Pot-soil experiments with sunflowers plants (hybrid PR64E83) were conducted 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 25-30C noon temperature; (2) 35-40% FWC (drought stress) and 25-30 C; (3) 75-80% FWC and 35-40C (high temperature stress) and (4) 35-40% FWC and 35-40C (combine stress). Photosynthetic performance of plants was judged by use of leaf gas exchange and chlorophyll 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 transpiration intensity in Pistor-treated plants. In conclusion, the first results obtained revealed that the fungicide Pictor improved photosynthetic performance of sunflower plants at drought conditions by better preservation of plant water relations.
Effects of the fungicide pictor on photosynthesis of sunflower plants exposed to drought and high temperature conditions