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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Photochemical dimerization of wasalexins in UV-irradiated Thellungiella halophila and in vitro generates unique cruciferous phytoalexins.
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.
PAL is also known to be involved in the lignification process and as a key enzyme in phenylpropanoid biosynthetic pathway, which is the gateway to many plant secondary metabolites such as flavonoids pigments, furanocoumarin, isoflavonoid, phytoalexin, wound protectant hydroxycinnamic acid esters and aromatic compound in the plant defense system (Dixon et al.
They would offer the consumer health-enhanced food choices and would also open new applications for many underutilized crops that produce phytoalexins.
Twenty years ago, a remarkable group of naturally occurring compounds known as phytoalexins was discovered.
Tomato is rich in phenolic compounds (flavonoids, flavones, cinnamic acid derivatives), phytoalexins, protease inhibitors, glycoalkaloids, and carotenoids, but especially in lycopene and [beta]-carotene.
He discovered phytoalexins, compounds produced by plants upon infection that resist the infecting organism, in his studies of black spot disease on canola and coffee trees.
Phytoalexins, which are phenolic phytochemicals found in legumes, have antimicrobial activity.
So, what kind of phytoalexins have evolved to combat this situation?
Glyceollins are a novel class of soybean phytoalexins with potential cancer-protective antiestrogenic benefits.