Paraquat-induced production of hydrocarbon gases

Paraquat dichloride (1,1′-dimethyI-4,4′-bipyridylium dichloride) induced the production of the hydrocarbon gases propane, ethane and ethylene in the xanthophycean microalga Bumilleriopsis filiformis. Formation of these gases was dependent on the light intensity and photosynthetic electron transport. Diquat dibromide (1,1′- ethylene-2,2′-bipyridylium dibromide), having a higher midpoint potential than paraquat dichloride, induced an even higher evolution of the gases. A total lack of oxygen inhibited the production of gas, while a low oxygen concentration (4–6% by volume) stimulated paraquat-induced gas formation. Culturing algae autotrophically, in a medium with a higher iron content, also increased the production of gases in the presence of the herbicide. Formation of these gases is an indication of the peroxidation of membrane lipids which, according to previous results, is correlated with a decrease of photosynthetic electron-transport activity.