Thigmonasty

Source: Wikipedia, the free encyclopedia.
Mimosa pudica in normal and touched state.

In

Dionaea and a wide range of pollination mechanisms.[3]

Distinctive aspects

Thigmonasty differs from

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

Mimosa 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.[4]

Botanical physiologists have discovered signalling molecules called turgorins, that help mediate the loss of turgor.[4] In species with the fastest response time, vacuoles are believed to provide temporary, high speed storage for calcium ions.[4]

Examples of plants exhibiting thigmonasty

In the Asteraceae

Thigmonasty other than leaf closure occurs in various species of thistles. 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.[5]

In the Droseraceae

The

turgor that accompany the reflex; 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.[6]

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. The speed of the movement varies by species.[7]

In the Fabaceae

Pulvinus in extended and contracted position

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

The pulvinus is a motor structure consisting of a rod of

fan
.

Many other Fabaceae react to touch with the same rapid leaf closure motion. The

Catclaw Brier, a prairie mimosa, native to North America, shuts its leaves on contact. The plant is attractive to herbivores, and this behavior presumably provides protection against grazing
.

In the Loasaceae

Members of the subfamily

Loasoideae exhibit rapid stamen 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.[8]

In the Oxalidaceae

Sensitive leaves also occur in plants of the

starfruit
).

Other forms

Some

fungi exhibit trap closure similar to the venus fly trap. Mycologists have discovered action potentials in fungi[9]
but it is not currently clear whether they have any significance to thigmonastic behavior.

See also

References

  1. ISBN 978-81-7141-247-1
    .
  2. ISBN 978-1-60595-043-3
    .
  3. ISBN 978-0-674-05943-6
    .
  4. ^
    ISBN 978-3-540-58016-4
    .
  5. ^ Knowlton Foote (March 2002). "Black-eyed Susan (Rudbeckia hirta L.)" (PDF). NYFA Newsletter. 13 (1). New York Flora Association: 4. Archived from the original (PDF) on December 17, 2008.
  6. ^ Williams, SE (2002). "Comparative physiology of the Droseraceae sensu stricto—How do tentacles bend and traps close?" (PDF). Proceedings of the 4th International Carnivorous Plant Society Conference. Tokyo. pp. 77–81.
  7. ^ Hartmeyer, I.; Hartmeyer, S. (2005). "Drosera glanduligera: Der Sonnentau mit 'Schnapp-Tentakeln'" [Drosera glanduligera: The Sundew with 'Snapping Tentacles']. Das Taublatt (in German) (2): 34–38.
  8. PMID 23603953
    .
  9. PMID 130926
    .

External links
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