Editing Tendril (section)

== Coiling mechanism ==
=== Circumnutation ===
The mechanism of tendril coiling begins with circumnutation of the tendril in which it is moving and growing in a circular oscillatory pattern around its axis.<ref name=":0">{{Cite journal|last=Kiss|first=John Z.|date=2009|title=Plants circling in outer space|journal=New Phytologist|language=en|volume=182|issue=3|pages=555–557|doi=10.1111/j.1469-8137.2009.02817.x|pmid=19422543|issn=1469-8137|doi-access=free|bibcode=2009NewPh.182..555K }}</ref> Circumnutation is often defined as the first main movement of the tendril, and it serves the purpose of increasing the chance that the plant will come in contact with a support system (physical structure for the tendril to coil around).<ref>{{Cite journal|last1=Malabarba|first1=Jaiana|last2=Reichelt|first2=Michael|last3=Pasquali|first3=Giancarlo|last4=Mithöfer|first4=Axel|date=2019-03-01|title=Tendril Coiling in Grapevine: Jasmonates and a New Role for GABA?|url=https://doi.org/10.1007/s00344-018-9807-x|journal=Journal of Plant Growth Regulation|language=en|volume=38|issue=1|pages=39–45|doi=10.1007/s00344-018-9807-x|s2cid=13792885|issn=1435-8107|hdl=21.11116/0000-0001-1BB3-7|hdl-access=free}}</ref> In a 2019 study done by Guerra et al., it was shown that without a support stimulus, in this case a stake in the ground, the tendrils will circumnutate towards a light stimulus. After many attempts to reach a support structure, the tendril will eventually fall to the ground.<ref name=":1">{{Cite journal|last1=Guerra|first1=Silvia|last2=Peressotti|first2=Alessandro|last3=Peressotti|first3=Francesca|last4=Bulgheroni|first4=Maria|last5=Baccinelli|first5=Walter|last6=D’Amico|first6=Enrico|last7=Gómez|first7=Alejandra|last8=Massaccesi|first8=Stefano|last9=Ceccarini|first9=Francesco|last10=Castiello|first10=Umberto|date=2019-11-12|title=Flexible control of movement in plants|journal=Scientific Reports|language=en|volume=9|issue=1|pages=16570|doi=10.1038/s41598-019-53118-0|pmid=31719580|pmc=6851115|bibcode=2019NatSR...916570G|issn=2045-2322}}</ref> However, it was found that when a support stimulus is present, the tendril’s circumnutation oscillation occurs in the direction of the support stimulus. Therefore, it was concluded that tendrils are able to change the direction of their circumnutation based on the presence of a support stimulus.<ref name=":1" /> The process of circumnutation in plants is not unique to tendril plants, as almost all plant species show circumnutation behaviors.<ref name=":0" />

