Abstract
The early time course (0-30 min) of the action of auxin (3-indoleacetic acid) on the elongation of segments from corn coleptiles was studied, using a high-resolution continuous recording technique. Two different effects of auxin were observed: (1) After addition of low auxin concentrations (2 × 10-7 M) to 4-mm sections, a very rapid (2-3 min) enhancement of elongation was found. Similar early responses were seen following the addition of low concentrations of the methyl ester of indoleacetic acid. (2) Following a large step-up in the auxin level (10-5, 10-4, or 10-3 M), a rapid transient decrease was observed one to three minutes after the addition of indoleacetic acid. It lasted 10-15 minutes at which time the steady rate of auxin-promoted elongation became evident.
Similar kinetic patterns of auxin effects other than on elongation and the implications of the findings on hypotheses of the primary action of auxin are discussed.
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Selected References
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