Describe endosperm development in coconut.

Hint: Endosperm development is different in angiosperms than gymnosperms. Coconut is an angiosperm and the coconut water which we most often drink is nothing but the endosperm of coconut. In angiosperms, endosperm develops from a triploid primary endosperm nucleus which is formed due to triple fusion.

Complete answer:
Endosperm is a specialized tissue found in the seeds of mostly higher plants. It mainly serves the function of providing nutrition to the growing embryo. Coconut is an angiosperm. In these plants, endosperm is formed as a result of triple fusion i.e. one sperm nucleus fuses with two polar nuclei. In the free nuclear type of endosperm development, the primary endosperm nucleus divides repeatedly by free mitotic divisions without formation of walls. This results in a large number of free nuclei in the embryo sac. A big central vacuole also develops in the embryo sac. Once all the divisions are completed, cell walls form which constitutes the periphery of the embryo sac.
Hence, in coconut, endosperm is free nuclear in the centre and multicellular at the periphery.
Most of the endosperm tissues contain starch which serves the purpose of nutrition to the embryo. It also contains certain hormones like cytokinin which aid the cell differentiation. Aleurone is the outer layer of endosperm which secretes amylase enzyme. Amylase breaks down the starch to sugars which can be easily utilised by growing seedling.

Note: Endosperm of grains of monocot seeds, like wheat, barley and corn are main sources of food for humans as well. In dicots like peas and gram seeds, endosperm is completely utilised during development and is then replaced by fleshy cotyledons.