A plant-tissue-based biophotonic method for herbicide sensing.

Herbicide application incurs water contamination and thus effective herbicide detection methods are needed. In this research, a kinetic model was developed to describe the processes of herbicide diffusion into plant tissues and binding to the active sites. DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea], a commonly used herbicide, was used as a test chemical and its diffusion into plant leaves and binding to plastoquinone B (Q(B)) sites were analyzed by using the model. The dependency of delayed fluorescence (DF) emission on unbound Q(B) sites was first derived theoretically and then observed experimentally. This yields a biophotonic method to measure the concentrations of DCMU and other herbicides that function by a similar mechanism. Experiments were performed to validate the developed method.