COMPARATIVE STUDY OF DROUGHT STRESS RESISTANCE IN TWO WINTER WHEAT VARIETIES RAISED AT AMBIENT AND DOUBLED CO2CONCENTRATION

In preparation for the abiotic stress effects likely to be caused by climate change the impact of doubled carbon dioxide concentration and drought stress on two winter wheat varieties, Mv Mambó and Mv Regiment, were studied in growth chambers at the Agricultural Research Institute of HAS. The meteorological parameters (temperature, humidity, radiation) were the same in both PGV-36 chambers but the carbon dioxide concentration was either ambient (380 ppm) or doubled (750 ppm). The effect of elevated CO2level and drought stress were examined in various phenological stages (first node appearance, heading and grain filling). The drought stress was continued for 3-7 days, during which period the soil water humidity decreased from 20-25 volumetric water content (VWC%) to 3-5 VWC%. Photosynthesis and antioxidant enzyme activities (catalase, glutathione reductase, glutathione S-transferase, ascorbate peroxidase, guaiacol peroxidase) were measured at various levels of water stress. Phenological and yield parameters were determined at the end of the vegetation period. Significant differences were found between the varieties and treatments in the antioxidant enzyme activity and a number of phenological parameters. Elevated CO2concentration improved stress tolerance increasing biomass production and the grain number in both varieties. High CO2concentration also reduced the negative effect of drought stress on yield parameters.