Effect of drought and heat stresses on transpiration and photosynthesis of wheat

Global warming and frequent extreme weather conditions affect crop yields worldwide. Drought and high temperatures are among stresses that often act simultaneously. Therefore the aim of the studies was to analyze effect of combined drought and heat stresses on growth and function of spring wheat. The experiment was conducted in a growth chamber conditions. Spring wheat cv Łagwa was planted in soil columns of 10cm in diameter and 45cm high filled with Orthic Luvisol developed from loess and grown up to the end of flowering. The treatments were: (C) control with optimum growth soil water potential 160 hPa (pF 2.2) , 250 µmol m-2s-1 PAR, 22/18 °C day / night temperatures and 60% air relative humidity throughout growing period; (D) drought stress with soil water potential 250 kPa (pF 3.4) at flowering; (HT) high temperature stress with air temperature 34/24°C and optimum soil water potential ; (DHT) drought (as above) and high temperature (34/24°C day / night) stresses at flowering. During the experiment photosynthesis rate, transpiration and stomatal conductance were measured using the gas exchange system GFS-3000 and DualPAM 100 (Walz, Germany). Drought stress reduced photosynthesis rate by 11%, high temperature by 19% and both stresses by 79% as compared to control (100%). However, drought stress decreased transpiration rate similarly as combined drought and high temperature stresses (by 60-63%). Transpiration rate under high temperature stress compared to control slightly increased