Distinguishing natural from anthropogenic stress in plants: physiology, fluorescence and hyperspectral reflectance

Remote Sensing of Explosives-Induced Stress in Plants: Hyperspectral Imaging Analysis for Remote Detection of Unexploded Threats

“…High internal scattering of longer wavelengths within leaves caused by cellulose, lignin, and other physical structures intensifies the signal captured compared to reflectance of VIS wavelengths [42]. Drought conditions can hinder photosynthesis and thereby decrease biomass production, but RDX uptake has been reported to not affect biomass, by direct measurement or spectra, at concentrations lower than 500 mg kg −1 [16,43] despite reducing rates of photosynthesis [14,16]. However, in this study less intense reflectance in NIR wavelengths was measured (Figure 6a,b) for AM and AMX indicating reduced biomass, accompanied with reductions in the Index correlated to photosynthesis, PRI (Figure 3b).…”

“…RDX is a nitroamine that readily moves into plants and is translocated into aerial portions of plants where it negatively affects leaf function and health.Plant stress can be caused by a variety of factors such as nutrient deficiencies or pests, and often manifests by way of reductions in pigment concentrations, decreased photosynthesis, necrosis, and changes in plant morphology and physiology are remotely detectable with hyperspectral imagery (HSI) [15]. Plant stress responses caused by environmental pollutants such as explosives can be remotely detected via hyperspectral sensors [14,16] leading to the possibility of scaling up detection to the field level. Importantly, to be effective in remotely detecting a specific contaminant, it is necessary to compare numerous sources of stress and differentiate between them to limit potential false positives or negatives.…”

“…As plant responses can be species-and explosive-specific, discriminating between both natural, i.e., drought or nutrient deficiency, and anthropogenic stressors is crucial for the accurate remote detection of explosives. Research is extremely limited on comparing drought conditions to plant stress caused by explosives [16]. Some studies have explored uptake of explosives by agronomic species [13,17] and how the reflectance of shrubs is affected by explosives [14,16,18], but none have done both.…”

“…Research is extremely limited on comparing drought conditions to plant stress caused by explosives [16]. Some studies have explored uptake of explosives by agronomic species [13,17] and how the reflectance of shrubs is affected by explosives [14,16,18], but none have done both. The research presented here was conducted in conjunction with a field-scale drought experiment that utilized the same genotypes assessed with the same aerial-based HSI methods.Hyperspectral imagery has been utilized for decades on vegetation for early stress detection to mitigate potential agricultural crop losses.…”

Plant roots and spectroscopic methods – analyzing species, biomass and vitality

“…Thus, the fluorophore absorbs energy in the form of light at a specific wavelength and emits energy in the form of light emitted at a lower energy level. Fluorescence spectroscopy (FS) is widely used for chemical analyses of auto-fluorescing molecules (Sharma and Schulman, 1999); in plants, chlorophyll fluorescence has been widely used to determine the physiological status of leaves (Zinnert et al, 2013). While in situ root observations on Glycine max showed that nutrient absorption and root elongation rates positively correlate to fluorescence intensity (Dyer and Brown, 1983) and that fluorescence can be influenced by microbial colonization (Gamalero et al, 2004) non-species-specific influences are questioning the applicability of simple fluorescence measurements for root classification.…”