Thermal dependence of the antioxidant enzymes superoxide dismutase, catalase and peroxidase in foliage of Iris pumila L

Thermal dependence of the enzymes SOD, CAT, and POD was investigated in leaves of Iris pumila plants inhabiting two contrasting light environments, a sun-exposed dune site and a woodland understory. A the same assay temperature, both the specific activity and the activation energy of SOD and CAT were higher in plants inhabiting vegetation shade than in those experiencing full sunlight. Conversely, the temperature optima for the two enzymes did not differ between alternative radiation environments. The specific activity of POD increased with temperature increase, and was always greater in plants growing under full sunlight than in those from vegetation shade. The activation energy of POD was higher than that of SOD or CAT, being lower in sun- than in shade-exposed plants.