CBSE Class 10 Answered
The diploid zygote gradually develops into the embryo. A well developed embryo shows radicle, plumule and one or 2 cotyledons. The triploid endosperm cells multiply and form a mass of nutritive tissue called endosperm.The endosperm may be consumed by the embryo, as in many legumes, which use the cotyledons as a food source during germination. In other species the endosperm persists until germination, when it is used as a food.
The ovule is gradually transformed into relatively dry and hard seed.
As the embryo develops, the integuments gets thickened and hardened to form seed coats. The outer coat of integuments forms testa and inner one forms tegmen.
The testa usually shows a scar called the hilum where the ovule was originally attached to the funicle. In some seeds a ridge along the testa called the raphe shows where the funicle originally was pressed against the ovule.
The micropyle of the ovule usually survives as a small pore in the seed coat that allows passage of water during germination of the seed.
The fruit of a flowering plant is the mature ovary. As seeds mature, the surrounding ovary wall forms a protective structure that may aid in dispersal. The surrounding ovary tissue is called the pericarp and consists of three layers. From the outside to inside, these layers are the exocarp, mesocarp, and endocarp.