Impact of nano ZnO on metabolic attributes and fluorescence kinetics of rice seedlings

Abstract

In this experimental analysis, application of nano-form of ZnO and their effects were compared with bulk form of ZnO by growing Oryza sativa (rice) plants in hydroponic condition. As, rice is a staple food in many countries like China, Japan, India and South Africa and has a great demand so, the assessment of their physiological response towards different concentration (50, 100, 500 and 1000ppm) of both bulk and nano-form of ZnO is one of the important aspects. The result showed that growth was maximally increased in seedlings grown under 50ppm, while after 100ppm i.e. 500 and 1000ppm, the ZnO nanoparticles exerted unfavorable effects on seedlings growth. The biomass accumulation is found to be higher in seedlings treated with nano- form of ZnO than that of its bulk-form. Higher biomass with nano-form of ZnO particularly at lower concentrations is linked with the reduction in the reactive oxygen species (ROS) generation that resulted in less production of malondialdehyde (MDA) and H2O2 contents. In-vivo visualization technique also supported the above statement i.e. reduction in the MDA and H2O2 contents at the lower concentration of nano ZnO. Further, these seedlings were also associated with prominent antioxidative enzymes (SOD, APX, DHAR, GST, CAT and POD). Along with this, the kinetics of PS II (Phi-E0, Psi- E0 and PIABS) showed higher values and energy fluxes parameters (ABC/RC, DI0/RC, TR0/RC and ET0/RC) showed lower values in seedlings grown under lower concentration (50 and 100ppm) of nano form of ZnO. Therefore, the present work has shown that only definite concentration of nano-form of ZnO would be able to improve the qualitative and quantitative characteristics of plants.