REGULAR ARTICLE Distinguishing natural from anthropogenic stress in plants: physiology, fluorescence and hyperspectral reflectance Julie C. Zinnert & Stephen M. Via & Donald R Young Received: 12 March 2012 / Accepted: 2 August 2012 / Published online: 23 August 2012 # Springer-Verlag (outside the USA) 2012 Abstract Background and Aims Explosives released into the environment from munitions production, processing facilities, or buried unexploded ordnances can be absorbed by surrounding roots and induce toxic effects in leaves and stems. Research into the mechanisms with which explosives disrupt physiological processes could provide methods for discrimination of anthro- pogenic and natural stresses. Our objectives were to experimentally evaluate the effects of natural stress and explosives on plant physiology and to link differ- ences among treatments to changes in hyperspectral reflectance for possible remote detection. Methods Photosynthesis, water relations, chlorophyll fluorescence, and hyperspectral reflectance were mea- sured following four experimental treatments (drought, salinity, trinitrotoluene and hexahydro- 1,3,5-trinitro-l,3,5-triazine) on two woody species. Principal Components Analyses of physiological and hyperspectral results were used to evaluate the differ- ences among treatments. Results Explosives induced different physiological responses compared to natural stress responses. Stomatal regulation over photosynthesis occurred due to natural stress, influencing energy dissipation path- ways of excess light. Photosynthetic declines in explo- sives were likely the result of metabolic dysfunction. Select hyperspectral indices could discriminate natural stressors from explosives using changes in the red and near-infrared spectral region. Conclusions These results show the possibility of us- ing variations in energy dissipation and hyperspectral reflectance to detect plants exposed to explosives in a laboratory setting and are promising for field applica- tion using plants as phytosensors to detect explosives contamination in soil. Keywords Drought . Salinity . RDX . TNT . Hyperspectral reflectance . Chlorophyll fluorescence . Photosynthesis Introduction Plants have evolved numerous mechanisms to protect against excess light energy under natural stress con- ditions (Flexas et al. 2002; Flexas and Medrano 2002; Flexas et al. 2004); however, plants are not adapted to withstand the numerous anthropogenic disturbances to which they are often exposed. For example, millions Plant Soil (2013) 366:133–141 DOI 10.1007/s11104-012-1414-1 Responsible Editor: Juan Barcelo. J. C. Zinnert US Army ERDC, Fluorescence Spectroscopy Lab, 7701 Telegraph Road, Alexandria, VA 22315, USA J. C. Zinnert (*) : S. M. Via : D. R. Young Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA e-mail: jczinner@vcu.edu