Plant perception (physiology)
From The Art and Popular Culture Encyclopedia
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.
Senses in plants
Plants have many strategies to fight off pests. For example, they can produce different toxins (so called phytoalexins) against invaders or they can induce rapid cell death of invaded cells to hinder the pests from spreading out. All these strategies depend on quick and reliable recognition-systems. Research of the last years revealed some amazing abilities of plants in this area. Plants not only can taste the spit of caterpillars, they can also smell, see, "feel" and hear, as Andy Coughlin reported in the New Scientist (26/9.98).
Wounded tomatoes are known to produce the volatile odour methyl jasmonate as an alarm-signal. Plants in the neighbourhood can then smell the danger and prepare for the attack by producing chemicals that defend against insects or attract insectivorous predators. And according to New Scientist: "Methyl jasmonate is often used in perfumes and this created problems for the researchers." "We had to warn the women not to use it in the greenhouse because it would mess up the experiment", said Bud Ryan (Washington State University).
Light and Electromagnetic waves
Many plant-organs contain photosensitive compounds, 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. More recently, researchers discovered that plants also can detect harmful ultraviolet B-rays and then start producing pigments which filter out these rays. "Plants make their own suntan cream in the presence of UVB", says Gareth Jenkins (University of Glasgow).
Many of us are familiar with the mimosa plant (Mimosa pudica); it 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. But a sense of touch is something every plant has, as Coughlin describes: "Ordinary plants need a sense of touch to respond to the buffeting of the wind, which can cause damage to foliage. They try to resist wind by strengthening tissues that are being swayed. The extra energy expended stiffening tissue can cost farmers dear, however. One experiment showed that when maize plants are shaken for 3 seconds each day, yields drop by 30 to 40% compared with unshaken plants", writes Coughlin (New Scientist).
Mordecai Jaffe (Wake Forest University) used an instrument that made a loud "warble" and got a doubling in the growth of dwarf pea plants. Jaffe suspects that the plant hormone gibberellic acid, which is instrumental in shoot elongation and seed germination, is involved in the "hearing" response. When Jaffe added chemicals to the pea plants inhibiting the biosynthesis of this hormone, he was unable to reproduce the original effects.
- 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 intelligence
- 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
- Plant communication
- Vine tendril reaches out softly, wraps around a wire and then dries and toughens