This article is about fruitstones. For the organelle within the chloroplast of some algae and hornworts, see pyrenoid. For other uses of "pyrene", see Pyrene (disambiguation).
A pyrena or pyrene (commonly called a "pit" or "stone") is the fruitstone within a drupe or drupelet produced by the ossification of the endocarp or lining of the fruit.[1] It consists of a hard endocarp tissue surrounding one or more seeds (also called the "kernel").[2][3] The hardened endocarp which constitutes the pyrene provides a protective physical barrier around the seed, shielding it from pathogens and herbivory.[4]
While many drupes are monopyrenous, containing only one pyrene, pome-type fruit with a hard, stony (rather than leathery) endocarp are typically polypyrenous drupes, containing multiple pyrenes.[5]
Cross-section of a peach, a monopyrenous drupe, cut to reveal the pyrene inside
Pyrene of a peach dissected to reveal a single seed inside
Pyrenes extracted from a single fruit of Crataegus punctata, a polypyrenous drupe
X-ray of a pyrene of Elaeocarpus ganitrus revealing 10 seed-bearing locules inside; the number of locules in E. ganitrus pyrenes is variable between individual fruits