The alleviation of salt stress on rice through increasing photosynthetic capacity, maintaining redox homeostasis and regulating soil enzyme activities by Enterobacter sp. JIV1 assisted with putrescine.

The detrimental impact of soil salinization on crop productivity and agricultural economy has garnered significant attention. A rhizosphere bacterium with favorable salt tolerance and plant growth-promoting (PGP) functions was isolated in this work. The bacterium was identified as Enterobacter through 16 S rDNA sequencing analysis and designated as Enterobacter sp. JIV1. Interestingly, the presence of putrescine (Put), which had been shown to contribute in reducing abiotic stress damage to plants, significantly promoted strain JIV1 to generate 1-aminocyclopropane-1-carboxylic (ACC) deaminase, dissolve phosphorus and secrete indole-3-acetic acid (IAA). However, the synergy of plant growth promoting rhizobacteria (PGPR) and Put in improving plant salt resistance has not been extensively studied. In this study, strain JIV1 and exogenous Put effectively mitigated the inhibitory impact of salt stress simulated by 200 mM NaCl on rice (Oryza sativa L.) growth. The chlorophyll accumulation, photosynthetic efficiency and antioxidant capacity of rice were also significantly strengthened. Notably, the combined application of strain JIV1 and Put outperformed individual treatments. Moreover, the co-addition of strain JIV1 and Put increased soil protease and urease activities by 451.97% and 51.70% compared to that of salt treatment group. In general, Put-assisted PGPR JIV1 provides a new perspective on alleviating the salt-induced negative impacts on plants.

Combined application of allantoin and strain JIT1 synergistically or additively promotes the growth of rice under 2, 4-DCP stress by enhancing the phosphate solubility, improving soil enzyme activities and photosynthesis.

Environmental pollution by 2, 4 dichlorophenol (2, 4-DCP) has become a widespread concern due to its detrimental influence on human and natural ecosystem. With the increasing accumulation of 2, 4-DCP in soil, it is of great significance to explore some appropriate approaches for enhancing plant tolerance to 2, 4-DCP stress. In the current study, a strain resistant to 2, 4-DCP was obtained from the tall fescue rhizosphere soil and named as Pseudomonas sp. JIT1. The strain JIT1 exhibited several remarkable plant growth-promoting traits, including the production of IAA, fixation of biological nitrogen and solubilization of phosphate. The inoculation of strain JIT1 significantly increased biomass, photosynthesis, antioxidant levels, chlorophyll contents and the osmotic substance contents in rice seedlings exposed to 2, 4-DCP. Meanwhile, inoculation of strain JIT1 also enhanced activities of soil alkaline phosphatase, urease, sucrase and cellulase. Moreover, under 2, 4-DCP stress, the content of allantoin in seedlings significantly increased and the pretreatment of exogenous allantoin noticeably ameliorated the negative effects caused by 2, 4-DCP stress in rice seedlings. Interesting, allantoin treatment also enhanced phosphate solubilization properties of strain JIT1. The chlorophyll contents, photosynthesis and osmotic substance further increased by combination use of strain JIT1 and allantoin, which improved the growth of seedlings, most likely to be attributed to the synergistic or additive effect between allantoin and strain JIT1. The results of this study highlight the important roles of combined use of strain JIT1 and allantoin for improving the tolerance of rice to 2, 4-DCP to stress.