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We previously demonstrated that the differential water stress tolerance of two wheat cvs (Triticum aestivum L cvs Oasis and Elite) were related with the capacity of each cv. to modulate the antioxidant system response. In order to investigate the possible occurrence of the cross-tolerance phenomenon, we have now analysed the antioxidant system response of these wheat cvs subjected to photooxidative stress induced by different paraquat concentrations combined with relative excess of light. Contrary to our previous idea, the drought-tolerant cv. Elite was more sensitive to paraquat treatment than the drought-sensitive cv. Oasis. Chlorophyll and protein degradation was higher in Elite than in Oasis. This behaviour of oxidative damage parameters was accompanied by different antioxidant system responses of the two cvs. In general, both antioxidant enzyme activities and nonenzymatic antioxidant compounds showed lower levels in Elite than in Oasis. These results are discussed in relation to the oxidative stress induced by paraquat treatment and by water stress. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.