Early Diagnosis of Mercury Stress of Wheat Seedlings Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy

The aim of the study was the non-destructive and rapid evaluation of the phytotoxicity of different concentrations of mercury (0.2, 0.4, 0.6, 0.8, and 1?mM) on the biochemical profile of wheat seedlings using attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy in combination with principal component analysis. Infrared spectra of the leaves of control and mercury-treated wheat seedlings were recorded in the spectral region from 4000 to 485?cm^?1. The preprocessing of the recorded spectra by second derivation enhanced the specificity of the infrared bands. The area of the bands estimated by curve fitting was used for the relative quantitative estimation of the biochemical changes involved. The principal component analysis of the acquired spectral measurements discriminated between the biochemicals of the control and mercury-treated wheat seedlings. The result showed that mercury (0.2–1?mM) significantly enhanced the content of the cell wall polysaccharides, amino acids, β-sheet component of proteins, and lipids in the leaves accompanied by reduction in the amount of α-helix. The change in β-sheet/α-helix ratio indicated mercury induced structural changes in the secondary structure of proteins. The increase in the levels of methylene bands and carboxyl bands indicates changes in lipid configuration and peroxidative damage caused by mercury. The results of this study demonstrate the potential of ATR–FTIR in combination with principal component analysis as an environmental monitoring tool for the identification of plant populations affected by environmental factors like heavy metal stress prior to the appearance of visual signs of toxicity.