Physiological responses of saplings of Caesalpinia echinata Lam., a Brazilian tree species, under ozone fumigation

Abstract

The effects induced by long-term (30 day) and short-term (6 h) exposures to ozone on the physiological parameters in young plants of Caesalpinia echinata Lam., a Brazilian tree species, were determined. Potted plants were maintained in open-top chambers in Valencia, Spain, under charcoal filtered air (mean O 3 level: 29 μg m 3), nonfiltered air (NF; 43 μg m 3), and nonfiltered air plus O 3 (NF+O 3; 68 μg m 3), simulating prevailing concentrations observed in the city of São Paulo, Brazil, during spring months (50 μg m 3 in 2002). In the plants kept in NF+O 3 for 30 days, although no foliar visible injuries were observed, the net carbon assimilation rate was reduced to 50%, stomatal conductance 42%, and transpiration 40%, when compared to the results for the NF plants. No changes in antioxidants, in leaf, stem, and root biomass, and in the root/shoot ratio were observed. Significant reductions were observed in gas exchange and in PSII photochemical efficiency ( F v /F m) after 6 h of exposure to an O 3 peak. The species was shown to be sensitive to ambient O 3 concentrations measured in São Paulo.