Impact of foliar spray of zinc oxide nanoparticles on the photosynthesis of Pisum sativum L. under salt stress

This study investigates the impacts of zinc oxide nanoparticles: bare (ZnO NPs) and ZnO NPs coated with silicon shell (ZnO-Si NPs), on Pisum sativum L. under physiological and salt stress conditions. The experimental results revealed that the foliar spray with ZnO-Si NPsand 200 mg/LZnO NPs didnot influence the stomata structure, the membrane integrity, and the functions of both photosystems under physiological conditions, while 400 mg/L ZnO-Si NPs had beneficial effects on the effective quantum yield of photosystem II (PSII) and the photochemistry of photosystem I (PSI). On the contrary, small phytotoxic effects were registered after spraying with 400 mg/L ZnO NPs accompanied by stimulation of the cyclic electron flow around PSI and an increase of the non-photochemical quenching (NPQ). The results also showed that both types of NPs (with exception of 400 mg/L ZnO NPs) decrease the negative effects of 100 mM NaCl on the photochemistry of PSI (P700 photooxidation) and PSII (qp, Fv/Fm, Fv/Fo, Phi(PSII), Phi(exc)), as well as on the pigment content, stomata closure and membrane integrity. The protective effect was stronger after spraying with ZnO-Si NPs in comparison to ZnO NPs, which could be due to the presence of Si coating shell. The role of Si shell is discussed.

Automated summary

This study found that under physiological conditions, ZnO-Si NPs and low concentrations of ZnO NPs have positive effects on Pisum sativum L. plants, while both types of nanoparticles can alleviate the negative effects of sodium chloride under salt stress conditions, with ZnO-Si NPs showing a stronger protective effect.