Superoxide dismutases (SODs) and abscisic acid (ABA) are implicated in the response to environmental stresses. We have evaluated the susceptibility of w-1, a mutant with ABA deficiency and a variant isoform of chloroplastic Cu/ZnSOD, to oxidative stress. The results indicate that w-1 leaves were less damaged by paraquat (MV) and H2O2 treatments in respect to the control. while no statistical differences were detected when water stress was imposed by leaf dehydration.

Spectrophotometric assays did not evidence a higher level of SOD activity in w-1 extracts than in the control, confirming that ABA concentration does not modify SOD actvity. The better response of w-1 leaves to MV treatment could be attributed to a higher efficiency of the chloroplastic isoform variant of SOD to induce the dismutation of superoxide anion radicals to hydrogen peroxide and oxygen, under oxidative stress.