PHOTOSYNTHESIS BY ISOLATED CHLOROPLASTS: SOME FACTORS AFFECTING INDUCTION IN CO2‐DEPENDENT OXYGEN EVOLUTION

SUMMARY Oxygen production by chloroplasts isolated from spinach was measured. The lag in oxygen production following first illumination of the chloroplasts was independent of light intensity and chlorophyll concentration. The length of the lag period was unaffected by addition of DCMU to the reaction mixture but was increased by addition of orthophosphate or arsenate. It was also longer at lower temperatures. The data are consistent with the view that the lag results from the time necessary for the concentration of photosynthetic metabolites to increase to a level that allows maximal rate of photosynthesis. However, anomalies in behaviour occur and their significance is discussed.