Effects of Indoleacetic Acid on CO₂ Fixation, Electron Transport and Phosphorylation in Isolated Chloroplasts

Abstract

The effects of indoleactic acid (IAA) on CO₂ fixation, electron transport and photophosphorylation were examined. The rate of CO₂ fixation by preparations of intact chloroplasts was not significantly increased by the addition of IAA (0.2 - 5 µM). Electron transport and coupled phosphorylations were similarly unaffected when measured with ferricyanide or methyl viologen as the electron acceptor. Cyclic phosphorylntion mediated by phenazine methosulfate was also not increased by IAA. It is concluded that the hormone does not affect photosynthesis by isolated chloroplasts in short-term experiments and that the increased CO₂ uptake observed with leaves following application of IAA may result from some effect of the hormone other than a direct interaction with the chloroplasts.