endosperm

Nutritive tissue in the seeds of most flowering plants. It surrounds the embryo and is produced by an unusual process that parallels the fertilization of the ovum by a male gamete. A second male gamete from the pollen grain fuses with two female nuclei within the embryo sac. Thus endosperm cells are triploid (having three sets of chromosomes); they contain food reserves such as starch, fat, and protein that are utilized by the developing seedling.

In ‘non-endospermic’ seeds, absorption of these food molecules by the embryo is completed early, so that the endosperm has disappeared by the time of germination.