Distinct responses to ozone of stomata in three poplar genotypes

Tropospheric ozone acts as a phytotoxin which produces an oxidative stress in plants. Two ways of defense are used, either by preventing ozone input through the regulation of stomatal conductance, or by detoxifying ozone and ROS in cells. It is known that stomatal movements are alt ered by ozone. We performed fumigation experiment on three euramerican poplar genotypes ( Po pulus deltoides x Populus Nigra : ‘Carpaccio’, ‘Cima’ and ‘Robusta’ ), cultivated in pots in phytotronic chambers submitted to 120 ppb ozone or filtered air. We explor ed the effects of ozone on stomatal responses to four environmental parameters (blue light, red light, CO 2 and VPD). We also find out using a porometer that the decrease of stomatal conductance due to ozone is earlier on the adaxial face than on abaxial fa ce. Finally, to better understand these impacts, we studied ultrastructure of guard cells by TEM, stomatal density and size of stomata by SEM, and we performed X - ray microanalysis of guard cells mineral content. These approaches are coupled with the study on microdissected stomata of expression of genes involved in regulation of stomatal movement