Write a short note on structure of an ovule of an angiospermic plant.

Explanation

Structure of The Ovule. The ovule is an integumented megasporangiam within which the meiosis and megaspore formation takes place from megaspore mother cell. It develops into a seed after fertilization. Each ovule usually consists of a nucellus enclosed by one or two integuments and a stalk (or funiculus) by which it is attached to the placenta of the ovary. The various parts of the ovule and their functions are-(i) Funiculus. It is the stalk-like structure which attaches the ovule to the placenta. (ii) Hilum. It is the point of attachment of the body of the ovule with the funiculus. (iii) Raphe. It is the longitudinal ridge formed by lengthwise fusion of funiculus with the body of ovule in a typical anatropous ovule, (iv) Nucellus. It is the mass of parenchymatous tissue surrounded by integuments. It encloses embryo sac and provides nourishment to the developing embryo. (v) Embryo sac. It is the female gametophyte which contains the egg apparatus, (vi) Integuments. These are outer coverings of ovule which provide protection to the developing embryo, (vii) Micropyle. It is a narrow pore or passage formed by the projection of the integuments through which the pollen tube enters into ovule. (viii) Chalaza. It is the place of origin of the integuments or the basal swollen part of the nucellus.