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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