Seed and fruit formation are stimulated by the act of fertilization. In angiosperms double fertilization produces two structures— a diploid zygote or oospore and a triploid primary endosperm cell.
The latter gives rise to a nutritive tissue called endosperm. Zygote forms the embryo. Endosperm provides nourishment to the growing embryo. With the growth of embryo the central part of the endosperm is eaten up. Endosperm in turn corrodes over the nucellus.
In some seeds, the endosperm persists in the seed as food storage tissue. Such seeds are called endospermic or aluminous, e.g., Castor, Maize, Wheat, Barley, rubber, coconut. In others the endosperm is completely eaten up by growing embryo. The food for later development of embryo is then stored in cotyledons which become massive.
Such seeds are non-endospermic or exalbuminous, e.g., Pea, Gram, Bean, Groundnut. In some seeds remains of nucellus persist. The residual nucellus which persists in the seed is called perisperm, e.g., Black pepper, Coffee, Castor, Cardamom, Nymphaea. As the embryo reaches maturity its further growth is suspended due to development of growth inhibitors, abscission of funiculus or changes in integuments.
The cells of the integuments lose their protoplasm, develop thick and impermeable walls. The integuments thus get transformed into seed coats, outer testa and inner tegmen. The moisture content of seed decreases and reaches 10-15%. In this dry seed, the embryo occurs in state of inactivity called dormancy. The micropyle of the ovule is changed in micropyle of seed. Through this pore, oxygen and water enter the seed at the time of germination.
The tissue of the ovary wall is also stimulated to grow with the development of the seed. It produces a fruit wall or pericarp. In some cases, thalamus and other floral parts also show proliferation along-with the development of the ovary wall. They are called false fruits, e.g., Apple, Strawberry, Cashew.
The fruits in which no part of the flower develops along-with ovary are called true fruits. Some fruits also develop without fertilization. They are seedless fruits and are called parthenocarpic fruits, e.g., Banana. Parthenocarpy or production of seedless fruits can be induced artificially by means of hormones.
Seed and fruit formation are stimulated by the act of fertilization. In angiosperms double fertilization produces two structures— a diploid zygote or oospore and a triploid primary endosperm cell.
The latter gives rise to a nutritive tissue called endosperm. Zygote forms the embryo. Endosperm provides nourishment to the growing embryo. With the growth of embryo the central part of the endosperm is eaten up. Endosperm in turn corrodes over the nucellus.
In some seeds, the endosperm persists in the seed as food storage tissue. Such seeds are called endospermic or aluminous, e.g., Castor, Maize, Wheat, Barley, rubber, coconut. In others the endosperm is completely eaten up by growing embryo. The food for later development of embryo is then stored in cotyledons which become massive.
Such seeds are non-endospermic or exalbuminous, e.g., Pea, Gram, Bean, Groundnut. In some seeds remains of nucellus persist. The residual nucellus which persists in the seed is called perisperm, e.g., Black pepper, Coffee, Castor, Cardamom, Nymphaea. As the embryo reaches maturity its further growth is suspended due to development of growth inhibitors, abscission of funiculus or changes in integuments.
The cells of the integuments lose their protoplasm, develop thick and impermeable walls. The integuments thus get transformed into seed coats, outer testa and inner tegmen. The moisture content of seed decreases and reaches 10-15%. In this dry seed, the embryo occurs in state of inactivity called dormancy. The micropyle of the ovule is changed in micropyle of seed. Through this pore, oxygen and water enter the seed at the time of germination.
The tissue of the ovary wall is also stimulated to grow with the development of the seed. It produces a fruit wall or pericarp. In some cases, thalamus and other floral parts also show proliferation along-with the development of the ovary wall. They are called false fruits, e.g., Apple, Strawberry, Cashew.
The fruits in which no part of the flower develops along-with ovary are called true fruits. Some fruits also develop without fertilization. They are seedless fruits and are called parthenocarpic fruits, e.g., Banana. Parthenocarpy or production of seedless fruits can be induced artificially by means of hormones.