The effect of combination of drought and heat stresses on plant transpiration and photosynthesis

Abstract

Expected increasing intensity and frequency of droughts with climate changes is often accompanied by increased air temperature resulting in decreased stability of crop yields. Owing to the complex nonlinear interactions between a plant and its environment, it is difficult to evaluate the effect of multi-stress on plant functioning.

The main aim of presented research was to analyse spring wheat response to combination of two abiotic stresses: drought and heat.

The growth chamber  experiment with controlled environment was conducted on spring wheat growing in cylindrical soil columns. Four treatments were compared: control with optimum soil moisture and air temperature (C), heat wave (HW) – as C but with temperature elevated up to 34°C for four days at flowering, drought (D) with soil water content decreasing from initially optimum level to water deficit (pF> 3.4) at flowering, drought and heat wave (DHW) - the combination of two stresses  .

The results indicated different course of leaf transpiration and photosynthesis rates in analysed treatments in response to soil water content . HW treatment during period of increased temperature were characterised by significantly increased average transpiration as compared to all other treatments. However photosynthesis rate in this treatment were slightly lower than in control plants.  Comparison of D and DHW treatments shows similarities in the trends of transpiration increase with increasing soil moisture with some offset to lower soil moisture in DHW resulting from higher evapotranspiration. Photosynthesis rate showed relatively large variation characterised by steeper increase with increasing soil water content  in D as compared to DHW.