Current ambient concentrations of ozone in Panama modulate the leaf chemistry of the tropical tree Ficus insipida.
© 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
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.
This research was supported by the U.S. Environmental Protection Agency (STAR Fellowship F13F31245), the U.S. National Science Foundation (DEB1135733, DEB-1405637), the University of Utah's Global Change and Sustainability Center, and the Smithsonian Tropical Research Institute.
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.
Vol. 172, pp. 363 - 372
Place of publication