Diagram of a typical drupe, in this case a peach, illustrating the layers of both the fruit and the seed; the pyrene is the hardened endocarp which encloses the seed
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]
Development
The hardening of the endocarp of a developing drupe occurs via secondary cell wall formation and lignification.[4] The biopolymerlignin, also found in wood, provides a structure within secondary cell walls which supports the polymerisation of cellulose and hemicellulose; together these polymers provide the endocarp with tensile strength and stiffness.[4] Further hardening occurs during the biomineralisation of the endocarp. The biomineralisation of pyrenes during the life of the plant can aid the preservation of fruit remains in archaeological findings.[6][7]
Gallery
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
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Dardick, Chris; Callahan, Ann M. (2014). "Evolution of the fruit endocarp: molecular mechanisms underlying adaptations in seed protection and dispersal strategies". Frontiers in Plant Science. 5: 284. doi:10.3389/fpls.2014.00284. ISSN 1664-462X. PMC 4070412. PMID 25009543.
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Messager, Erwan; Badou, Aïcha; Fröhlich, François; Deniaux, Brigitte; Lordkipanidze, David; Voinchet, Pierre (2010). "Fruit and seed biomineralization and its effect on preservation" (PDF). Archaeological and Anthropological Sciences. 2 (1): 25–34. Bibcode:2010ArAnS...2...25M. doi:10.1007/s12520-010-0024-1. S2CID 128691588.
Potter, D.; Eriksson, T.; Evans, R.C.; Oh, S.; Smedmark, J.E.E.; Morgan, D.R.; Kerr, M.; Robertson, K.R.; Arsenault, M.; Dickinson, T.A.; Campbell, C.S. (2007). "Phylogeny and classification of Rosaceae". Plant Systematics and Evolution. 266 (1–2): 5–43. Bibcode:2007PSyEv.266....5P. doi:10.1007/s00606-007-0539-9. S2CID 16578516.
