The Antiozonant Ethylenediurea Does Not Act via Superoxide Dismutase Induction in Bean

It has been proposed that the mode of action of ethylenediurea, a very effective antiozonant, is via an increase in the antioxidant enzyme superoxide dismutase (EH Lee, JH Bennett [1982] Plant Physiol 69: 1444-1449). Data presented here refute that hypothesis. No ethylenediurea-associated increases in Cu/Zn-superoxide dismutase or Mn-superoxide dismutase activity, nor in steady-state Cu/Zn-superoxide dismutase protein levels, were found in soluble extracts of bean (Phaseolus vulgaris L. cv Bush Blue Lake 290) leaves. However, the cytosolic Cu/Zn-superoxide dismutase increased as a result of ozone fumigation and subsequent injury. Also noted was a developmentally related difference between chloroplastic and cytosolic Cu/Zn-superoxide dismutase, the latter declining during maturation of the leaf.