Metabolic profile and physiological mechanisms underlying the promoting effects of TiO2NPs on the photosynthesis and growth of tomato

Abstract

Titanium dioxide nanoparticles (TiO2NPs) are photocatalysts that can boost crop photosynthesis. However, the effects of TiO2NPs on photosynthesis performance in tomato plants as well as the underlying mechanisms are unknown. In this research, the effects of synthesized TiO2NPs on growth, photosynthetic performance and the mechanism underlying enhanced photosynthesis performance were assessed in tomato plants. The results showed that the positive effect of TiO2NPs on growth is concentration-dependent, with 0.5 g L−1 of TiO2NPs stimulated the maximum growth in tomato plants. However, TiO2NPs negatively influenced the growth of tomato plants when it was applied at ≥1 g L−1. At 0.5 g L−1 of TiO2NPs, agronomic traits such as plant height, stem diameter and root system were significantly promoted in the treated plants compared to the other concentrations. In addition, the photosynthetic performance of tomato plants was significantly promoted when they were treated with 0.5 g L−1 of TiO2NPs. Further investigation revealed that TiO2NPs significantly increased the net photosynthetic efficiency, the activity of Rubisco and chloroplast F1F0-ATP synthase, and the content of NADPH in the chloroplast. The results also showed that this photocatalyst positively improved stomatal conductance, transpiration rate, and water use efficiency in the treated plants when applied at 0.5 g L−1. In addition, TiO2NPs significantly increased the electron transport rate, actual quantum yield, and photochemical quenching coefficient, while it reduced the non-photochemical quenching parameter and non-photochemical quenching coefficient when applied at 0.5 g L−1. Taken together, the results of this study revealed that TiO2NPs can improve the growth of tomato plants by enhancing photosynthesis rate and improving photosynthetic parameters.