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

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s and

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent. Structures that do not open in this way are called indehiscent, and rely on other mechanisms such as decay, digestion by herbivores, or predation to release the contents. 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 Anthesis is the period during which a flower is fully open and functional. It may also refer to the onset of that period. The onset of anthesis is spectacular in some species. In ''Banksia'' species, for example, anthesis involves the extension ...

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 Abscission () is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a ...

. The lost structures are said to be

caducous Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that op ...

Association with crop breeding

Manipulation of dehiscence can improve crop yield since a trait that causes seed dispersal is a disadvantage for farmers, whose goal is to collect the seed. Many agronomically important plants have been bred for reduced shattering.

Mechanisms

Explosive dehiscence

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 ''Impatiens'' is a genus of more than 1,000 species of flowering plants, widely distributed throughout the Northern Hemisphere and the tropics. Together with the genus ''Hydrocera'' (one species), ''Impatiens'' make up the family (biology), f ...

'', 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 ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...

''.

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. File:Rhododendron tomentosum 004.JPG, Septicidal dehiscence. The septa between the locules of '' Ledum palustre'' capsules split as the fruit opens, and the seeds are released. File:Crepe myrtle 1.jpg, Loculicidal dehiscence. The locules of '' Lagerstroemia'' capsules split as the fruit opens, and the septa remain intact. File:Peganum harmala Baikonur 09.jpg, Loculicidal dehiscence in ''

Peganum harmala ''Peganum harmala'', commonly called wild rue, Syrian rue, African rue, esfand or espand,Mahmoud OmidsalaEsfand: a common weed found in Persia, Central Asia, and the adjacent areasEncyclopædia Iranica Vol. VIII, Fasc. 6, pp. 583–584. Origina ...

'' File:Hibiscus trionum 3.jpg, A complex form of dehiscence. The calyx of ''

Hibiscus trionum ''Hibiscus trionum'', commonly called flower-of-an-hour, bladder hibiscus, bladder ketmia, bladder weed, puarangi and venice mallow, is an annual plant native to the Old World tropics and subtropics. It has spread throughout southern Europe bot ...

'' 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. File:Anther morphology dehiscence transverse.png, Transverse dehiscence of a pair of anthers File:Anther morphology dehiscence longitudinal.png, Longitudinal dehiscence of a pair of anthers File:Anther morphology dehiscence valvular.png, Valvular dehiscence of a pair of anthers File:Anther morphology dehiscence poricidal.png, 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 dehiscence or operculate dehiscence) that is referred to as an operculum or it may not (inoperculate poricidal dehiscence or inoperculate dehiscence). Poricidal dehiscence occurs in many unrelated organisms, in fruit, causing the release of seeds, and also in the

of many organisms (flowering plants, ferns, fungi,

slime molds Slime mold or slime mould is an informal name given to a polyphyly, polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are near-microscopic; those in the Myx ...

). Poricidal

s of various flowers are associated with

buzz pollination Buzz pollination or sonication is a technique used by some bees, such as solitary bees and bumblebees, to release pollen which is more or less firmly held by the anthers. The anthers of buzz-pollinated plant species are typically tubular, with an ...

by insects.

Circumscissile dehiscence

Circumscissile dehiscence involves a horizontal opening that causes a lid to separate completely. This type of dehiscence occurs in some fruit and anthers 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

locule A locule (: locules) or loculus (; : loculi) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usually refers to a chamber within an ovary ...

s of each

theca In biology, a theca (: thecae) is a sheath or a covering. Botany In botany, the theca is related to plant's flower anatomy. The theca of an angiosperm consists of a pair of microsporangia that are adjacent to each other and share a common ar ...

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

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

cells is part of a developmentally timed cell-death program. Expansion of the endothecial layer and subsequent drying are also required for dehiscence. The endothecium tissue is responsible for the tensions that lead to splitting of the anther. This tissue is usually one to several layers thick, with cells walls of uneven thickness due to uneven

lignification Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

. The cells lose water, and the uneven thickness causes the thinner walls of the cells to stretch to a greater extent. This creates a tension that eventually leads to the anther being split along its line of weakness and releasing pollen grains to the atmosphere. image:Milk Pea dehiscence.jpg, Before/During images of anther dehiscence in the common Milk Pea image:Solanum anther-terminal-pores.jpg, Poricidal anther dehiscence image:Anther dehiscence in Lilium.jpg, Longitudinal latrorse anther dehiscence

Flower buds

Flower buds of ''

Eucalyptus ''Eucalyptus'' () is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of ''Eucalyptus'' are trees, often Mallee (habit), mallees, and a few are shrubs. Along with several other genera in the tribe Eucalyp ...

'' and related genera open with circumscissile dehiscence. A small cap separates from the remainder of the bud along a circular horizontal zone. image:Eucalyptus ficifolia dehiscent flower bud.jpg, ''

Corymbia ficifolia ''Corymbia ficifolia'', commonly known as red flowering gum, is a species of small tree that is Endemism, endemic to the South West (Western Australia), south-west of Western Australia. It has rough, fibrous bark on the trunk and branches, eg ...

