Remote detection of plant physiological responses to TNT soil contamination

Abstract

Our study was aimed at understanding physiological responses to trinitrotoluene (TNT) soil contamination, and using optical methods to detect TNT-induced stress in a woody plant prior to visible changes. Myrica cerifera plants were potted in soil concentrations of TNT ranging from 30–500 mg kg−1. Physiological measurements were significantly affected by TNT exposure at all treatment levels, and photosynthetic decline likely resulted from metabolic impairment rather than stomatal closure as the experiment progressed. Several reflectance indices were able to detect TNT-induced stress before any changes in chlorophyll concentrations occurred. The most sensitive index was the simple ratio R761/R757 which is linked to fluorescence in-filling of the 02 atmospheric absorption. Changes at R740/R850 and R735/R850 may be attributed to both fluorescence and structural characteristics of leaf anatomy in the near infrared region. This could have been influenced by transformation and conjugation of TNT metabolites with other compounds. chlorophyll index (CHL) or in the water band index (WBI970), which are indices typically associated with drought stress, and may provide a means of separating stress due to explosives. Further studies need to be conducted with a combination of stressors (TNT and natural) to determine if responses are in fact generalized or if any of these changes are separable from natural stress.