Phytofunctionalized ZnO nanoparticles ameliorate water stress and its recovery in Oryza sativa L.

Nanoparticles have the potential to provide efficient solution to agriculture sector to overcome abiotic stress. Water stress (drought) in rice field is a serious impediment to rice production that can be mitigated using ZnO nanoparticle-based nanonutrition. Such ZnO nanoparticles can be synthesized using chemical and green method. However, chemical method of nanoparticle synthesis has several disadvantages such as phytotoxicity, non-biocompatibility, poor bioavailability, retarded absorptivity and high synthesis cost that can be addressed by green method. The present investigation aims to highlight the advantages of green method (ZnO NP-II of size = 75 nm) of nanoparticle synthesis using Lawsonia inermis extract over chemical method (ZnO NP-I of size = 100 nm) and also perform comparative assessment of their role in ameliorating water stress as well as post-stress recovery potential in rice (Oryza sativa) cultivars seedlings namely Kopilee using hydroponic system by analyzing growth, ROS and antioxidant enzyme activity. The synthesized nanoparticles were characterized by UV spectroscopy, XRD, SEM, TEM and DLS. The results indicated that both ZnO NP-I and II could counter the hazards associated with water stress by increasing fresh mass, dry mass and length as well as decreasing the hydrogen peroxide and superoxide anion content by boosting the antioxidant enzyme activity (CAT, GPx, SOD and GR activity). However, green synthesized ZnO NP-II exhibited enhanced water stress ameliorating efficiency due to smaller size, improved mean surface charge (zeta), reduced hydrodynamic size, better aqueous dispersion and dissolution thereby enabling better accessibility to root exudate, improved Zn2+ extraction and absorption compared to ZnO NP-I.

Automated summary

This study compares green synthesis and chemical synthesis of ZnO nanoparticles and finds that green synthesized ZnO nanoparticles have better efficiency in mitigating water stress due to their smaller size, improved surface charge, better aqueous dispersion, and dissolution, enabling easier absorption by plant roots.