Abstract

Decreased IAA-destruction activity by tobacco calluses (T22 and XD6S2) was observed only when the calluses were cultured on a medium favorable for auxin-nonrequiring callus induction. The medium used to induce auxin-nonrequiring calluses from auxin-requiring ones contained 0.1 mg/liter IAA for callus T22 and 10 mg/liter NAA for XD6S2. It was clearly demonstrated both in vivo and in vitro that the result was not due to decreased IAA-destroying enzyme activity itself, but to the increase of an inhibitor(s) of IAA-destruction activity. The accumulated inhibitor(s), which induced a lag in IAA oxidation, was a heat-stable low molecular weight substance(s), unstable in air at room temperature.

The possible involvement of an inhibitor(s) of IAA-destruction in the process of induction for auxin-nonrequiring calluses was discussed.

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