Spectroscopic Characterization of the Biochemical Profile of Mung Seedlings Following Treatment by Copper Oxide Nanoparticles

Abstract

The present study aims to assess the physiological and biochemical changes in the mung plants (Vigna radiata L) due to the impact of copper oxide nanoparticles using laser-induced fluorescence, ultraviolet-visible and confocal micro-Raman spectroscopy. The mung seedlings were treated with copper oxide nanoparticles with concentrations of 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 and 1.8 mM. The growth parameters of the mung seedlings show considerable decreases at higher concentrations of nanoparticles. The laser-induced fluorescence measurements showed a decrease in photosynthetic activity as indicated by the increase in the intensity ratio (I685/I732) with the nanoparticle concentration. Further, the ultraviolet-visible measurements show a decrease in the plant pigments chlorophyll a, chlorophyll b and carotenoids with the concentration of nanoparticles. Except for 0.2 mM, the Raman spectral signatures obtained from the leaves of mung-treated copper oxide nanoparticles reveal that the cell wall component proteins, lignin, pectin, carbohydrates, aliphatics and carotenoids declined with the treatment of nanoparticles. The decreasing intensity of carotenoids from the Raman measurements and the decreasing chlorophyll and carotenoid content in laser-induced fluorescence and ultraviolet-visible measurements suggest that copper oxide nanoparticles are toxic to mung plants. The spectroscopic techniques along with discriminatory and data processing approaches such as principal component analysis (PCA) are demonstrated to provide noninvasive, nondestructive, sensitive, rapid and effective screening of plants under various stresses.