Abstract
1. Measured were the activities of pectin methylesterase and polygalacturonase and the water uptake of etiolated pea stem which had been treated by auxin.
2. A remarkable parallelism was observed between the pectin methylesterase activity and the water absorption of the tissue, in respect to a) the concentration effect of IAA, b) the contrast between the aerobic and the anaerobic IAA treatments, and c) the weaker effects of naphthaleneacetic acid and phenylacetic acid as compared with IAA.
3. The activity of polygalacturonase was comparatively low, and the effect of IAA on it was not well paralleled by that on the water absorption.
4. The results appear favourable to the theory that the cell wall would become elongated the plasticization by pectin methylesterase activated by IAA.
