Enhancement of Lead Phytoremediation by Perennial Ryegrass (Lolium perenne L.) Using Agent of Streptomyces pactum Act12

Abstract

It has been well recognized that microbes can assist phytoremediation of lead (Pb) by promoting plant growth and metal uptake. However, little is known about the potential of soil inoculation with actinomycetes to enhance Pb uptake and translocation in plants, particularly in semi-arid water-deficient areas. This study was focused on exploring the resistance of a soil actinomycete strain (Streptomyces pactum Act12) to Pb and its effects on plant growth, antioxidant responses, Pb uptake and translocation in perennial ryegrass (Lolium perenne L.). Special attention was given to experimental conditions in semi-arid area in Northerwest China. A fermentation culture of Act12 was applied in powder form to soil with or without Pb treatment (0–1,000 mg kg-1), and ryegrass plants were immediately grown in this soil, in pots, for 60 days under 20% relative soil moisture. Act12 showed tolerance to up to 1,200 mg Pb L-1 in plate culture and well colonized the soil containing less than 500 mg Pb kg-1. Under Pb stress, inoculated plants had higher biomass with greater plant height and root tiller number than the uninoculated controls. Additionally, higher catalase, superoxide dismutase and peroxidase activities were detected in leaves of inoculated plants under Pb stress. Inoculating soil with Act12 significantly increased Pb concentrations and uptake in plants grown in soil containing 200 to 1,000 mg Pb kg-1. The translocation and bioconcentration factors of inoculated plants were 10.5–36.2% and 37.3–133.1% higher than uninoculated plants, respectively. Streptomyces pactum Act12 can enhance Pb phytoremediation by perennial ryegrass and its powder form facilitates the use in semi-arid areas.