Influence of Plant Growth-Promoting Rhizobacteria on the Growth of Stylosanthes guianensis in Coppeter-Contamination Soil

Abstract

Plant growth-promoting rhizobacteria or PGPR are a group of bacteria that aggressively colonize the roots of plants and exert beneficial effects on plant growth and development. Rhizobia are a group of PGPR that fix nitrogen in symbiosis with legumes. Studies have been reported on the association of bacteria and legumes for possible remediation of heavy metal-contaminated soil. To examine the possible use of PGPR and legume in bioremediation, experiments were conducted to study the effect of PGPR and rhizobia on the growth of Stylosanthes guianensis in a copper-contaminated soil. S. guianensis seeds were inoculated with PGPR strains B4B (Klebsiella pneumoniae) and BTToRe (Enterobacter spp.) alone and in combination with CB 756 (Bradyrhizobium spp.) under sterile conditions in a growth room and non-sterile conditions in a screen house. After twelve weeks, growth of the plants was evaluated based on parameters such as plant height, number of trifoliate leaves, number of lateral branches, total length of lateral branches, shoot dry weight, root dry weight, nodule dry weight and nodule number. Dried shoots from the nonsterile setup were analyzed for plant copper uptake. Results of the experiment showed that PGPR and .rhizobial inoculation did not significantly increase the growth of S. guianensis plants in copper-contaminated soil based on the growth parameters measured. The inoculation of PGPR strains also did not significantly enhance the uptake of copper from the soil by the plant. Further studies are needed to fully explore the potential of PGPR in the remediation of contaminated soils.