DOI: n/a
Resume
Pot-soil experiment with sunflower plants (hybrid PR64E83) were conducted in the in the Agricultural University of Plovdiv during 2010. Plants were sprayed by the fungicide Pictor (50 ml / da; 30 L / da) at the beginning of the third pair of leaves and exposed to different climatic conditions, namely: (1) 75-80% of field water capacity (FWC) and 25-30°C noon temperature; (2) 35-40% FWC (drought stress) and 25-30°C; (3) 75-80% FWC and 35-40°C (high temperature stress) and (4) 35-40% FWC and 35-40°C (combine stress). Photosynthetic performance of plants was judged by use of leaf gas exchange and chlorofyll fluorescence parameters ten days after the beginning of stress exposure. It was found that the treatment by the fungicide Pictor diminished the effect of drought stress on sunflower plants, but had no significant effect at high temperature stress and combine stress. Net photosynthetic rate of drought-exposed plants was 15% higher as compared to non-treated by Pictor. The positive effect corresponded to 22% higher trancpiration intensity in Pictor-treated plants. In conclusion, the first results obtained revealed that the fungicide Pictor improved photosynthetic performance of sunflower plants at drought conditions by brtter preservation of plant water relations.