A seed is
defined as a fertilized mature ovule consisting of embryo, stored food material
and protective coats.
Seeds
may be broadly classified as dicotyledons and monocotyledons, depending on the
number of cotyledons.
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Seed
coat
It
is the outer covering of seed and gives protection. It develops from the 2
integuments of ovule. Outer layer of the seed coat which is smooth and rough is
known as the testa and is formed from the outer integument.
Embryo
It
is the mature ovule consisting of an embryonic plant together with a store of
food, all surrounded by a protective coat, which gives rise to a plant similar
to that of its mother. It is a miniature plant consists of plumule, radicle and
cotyledon.
Radicle
Rudimentary
root of a plant compressed in the embryo is the radicle, which forms the
primary root of the young seedling. It is enclosed in a protective cover known
as coleorhiza.
Plumule
It
is the first terminal bud of the plant compressed in the embryo and it gives
rise to the first vegetative shoot of the plant. It is enclosed in a protective
cover known as coleoptile.
Cotyledon
Cotyledons
are the compressed seed leaves. A single cotyledon (Scutellum) is present in
monocots while two cotyledons are present in dicots, hence they are named as
monocots and dicots, respectively.
In dicots they serve as storage tissue and are
well developed, while scutellum is a very tiny structure in monocots.
Endosperm
Endosperm
develops from the endosperm nuclei which is formed by the two polar nuclei and
one sperm nuclei. It stores food for the developing embryo.