Development of Endosperm
In a fertilized embryo sac, the primary endosperm nucleus is generally observed below the zygote. It divides, and further divisions of its products give rise to an endosperm. The nutritive role of endosperm has long been recognized. It nurses the embryo from the proembryo stage until it becomes self-sufficient, and completes its development. The endosperm tissue is the source of growth regulator such as gibberellins and cytokinins. Coconut water and sometimes the extract of corn endosperm, at the milk stage are added to the nutrient media of tissue cultures to stimulate growth. The developing endosperm derives nutrients from the food reserves stored in nucleus and integuments. In several families the development of chalazal, micropylar or secondary endosperm haustoria leads to partial or entire absorption of integuments. Based on the mode of development, three main types of endosperms have been recognized in angiosperms: