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Thigmotropism

January 01, 1970

In plant biology, thigmotropism is a directional growth movement which occurs as a mechanosensory response to a touch stimulus. Thigmotropism is typically found in twining plants and tendrils, however plant biologists have also found thigmotropic responses in flowering plants and fungi. This behavior occurs due to unilateral growth inhibition.[1] That is, the growth rate on the side of the stem which is being touched is slower than on the side opposite the touch. The resultant growth pattern is to attach and sometimes curl around the object which is touching the plant. However, flowering plants have also been observed to move or grow their sex organs toward a pollinator that lands on the flower, as in Portulaca grandiflora.[2]

Redvine (Brunnichia ovata) tendrils coil upon contact.

Physiological factors edit

Since growth is a complex developmental procedure, there are indeed many requirements (both biotic and abiotic) that are needed for both touch perception and a thigmotropic response to occur. One of these is calcium. In a series of experiments in 1995 using the tendril Bryonia dioica, touch-sensing calcium channels were blocked using various antagonists. Responses to touch in treatment plants which received calcium channel inhibitors were diminished compared to control plants, indicating that calcium may be required for thigmotropism. Later in 2001, a membrane depolarization pathway was proposed in which calcium was involved: when a touch occurs, calcium channels open and calcium flows into the cell, shifting the electrochemical potential across the membrane. This triggers voltage-gated chloride and potassium channels to open and leads to an action potential that signals the perception of touch.[3]

The plant growth hormone auxin has also been observed to be involved in thigmotropic behavior in plants, but its role is not well understood. Instead of asymmetric auxin distribution influencing other tropisms, it has been shown that a unidirectional thigmotropic response can occur even with a symmetric distribution of auxin. It has been proposed that the action potential arising from a touch stimulus leads to an increase of auxin in the cell, which causes the production of an contractile protein on the side of the touch that allows the plant to grip onto an object.[4] Further, it has been shown that when auxin (typically leading to growth away from the side of its localization) and a touch stimulus (causing a tropic response toward its localization) were applied on the same side of a cucumber hypocotyl, the stem will curve towards the touch.[5]

Ethylene, another plant hormone, has also been shown to be an important regulator to the thigmotropic response in Arabidopsis thaliana roots. Under normal circumstances, high ethylene concentrations in the roots promote straight growth. When the root encounters a rigid object, the thigmotropic response is activated and ethylene production is down-regulated, leading to the root to bend while growing rather than growing straight.[6]

Like phototropism, a thigmotropic response in stems requires light. Plant biologist Mark Jaffe performed a simple preliminary experiment using pea plants that led to this conclusion.[7] He found that when he snipped a tendril off of a pea plant and placed it in the light, then repeatedly touched one side of it, the tendril would begin to curl. However, when performing this same experiment in the dark, the tendril would not curl.

In roots edit

Roots also rely on touch to navigate their way through the soil. Generally, roots have a negative touch response, meaning when they feel an object, they would grow away from the object. This allows the roots to go through the soil with minimum resistance. Because of this behavior, roots are said to be negatively thigmotropic. Research suggests that this active obstacle avoidance by roots is driven by polar auxin transport.[8] Thigmotropism seems to be able to override the strong gravitropic response of even primary roots. Charles Darwin performed experiments where he found that in a vertical bean root, a contact stimulus could divert the root away from the vertical.

Misconception edit

Mimosa pudica is well known for its rapid plant movement. The leaves close up and droop when touched. However, this is not a form of tropism, but a nastic movement, a similar phenomenon. Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are usually associated with plants.

References edit

  1. ^ Mordecai, Jaffe (March 2002). "Thigmo Responses in Plants and Fungi". American Journal of Botany. 89 (3): 375–382. doi:10.3732/ajb.89.3.375. PMID 21665632. S2CID 7410822.
  2. ^ Scorza, Livia Camilla Trevisan; Dornelas, Marcelo Carnier (2011-12-01). "Plants on the move". Plant Signaling & Behavior. 6 (12): 1979–1986. doi:10.4161/psb.6.12.18192. ISSN 1559-2316. PMC 3337191. PMID 22231201.
  3. ^ Fasano, Jeremiah M.; Massa, Gioia D.; Gilroy, Simon (2002-06-01). "Ionic Signaling in Plant Responses to Gravity and Touch". Journal of Plant Growth Regulation. 21 (2): 71–88. doi:10.1007/s003440010049. ISSN 0721-7595. PMID 12016507. S2CID 21503292.
  4. ^ Reinhold, Leonora (1967-11-10). "Induction of Coiling in Tendrils by Auxin and Carbon Dioxide". Science. 158 (3802): 791–793. Bibcode:1967Sci...158..791R. doi:10.1126/science.158.3802.791. ISSN 0036-8075. PMID 6048120. S2CID 22274215.
  5. ^ Takahashi, Hideyuki; Jaffe, Mordecai J. (1990-12-01). "Thigmotropism and the modulation of tropistic curvature by mechanical perturbation in cucumber hypocotyls". Physiologia Plantarum. 80 (4): 561–567. doi:10.1111/j.1399-3054.1990.tb05679.x. ISSN 1399-3054.
  6. ^ Yamamoto, Chigusa; Sakata, Yoichi; Taji, Teruaki; Baba, Tadashi; Tanaka, Shigeo (2008-07-18). "Unique ethylene-regulated touch responses of Arabidopsis thaliana roots to physical hardness". Journal of Plant Research. 121 (5): 509–519. doi:10.1007/s10265-008-0178-4. ISSN 1618-0860. PMID 18636310. S2CID 19467930.
  7. ^ Chamovitz, Daniel (2012). What a Plant Knows: A Field Guide to the Senses. New York: Scientific American. p. 114.
  8. ^ Lee, Hyo‐Jun; Kim, Hyun‐Soon; Park, Jeong Mee; Cho, Hye Sun; Jeon, Jae Heung (2019-08-16). "PIN-mediated polar auxin transport facilitates root−obstacle avoidance". New Phytologist. 225 (3): 1285–1296. doi:10.1111/nph.16076. ISSN 0028-646X. PMID 31336402.

External links edit

  • Thigmotropism in Tendrils

January 01, 1970
thigmotropism, plant, biology, thigmotropism, directional, growth, movement, which, occurs, mechanosensory, response, touch, stimulus, typically, found, twining, plants, tendrils, however, plant, biologists, have, also, found, thigmotropic, responses, flowerin. In plant biology thigmotropism is a directional growth movement which occurs as a mechanosensory response to a touch stimulus Thigmotropism is typically found in twining plants and tendrils however plant biologists have also found thigmotropic responses in flowering plants and fungi This behavior occurs due to unilateral growth inhibition 1 That is the growth rate on the side of the stem which is being touched is slower than on the side opposite the touch The resultant growth pattern is to attach and sometimes curl around the object which is touching the plant However flowering plants have also been observed to move or grow their sex organs toward a pollinator that lands on the flower as in Portulaca grandiflora 2 Redvine Brunnichia ovata tendrils coil upon contact Contents 1 Physiological factors 2 In roots 3 Misconception 4 References 5 External linksPhysiological factors editSince growth is a complex developmental procedure there are indeed many requirements both biotic and abiotic that are needed for both touch perception and a thigmotropic response to occur One of these is calcium In a series of experiments in 1995 using the tendril Bryonia dioica touch sensing calcium channels were blocked using various antagonists Responses to touch in treatment plants which received calcium channel inhibitors were diminished compared to control plants indicating that calcium may be required for thigmotropism Later in 2001 a membrane depolarization pathway was proposed in which calcium was involved when a touch occurs calcium channels open and calcium flows into the cell shifting the electrochemical potential across the membrane This triggers voltage gated chloride and potassium channels to open and leads to an action potential that signals the perception of touch 3 The plant growth hormone auxin has also been observed to be involved in thigmotropic behavior in plants but its role is not well understood Instead of asymmetric auxin distribution influencing other tropisms it has been shown that a unidirectional thigmotropic response can occur even with a symmetric distribution of auxin It has been proposed that the action potential arising from a touch stimulus leads to an increase of auxin in the cell which causes the production of an contractile protein on the side of the touch that allows the plant to grip onto an object 4 Further it has been shown that when auxin typically leading to growth away from the side of its localization and a touch stimulus causing a tropic response toward its localization were applied on the same side of a cucumber hypocotyl the stem will curve towards the touch 5 Ethylene another plant hormone has also been shown to be an important regulator to the thigmotropic response in Arabidopsis thaliana roots Under normal circumstances high ethylene concentrations in the roots promote straight growth When the root encounters a rigid object the thigmotropic response is activated and ethylene production is down regulated leading to the root to bend while growing rather than growing straight 6 Like phototropism a thigmotropic response in stems requires light Plant biologist Mark Jaffe performed a simple preliminary experiment using pea plants that led to this conclusion 7 He found that when he snipped a tendril off of a pea plant and placed it in the light then repeatedly touched one side of it the tendril would begin to curl However when performing this same experiment in the dark the tendril would not curl In roots editRoots also rely on touch to navigate their way through the soil Generally roots have a negative touch response meaning when they feel an object they would grow away from the object This allows the roots to go through the soil with minimum resistance Because of this behavior roots are said to be negatively thigmotropic Research suggests that this active obstacle avoidance by roots is driven by polar auxin transport 8 Thigmotropism seems to be able to override the strong gravitropic response of even primary roots Charles Darwin performed experiments where he found that in a vertical bean root a contact stimulus could divert the root away from the vertical Misconception editMimosa pudica is well known for its rapid plant movement The leaves close up and droop when touched However this is not a form of tropism but a nastic movement a similar phenomenon Nastic movements are non directional responses to stimuli e g temperature humidity light irradiance and are usually associated with plants References edit Mordecai Jaffe March 2002 Thigmo Responses in Plants and Fungi American Journal of Botany 89 3 375 382 doi 10 3732 ajb 89 3 375 PMID 21665632 S2CID 7410822 Scorza Livia Camilla Trevisan Dornelas Marcelo Carnier 2011 12 01 Plants on the move Plant Signaling amp Behavior 6 12 1979 1986 doi 10 4161 psb 6 12 18192 ISSN 1559 2316 PMC 3337191 PMID 22231201 Fasano Jeremiah M Massa Gioia D Gilroy Simon 2002 06 01 Ionic Signaling in Plant Responses to Gravity and Touch Journal of Plant Growth Regulation 21 2 71 88 doi 10 1007 s003440010049 ISSN 0721 7595 PMID 12016507 S2CID 21503292 Reinhold Leonora 1967 11 10 Induction of Coiling in Tendrils by Auxin and Carbon Dioxide Science 158 3802 791 793 Bibcode 1967Sci 158 791R doi 10 1126 science 158 3802 791 ISSN 0036 8075 PMID 6048120 S2CID 22274215 Takahashi Hideyuki Jaffe Mordecai J 1990 12 01 Thigmotropism and the modulation of tropistic curvature by mechanical perturbation in cucumber hypocotyls Physiologia Plantarum 80 4 561 567 doi 10 1111 j 1399 3054 1990 tb05679 x ISSN 1399 3054 Yamamoto Chigusa Sakata Yoichi Taji Teruaki Baba Tadashi Tanaka Shigeo 2008 07 18 Unique ethylene regulated touch responses of Arabidopsis thaliana roots to physical hardness Journal of Plant Research 121 5 509 519 doi 10 1007 s10265 008 0178 4 ISSN 1618 0860 PMID 18636310 S2CID 19467930 Chamovitz Daniel 2012 What a Plant Knows A Field Guide to the Senses New York Scientific American p 114 Lee Hyo Jun Kim Hyun Soon Park Jeong Mee Cho Hye Sun Jeon Jae Heung 2019 08 16 PIN mediated polar auxin transport facilitates root obstacle avoidance New Phytologist 225 3 1285 1296 doi 10 1111 nph 16076 ISSN 0028 646X PMID 31336402 External links editThigmotropism in Tendrils Retrieved from https en wikipedia org w index php title Thigmotropism amp oldid 1184539252, wikipedia, wiki, book, books, library,

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