=== Contact coiling ===
[[Thigmotropism]] is the basis of the input signal in the tendril coiling mechanism. For example, pea tendrils have highly sensitive cells in the surfaces of cell walls that are exposed. These sensitized cells are the ones that initiate the thigmotropic signal, typically as a calcium wave.<ref>{{Cite journal|last1=Jaffe|first1=M. J.|last2=Leopold|first2=A. C.|last3=Staples|first3=R. C.|date=2002-03-01|title=Thigmo responses in plants and fungi|journal=American Journal of Botany|language=en|volume=89|issue=3|pages=375–382|doi=10.3732/ajb.89.3.375|pmid=21665632|issn=0002-9122|doi-access=free}}</ref> The primary touch signal induces a signaling cascade of other phytohormones, most notably [[gamma-Aminobutyric acid]] (GABA) and [[Jasmonate]] (JA). In grapevine tendrils, it recently has been shown that GABA can independently promote tendril coiling. It has also been shown that jasmonate phytohormones serve as a hormonal signal to initiate tendril coiling.<ref>{{Cite journal|last1=Malabarba|first1=Jaiana|last2=Reichelt|first2=Michael|last3=Pasquali|first3=Giancarlo|last4=Mithöfer|first4=Axel|date=March 2019|title=Tendril Coiling in Grapevine: Jasmonates and a New Role for GABA?|url=http://link.springer.com/10.1007/s00344-018-9807-x|journal=Journal of Plant Growth Regulation|language=en|volume=38|issue=1|pages=39–45|doi=10.1007/s00344-018-9807-x|s2cid=13792885|issn=0721-7595|hdl=21.11116/0000-0001-1BB3-7|hdl-access=free}}</ref> This cascade can activate [[plasma membrane H+-ATPase]], which also plays a role in the contact coiling mechanism as a proton pump. This pump activity establishes an electrochemical of H+ ions from inside the cell to the [[apoplast]], which in turn creates an osmotic gradient. This leads to loss of turgor pressure; the differences in cell size due to the loss of turgor pressure in some cells creates the coiling response.<ref>{{Cite journal|last1=Jaffe|first1=M. J.|last2=Galston|first2=A. W.|date=1968-04-01|title=Physiological Studies on Pea Tendrils. V. Membrane Changes and Water Movement Associated with Contact Coiling|journal=Plant Physiology|language=en|volume=43|issue=4|pages=537–542|doi=10.1104/pp.43.4.537|issn=0032-0889|pmc=1086884|pmid=16656803}}</ref> This contractile movement is also influenced by gelatinous fibers, which contract and [[Lignin|lignify]] in response to the thigmotropic signal cascade.<ref>{{Cite journal|last1=Bowling|first1=Andrew J.|last2=Vaughn|first2=Kevin C.|date=April 2009|title=Gelatinous fibers are widespread in coiling tendrils and twining vines|journal=American Journal of Botany|language=en|volume=96|issue=4|pages=719–727|doi=10.3732/ajb.0800373|pmid=21628227|doi-access=free}}</ref>

=== Self-discrimination ===
Although tendrils twine around hosts based on [[Thigmotropism|touch perception]], plants have a form of self-discrimination<ref name=":2">{{cite journal |last1=Fukano |first1=Yuya |last2=Yamawo |first2=Akira |title=Self-discrimination in the tendrils of the vine is mediated by physiological connection |journal=Proceedings of the Royal Society B: Biological Sciences |date=26 August 2015 |volume=282 |issue=1814 |pages=20151379 |doi=10.1098/rspb.2015.1379 |pmid=26311669 |pmc=4571702}}</ref> and avoid twining around themselves or neighboring plants of the same species{{snd}}demonstrating [[chemotropism]] based on [[chemoreception]].<ref name=":3">{{cite journal |last1=Fukano |first1=Yuya |title=Vine tendrils use contact chemoreception to avoid conspecific leaves |journal=Proceedings of the Royal Society B: Biological Sciences |date=15 March 2017 |volume=284 |issue=1850 |pages=20162650 |doi=10.1098/rspb.2016.2650 |pmid=28250182 |pmc=5360923}}</ref> Once a tendril comes in contact with a neighboring [[Conspecific|conspecific plant]] (of the same species) signaling molecules released by the host plant bind to chemoreceptors on the climbing plant’s tendrils. This generates a signal that prevents the thigmotropic pathway and therefore prevents the tendril from coiling around that host.<ref name=":2" />

Studies confirming this pathway have been performed on the climbing plant ''[[Cayratia japonica]]''. Research demonstrated that when two ''C. japonica'' plants were placed in physical contact, the tendrils would not coil around the conspecific plant. Researchers tested this interaction by isolating [[oxalate]] crystals from the leaves of a ''C. japonica'' plant and coating a stick with the oxalate crystals. The tendrils of ''C. japonica'' plants that came in physical contact with the oxalate-coated stick would not coil, confirming that climbing plants use chemoreception for self-discrimination.<ref name=":3" />

Self-discrimination may confer an evolutionary advantage for climbing plants to avoid coiling around conspecific plants. This is because neighboring climbing plants do not provide as stable of structures to coil around when compared to more rigid nearby plants. Furthermore, by being able to recognize and avoid coiling around conspecific plants, the plants reduce their proximity to competition, allowing them to have access to more resources and therefore better growth.<ref name=":2" />