Describe Endosperm formation and its function

Development of Endosperm

It begins before that of the embryo, arises from the primary endosperm nucleus (also known as triple fusion nucleus) formed as a result of the triple fusion of three nuclei i.e. two polar nuclei and a male nucleus. The primary endosperm nucleus is triploid (3N). It undergoes a series of divisions resulting in the formation of many free nuclei lying within the embryo sac. A vacuole appears in the center so that the nuclei are pushed to the periphery.

Later on, unless the endosperm is absorbed by the embryo in the free nuclear stage, wall formation takes place starting from the periphery towards the center of the embryo sac, and by further centripetal growth, the embryo sac is filled with a compact cellular tissue around the embryo without any intercellular spaces. This tissue is endosperm occasionally as in coconut a vacuole persists in the center of the embryo sac as it is not completely filled by the endospermic tissue. This type of endosperm development since it involves the process of free nuclear division is called the nuclear type e.g. Fritillaria bi flora. This is the most common method of endosperm development. In some plants as in Silphium Lacimatum, each division of the primary endosperm nucleus is followed by wall formation, so that the endosperm is formed at once. This type of endosperm development is known as the cellular type.

In some groups, endosperm may develop as a few free nuclei only so that it may be regarded as suppressed as in Helobiales and orchids. Several members of Sympetalae a few families of Archichlamydae and monocotyledons show prominent endospermic Fostoria which forms a very efficient absorptive system.

Function of endosperm

Endosperm serves as storage tissue as its cells are laden up with food material absorbed through the placenta. The reserve food is stored in large quantities in its cells. This may be deposited as Hemi cellulose on the cell walls which often become very thick as in the date and so-called vegetable ivory. In most monocots and some dicots (e.g. castor, buttercup, cotton, and all grasses) endosperm persists as permanent tissue in the seed. Such seeds are called albuminous or endospermic.

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