Antioxidative responses of shoots and roots of wheat to increasing NaCl concentrations

The effect of NaCl was studied in seedlings of two cvs. of Triticum durum Desf., differently sensitive to drought and to heavy metals (cv. Ofanto more tolerant than cv. Adamello). The seedlings were grown for 9 days in Hoagland's 2 solution, added with increasing NaCl concentrations (0, 50 and 100 mmoI/L). Comparisons of control and salt-stressed plants included ascorbate and glutathione contents, their reduction states and the activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. The results indicated an involvement of activated oxygen species in the mechanism of cellular toxicity of NaCl and pointed out differences in the induction of antioxidant defences among the two cvs. Indeed, notwithstanding a higher constitutional content of ascorbate in cv. Adamello, cv. Ofanto was able to induce ascorbate synthesis when subjected to salt stress. Higher levels of NaCl resulted in increasing glutathione contents in the roots of both cvs., likely for an increased requirement of antioxidants in the organs that firstly suffer stress. Only the roots of N. Ofanto showed glutathione oxidation following treatments. The general trend for the antioxidative enzyme activities was an increase in the shoots and a decrease in the roots. The experimental evidence suggested a more marked effect of NaCl stress on cv. Adamello when compared with cv. Ofanto.