EFFECT OF SALINITY ON METALLOENZYMES OF OXYGEN-METABOLISM IN 2 LEGUMINOUS PLANTS

Superoxide dismutase (SOD) pattern, catalase, Cyt c oxidase and fumarase activity were studied in leaves of Phaseolus vulgaris and Vigna unguiculata plants growth in two sodium chloride (NaCl) concentrations (35 mM and 100 mM). In bean plants growth with NaCl, leaf chloride (Cl-) contents were higher than in control plants, and the same was found for sodium (Na+) and potassium (K+) contents, although to a lesser degree. In cowpea leaves, Na+ and Cl- had a similar increase due to salt-growth conditions. Under salinity, all changes in the antioxidant (SOD and catalase) enzymes levels were smaller in bean than in cowpea plants. In Phaseolus at 15 days growth, Cu, Zn-SOD I showed an increase by the effect of salt treatment, but this induction did not occur at 30 days growth, and both Mn-SOD and Cu, Zn-SOD II did not show variations due to salt-stress. In Vigna, Mn-SOD was decreased by salinity but this was compensated by an increase in Cu, Zn-SOD I activity in plants at 30 days growth, whereas in young leaves under saline conditions, both isozymes were also decreased. Likewise, there was a rise in cytochrome c oxidase and fumarase activity in leaves of NaCl-treated plants compared to the control. The activity changes observed are discused in term of their possible relevance to plant sensitivity to saline conditions.