Pseudomonas species isolated from tobacco seed promote root growth and reduce lead contents in Nicotiana tobacum K326.

Endophytic bacteria are generally helpful for plant growth and protection. We isolated three Pseudomonas strains (K03, Y04 and N05) from tobacco seeds, which could produce siderophores, Indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase, fix nitrogen, dissolve phosphorus/potassium and tolerate heavy metals. In pot experiments, the three isolated strains significantly promoted root growth and increased the root enzyme activity in Nicotiana tobacum K326. Furthermore, bacterial inoculations increased the proportion of residual lead (Pb) by 8.36-51.63% and decreased the total Pb content by 3.28-6.38% in the contaminated soil during tobacco planting, compared to those without inoculation. An effective decrease in Pb content had also been found in tobacco leaves with bacterial inoculations. K03 inoculation decreased the Pb content in the upper leaf by 49.80% and Y04 inoculation had the best effect on decreasing the Pb content in the middle leaf by 70.12%. Additionally, soil pH and root activity had significant effects on transformation and translocation of Pb. The study suggested that, to respond to Pb pollutions in soil, the reasonable application of endophytes (e.g., Pseudomonas) might be a promising approach in promoting tobacco growth and reducing Pb contents in tobacco, while simultaneously enhancing Pb stabilization in soils.