The Role of Endosperm in Seed Development
In some groups (e.g. grains of the family Poaceae) the endosperm persists to the mature seed stage as a storage tissue, in which case the seeds are called "albuminous" or "endospermous", and in others it is absorbed during embryo development (e.g., most members of the family Fabaceae, including the common bean, Phaseolus vulgaris), in which case the seeds are called "exalbuminous" or "cotyledonous" and the function of storage tissue is performed by enlarged cotyledons ("seed leaves"). In certain species (e.g. corn, Zea mays); the storage function is distributed between both endosperm and the embryo. Some mature endosperm tissues store fats (e.g. castor bean, Ricinis communis) and others (including grains, such as wheat and corn) store mainly starches.
The dust-like seeds of orchids have no endosperm. Orchid seedlings are mycoheterotrophic in their early development. In some other species, such as coffee, the endosperm also does not develop. Instead the nucellus produces a nutritive tissue termed "perisperm". The endosperm of some species is responsible for seed dormancy. Endosperm also mediates the transfer of nutrients from the mother plant to the embryo, it acts as a location for gene imprinting, and is responsible for aborting seeds produced from genetically mismatched parents. In angiosperms, the endosperm contain hormones such as cytokinins, which regulate cellular differentiation and embryonic organ formation.
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