Biogenic Volatile Organic Compounds in Amazonian Ecosystems
Biochemical fingerprints provide clues on tropical forest processes.
Many cellular processes leave unique volatile fingerprints behind that can be studied through the acquisition of gas-phase metabolite profiles in the headspace atmospheres of plants across a wide range of spatial and temporal scales, from enzymes to ecosystems and from seconds to seasons. While generally studied for their strong impact on atmospheric properties, recent research results from U.S. Department of Energy–funded GoAmazon 2014/5 and Next-Generation Ecosystem Experiments (NGEE)–Tropics projects in the central Amazon highlight the potential for emissions of volatile metabolites as quantitative tracers of biological processes including carbon and energy metabolism (photosynthesis, photorespiration, respiration, and fermentation), cell wall expansion and growth, acetyl-CoA and fatty acid metabolism and degradation, and antioxidant defense and signaling during abiotic and biotic stress.
The emerging field of volatile ecosystem metabolomics integrates chemical, physical, and biological processes involved in the metabolism of volatiles within the land-atmosphere interface including potential perturbations of the system by anthropogenic activities such as climate warming. An emerging approach evaluated in this study is the use of volatiles as sensitive ecosystem biomarkers of response to abiotic stress including temperature and drought. Examples include temperature-dependent isoprenoid composition and oxidation product formation; senescence and mortality through green leaf volatiles and isoprenoid emissions from storage resins; fermentation volatiles; and volatiles associated with cell wall growth, stress, and repair. The integration of volatiles into plant central metabolism is discussed in term of a predictive understanding of the integration of land processes (plant physiology and biochemistry) with atmospheric processes (atmospheric chemistry and climate). Therefore, volatile metabolomics provides noninvasive techniques to study plant metabolism from a variety of spatial and temporal scales. The application of these methods in the tropics may improve the mechanistic understanding of how environmental and biological variables associated with climate and land-use change affect the carbon and energy metabolism of natural and managed forests. Genetic engineering of plant metabolism of volatiles is highlighted as a new research tool with application in enhancing plant productivity and abiotic stress tolerance in agricultural, biofuel, and biomaterial industries.
Biogenic volatile organic compounds (BVOCs) are produced directly within plants via biochemical pathways associated with primary and secondary metabolic processes. Although nonvolatile metabolites are typically bound within specific cellular organelles in lipids or aqueous phases, BVOC volatile metabolites can readily partition between these phases and the intracellular airspace. Thus, many BVOCs may freely exchange among cellular organelles, cells, and tissues, contributing to an integration of whole-organism carbon and energy metabolism. Moreover, exchange of the intracellular airspace with the atmosphere may help coordinate the metabolisms of different plants within an ecosystem in response to environmental and biological factors. In addition, land-atmosphere exchange of VOCs integrates local and regional atmospheric chemistry with plant metabolism. In this chapter, select examples of the physiological roles BVOCs in plants is presented with a focus on key results from the DOE-funded GoAmazon 2014/5 project in central Amazonia.
Kolby J. Jardine
Climate and Ecosystem Sciences Division (CESD), Lawrence Berkeley National Laboratory (LBNL)
This research was supported as a part of the GoAmazon 2015/6 and Next-Generation Ecosystem Experiments (NGEE)–Tropics project in the central Amazon by the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science under Contract No. DE-AC02-05CH11231, as part of their Terrestrial Ecosystem Science Program.
Jardine, K., and Jardine, A. “Biogenic volatile organic compounds in Amazonian forest ecosystems.” Chapter 4 in Interactions Between Biosphere, Atmosphere and Human Land Use in the Amazon Basin (Eds: Nagy L., Forsberg B., and Artaxo P.). Ecological Studies (Analysis and Synthesis), vol. 227. Springer, Berlin, Heidelberg. [DOI:10.1007/978-3-662-49902-3_2].