Factors Affecting Light Induced Fixation of Carbon Dioxide by Isolated Spinach Chloroplasts.

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Abstract
The effect of various factors on the light induced fixation of Cl4O2 by isolated spinach chloroplasts has been investigated. The rate routinely observed with hydroponic grown material was 2.5 [mu]M of CO2 assimilated/hour/mg chlorophyll. Lower rates were obtained with field grown, store bought or potted plants. The pH optimum of the system was 7.5 to 7.6. Observation of the action of several metabolic inhibitors revealed that iodoacetamide, p-chloromercuribenzoate and arsenite were highly effective in inhibiting cl4O2-fixation. Arsenite inhibition, in contrast to the inhibition effect by p-chloromercuribenzoate, could not be prevented markedly by glutathione. This would suggest a specific effect of the trivalent arsenical. While low concentration of arsenate (10-6) and phosphate (10-4) accelerated C assimilation, higher concentration of each caused strong inhibition. The inhibition effected by the ammonium ion was not relieved by adenosine triphosphate. The significance of these findings are evaluated in relation to other light induced reactions of the chloroplast.