Mitigation of arsenic stress in Brassica juncea L. using zinc oxide-nanoparticles produced by novel hydrothermal synthesis

Abstract

In the current study, we successfully synthesized the zinc oxide nanoparticles (ZnO-NPs) via an efficient, facile, and cost-effective method of the modified hydrothermal synthesis approach, and examined their effectiveness in alleviating arsenic (As) stress in Brassica juncea. The synthesized ZnO-NPs were analyzed using a variety of experimental techniques viz. XRDs, SEM micrographs, EDAX/Mapping pattern, Raman Spectroscopy Pattern, and X-ray photoemission spectroscopy analysis. All of these analyses revealed that ZnO-NPs were highly pure with no internal defects and could potentially be used in plant applications. Hence, we further determined the effect of these nanoparticles in modulation of As tolerance in B. juncea plants by examining the various growth attributes, photosynthesis parameters, antioxidant activities, and enzyme activities. Our results demonstrated that As-stress inhibited growth, photosynthesis-related parameters, reduced protein content, as well as carbonic anhydrase, nitrate reductase, and RuBisCO; however, these attributes were substantially up-regulated by the supply of ZnO-NPs to the leaves. Furthermore, As stress-induced increases in malondialdehyde and H2O2 levels are partially reversed by ZnO-NP in the As-stressed plants. Overall, supplementation positively regulated As tolerance in B. juncea by altering the key enzymes involved in ROS detoxification, which in turn prevented As-induced oxidative damage to the plant tissues. Hence, our study clarified the potential involvement of the newly synthesized ZnO-NPs in alleviating As stress in plants. Furthermore, this is the first report to elucidate the effect of the ZnO-NPs synthesized by the hydrothermal reaction route on As-stress modulation in B. juncea.