A pyrena () or pyrene, commonly called a pit or stone, is the fruitstone inside certain types of fruit, namely or , and consists of a hardened shell-like layer surrounding one or more (also called the "kernel"). It is produced by the ossification of the inner lining tissue of the fruit, called the endocarp. The hardened endocarp which constitutes the pyrene provides a protective physical barrier around the seed, shielding it from and herbivory.
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.
Development
The hardening of the endocarp of a developing drupe occurs via secondary cell wall formation and
lignification. 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. 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
Archaeology findings.
Uses and culture
Pyrenes have been employed worldwide in many cultures for many uses. The stones of some fruits, such as peaches, are sometimes used to infuse flavours into foods and drinks, including peach pit jelly, vinegar, and alcoholic beverages like
ratafia. In
China, fruitstones are used in a traditional
folk handicraft, namely fruit pit carving (核雕), to make jewellery and sculptures.
Shaivite and
Buddhist practitioners use the stones of the fruit of
Elaeocarpus ganitrus, called
rudraksha, as prayer beads for
akshamala.
Gallery
See also
Bibliography
