The uptake of O3 by poplar leaves: the impact of a long-term exposure to low O3-concentrations

摘要: Abstract Poplar shoots were exposed for 3–4 weeks to filtered air, ambient (maximum values 50–60 nl l-1) or two times O3-concentrations under controlled environmental conditions in fumigation chambers. A sensitive (Populus nigra ‘Brandaris’) and a tolerant (P. euramericana ‘Robusta’) cultivar used. At regular intervals the uptake of O3, transpiration CO2 assimilation rate (Pn) full-grown leaves measured with leaf cuvettes. For unaffected leaves, flux O3 into appeared be larger than can calculated using stomatal conductance (gs,o) estimated from rates same leaves. Resistance analysis revealed that difference was partly result reaction external surface. However, when corrected this reaction, it still gs,o. As consequence, negative residual internal resistances (ri) transport assessed. It is postulated molecules moving follow shorter pathway effluxing H2O-molecules. P. ‘Brandaris’ showed reduction Pn after 12 days exposure O3-concentrations, whereas ‘Robusta’ only observed at concentrations. simultaneous decline O3-flux found both cases. The occurred before decrease gs,o suggesting affected first hindered by factors. became smaller and, consequently, positive ri-values estimated. change ri suggests not penetrated deeper leaf, but also accumulating prolonged exposure. Our results indicate may potentially important component overall resistance O3-uptake, which have consequences estimating water vapour data.