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Inbotany, acaryopsis (pl. caryopses) is a type of simplefruit—one that is monocarpellate (formed from a singlecarpel) andindehiscent (not opening at maturity)[1] and resembles anachene, except that in a caryopsis thepericarp is fused with the thinseed coat.
The caryopsis is popularly called agrain and is the fruit typical of the familyPoaceae (or Gramineae), which includeswheat,rice,maize,[2] andoat.[3]
The termgrain is also used in a more general sense as synonymous withcereal (as in "cereal grains", which include some non-Poaceae). Considering that the fruit wall and the seed are intimately fused into a single unit, and the caryopsis or grain is adry fruit, little concern is given to technically separating the termsfruit andseed in these plant structures. In many grains, the "hulls" to be separated before processing are flowerbracts.
The namecaryopsis is derived from the Greek wordskaryon and-opsis (κάρυον andὄψις), meaning 'nut' and 'having the appearance of', respectively. The term was first used byAchille Richard to refer to the dry, monospermic, indehiscent fruit commonly found in grasses.[4]
This definition of fruit for the Gramineae family has persisted to the modern day, but some botanists have challenged the idea that the dry caryopsis is a defining characteristic of the family. The other forms of fruit proposed to be borne by grasses includeachenes,[5]utricles,[5]berries,[6] andnuts.[7] However, others have suggested that these differing fruit structures are representative of caryopsis diversity rather than of entirely different structures.[8] This diverse form of the caryopsis would include the follicle-like form ofCrypsis andEleusine where a free pericarp adjoins the seeds which are extruded when moistened (as in an achene or utricle), the berry-like form found in some bamboo genera includingDinochloa andOlmeca where the pericarp is more thick and fleshy, and the nut-like form found inDendrocalamus andSchizostachyum. By this definition, the caryopsis is truly the only fruit type found in the Gramineae. The types of caryopsis are often distinguished by the terms "modified caryopsis", referring to caryopses with a pericarp not wholly adnate to the seed coat, and "true caryopsis", referring to those with a pericarp totally adherent to the seed coat.[9]
