EFFECTS OF TRIAZOLE INHIBITORS OF STEROL BIOSYNTHESIS ON THE FREE ANDESTERIFIED STEROL COMPOSITION OF CELERY CELL-SUSPENSION CULTURES

Treatment of celery cell suspension cultures with paclobutrazol and th ree other triazoles resulted in decreased growth and an accumulation o f 14alpha-methylsterols in both the free sterol and the steryl ester p ools, thus indicating that the triazoles were inhibiting the action of the plant obtusifoliol 14alpha-demethylase system. Obtusifoliol, 14al pha-methylcampesta-8,24(24(1))-dien-3beta-ol and 14alpha-methylcampest -8-en-3beta-ol were the main 14alpha-methylsterols to increase in the free sterol pool. In the presence of the triazoles the steryl esters b ecame virtually depleted of sitosterol, campesterol, stigmasterol and isofucosterol, which were replaced by 14alpha-methylsterols with obtus ifoliol becoming the dominant esterified sterol. Treatment of the cele ry culture with a fourth triazole which did not have a noticeable effe ct on growth and caused negligible accumulation of 14alpha-methylstero ls in the free sterol pool nevertheless produced some enrichment of th e steryl esters in obtusifoliol. The results indicate that, following triazole treatment, a rapid esterification of the accumulating 14alpha -methylsterol intermediates occurs before they start to build up in si gnificant amount in the free sterol pool.