THE MECHANISM OF AUXIN ACTION

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Abstract
The effect of various concs. of indole-3-acetic acid on the rate of absorption of KC1 (from a dilute soln.) and water by slices of potato tuber tissue was studied. Both processes are affected by indole-3-acetic acid, a maximum stimulation occurring at a conc. of 10-20 mgm. per liter. The shape of the curve is similar to the function relating auxin conc. to its effect on growth processes. Expts. with sections of Avena coleop-tiles yielded similar results. It is concluded that the effect of indole-3-acetic acid on cell enlargement is probably due to a stimulation of the salt absorption system which results in an increase in the amt. of osmotically active sap solute. The latter effect is the cause of the rapid uptake of water which is the driving force of cell enlargement. It is also suggested that the metabolic basis of salt absorption and the auxin effect is the 4-C dicarboxylic acid system of H transport.

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