Seeds-Structure and Germination
The structure of Dicot Seed:
A bean (dicot) seed is normally kidney shaped, flat and has a notch on one side.
Dicots have two seed leaves inside the seed coat. They are usually rounded and fat
because they contain the endosperm to feed the embryo plant.
Dicot seed consists of the following parts:
▪ Hilum:
The hilum is the point where the seed is attached to the inner margin of the fruit.
▪ Micropyle:
This is the opening through which the pollen tube enters the ovule. In the seed, the
Micropyle imbibes water and softens the seed coats and allows the embryo to emerge.
It allows diffusion of gases for respiration of the embryo.
▪ Seed coats:
In dicots, the seed coat is further divided into an outer coat, known as the testa, and
inner coat, known as the tegmen. The inner coat is thin, membranous and generally
united with the testa. The seed coat is tough and waterproof. It covers and protects the
embryo and the food supply.
▪ Embryo:
The embryo is the baby plant, which emerges from the seed and germinates into a
mature plant. The embryo consists of Cotyledons or seed leaves or nurse leaves. They
are fleshy, green, leaf-like structures and provide nourishment to the growing embryo.
It also consists of Radicle or future root of the plant. It is the first to emerge out of the
Micropyle during germination and develops into a tap root in the bean plant. Plumule
or the embryonic shoot system. It has a growing point covered by undeveloped,
delicate tiny leaves. It is attached to the radicle by the hypocotyl.
The structure of Dicot Seed:
A bean (dicot) seed is normally kidney shaped, flat and has a notch on one side.
Dicots have two seed leaves inside the seed coat. They are usually rounded and fat
because they contain the endosperm to feed the embryo plant.
Dicot seed consists of the following parts:
▪ Hilum:
The hilum is the point where the seed is attached to the inner margin of the fruit.
▪ Micropyle:
This is the opening through which the pollen tube enters the ovule. In the seed, the
Micropyle imbibes water and softens the seed coats and allows the embryo to emerge.
It allows diffusion of gases for respiration of the embryo.
▪ Seed coats:
In dicots, the seed coat is further divided into an outer coat, known as the testa, and
inner coat, known as the tegmen. The inner coat is thin, membranous and generally
united with the testa. The seed coat is tough and waterproof. It covers and protects the
embryo and the food supply.
▪ Embryo:
The embryo is the baby plant, which emerges from the seed and germinates into a
mature plant. The embryo consists of Cotyledons or seed leaves or nurse leaves. They
are fleshy, green, leaf-like structures and provide nourishment to the growing embryo.
It also consists of Radicle or future root of the plant. It is the first to emerge out of the
Micropyle during germination and develops into a tap root in the bean plant. Plumule
or the embryonic shoot system. It has a growing point covered by undeveloped,
delicate tiny leaves. It is attached to the radicle by the hypocotyl.
