What do you mean by phytoalexin?
A phytoalexin is a compound which inhibits the developmentof the fungus in hypersensitive tissues and is formed or activated only when the host plants come in contact withthe parasite.
What is the function of Phytoalexin?
Function. Phytoalexins are produced in plants to act as toxins to the attacking organism. They may puncture the cell wall, delay maturation, disrupt metabolism or prevent reproduction of the pathogen in question.
Is Phytoalexin a phenolic compound?
Phytoalexins are inducible secondary metabolites possessing antimicrobial activity against phytopathogens. Until very recently, flavonoid sakuranetin was the only known phenolic phytoalexin in rice. However, recent studies have shown that phenylamides are involved in defense against pathogen attacks in rice.
What is phytoalexin in plant pathology?
Phytoalexins are low molecular weight antimicrobial compounds that are produced by plants as a response to biotic and abiotic stresses. As such they take part in an intricate defense system which enables plants to control invading microorganisms.
What is Phytoalexin in plant pathology?
How are elicitors synthesized?
Role of Elicitors Their production is due to the action of plant hydrolases, released by necrotic plant cells, on the pathogen. The host plant then recognizes the elicitor molecule by means of a plasma membrane receptor, and this results ultimately in the synthesis of antimicrobial compounds by healthy tissue.
What is the phytoalexin response?
The phytoalexin response is not confined to warding off fungal pathogens. While fungal inoculation usually gives the most reproducible results, infections with bacteria, e.g., Pseudomonas syringae, and with viruses, e.g., tobacco mosaic virus, have also resulted in de novo synthesis of phytoalexins.
What are some examples of phytoalexin biosynthesizers?
Gossypol from cotton, casbene from castor bean, and rishitin from plants in the Solanaceae are examples of phytoalexins biosynthesized by the mevalonic acid pathway ( Fig. 13.5 ). There has been extensive study of the accumulation, distribution, enzymology, and molecular biology of phytoalexin synthesis following pathogen attack.
Are phytoalexins harmful to plants?
Most known phytoalexins are toxic to and inhibit the growth of fungi pathogenic to plants, but some are also toxic to bacteria, nematodes, and other organisms. More than 300 chemicals with phytoalexinlike properties have been isolated from plants belonging to more than 30 families.
How many Phytoalexins are there in the world?
Hundreds of phytoalexins have been characterized. They are especially widespread in the Fabaceae (Leguminosae) and Solanaceae but are also found in about 15 other families.