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A dehiscent fruit opens naturally as it matures, releasing its seeds. This opening is fruit dehiscence. In an indehiscent fruit, by contrast, the mature enclosing pericarp remains intact during normal release of the fruiting unit. A cypsela carried with its pappus therefore disperses differently from a fruit that opens to free its enclosed seeds.^[ref]

Opening is a regulated part of plant development. In 2000, Sarah J. Liljegren and collaborators compared Arabidopsis thaliana carrying changes in SHATTERPROOF1, SHATTERPROOF2 or both genes. Individual mutants lacked the new opening defect, whereas the double mutant revealed that the two genes could compensate for one another. Mutant and constitutive-expression experiments connected their activity to differentiation of the opening zone and deposition of lignin in adjacent cells.^[ref]

A cracked specimen is not enough to identify a dehiscent fruit: accidental damage can tear an indehiscent fruit. Observe the normal mature structure and its reproducible opening pattern. Fruit dehiscence also differs from germination, which is development of the enclosed seed rather than opening of the fruit around it.

An indehiscent fruit remains closed at maturity instead of splitting open in a regular way to release its seeds. The category describes the opening behaviour of the fruit, rather than the number of seeds or the origin of its floral tissues.^[ref]

An achene and a caryopsis are illuminating examples. Both remain closed, but their internal construction differs: in an achene, the seed is free from the pericarp; in a caryopsis, the pericarp and seed coat are fused. Thus knowing that a fruit is indehiscent does not identify its precise fruit type.^[ref]

Closed does not mean permanently sealed against every later event. A fruit may eventually decay or be broken by an animal. The distinction from a dehiscent fruit concerns its normal opening at maturity, not whether a person can cut it open or its seed can eventually emerge during germination.