CUMULATIVE ABIOTIC STRESSES AND THEIR EFFECT ON THE ANTIOXIDANT DEFENSE SYSTEM IN TWO SPECIES OF WHEAT, TRITICUM DURUM DESF AND TRITICUM AESTIVUM L.

The combined effects of heat and UV-B on the antioxidant system and photosynthetic pigments were investigated in the leaves of T. durum Desf. and Triticum aestivum L. The photosynthetic pigment content, in vitro evaluation of the antioxidant system activities including DPPH radical scavenging activity, and super oxide anion radical scavenging activity were determined. In addition, the antioxidant enzyme activities, such as superoxide dismutase (SOD) and guaiacol peroxidase (GPX), were determined Heat and UV-B irradiation alone caused a significant decrease in the photosynthetic pigment content, radical scavenging activity and super oxide radical scavenging activity in the two studied plants. The antioxidant enzymes SOD and GPX were stimulated in response to UV and/or heat stresses. The elevation of enzyme activities was higher under heat than under UV-B, especially in T. aestivum. According to our findings, it can be concluded that combined heat and UV-B provided cross-tolerance; otherwise, single stress was found to aggravate the responses.