Dehiscence (botany)

Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among

A similar process to dehiscence occurs in some flower buds (e.g., Platycodon, Fuchsia), but this is rarely referred to as dehiscence unless circumscissile dehiscence is involved; anthesis is the usual term for the opening of flowers. Dehiscence may or may not involve the loss of a structure through the process of abscission. The lost structures are said to be caducous.

Association with crop breeding

Manipulation of dehiscence can improve crop yield since a

Explosive dehiscence is a ballistic form of dispersal that flings seeds or spores far from the parent plant. This rapid plant movement can achieve limited dispersal without the assistance of animals. A notable example is the sandbox tree (Hura crepitans), which can fling seeds 100 meters (300 ft) and has been called the "boomer plant" due to the loud sound it generates. Another example is Impatiens, whose explosive dehiscence is triggered by being touched, leading it to be called the "touch-me-not". Ecballium elaterium, the "squirting cucumber", uses explosive dehiscence to disperse its seeds, ejecting them from matured fruit in a stream of mucilaginous liquid. Explosive dehiscence of sporangia is a characteristic of Sphagnum.^[1]

Septicidal and loculicidal dehiscence

In loculicidal dehiscence, the locule wall splits between the septa, leaving the latter intact, while in septicidal dehiscence the split is at the septum that separates the loculi. Septicidal and loculicidal dehiscence may not be completely distinct; in some cases both the septa and the walls of the locules split.

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  Septicidal dehiscence. The septa between the locules of

  Ledum palustre

  capsules split as the fruit opens, and the seeds are released.
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  Loculicidal dehiscence. The locules of Lagerstroemia capsules split as the fruit opens, and the septa remain intact.
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  Loculicidal dehiscence in Peganum harmala
• 
  A complex form of dehiscence. The calyx of Hibiscus trionum has opened apically to reveal the capsule (ovary) inside. The capsule has split vertically in the centre, as well as through the locule walls.

Types

Dehiscence occurs through breakage of various parts of the enclosing structure; the mechanisms can be classified in various ways, but intermediate forms also occur.

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  Transverse dehiscence of a pair of anthers
• 
  Longitudinal dehiscence of a pair of anthers
• 
  Valvular dehiscence of a pair of anthers
• 
  Poricidal dehiscence of a pair of anthers

Poricidal dehiscence

Dehiscence through a small hole (pore) is referred to as poricidal dehiscence. The pore may have a cover (operculate poricidal dehiscense or operculate dehiscence) that is referred to as an operculum or it may not (inoperculate poricidal dehiscense or inoperculate dehiscence).

Poricidal dehiscence occurs in many unrelated organisms, in fruit, causing the release of seeds, and also in the

Circumscissile dehiscence involves a horizontal opening that causes a lid to separate completely. This type of dehiscence occurs in some fruit and anthers[2] and also in some flower buds.

Anther dehiscence

Anther dehiscence is the final function of the anther that causes the release of pollen grains. This process is coordinated precisely with pollen differentiation, floral development, and flower opening.

The anther wall breaks at a specific site. Usually this site is observed as an indentation between the locules of each theca and runs the length of the anther, but in species with poricidal anther dehiscence it is instead a small pore. If the pollen is released from the anther through a split on the outer side (relative to the center of the flower), this is extrorse dehiscence, and if the pollen is released from the inner side, this is introrse dehiscence. If the pollen is released through a split that is positioned to the side, towards other anthers, rather than towards the inside or outside of the flower, this is latrorse dehiscence.

The stomium is the region of the anther where dehiscence occurs. The degeneration of the stomium and

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  Before/During images of anther dehiscence in the common Milk Pea
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  Poricidal anther dehiscence
• 
  Longitudinal latrorse anther dehiscence

Flower buds

Flower buds of Eucalyptus and related genera open with circumscissile dehiscence. A small cap separates from the remainder of the bud along a circular horizontal zone.

• 
  Corymbia ficifolia
• 
  Eucalyptus globulus

Fruit dehiscence

There are many different types of fruit dehiscence involving different types of structures. Some fruits are indehiscent, and do not open to disperse the seeds. Xerochasy is dehiscence that occurs upon drying, and hygrochasy is dehiscence that occurs upon wetting, the fruit being

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  Poppy fruit showing poricidal dehiscence; the seeds exit through pores beneath the "crown"
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  Peanuts: an indehiscent subterranean legume fruit
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  Thlaspi arvense, with fruit that are dehiscent siliques
• 
  Rhododendron capsules have septicidal dehiscence; the fruit splits through the septa between the carpels
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  Iridaceae capsules have loculicidal dehiscence; the fruit splits through the ovary wall of each carpel, allowing the seeds to exit directly from the locule
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  Anagallis fruits open with circumscissile dehiscence. A small cap separates from the remainder of the fruit along a circular horizontal zone.
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  Anagallis fruit, circumscissile dehiscence
• 
  Spathoglottis plicata capsules, like in most orchids, split longitudinally along three to six slits while remaining closed at both ends

Sporangium dehiscence in bryophytes

This section needs expansion. You can help by adding to it. (January 2010)

Endothecium tissue found in moss capsules functions in a similar way in dehiscence to the endothecium in the walls of anthers (see above).

Sporangium dehiscence in ferns

This section needs expansion. You can help by adding to it. (April 2022)

Many

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  Sporangium dehiscence through a horizontal slit in Botrychium, a eusporangiate fern.

Sporangium dehiscence in fungi and myxomycetes

This section needs expansion. You can help by adding to it. (January 2010)

• 
  Various sporangia of myxomycetes that dehisce in varied ways

See also

• Abscission—separation of structures that leads to their loss
• Anthesis—the opening of flowers
• Elaters—structures that form inside a sporangium and aid in spore dispersal of horsetails, liverworts, and hornworts
• Loment—a type of fruit that breaks apart but is not dehiscent
• Schizocarp—a type of fruit that breaks apart and may or may not be dehiscent.

References