Rapid analyses of stress of copper oxide nanoparticles on wheat plants at an early stage by laser induced fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy

Abstract

This study was undertaken to investigate the effect of copper oxide nanoparticles on physiological and biochemical response of wheat seedlings using non-destructive, sensitive and advance spectroscopic probes: laser induced fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy. The wheat seedlings were exposed to different concentrations of copper oxide nanoparticles (0, 10, 100, 200, 300, 400, 500, 600, 700 and 800mg/L). The laser induced fluorescence measurements showed increase in the ratio of the peak intensity of the chlorophyll bands at wavelengths 685 and 730nm (IF685/IF730). This was considered as a sensitive indicator of decrease in the chlorophyll content of the wheat seedlings. Effect of copper oxide nanoparticles on the cell wall polysaccharide, lignin, lipid, amide I and amide II content of wheat seedling was determined by attenuated total reflectance Fourier transform infrared spectroscopy. The changes in these biochemical contents were determined by analyzing the infrared spectra using resolution enhancement approaches: second order derivative and curve fitting. The band area obtained by curve fitting was used for the relative quantitative assessment of the changes in biochemical contents. The result indicated significant changes in the content and conformation of cell wall polysaccharides. An increase in the content of pectin was observed upon the treatment of copper oxide nanoparticles with the concentration 500, 600, 700, and 800mg/L. The pectin bands at 1240 and 1320cm−1 showed conformational sensitivity towards copper oxide nanoparticles treatment. The amide I and amide II content increased in the plants exposed copper oxide nanoparticles. The increase in the area of the band at 1507cm−1 indicated an increase in the lignin content in the leaves. Significant reduction in the band area of symmetric and asymmetric stretching vibration of methylene (CH2) for lipid was observed in plants exposed to 10–500mg/L copper oxide nanoparticles. An increase in the absorbance ratio of the bands at 1748 and 2960cm−1 (A1748/A2960) indicated increased lipid peroxidation to the copper oxide nanoparticles exposed plants. The study showed toxic response of copper oxide nanoparticles on the biochemical contents of wheat plants.