perispermic

Perispermic is a term used in seed biology to describe seeds that have perisperm as the nutritive tissue surrounding the embryo. In perispermic seeds, the endosperm is absent or greatly reduced, and the perisperm derived from the nucellus serves as the primary fuel reserve for the developing embryo and subsequent seedling.

Developmentally, after fertilization the nucellus tissue may persist instead of degenerating, differentiating into perisperm. This tissue fills or surrounds the embryo within the seed and acts as a nutrient source during germination. The presence of perisperm marks a departure from the more common seed condition in which endosperm forms from the triploid endosperm tissue following double fertilization.

Taxonomic distribution and significance are that perispermic seeds occur in a variety of angiosperm lineages, encompassing both monocots and eudicots, though they are not the predominant seed type. The occurrence reflects evolutionary variation in the origin of seed nourishment and can influence aspects of seed structure, density, and germination ecology. In scientific descriptions, the term perispermic helps distinguish nutritive tissue that originates from nucellus (perisperm) from tissues formed as endosperm.

In summary, perispermic seeds are characterized by nucellus-derived perisperm as the main nutrient source for the embryo, with endosperm absent or reduced, highlighting diverse evolutionary strategies for seed nourishment in flowering plants.