Endosperm | Definition, Description, & Importance | Britannica (original) (raw)

Science Biology Life Cycle, Processes & Properties

endosperm, tissue that surrounds and nourishes the embryo in the seeds of angiosperms (flowering plants). In some seeds the endosperm is completely absorbed at maturity (e.g., pea and bean), and the fleshy food-storing cotyledons nourish the embryo as it germinates. In others, some of the endosperm is present until germination (e.g., wheat, castor bean), and the cotyledons are typically thin and membranous and serve to absorb the stored food from the endosperm upon germination. In the coconut, the liquid endosperm contains important growth substances. Endosperm accounts for the economic importance of cereal grains and oilseeds.

how flowering plants reproduceReproduction in flowering plants begins with pollination, the transfer of pollen from anther to stigma on the same flower or to the stigma of another flower on the same plant (self-pollination) or from the anther on one plant to the stigma of another plant (cross-pollination). Once the pollen grain lodges on the stigma, a pollen tube grows from the pollen grain to an ovule. Two sperm nuclei then pass through the pollen tube. One of them unites with the egg nucleus and produces a zygote. The other sperm nucleus unites with two polar nuclei to produce an endosperm nucleus. The fertilized ovule develops into a seed.

The initiation of endosperm is a definitive characteristic of the double fertilization of angiosperms. Its development requires the fusion of at least one polar nucleus in the embryo sac with one of the two sperm nuclei from the pollen grain. In gymnosperms the nutritive material of the seed is present before fertilization.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Melissa Petruzzello.