The effect of phenolic acids on metabolism and nutrient uptake of roots

During the microbial degradation of lignin and humus phenolic acids are formed. Vanillic, p-hydroxybenzoic and p-coumaric acids occur most frequently in soil while ferulic and protocatechuic acids occur to a lesser extent. Phenolic acids are assimilated by plants and influence plant metabolism. Vanillic and protocatechuic acids inhibit the activity of glucose-6-phosphatedehydrogenase in the excised roots of pea whereas gallic acid stimulates the activity of this enzyme in the roots of whole plants.