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Salicylic acid is a phenolic phytohormone, and is found in plants with roles in plant growth and development, photosynthesis, transpiration, and ion uptake and transport. [53] Salicylic acid is involved in endogenous signaling, mediating plant defense against pathogens . [ 54 ]
Salicylic acid. Salicylic acid (SA) is a hormone with a structure related to benzoic acid and phenol. It was originally isolated from an extract of white willow bark (Salix alba) and is of great interest to human medicine, as it is the precursor of the painkiller aspirin. In plants, SA plays a critical role in the defense against biotrophic ...
Salicin is found in the bark of and leaves of willows, poplars and various other plants. [5] Derivates are found in castoreum.Salicin from meadowsweet was used in the synthesis of aspirin (acetylsalicylic acid), [6] in 1899 by scientists at Bayer.
JA mutants, which lack the gene encoding jasmonic acid, are killed by insect herbivore damage that would otherwise not harm normal-type plants. Upon the application of JA to the same mutants, resistance is restored. [7] Signaling agents such as ethylene, methyl salicylate, and salicylic acid can pair with JA and enhance JA responses. [7]
Infections also stimulate the cross-linking of molecules in the cell wall and the deposition of lignin, responses that set up a local barricade that slows spread of the pathogen to other parts of the plant. [2] Salicylic acid plays a role in the resistance to pathogens by inducing the production of pathogenesis-related proteins. [3]
As mentioned, salicylic acid is the mode of action for the SAR pathway. ISR enhances the defense systems of the plant by jasmonic acid (JA) mode of action. Both act on the effect of the NPR-1, but SAR utilizes PR genes. It is important to note that the two mediated responses have regulatory effects on one another.
Systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen.SAR is analogous to the innate immune system found in animals, and although there are many shared aspects between the two systems, it is thought to be a result of convergent evolution. [1]
At the base of the petiole a pair of stipules form. These may fall in spring, or last for much of the summer or even for more than one year (marcescence).Willows all have abundant watery bark sap, which is heavily charged with salicylic acid, soft, usually pliant, tough wood, slender branches, and large, fibrous, often stoloniferous roots.