Germination of Seed : Parts of Seed
Seed is aripened ovule which contains the embryo or the miniature of plant body. Seeds of different plants vary in their size and shape. However, the general plan of structural organization of seed remains almost the same.
Part of a seed
Every seed an outer covering called seed coat. It develops from the integuments of the ovule. The outer coat is called testa and the inner layer is called tegmen. If only one covering is present in the seed, it is called testa. The testa is hard andleathery whereas tegmen is thin and membranous. Sometimes tegmen remains fused with the testa. The outer surface of seed shows a scar or mark of attachement with the seed stalk. It is calledhilum.There is a small pore, called micropyle, which represents the micropyle of ovule. Some seeds also show the place of origin of seed coats (chalaza) and the part of funiculus fused with seed wall (raphe).
The seed coat encloses an embryo which is differentiated into radicle, plumule and cotyledons. The radicle, when elongated, gives rise to primary root whereas the plumule gives rise to aerial shoot.
The number of cotyledons or seed leaves may be one as in monocotyledons or two as in dicotledons.sometimes, they store reserve food materials eg. Gram, Pea, Almond, Cashewnut, etc. or serve as photosynthetic organs in young seedling. the part of embryonic axis between the radicle and the point of attachment of cotyledons is called hydocotyl. Similarly, the part of embryonic axis between the plumule and the point of the attachment of cotyledons is called epicotyl.
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