PHOSPHITES

STIMULATION OF PHYTOALEXINES

When a pathogen succeeds in invading a host plant, the plant mounts the first of two lines of immune defense, which ultimately results in a chemical attack that isolates the pathogen and prevents its spread from the site of infection. This first line of immune defense, called PAMP- triggered immunity, depends on the plant’s ability to recognize pathogen-associated molecular patterns (PAMPs; formerly called elicitors), molecular sequences that are specific to certain pathogens. The innate immune system is an evolutionarily old defense strategy and is the dominant immune system in plants, fungi, insects, and primitive multicellular organisms. Unlike vertebrates, plants do not have an adaptive immune system: Plants neither generate antibody or T cell responses nor possess mobile cells that detect and attack pathogens.
PAMP recognition in plants leads to a chain of signaling events that lead ultimately to the local production of broad spectrum, antimicrobial chemicals called phytoalexins, which are compounds having fungi-toxic and bacterio-static properties.