External Exposure e. g Concentrations, AOT40 Uptake mainly controlled by stomatal conductance Uptake e. g FlUx, Cumulative Uptake Initial effects in cell wall (apoplast) and cell membrane Biological Effect (plasmalemma) Biological effect on cells depending on defence acitivity Scheme of o3 uptake and biological effect on leaves. st-stoma,sc- substomatal cavity(气孔下腔),c- cuticle(角质层), e-epidermis,m- mesophyll, gS-stomatal conductance8 Scheme of O3 uptake and biological effect on leaves. st-stoma, sc-substomatal cavity(气孔下腔), c- cuticle（角质层）, e-epidermis, m￾mesophyll, gs-stomatal conductance