Antioxidative enzymes in two wheat cultivars, differently sensitive to drought and subjected to subsymptomatic copper doses

Two wheat cultivars (Triticum durum L. Desf.) differently sensitive to drought (cultivar Ofanto less sensitive than cultivar Adamello) were grown in a controlled environment with subsymptomatic concentrations of Cu. Ethylene emission and enzymes involved in oxygen free radical scavenging were determined. On the basis of a rooting test, cv. Ofanto was shown to be more tolerant to Cu than cv. Adamello. In the leaves, Cu contents were higher in cv. Ofanto than in cv. Adamello, whereas in the roots, Cu level was higher in Adamello, both before and after desorption. During Cu treatment, the increase in ethylene emission was earlier in the more tolerant cultivar, whereas in the leaves, all peroxidase enzymes (ascorbate peroxidase, APOD; guaiacol peroxidase, GPOD; and syringaldazine peroxidase, SPOD) were induced. In both cvs., enzyme activities of SPOD, GPOD, APOD, and superoxide dismutase (SOD) were many-folds higher in the roots than in the leaves. In contrast, catalase (CAT) activity was higher in the leaves than in the roots. In the control leaves of Adamello, all enzymes showed higher activity in comparison with Ofanto, whereas in the control roots, APOD, GPOD, and SOD were higher in cv. Ofanto than in cv. Adamello. In both cvs., SOD was not involved in the response to Cu excess. CAT activity was not induced in Ofanto leaves and roots under Cu treatment, while an induction was observed in roots and leaves of Adamello subjected to 0.25 μmol/L Cu. In conclusion, the more tolerant cv. (Ofanto) responds to Cu near threshold concentrations with the induction of peroxidases in the leaves, whereas CAT seems to have a major role in the more sensitive cv. (Adamello).