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A Handbook of Biology
THË SËËD
Cotyledon
Plumule
Radicle
It is the mature ovule developed after
fertilisation.
A seed is made up of a seed coat and an
embryo.
Embryo is made up of a radicle, an
embryonal axis and one (e.g. wheat, maize)
or 2 cotyledons (e.g. gram & pea)
1. STRÜÇTÜRË ØF DÏÇØTÝLËDØÑØÜS SËËD.
The outermost covering of a seed is the seed
coat.
Seed coat has 2 layers: outer testa and inner
tegmen.
The hilum is a scar on the seed coat through
which the developing seeds were attached to
the fruit.
(NEET 2020)
Above the hilum is a small pore called the micropyle.
Within the seed coat is the embryo, consisting of an embryonal axis and
two cotyledons.
The cotyledons are often fleshy and full of reserve food materials. At the
two ends of the embryonal axis are present the radicle and the plumule.
In some seeds such as castor, the endosperm is formed due to double
fertilisation. It is a food storing tissue.
(AIPMT 2008)
In plants such as bean, gram and pea, the seeds are non-
endospermous (endosperm is not seen in mature seeds).
2. STRÜÇTÜRË ØF MØÑØÇØTÝLËDØÑØÜS SËËD
Seed coat & fruit-wall
Aleurone layer
Endosperm
Scutellum
Coleoptile
Plumule
Radicle
Coleorhiza
Endosperm
Embryo
Seed coat
Hilum
Micropyle