Improvement of leaf K + retention is a shared mechanism behind CeO 2 and Mn 3 O 4 nanoparticles improved rapeseed salt tolerance.

Salinity is a global issue limiting efficient agricultural production. Nanobiotechnology has been emerged as an effective approach to improve plant salt tolerance. However, little known is about the shared mechanisms between different nanomaterials-enabled plant salt tolerance. In this study, we found that both PNC [polyacrylic acid coated nanoceria (CeO 2 nanoparticles)] and PMO (polyacrylic acid coated Mn 3 O 4 nanoparticles) nanozymes improved rapeseed salt tolerance. PNC and PMO treated rapeseed plants showed significantly fresh weight, dry weight, higher chlorophyll content, Fv/Fm, and carbon assimilation rate than control plants under salt stress. Results from confocal imaging with reactive oxygen species (ROS) fluorescent dye and histochemical staining experiments showed that the ROS over-accumulation level in PNC and PMO treated rapeseed was significantly lower than control plants under salt stress. Confocal imaging results with K + fluorescent dye showed that significantly higher cytosolic and vacuolar K + signals were observed in PNC and PMO treated rapeseed than control plants under salt stress. This is further confirmed by leaf K + content data. Furthermore, we found that PNC and PMO treated rapeseed showed significantly lower cytosolic Na + signals than control plants under salt stress. While, compared with significantly higher vacuolar Na + signals in PNC treated plants, PMO treated rapeseed showed significantly lower vacuolar Na + signals than control plants under salt stress. These results are further supported by qPCR results of genes of Na + and K + transport. Overall, our results suggest that besides maintaining ROS homeostasis, improvement of leaf K + retention could be a shared mechanism in nano-improved plant salt tolerance.