Pyrena

File:Drupe fruit diagram.svg

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 (Template:IPAc-en) 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.Template:Sfnp It consists of a hard endocarp tissue surrounding one or more seeds (also called the "kernel").Template:SfnpTemplate:Sfnp The hardened endocarp which constitutes the pyrene provides a protective physical barrier around the seed, shielding it from pathogens and herbivory.Template:Sfnp

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.Template:Sfnp

Development

The hardening of the endocarp of a developing drupe occurs via secondary cell wall formation and lignification.Template:Sfnp The biopolymer lignin, 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.Template:Sfnp 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.Template:SfnpTemplate:Sfnp

See also

• Nut (fruit)