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 drou ght (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 determ ined. On the basis of a rooting test, cv. Ofanto was shown to be more toler ant 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 A damello, both before and after desorption. During Cu treatment, the increas e in ethylene emission was earlier in the more tolerant cultivar, whereas i n the leaves, all peroxidase enzymes (ascorbate peroxidase, APOD; guaiacol peroxidase, GPOD; and syringaldazine peroxidase, SPOD) were induced. In bot h cvs., enzyme activities of SPOD, GPOD, APOD, and superoxide dismutase (SO D) were many-folds higher in the roots than in the leaves. In contrast, cat alyse (CAT) activity was higher in the leaves than in the roots. In the con trol leaves of Adamello, all enzymes showed higher activity in comparison w ith Ofanto, whereas in the control roots, APOD, GPOD, and SOD were higher i n cv. Ofanto than in cv. Adamello. In both cvs., SOD was not involved in th e 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 leav es of Adamello subjected to 0.25 mu mol/L Cu. In conclusion, the more toler ant cv. (Ofanto) responds to Cu near threshold concentrations with the indu ction of peroxidases in the leaves, whereas CAT seems to have a major role in the more sensitive cv. (Adamello).