Conjugation of Allelochemicals by Plants Enzymatic Glucosylation of Salicylic Acid by Avena sativa

Plants have the ability to conjugate endogenous compounds to most allelochemicals absorbed from the environment. Conjugation reactions are thought to be important for detoxication of secondary products such as allelochemicals because conjugation increases the water solubility and decreases the chemical reactivity of the parent compound. Glucosylation, conjugation with glucose, is one of the most common conjugation reactions in plants. Numerous glucosyltransferase enzymes have been extracted from plants. Uridine diphosphate glucose (UDPG) is the preferred glucose donor for these enzymes. The range of secondary products a particular glucosyltransferase can conjugate has not been determined nor has the ability of allelochemicals to induce different glucosyltransferases in plants. Roots of Avena sativa conjugated glucose to salicylic acid, a phenolic" acid, when the allelochemical was present in solution bathing the tissue. The tissue's capacity to conjugate salicylic acid increased with time suggesting induction of glucosyltransferase activity in the tissue. A glucosyltransferase that transfers glucose from UDPG to the phenolic hydroxyl of salicylic acid was purified about 54-fold.