Thigmonasty or seismonasty is the nastic response of a

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

fungus A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

to touch or vibration. Conspicuous examples of thigmonasty include many species in the leguminous subfamily

Mimosoideae The Mimosoideae are a traditional subfamily of trees, herbs, lianas, and shrubs in the pea family (Fabaceae) that mostly grow in tropical and subtropical climates. They are typically characterized by having radially symmetric flowers, with petals ...

, active

carnivorous plant Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants still generate some of their energy from photosynthesis. Ca ...

s such as Dionaea and a wide range of pollination mechanisms.

Distinctive aspects

Thigmonasty differs from thigmotropism in that nastic motion is independent of the direction of the stimulus. For example, tendrils from a climbing plant are thigmotropic because they twine around any support they touch, responding in whichever direction the stimulus came from. However, the shutting of a venus fly trap is thigmonastic; no matter what the direction of the stimulus, the trap simply shuts (and later possibly opens). The time scales of thigmonastic responses tend to be shorter than those of thigmotropic movements because many examples of thigmonasty depend on pre-accumulated

turgor Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibriu ...

or on bistable mechanisms rather than growth or cell division. Certain dramatic examples of rapid plant movement such as the sudden drooping of '' Mimosa pudica'' or the trapping action of ''Dionaea'' or ''

Utricularia ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, Br ...

'' are fast enough to observe without time lapse photography; some take less than a second. Speed is no clear distinction however; for example the re-erection of ''

Mimosa ''Mimosa'' is a genus of about 590 species of herbs and shrubs, in the mimosoid clade of the legume family Fabaceae. The generic name is derived from the Greek word (''mimos''), an "actor" or "mime", and the feminine suffix -''osa'', "resemb ...

'' leaves is nastic, but typically takes some 15 to 30 minutes, rather than a second or so. Similarly, re-opening of the ''Dionaea'' trap, though also nastic, typically takes days to complete. Botanical physiologists have discovered signalling

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

s called turgorins, that help mediate the loss of turgor. In species with the fastest response time, vacuoles are believed to provide temporary, high speed storage for calcium ions.

Examples of plants exhibiting thigmonasty

In the Asteraceae

Thigmonasty other than leaf closure occurs in various species of

thistle Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves ...

s. When an insect lands on a flower, the anthers shrink and rebound, loading the insect with pollen. The effect results from turgor changes in specialized, highly elastic cell walls of the anthers. Similar pollination strategy occurs in ''

Rudbeckia hirta ''Rudbeckia hirta'', commonly called black-eyed Susan, is a North American flowering plant in the family Asteraceae, native to Eastern and Central North America and naturalized in the Western part of the continent as well as in China. It has now b ...

''.

In the Droseraceae

The

Venus Flytrap The Venus flytrap (''Dionaea muscipula'') is a carnivorous plant native to subtropical wetlands on the East Coast of the United States in North Carolina and South Carolina. It catches its prey—chiefly insects and arachnids—with a trapping ...

(''Dionaea muscipula'') presents a spectacular example of thigmonasty; when an insect lands on a trap formed by two curved lobes of a single leaf, the trap rapidly switches from an open to a closed configuration. Investigators have observed an

action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...

and changes in leaf

that accompany the

reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...

; they trigger the rapid elongation of individual cells. The common term for the elongation is acid growth although the process does not involve

cell division Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there ar ...

. The sundews (genus ''Drosera'') are all capable of moving their glandular tentacles toward the center of a leaf in response to a prey item landing on it. How rapid the movement occurs varies by species.

In the Fabaceae

''Mimosa pudica'' is a plant with compound leaves that droop abruptly when stimulated. This is a classic example of thigmonastic action and has attracted detailed investigation. Contact or injury that causes leaflets to deform, will trigger an action potential. The action potential travels through the plant, initiating drooping of the leaflets as it passes. However, it does not pass the

pulvinus A pulvinus (pl. ''pulvini'') is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvini are common, for example, in members of the bean family Fabaceae (Leguminosae) and the prayer plan ...

at the base of a petiole, and so a local disturbance will not cause all the leaves on the plant to collapse. The

is a motor structure consisting of a rod of sclerenchyma surrounded by collenchyma. Such pulvini occur widely in the Fabaceae. In its extended position, the cells of the entire collar of collenchyma are distended with water. On receiving the action potential signal, the cells in the lower half of the pulvinus respond by expelling

potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosp ...

and

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...

ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

and taking up of

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

ions. This results in an osmotic gradient that draws water out of the affected cells, so that they temporarily shrink. This pulls the entire structure downward like a folding fan. Many other Fabaceae react to touch with the same rapid leaf closure motion. The pea vine thigmonastically closes its leaves around a support.

Catclaw Brier ''Mimosa nuttallii'', the Nuttall's sensitive-briar, catclaw brier, or sensitive brier, is an herbaceous perennial legume in the subfamily Mimosoideae native to the central United States. It has a trailing semi-woody vine covered with small recu ...

, a prairie mimosa, native to North America, shuts its leaves on contact. The plant is attractive to

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...

s, and this behavior presumably provides protection against grazing.

In the Loasaceae

Members of the subfamily

Loasoideae Loasaceae is a family of 15–20 genera and about 200–260 species of flowering plants in the order Cornales, native to the Americas and Africa. Members of the family include annual, biennial and perennial herbaceous plants, and a few shrubs an ...

exhibit rapid

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

movement when pollinators are present. In order to obtain nectar, specialized floral components known as nectar scales must be manipulated by the pollinator. This action causes the stamens to move between 90 and 120 degrees toward the center of the flower within 1-2 minutes. When there is a lack of pollinators the stamen movement is slower and dependent upon ambient light and temperature. The plants are capable of extending their staminate and carpellate phases to ensure

self-pollination Self-pollination is a form of pollination in which pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen is transferred t ...

In the Oxalidaceae

Sensitive leaves also occur in plants of the wood sorrel family. Examples include many species of ''

Oxalis ''Oxalis'' ( (American English) or (British English)) is a large genus of flowering plants in the wood-sorrel family Oxalidaceae, comprising over 550 species. The genus occurs throughout most of the world, except for the polar areas; species d ...

'', '' Biophytum sensitivum'', and Averrhoa carambola (the plant which produces

starfruit Carambola, also known as star fruit, is the fruit of ''Averrhoa carambola'', a species of tree native to tropical Southeast Asia. The mildly poisonous fruit is commonly consumed in parts of Brazil, Southeast Asia, South Asia, the South Pacif ...

Other forms

Some

fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

exhibit trap closure similar to the venus fly trap. Mycologists have discovered action potentials in fungi but it is not currently clear whether they have any significance to thigmonastic behavior.

References

External links

Two videos showing severe thigmonasty in mimosa plantsPulvinus-actuated leaf movementsThigmonastic Movement
* {{Tropism Plant physiology Plant cognition