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Pyrena

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This article is about fruitstones. For the video game development company, see Pyrena Studios. For the organelle within the chloroplast of some algae and hornworts, see pyrenoid. For other uses of "pyrene", see Pyrene (disambiguation).

Not to be confused with Pirene.

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 () (pl.: pyrenae) or pyrene, commonly called a pit or stone, is the fruitstone inside certain types of fruit, namely drupes or drupelets, and consists of a hardened shell-like layer surrounding one or more seeds (also called the "kernel").[1][2] It is produced by the hardening of the inner lining tissue of the fruit, called the endocarp.[3] This hardened structure provides a protective physical barrier around the seed, shielding it from pathogens and herbivory.[4]

The hardening of the endocarp of a developing drupe occurs via secondary cell wall formation and lignification.[4] 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.[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.[5][6]

Boat Carved from an Olive Stone, at the National Palace Museum. Taiwan

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.[7] In China fruitstones are used in a traditional folk handicraft, namely fruit pit carving (核雕), to make jewellery and sculptures.[8] Shaivite and Buddhist practitioners use the stones of the fruit of Elaeocarpus angustifolius, called rudraksha, as prayer beads for akshamala.[9][10]

  • Cross-section of a peach, a monopyrenous drupe, cut to reveal the pyrene inside

    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

    Pyrene of a peach dissected to reveal a single seed inside

  • Pyrenes extracted from a single fruit of Crataegus punctata, a polypyrenous drupe

    Pyrenes extracted from a single fruit of Crataegus punctata, a polypyrenous drupe

  • X-ray of a pyrene of Elaeocarpus angustifolius revealing 10 seed-bearing locules inside; the number of locules in E. angustifolius pyrenes is variable between individual fruits

    X-ray of a pyrene of Elaeocarpus angustifolius revealing 10 seed-bearing locules inside; the number of locules in E. angustifolius pyrenes is variable between individual fruits

  1. ^ Beentje & Williamson (2010).
  2. ^ Hickey & King (2001).
  3. ^ Eckel (2011).
  4. ^ a b c Dardick & Callahan (2014).
  5. ^ Allué et al. (2015).
  6. ^ Messager et al. (2010).
  7. ^ Bush (1971).
  8. ^ Wang (1999), p. 140.
  9. ^ Jones & Ryan (2006), p. 22.
  10. ^ Beer (1999), pp. 216–217.