phytoalexin

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Phytoalexin

Any antibiotic produced by plants in response to microorganisms. Plants use physical and chemical barriers as a first line of defense. When these barriers are breached, however, the plant must actively protect itself by employing a variety of strategies. Plant cell walls are strengthened, and special cell layers are produced to block further penetration of the pathogen. These defenses can permanently stop a pathogen when fully implemented, but the pathogen must be slowed to gain time.

The rapid defenses available to plants include phytoalexin accumulation, which takes a few hours, and the hypersensitive reaction, which can occur in minutes. The hypersensitive reaction is the rapid death of plant cells in the immediate vicinity of the pathogen. Death of these cells is thought to create a toxic environment of released plant components that may in themselves interfere with pathogen growth, but more importantly, damaged cells probably release signals to surrounding cells and trigger a more comprehensive defense effort. Thus, phytoalexin accumulation is just one part of an integrated series of plant responses leading from early detection to eventual neutralization of a potentially lethal invading microorganism.

The tremendous capacity of plants to produce complex chemical compounds is reflected in the structural diversity of phytoalexins. Each plant species produces one or several phytoalexins, and the types of phytoalexins produced are similar in related species. The diversity, complexity, and toxicity of phytoalexins may provide clues about their function. The diversity of phytoalexins may reflect a plant survival strategy. That is, if a plant produces different phytoalexins from its neighbors, it is less likely to be successfully attacked by pathogens adapted to its neighbor's phytoalexins. Diversity and complexity, therefore, may reflect the benefits of using different deterrents from those found in other plants. See Plant pathology

phytoalexin

[′fīd·ȯ·ə′lek·sən]
(biochemistry)
A natural substance that is toxic to fungi and is synthesized by a plant as a response to fungal infection.
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References in periodicals archive ?
onde se lia: "Once they are no pathogenic organisms, their mechanism of action is the induced systemic resistance, not causing symptoms such as necrosis and activating the defense response of plants such as the production of PRPs and phytoalexins.
Effect of glyceollin, a soybean phytoalexin, on feeding by three phytophagous beetles (Coleoptera: Coccinellidae and Chrysomelidae): dose versus response.
Acifluorfen increases the leaf content of phytoalexins and stress metabolites in several crops.
Phytoalexins, such as zealexins and kauralexins, are sure to be part of that story.
Identification of two chromone phytoalexins in the sweet pea, Lathyrus odoratus.
Phenylalanine ammonia lyase enzyme catalyzes the first step in the phenylpropanoid metabolism, which is the conversion of L-phenylalanine to trans-cinnamic acid which leads to the synthesis of defense related compounds including lignins and phytoalexins (Rookes and Cahill, 2003).
Gruenwald noted that newly discovered phytoalexins, which are substances that are produced by "strcssed" plants, could offer significant market po tential.
More recent research into the use of plant phytoalexins as nutritional components has opened up a new area of food science.
Fungi not only produce toxic compounds in the metabolites that directly inhibit growth from other fungi, they also produce some non-toxic compounds (glycoprotein so-called elicitors) that have no direct function on other fungi but can induce trees to produce phytoalexins against invasion from pathogens.
2003) report that sub-doses of glyphosate may facilitate the attack of pathogens due to a reduction in accumulation of phytoalexins and lignin (Levesque and Rahe, 1992) which are both considered physical-physiological barriers of the plant.
Twenty years ago, a remarkable group of naturally occurring compounds known as phytoalexins was discovered.
Usually these phytoalexins are low molecular weight antimicrobial compounds that are synthesized and accumulated in the cells.