'' image:Eucalyptus_globulus_-_Köhler–s_Medizinal-Pflanzen-147.jpg, ''

Eucalyptus globulus ''Eucalyptus globulus'', commonly known as southern blue gum or blue gum, is a species of flowering plant in the family Myrtaceae. It is a tall, evergreen tree Endemism, endemic to southeastern Australia. This ''Eucalyptus'' species has most ...

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

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

. Dehiscent fruits that are derived from one

carpel Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more ...

are follicles or

legume Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...

s, and those derived from multiple carpels are capsules or

silique A silique or siliqua (plural ''siliques'' or ''siliquae'') is a type of fruit (seed capsule) having two fused carpels with the length being more than three times the width. When the length is less than three times the width of the dried fruit ...

s.Esau, K. 1977. ''Anatomy of seed plants''. John Wiley and Sons, New York. One example of a dehiscent fruit is the

. This fruit develops from a

gynoecium Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl (botany), whorl of a flower; it consists ...

composed of two fused

s, which, upon fertilization, grow to become a silique that contains the developing

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s. After seed maturation, dehiscence takes place, and valves detach from the central

, thus freeing the seeds. This is also known as shattering and can be important as a

seed dispersal In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

mechanism. This process is similar to anther dehiscence and the region that breaks (dehiscence zone) runs the entire length of the fruit between the valves (the outer walls of the ovary) and the replum (the persisting septa of the ovary). At maturity, the dehiscence zone is effectively a non-lignified layer between two regions of lignified cells in the valve and the replum. Shattering occurs due to the combination of cell wall loosening in the dehiscence zone and the tensions established by the differential hygro-responsive properties of the drying cells. image:Pavot.JPG,

Poppy A poppy is a flowering plant in the subfamily Papaveroideae of the family Papaveraceae. Poppies are herbaceous plants, often grown for their colourful flowers. One species of poppy, '' Papaver somniferum'', is the source of the narcotic drug ...

fruit showing poricidal dehiscence; the seeds exit through pores beneath the "crown" image:Peanut 9417.jpg,

Peanut The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...

s: an indehiscent subterranean

fruit image:Thlaspi arvense ENBLA05.jpg, '' Thlaspi arvense'', with fruit that are dehiscent siliques image:Illustration Ledum palustre0.jpg, ''

Rhododendron ''Rhododendron'' (; : ''rhododendra'') is a very large genus of about 1,024 species of woody plants in the Ericaceae, heath family (Ericaceae). They can be either evergreen or deciduous. Most species are native to eastern Asia and the Himalayan ...

'' capsules have septicidal dehiscence; the fruit splits through the septa between the carpels image:Starr 071024-0245 Unknown iridaceae.jpg,

Iridaceae Iridaceae () is a family of plants in order Asparagales, taking its name from the Iris (plant), irises. It has a nearly global distribution, with 69 accepted genera with a total of about 2500 species. It includes a number of economically importan ...

capsules have loculicidal dehiscence; the fruit splits through the ovary wall of each carpel, allowing the seeds to exit directly from the

image:Anagallis spp Sturm60.jpg, ''

Anagallis ''Anagallis'' is a formerly recognized genus of flowering plants in the family (biology), family Primulaceae. It had about 20–25 species, commonly called pimpernels. Molecular phylogenetics, Molecular phylogenetic studies showed that ''Anagal ...

'' fruits open with circumscissile dehiscence. A small cap separates from the remainder of the fruit along a circular horizontal zone. image:Lysimachia arvensis pyxis.jpg, ''Anagallis'' fruit, circumscissile dehiscence image:Spathoglottis plicata (Philippine ground orchid) capsule dehisced.jpg, '' Spathoglottis plicata'' capsules, like in most

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...

s, split longitudinally along three to six slits while remaining closed at both ends

Sporangium dehiscence in bryophytes

Endothecium tissue found in

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

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

Sporangium dehiscence in ferns

Many

leptosporangiate ferns The Polypodiidae, commonly called leptosporangiate ferns, formerly Leptosporangiatae, are one of four subclasses of ferns, the largest of these being the largest group of living ferns, including some 11,000 species worldwide. The group has also ...

have an annulus around the sporangium, which ejects the spores.

Eusporangiate fern Eusporangiate ferns are vascular spore plants, whose sporangia arise from several epidermal cells and not from a single cell as in leptosporangiate ferns. Typically these ferns have reduced root systems and sporangia that produce large amounts ...

s do not generally have specialized dehiscence mechanisms. image:Botrychium lunaria-matricariae nf.jpg, Sporangium dehiscence through a horizontal slit in ''Botrychium'', a eusporangiate fern.

Sporangium dehiscence in fungi and myxomycetes

image:Haeckel Mycetozoa.jpg, Various sporangia of myxomycetes that dehisce in varied ways

References

Bibliography

External links

* * {{cite web , title=Anther dehiscence , url=https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dehiscence , access-date=25 March 2024 Fruit morphology Plant physiology Plant morphology