Physiological and Molecular Dissociation of Photosynthesis in Solanum lycopersicum L. Treated with Titanium Dioxide Nanoparticles
摘要
This study aims to evaluate the effects of titanium dioxide nanoparticles (TiO2 NPs) applications on Solanum lycopersicum L. seedlings at the physiological, biochemical, and molecular levels. The experiment involved treating seeds with TiO2 NPs at 1000 and 2000 mg L− 1, using TiO2 microparticles (µPs) at 2000 mg L− 1 as a size control, and ultrapure water as an absolute control. The seedlings were grown for 30 days in a growth chamber under controlled UV-A spectrum (315–400 nm) to activate NPs, and were used for measuring gas exchange and photosynthesis capacity parameters in vivo. The antioxidant system, specific metabolites, and expression of psbA, psbB, rbcS, and rbcL genes were measured in fully-expanded leaves. We observed that NPs treated plants exhibited lower photosynthesis capacity associated with reduced mesophyll conductance (gm) and photochemical performance. The psbA, psbB, rbcS, and rbcL genes were overexpressed by 1.8-fold on average at 1000 mg L− 1 but downregulated at 2000 mg L− 1. We postulate that the physiological and molecular dissociation is probably due to photochemical impairment and/or morphological leaf changes, evidenced by low gm, as well as post-transcriptional barriers. Additionally, the application of NPs promoted minor stress which resulted in higher antioxidant activity, mainly attributed to the concentration of anthocyanins. These findings underscore the need for dose-size optimization in nano-priming strategies for crop management. TiO2 NPs and µPs applied to S. lycopersicum seeds provoked a physiological-molecular dissociation expressed by a decrease in gm and photochemical damage and slight stress, as well as the overexpression of psbA, psbB, rbcS and rbcL genes, that triggered lower gas exchange and photosynthetic capacity in young plants.