Effects of ozone on stomatal responses to environmental parameters (blue light, red light, CO2 and vapour pressure deficit) in three Populus deltoides × Populus nigra genotypes

The effect of ozone (O3) on stomatal regulation was studied in three Euramerican poplar genotypes (Populus deltoides × Populus nigra: Carpaccio, Cima and Robusta). The impact of O3 on stomatal conductance responses to variations in blue light, red light, CO2 concentration and vapour pressure deficit (VPD) was studied. Upon O3 exposure, a sluggish response of stomatal movements was observed, characterized by slower reactions to increases in blue light intensity, CO2 concentration and VPD, and lower amplitude of the response to variations in light intensity. That sluggish response should be taken into account in stomatal conductance models for phytotoxic ozone dose (PODY) calculations. The speed of the response to variations in environmental parameters appears as a determining factor of genotype-related sensitivity. ► Slow stomatal movements are a determining factor of ozone sensitivity. ► Ozone decreases the stomatal conductance. ► O3 decreases the photosynthesis and increases the respiration. ► O3 slows the stomatal movements to increase of blue light, red light, CO2 and VPD. ► O3 effects on stomatal conductance must be taken into account in PODY calculation. Taking into account stomatal behaviour upon exposure to high ozone levels is essential for improving phytotoxic ozone dose assessment.