UPTAKE AND DETOXIFICATION OF SALICYLIC-ACID BY VICIA-FABA AND FAGOPYRUM-ESCULENTUM

Roots of Vicia faba and Fagopyrum esculentum showed a characteristic tri-phasic uptake of salicylic acid. During the first, short phase, absorption was unaffected by O2 depletion, vanadate or cysteine, which suggests a diffusion of salicylic acid into the apoplast and some penetration into the cytoplasm. The second phase, continuing for about 6-8 (V. faba) and 5-8 hr (F. esculentum), was stationary and no obvious uptake was observed. The third phase was characterized by an active uptake. The absorbed salicylic acid was differently detoxified by the two species and the resulting compounds were identified. Vicia faba glucosylated salicylic acid to form o-beta-D-glucosylhydroxybenzoic acid, whereas F. esculentum oxidized it to 2,5-dihydroxybenzoic acid and glucosylated this product at the 5-OH group. The enzymes involved seemed to be induced by salicylic acid. Most of the detoxification occurred during the phase of active uptake.