Write a short note on endosperm formed in an angiosperm.

Explanation

Endosperm (3N) Formation. Endosperm is meant for nourishing the embryo. In angiosperms, it is triploid because it is formed after triple fusion between one male gamete and two polar nuclei: Endosperm formation is accompanied by degeneration of nucellus. Endosperm is of following three types-
1. Nuclear Endosperm. Primary endosperm nucleus divides and redivides to form a large number of free nuclei. Wall formation occurs and multicellular endosperm is formed.
e.g., Maize, wheat, rice, coconut, etc. Nuclear endosperm is the most common type of endosperm. It is named so because it contains free nuclei in the beginning.

2. Cellular Endosperm. Every division of the primary endosperm nucleus is followed by cytokinesis. Therefore, endosperm becomes cellular from the very beginning, e.g., Balsam, Datura, Petunia.

3. Helobial Endosperm. First division of primary, endosperm nucleus is followed by cytokinesis to produce two cells-micropylar and chalazal, within each of which free nuclear division occurs but ultimately they may become cellular e. g., Asphodelus, Eremurus.
Endosperm may persist in the seed. It is called as endospermic seed or albuminous seedy e.g., Castor. It may be consumed by the embryo. In such a case food is generally stored in the cotyledons. Such seeds are called non-endospermic or exalbuminuous, e.g., Groundnut.