Correlation between induction of auxin-nonrequiring tobacco calluses and increase in inhibitor (s) of IAA-destruction activity

Decreased IAA-destruction activity by tobacco calluses (T22and XD6S2) was observed only when the calluses were culturedon a medium favorable for auxin-nonrequiring callus induction.The medium used to induce auxin-nonrequiring calluses from auxin-requiringones contained 0.1 mg/liter IAA for callus T22 and 10 mg/literNAA for XD6S2. It was clearly demonstrated both in vivo andin vitro that the result was not due to decreased IAA-destroyingenzyme activity itself, but to the increase of an inhibitor(s)of IAA-destruction activity. The accumulated inhibitor(s), whichinduced a lag in IAA oxidation, was a heat-stable low molecularweight substance(s), unstable in air at room temperature. The possible involvement of an inhibitor(s) of IAA-destructionin the process of induction for auxin-nonrequiring calluseswas discussed. (Received July 15, 1978; )