A plant seed refers to the structure which is formed from the maturation of the ovule after the fertilisation occurs in the plant. The seed is present only in two major groups of plants: the gymnosperms and the angiosperms.
The seeds inside it contain the nucellus in the central portion which inside it encloses the embryo sac. The embryo sac contains the egg cell which after fertilisation forms the zygote and ultimately embryo. The embryo requires the nutrition which is supplied either by the nucellar portion or the endosperms in the angiosperms.
