The Seed

A seed is the final product of sexual reproduction in angiosperms. It is a fertilised, mature ovule that contains an embryo, stored food material (endosperm), and a protective coat (seed coat).

After fertilisation, the following simultaneous transformations occur in the ovule:

A typical seed has three primary components:

Seed Coat: Protective outer layer derived from integuments.

• Testa - Outer hard, thick layer
• Tegmen - Inner thin, papery layer

Endosperm: Triploid (3n) food-storing tissue formed by triple fusion during double fertilisation.

Embryo: The miniature plant. Consists of:

• Radicle - Develops into the root
• Plumule - Develops into the shoot
• Embryonal axis - Connects radicle and plumule
• Cotyledon(s) - Seed leaf/leaves (1 in monocots, 2 in dicots)

• The seed remains attached to the placenta via a stalk-like structure called the funicle.
• When detached, the point of attachment leaves a scar called the hilum.
• In some seeds, a bright-coloured outgrowth develops on the surface called the aril.

Seeds show remarkable variation in size, shape, colour and surface. Some plants can even be identified on the basis of seeds alone.

A state of metabolic inactivity in mature seeds where germination does not occur even under seemingly favourable conditions.

As the seed matures, its water content drops to 10–15% by mass, metabolic activity of the embryo slows down, and the seed enters dormancy. Germination is triggered when the seed receives:

• Adequate moisture
• Oxygen
• Suitable temperature

Seed Viability Records:

As ovules mature into seeds, the ovary simultaneously develops into a fruit. The ovary wall becomes the pericarp (fruit wall = epicarp + mesocarp + endocarp).

• Seed is the fertilised ovule and final product of sexual reproduction in angiosperms.
• It consists of seed coat, cotyledons and embryo axis; food is stored mainly in cotyledons or endosperm.
• Seeds may be albuminous (endosperm present) or non-albuminous (endosperm absent); perisperm may persist in some seeds.
• Dormancy and dehydration help seeds survive adverse conditions and allow long-term storage.
• Seeds ensure dispersal, protection, nourishment of embryo, genetic variation and agricultural sustainability.