Plant perception (physiology)

This article is about The physiology of perception and response in multicellular plants'. For plant emotion especially as applies to the work of Cleve Backster, see Plant perception (paranormal).

Vine tendril. Note how the plant reaches for and purposely wraps around the galvanised wire provided for the purpose. This is a very tough twig and appears to have no other purpose than support for the plant. Nothing else grows from it. It must reach out softly, then wrap around and then dry and toughen. See more at thigmotropism.

In botany, plant perception is the ability of plants to sense the environment and adjust their morphology, physiology and phenotype accordingly. Research draws on the fields of plant physiology, ecology and molecular biology.

The sunflower, a common heliotropic plant which perceives and reacts to sunlight by slow turning movement

Summary

In the study of plant physiology plant perception is a term used to describe mechanisms by which plants recognize changes in the environment. Examples of stimuli which plants perceive and can react to include chemicals, gravity, light, moisture, infections, temperature, oxygen and carbon dioxide concentrations, parasite infestation, physical disruption, and touch. Plants have a variety of means to detect such stimuli and a variety of reaction responses or behaviors.

Plant perception occurs on a cellular level and its concomitant reactive behavior is mediated by phytochromes, kinins, hormones, antibiotic or other chemical release, changes of water and chemical transport, and other means. These responses are generally slow, taking at minimum a number of hours to accomplish, and can best be observed with time-lapse cinematography, but rapid movements can occur as well.

Research published in September 2006 has shown, certainly in the case of Arabidopsis thaliana, the role of cryptochromes in the perception of magnetic fields by plants.

Plants have many strategies to fight off pests. For example, they can produce different toxins (phytoalexins) against invaders or they can induce rapid cell death in invading cells to hinder the pests from spreading out. These strategies depend on quick and reliable recognition-systems.

Signal response

Plants respond to volatile signals produced by other plants.

Alarm signals

Wounded tomatoes are known to produce the volatile odour methyl-jasmonate as an alarm-signal. Plants in the neighbourhood can then detect the chemical and prepare for the attack by producing chemicals that defend against insects or attract predators.

Light

Main articles: Photomorphogenesis and photoperiodism

Many plant-organs contain photo-sensitive compounds (phototropins, cryptochromes and phytochromes) each reacting very specifically to certain wavelengths of light. These light-sensors tell the plant if it's day or night, how long the day is,how much light is available and from where the light comes. Shoots grow towards light and roots usually grow away from light. These responses are called phototropism and skototropism respectively. They are brought about by light sensitive pigments like phototropins and phytochromes and the plant hormone auxin. Many plants exhibit certain phenomena at specific times of the day, for example certain flowers open only in the mornings. Plants keep track of the time of the day with a molecular clock. This internal clock is set to the solar clock every day using sunlight. The internal clock coupled with the ability to perceive light also allows plants to measure the time of the day and so find the season of the year. This is how many plants know when to flower. (see photoperiodism) The seeds of many plants sprout only after they are exposed to light. This response is carried out by phytochrome signalling. Plants are also able to sense the quality of light and respond appropriately, for example in low light conditions plants produce more photosynthetic pigments whereas when the light is very bright and/or if the levels of harmful UV increase, plants produce more of their protective pigments that act as sunscreens.

Contact Stimuli

Main articles: Thigmotropism and Thigmomorphogenesis

The mimosa plant (Mimosa pudica) makes its thin leaves point down at the slightest touch and carnivorous plants such as the Venus flytrap snap shut by the touch of insects.^{[citation needed]}

Mechanical perturbation can also be detected by plants. Jasmonate levels also increase rapidly in response to mechanical perturbations such as tendril coiling.

Poplar stems can detect reorientation and inclination (equilibrioception).

See also

• Auxin - A plant hormone which mediates responses
• Chemotropism - Plant response to chemicals
• Cryptochrome - A light receptor pigment
• Ethylene - A plant hormone which mediates responses
• Gravitropism - Behavior associated with gravitic perception
• Heliotropism - Behavior associated with sunlight perception
• Hormonal sentience - Plant information processing theory
• Hydrotropism - Plant response to moisture
• Hypersensitive response - Local reaction produced in response to infection by microbes
• Kinesis (biology) - Movement
• Nastic movements - A type of rapid response to non-directional stimulus
• Osmosis - A means of water transportation on the cellular level
• Phototropin - A light receptor pigment
• Phototropism - A behavior associated with light perception
• Phytochrome - A light receptor pigment
• Phytosemiotics - Analysis of vegetative processes on the basis of semiotic theory
• Plant defense against herbivory - Some plant responses to physical disruption
• Plant hormone - A mediator of response to stimuli
• Plant physiology - The science of plant function
• Rapid plant movement - Description of rapid plant movements
• Sensory receptors - Discussion of organs of perception in organisms
• Statolith - An organ of gravity perception
• Stoma - A plant pore which responds to stimulus and which regulates gas exchange
• Systemic acquired resistance - A "whole-plant" resistance response to microbial pathogens that occurs following an earlier, localized response
• Taxis - A type of response to a directional stimulus seen in motile developmental stages of lower plants
• Thermotropism - Plant response to heat
• Thigmotropism - Plant response to touch
• Tropism - A type of response to a directional stimulus

External links

• Miller, Deborah; Whitney Hable, Jennifer Gottwald, Mary Ellard-Ivey, Taku Demura, Terri Lomax, Nick Carpita (1997). "Connections: The Hard Wiring of the Plant Cell for Perception, Signaling, and Response". The Plant Cell 9(12). pp. 2105–2117. http://www.plantcell.org/cgi/reprint/9/12/2105. Retrieved 2006-12-25. 

• Keen, Noel T; Shigeyuki Mayama, Jan E. Leach, and Shinji Tsujumu (eds) (2001). Delivery and Perception of Pathogen Signals in Plants. APS Press. p. 268. ISBN 0-89054-259-7. 

• Taiz, Lincoln; Eduardo Zeiger (2006). Plant Physiology, fourth edition. Sinauer Associates. p. 700 (est). ISBN 0-87893-856-7. http://www.sinauer.com/detail.php?id=8567. 

• Taiz, Lincoln; Eduardo Zeiger (2002). "Plant Physiology Online". a companion to Plant Physiology, Third Edition. Sinauer Associates. Archived from the original on 7 December 2006. http://web.archive.org/web/20061207153105/http://3e.plantphys.net/book.php. Retrieved 2006-12-26. 

• Dierk Scheel and Claus Wastermack (May 2002). Plant Signal Transduction. Oxford University Press. p. 346. ISBN 978-0-19-963879-6. http://www.oup.com/us/catalog/general/subject/LifeSciences/Botany/?view=usa&ci=9780199638796. Retrieved 2006-12-25.