Endosperm—Its Morphology, infrastructure, and Histochemistry

Abstract

Publisher Summary This chapter discusses the morphology, ultrastructure and histochemistry of endosperm. Endosperm is formed by the repeated divisions of the primary endosperm nucleus. It is the main source of food for the embryo in angiosperms. The central cell is a highly active cell that performs several important functions in the embryo sac. The fusion of the secondary nucleus or the polar nuclei with the sperm nucleus gives rise to the primary endosperm nucleus, which is generally triploid. The primary endosperm nucleus is associated with aggregates of dense material in the perinuclear cytoplasm. The primary endosperm nucleus divides rapidly to form the endosperm tissue. The endosperm nuclei increase in size as the development proceeds. In angiosperms there are three types of endosperm development— namely, nuclear, cellular, and helobial. The mature endosperm in some plants shows rumination that is caused by the seed coat activity or by the endosperm itself. The endosperm haustoria are of widespread occurrence in angiosperms. The haustorial cells undergo enlargement and aggressive growth during development that results in the destruction of ovular tissues adjacent to the invading haustoria. When endosperm cells are actively dividing, the haustoria become involved in the nutrition of the endosperm cells. The cytoplasm of the aleurone cell is characterized by many small to large electron-transparent osmiophilic lipid bodies/droplets, also known as, spherosomes. The reserve materials of endosperm tissue undergo autolysis to yield simpler components that are used up during the growth and germination of embryo.