Abstract

Plant growth promoting bacteria are important for plant growth and heavy metal uptake of metal-polluted soils. In this study, to isolate (cadmium and lead) Cd and Pb-resistant bacteria, seven strains of Pseudomonas putida and Pseudomonas fluorescens were plated onto Tryptone Soya Broth supplemented with different concentrations of Pb(No₃)₂and CdCl₂ (0, 30, 60 mg L^-1). Three heavy metals resistant isolated strains included P. putida strain 11 (P.p.11), P. putida strain 4 (P.p.4) and P. fluorescens strain 169 (P.f.169)were investigated. The bacteria were able to produce indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylic deaminase (ACCD). They were inoculated to canola and barly seeds in a soil artificially contaminated with Cd (10 and 20 mg kg^-1) and Pb (300 and 600 mg kg^-1) in a pot experiment. Results showed that the inoculation with these PGPR increased shoot dry matter of canola. An increase in Cd and Pb uptake was observed in canola inoculated with P.p.11 and P.f.169. Translocation factor indicated that inoculated canola with P.f.169 and barley with all of the three strains had abilities of Cd and Pb phytoextraction in the contaminated soil respectively. The bacterial strains protected the plants against the inhibitory effects of cadmium and lead probably due to production of IAA, siderophore and ACCD activity.

Key words: 1-aminocyclopropane-1-carboxylic deaminase (ACC deaminase), canola, heavy metals, phytoextraction, Pseudomonas.