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