Non-Methane Hydrocarbon Emissions from Plants

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Natural hydrocarbon emissions from plants, estimated to be 830 Tg per year globally, play an important role in the generation of tropospheric ozone, regulation of daytime OH concentration, and are precursors of CO. However, there are many uncertainties in regional and global inventories of these biogenic compounds. Much of the uncertainty arises because there is a lack of precise data relating hydrocarbon emissions to key environmental variables that regulate such emissions from vegetation. This is especially true for emissions of isoprene (2-methyl-1,3-butadiene), the single most abundant hydrocarbon emitted from plants. Many questions can be posed concerning NMHC emissions, 1. What major NMHC are emitted from plants? 2. What environmental variables control NMHC emissions? 3. Do environmental stresses increase or decrease NMHC emissions? 4. What are the biochemical pathways for biosynthesis of NMHC and where is synthesis located in plant cells? 5. Can we develop a mechanism based model to explain NMHC emissions from plants? 6. Why do plants emit NMHC such as isoprene? The major goal of this work is to attempt to answer these questions in the case of isoprene emission from plants. Second, the project addresses a subset of these question in plants that emit a mixture of NMHC, focusing on the simultaneous measurement of isoprene and monoterpene emissions from the same leaves. This will provide new details for the environmental control for monoterpene emissions. Third, while the above experiments are conducted there will be simultaneous monitoring of emissions of oxygenated hydrocarbons (oxHC), such as acetone, methanol, ethanol and acetaldehyde. This will provide a framework for understanding the physiological and environmental conditions that lead to the emission of oxHC from plants.