title: Current ambient concentrations of ozone in Panama modulate the leaf chemistry of the tropical tree Ficus insipida.
abstract: Tropospheric ozone (O3) is a major air pollutant and greenhouse gas, affecting carbon dynamics, ecological interactions, and agricultural productivity across continents and biomes. Elevated [O3] has been documented in tropical evergreen forests, the epicenters of terrestrial primary productivity and plant-consumer interactions. However, the effects of O3on vegetation have not previously been studied in these forests. In this study, we quantified ambient O3in a region shared by forests and urban/commercial zones in Panama and found levels two to three times greater than in remote tropical sites. We examined the effects of these ambient O3levels on the growth and chemistry of seedlings of Ficus insipida, a regionally widespread tree with high stomatal conductance, using open-top chambers supplied with ozone-free or ambient air. We evaluated the differences across treatments in biomass and, using UPLC-MS-MS, leaf secondary metabolites and membrane lipids. Mean [O3] in ambient air was below the levels that induce chronic stress in temperate broadleaved trees, and biomass did not differ across treatments. However, leaf secondary metabolites - including phenolics and a terpenoid - were significantly downregulated in the ambient air treatment. Membrane lipids were present at lower concentrations in older leaves grown in ambient air, suggesting accelerated senescence. Thus, in a tree species with high O3uptake via high stomatal conductance, current ambient [O3] in Panamanian forests are sufficient to induce chronic effects on leaf chemistry.
authors.affiliation: Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA. Electronic address: gerald.schneider@utah.edu.
authors.forename: Gerald F
authors.initials: GF
authors.lastname: Schneider
authors.affiliation: College of Science & Engineering, James Cook University, Cairns, Queensland, 4870, Australia.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Cheesman
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Klaus
authors.initials: K
authors.lastname: Winter
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Turner
authors.affiliation: Department of Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, United Kingdom.
authors.forename: Stephen
authors.initials: S
authors.lastname: Sitch
authors.affiliation: Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Kursar
mesh_terms: D018533:Biomass; D002244:Carbon / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D030681:Ficus / Q000737:chemistry*; D065928:Forests; D005843:Geography; D016018:Least-Squares Analysis; D010126:Ozone / Q000737:chemistry*; D010176:Panama; D010636:Phenols / Q000737:chemistry; D010788:Photosynthesis; D018515:Plant Leaves / Q000737:chemistry*; D036226:Seedlings / Q000737:chemistry*; D013729:Terpenes / Q000737:chemistry; D014197:Trees / Q000737:chemistry*
chemical_list: D010636:Phenols; D013729:Terpenes; D002245:Carbon Dioxide; D010126:Ozone; D002244:Carbon
keywords: Open-top chamber; Ozone; Secondary metabolite; Senescence; Stomatal conductance; Tropical forest