12 - Heavy metal stress alleviation in plants by ZnO and TiO2 nanoparticles

Abstract

For more than a decade, zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) have been tested in various conditions to evaluate their influence on plants, including alleviating stress exerted by heavy metals. Heavy metal contamination has become a common problem in many countries worldwide. Due to their unique and easily adjustable physicochemical properties, the amelioration of heavy metal stress in plants by engineered inorganic nanoparticles gained attention in recent years. ZnO NPs and TiO2 NPs are among the most studied nanoparticles in this area. They represent two opposites, ZnO NPs being easily dissolved with the well-understood mode of action similar to ionic forms of Zn and TiO2 NPs having negligible dissolution and unclear mechanisms of action. This chapter focuses on the literature summary of the positive effects of ZnO NPs and TiO2 NPs in the amelioration of heavy metal stress in plants. Possible mechanisms of interaction between ZnO NPs and TiO2 NPs and heavy metals in plants and agriculture systems are deliberated, and a broad overview of recent advances is provided. The chapter also highlights the need for research and knowledge gaps that can be of interest shortly to progress in sustainable agriculture.