floral parts i.e. sepals, petals, stigma shrivel and fall off. This ripened ovary with seeds is the fruit.

   Parthenocarple fruits may be formed by the ovary in which no fertilization occurs as it happens in fruits of banana, seedless varieties of grapes etc. in some other plants, unfertilized egg develops into few plants and this process is called parthenogenesis.

    

       Dispersal of seeds and fruits:

   The seeds are the embryos of flowering plants in dormant stage. Fruits protect the seeds and help in the dispersal of the plant i.e. seeds and fruits may be carried a long distance from the parent plant. This reduces competition for light, water and other nutrient among the members of same species. The seeds and fruits may be dispersed by wind, by animal or by water.

1).   Dispersal by wind

    The smaller seeds and fruits are carried by wind to distant places. These seeds and fruits are light in weight and may also have wings or hairs. This helps them to be carried away by wind, away from the parent plant.

2).   Dispersal by animals

    The fruit and seeds of some plants have hooks or spines, which may be entangled in the fur of many mammals and are taken away from the site of parent plant. For example, medicogo (maina), cooklebur, and achyranthus (puthkanda).

3)    Dispersal by water

      The fruits and seeds of some plants which grow in or in near water are dispersed by water. The fruits of these may contain spongy tissues or fibrous fruit walls which allow them to float on the surface of water to be carried to distant places e.g., fruit of lotus, and daffodils.