Abstract:Tobacco calli, induced from leaf explants on MS medium supplemented with 0.2 mg L-1 NAA, 0.2 mg L-1 kinetin and 1 mg L-1 2,4-D, were cultured on MS medium containing 0.1 mmol/L 2-aminoindan-2-phosphonic acid (AIP, inhibitor of phenylalanine ammonia lyase) or 1 mmol/L aminoxyacetic acid [AOA, inhibitor of ACC(1-aminocyclopropane-1-carboxylic acid) synthase], or 0.1 mmol/L AIP and 1 mmol/L AOA in combination. The calli were then treated with 1 mg ml-1 methyl jasmonate (MJ) to determine the activities of peroxidase (POD)，phenylalanine ammonia lyase(PAL)，β l,3-glucanase，polyphenol oxidase，and chitinase．The result showed that MJ markedly increased the activities of POD，β l,3-glucanase，exochitinase and slightly increased the activities of PAL and polyphenol oxidase(PPO)，while it inhibited the activity of endochitinase．AOA and AII)significantly inhibited the induction effect of MJ on the activities of POD and β 1,3-glucanase，but the induction effect of MJ on PAL and polyphenol activities was less． AOA could partially relieve the inhibition effect of MJ on endochitinase, but had less effect on MJ-induced exochitinase activity．AIP inhibited the activity ofendochitinase and the induction effect of MJ as wel1．It is inferred that the efrect of MJ on POD, PPO and endochitinase may be through the signal transduction of ethylene，and on β 1,3-glucanase and exochitinase through salicylic acid, while on PAL there exists another pathway.