EFFECTS OF GROWTH SUBSTANCES ON PHOTOSYNTHESIS

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Abstract
The effects of the acids, 2,4-dichlorophenoxyacetic, indole-3-acetic, gamma (indole-3)-n-butyric, beta-naphthoxyacetic, and para-chlorophenoxyacetic, on apparent photosynthesis and respiration in Phaseolus vulgaris were detd. Each growth substance, except naphthoxyacetic acid, at a concn. of 100 ppm. in a water spray resulted in a decrease in apparent photosynthesis. Naphthoxyacetic acid caused a temporary acceleration of photosynthesis. Changes in the rates of photosynthesis cannot be accounted for on the basis of variations in the rates of respiration. Each growth substance, except indole-butyric acid, caused a temporary increase in respiration. Indole-butyric acid treatment was followed by a decrease in CO2 production. The first effect of 2,4-D was a drop in respiration. Three days after treatment with either indoleacetic or chloro-phenoxyacetic acid respiration was depressed.