THE BIOSYNTHESIS OF SALICYLIC-ACID IN POTATO PLANTS

Spraying potato (Solanum tuberosum L.) leaves with arachidonic acid (A A) at 1500 mu g mL(-1) led to a rapid local synthesis of salicylic aci d (SA) and accumulation of a SA conjugate, which was shown to be 2-O-b eta-glucopyranosylsalicylic acid. Radiolabeling studies with untreated leaves showed that SA was synthesized from phenylalanine and that bot h cinnamic and benzoic acid were intermediates in the biosynthesis pat hway. Using radiolabeled phenylalanine as a precursor, the specific ac tivity of SA was found to be lower when leaves were treated with AA th an in control leaves. Similar results were obtained when leaves were f ed with the labeled putative intermediates cinnamic acid and benzoic a cid. Application of 2-aminoindan-2-phosphonic acid at 40 mu M, an inhi bitor of phenyl-alanine ammonia-lyase, prior to treatment with AA inhi bited the local accumulation of SA. When the putative intermediates we re applied to leaves in the presence of 2-aminoindan-2-phosphonic acid , about 40% of the expected accumulation of free SA was recovered, but the amount of the conjugate remained constant.