H2O2 signaling regulates seed germination in ZnO nanoprimed wheat (Triticum aestivum L.) seeds for improving plant performance under drought stress

Abstract

Nanopriming has proved to be an effective technique to protect plants from various stresses. The aim of the present work is to investigate the underlying mechanism of zinc oxide (ZnO) nanopriming in imparting drought stress tolerance in wheat. The changes in primed and unprimed wheat plants associated during drought stress were studied by monitoring their physiological and biochemical performance. Results showed that zinc oxide nanoparticles (ZnO NPs) pre-treatment prevented chlorophyll degradation under drought condition thereby improving overall photosynthetic performance and overall plant growth. Study of Chl a fluorescence induction kinetics showed a drastic increase in various photosynthetic parameters in primed drought stressed plants. Nanopriming seems to have protected the photosynthetic apparatus of plant by improving the efficiency of primary photochemistry of PSII under drought stress conditions. Furthermore, the activity of antioxidant enzymes such as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione reductase (GR) as well as malondialdehyde (MDA) content were decreased significantly in nanoprimed drought stressed (NP + DS) plants as compared to unprimed drought stressed (UP + DS) plants. Generation of more reactive oxygen species (ROS) mainly hydrogen peroxide (H2O2) was observed in nanoprimed germinating seeds. We propose role of H2O2 to act as signaling molecule in improving seed germination and vigor by enhancing activity of α-amylase. Lower levels of reactive oxygen species (ROS) production in NP + DS plants was observed which indicates better tolerance to drought stress in nanoprimed plants. It is concluded that nanopriming facilitates improved seed germination and increased seedling vigor through H2O2 signaling networks.