Structure and function of endosperm
Endosperm is present in the seeds of most of the angiosperms. It provides nourishment to the growing embryo. Endosperm is replaced by fleshy cotyledons in dicotyledonous plants. In monocotyledons, endosperm persists in mature seeds too and stores the food. Endosperm tissue is rich in carbohydrates and also contains proteins and lipids. Endosperm development takes place by the triploid cell(3n) in the embryosac the second male gamete fuses with the diploid secondary nucleus(2 polar nuclei) to form PEN(Primary Endosperm Nucleus) and a triploid cell. This process is known as triple fusion. In some of the dicots, mature seeds contain food stored in the endosperm, they are called endospermic seeds. In beans, peas, green seeds, the endosperm is completely absorbed during development and food is stored in two cotyledons. They are called non endospermic Or exalbuminous seeds. Endosperm provide nutrients to seeds during dormancy. Endosperm also contains certain harmones like cytokinins and helps in cell differentiation. The outer layer of endosperm is the aleurone layer it secretes the amyalase enzyme which breaks down the starch contained in the endosperm to sugars for utilisation by seedlings.
Function of endosperm:
- Endosperm is important for the growth of an embryo and stores the food reserve.
- They supply nutrients and provide protection to the developing embryo.
- Endosperm induces signals according to environmental conditions and regulates embryonic growth.
- The endosperm contains cytokinin, which regulates cellular differentiation.
- It may induce abortion of seeds from the genetically mismatched cross.