ANTIOXIDANTS AND PHOTOSYNTHESIS IN THE LEAVES OF TRITICUM-DURUM L SEEDLINGS ACCLIMATED TO LOW, NON-CHILLING TEMPERATURE

The foliar antioxidant status and the photosynthetic capacity were compared in leaves of Triticum durum cv. Duilio seedlings grown under low light at an optimal temperature of 25-degrees-C or at a suboptimal, non-chilling temperature of 10-degrees-C. The leaves grown at 10-degrees-C did not show the responses commonly observed in cold-unhardened plants exposed to chilling- and chilling/light stress, such as reductions of leaf dry weight, net photosynthesis, photon yield and stomatal conductance to CO2 transport and uptake. The main chlorophyll fluorescence characteristics suggested that photoinhibition of photosynthesis was not likely to occur under the adopted low temperature and light conditions. There was no evidence of oxidative stress and/or damage in leaves grown at 10-degrees-C, as judged by measuring superoxide dismutase, catalase and peroxidase, activities, malondihaldehyde contents and foliar electrolyte retention capacity. Nevertheless, growth at low temperature almost tripled the amount of chlorophylls and carotenoids present, and induced significant increases in the foliar pools of ascorbic acid and glutathione. These changes could be regarded as preparatory adjustments aimed to anticipate a possible enhanced requirement of pigments and antioxidants in case of cold-induced oxidative stress and damage.