Physiological effects of maize with mesotrione using fluorescence spectroscopy and two-dimensional correlation analysis technique

To clarify the physiological effect of mesotrione stress on maize and its use safety in a maize field, the effects of different concentrations of mesotrione on chlorophyll and carotenoid contents in leaves, fresh weights of roots, stems, and leaves, and fluorescence substances in root exudates of maize were studied using UV visible absorption spectrum, synchronous fluorescence spectrum, three-dimensional fluorescence spectrum, and two-dimensional correlation analysis (2D-COS) technique. The results showed that the chlorophyll and carotenoid contents in leaves and the fresh weights of roots, stems, and leaves of maize were significantly decreased after 10 and 14 d of stress with 5 and 10 mg/L mesotrione. The analysis of synchronous fluorescence spectrum, three-dimensional fluorescence spectrum, and 2D-COS technology revealed that the fluorescence intensity of protein-like and humus-like substances in the root exudates of maize had changed significantly, and the above changes were more notable with the increase of the concentration of mesotrione and the prolongation of the stress time. However, the intensity of the protein-like fluorescent peak at 225-235 nm was enhanced at 7, 10, and 14 d of stress. Combined with 2D-COS analysis, it was found that the protein-like fluorescent group at 280-325 nm exhibits preference binding to mesotrione. The results showed that when the concentration of mesotrione is higher than 5 mg/L, the normal growth of maize would be adversely affected after 10 d of stress. The research results can provide a theoretical basis for evaluating the safety of mesotrione on maize.