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Salt stress is an environmental stress that severely limits plant growth, development and productivity. The use of symbiotic relationships with beneficial microorganisms provides an efficient, cost-effective and environmentally friendly preventative method. The plant growth-promoting rhizobacteria (PGPR) Rahnella aquatilis JZ-GX1 is a moderately salinophilic strain with good probiotic properties, although its ability to improve woody plant salt tolerance has not been reported. In this study, the effect of JZ-GX1 on Cinnamomum camphora under different salt concentrations (0, 50 and 100 mM NaCl) was investigated to reveal the mechanism by which JZ-GX1 improves salt tolerance in C. camphora. The results showed that JZ-GX1 promoted plant growth and root development. The relative electrolyte leakage (REL) and malondialdehyde (MDA) production of inoculated C. camphora plants were reduced by 37.38% and 21.90%, respectively, and the superoxide dismutase (SOD) activity in the leaves was enhanced by 321.57% under a 100 mM NaCl treatment. It was observed by transmission electron microscopy that under 100 mM salt concentration conditions, the inoculated C. camphora leaf cells showed a significant reduction in plasma membrane–cell wall separation and intact chloroplast structures, with tightly packed thylakoids. Importantly, inoculation reduced Na+ accumulation and promoted K+ accumulation in the seedlings, and these changes were consistent with the upregulated expression of the K+ channel SKOR and the vesicular membrane (Na+, K+)/H+ reverse cotransporter NHX1 in the plant roots. This study revealed the mechanism of the Rahnella aquatilis JZ-GX1 enhancing salt tolerance of C. camphora. |
