ADVANCES OF STUDIES ON BACTEROID REPRODUCTION OF R.trifolii,Rhizobium leguminosarum, AND FAST-GROWING SOYBEAN RHIZOBIUM Study of resources distribution and ecology of Rhizobium sp.(Caragana) in Shanxi Province ULTRASTRUCTURAL STUDY ON THE FUSION AND SENESCENT DISINTEGRATION OF PERIBACTEROID MEMBRANE IN ACACIA ROOT NODULES Effects of copper on rhizobia-Acacia auriculaeformis symbiotic association The competitiveness of Bradyrhizobium sp. (Arachis) studied by using luxAB marker gene technique