The Effects of Some Chelating Agents and Their Copper Complexes on Photosynthesis in Scenedesmus quadricauda

Abstract

The effects on apparent photosynthesis in the green alga Scenedesmus quadricauda of four chelating substances, 8‐hydroxyquinoline (= oxine), β‐isopropyltropolone (=β‐thujaplicin), sodium dimethyldithiocarbamate and 3‐(β‐hydroxyethyl)‐C‐pentamethylene‐3‐aza‐dithiocarbamate have been investigated. The first three compounds mentioned had all an inhibitory effect on photosynthesis, measured as oxygen production with a manometric, a volumetric or a polarographic method. In combination with certain concentrations of CuSO4 bimodal dose response curves were observed, similar to those obtained on the growth of different microorganisms. Calculations of the amounts of different complexes that appeared in the nutrient solutions during the experiments are compared with the recorded degrees of inhibition. The results strongly indicate that the 1: 1‐complexes between Cu2+ and the chelating substances are the most toxic agents at low concentrations of these compounds.