Chamber Measurements of Trace Gas Exchanges for Several Oak Species Exposed to Ozone and Drought
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Several species of oak were used in a series of chamber based experiments. The species of oaks chosen (Quercus alba, muehlenbergii, and virginiana) were selected because they are all emitters of the volatile organic compound isoprene. Isoprene emissions as well as several physiological parameters such as photosynthesis and stomatal conductance were monitored under normal conditions, as well as while stressors such as drought and high external ozone were introduced. Ozone fluxes to the plants were partitioned into stomatal and surface fluxes for leaves treated with an isoprenoid coating as well as untreated leaves. It was found that the coating on the leaves acted as a strong surface ozone sink, which reduced ozone concentrations in the leaf boundary layer and resulted in significantly reduced stomatal fluxes of ozone. Measurements of drought stressed specimens displayed significant declines in photosynthesis and stomatal conductance, however isoprene emissions remained constant. This resulted in a significant increase in the percentage of assimilated carbon emitted as isoprene during times of water stress and represented a decoupling of photosynthesis from isoprene production. The level of circadian control over isoprene emissions was assessed for a Q. muehlenbergii specimen by exposing it to constant light for several days. No circadian control over isoprene emissions was noted for this specimen despite past research demonstrating circadian control over isoprene emissions for several other species.
Watson, Matthew Raymond (2016). Chamber Measurements of Trace Gas Exchanges for Several Oak Species Exposed to Ozone and Drought. Master's thesis, Texas A & M University. Available electronically from