CONJUGATION AND METABOLISM OF SALICYLIC-ACID IN TOBACCO

The metabolism of [7-C-14]-Salicylic acid (SA) was quantitatively studied in leaf disks of tobacco (Nicotiana tabacum). Over the first 8 h the uptake and metabolism of SA was slow with SA 2-O-B-D-glucose as the major metabolite identified in the leaf tissue. By 24 h a more complex range of 2-O-glycosides was observed with the SA ester glucoside present as a minor metabolite. Increased conjugation of SA was associated with the evolution of (14)C(O)2 and by 36 h the administered radioactivity was distributed equally between expired (CO2)-C-14, conjugates of SA present in the cell and unchanged SA remaining in the medium. Tobacco leaves and cell cultures contained O-glucosyltransferases capable of synthesising both the ester-and 2-O-glucosides of SA. Both activities were partialy characterised and their specific activities in tobacco leaves were shown to be differentially induced by a 24 h treatment with SA (0.1-1 mM).