Comparison of calculated and measured foliar O₃ flux in crop and forest species

Abstract

We designed a new gas exchange system that concurrently measures foliar H₂O, O₃, and CO₂ flux (HOC flux system) while delivering known O₃ concentrations. Stomatal responses of three species were tested: snapbean, and seedlings of California black oak (deciduous broadleaf) and blue oak (evergreen broadleaf). Acute O₃ exposure (120-250 ppb over an hour) was applied under moderate light and low vapor pressure deficits during near steady state conditions. The rate of stomatal closure was measured when the whole plant was placed in the dark. An adjacent leaf on each plant was also concurrently measured in an O₃-free cuvette. Under some conditions, direct measurements and calculated foliar O₃ flux were within the same order of magnitude; however, endogenously low gs or O₃ exposure-induced depression of gs resulted in an overestimation of calculated O₃ fluxes compared with measured O₃ fluxes. Sluggish stomata in response to light extinction with concurrent O₃ exposure, and incomplete stomatal closure likewise underestimated measured O₃ flux.

Citation

Grulke, N.E.; Paoletti, E.; Heath, R.L. 2007.Comparison of calculated and measured foliar O₃ flux in crop and forest species. Environmental Pollution. 146(3): 640-647. https://doi.org/10.1016/j.envpol.2006.04.014.