CO-INOCULATION WITH AM FUNGUS Glomus caledonium AND THE PHOTOHETEROTROPHIC PURPLE NONSULFUR BACTERIUM Rhodopseudomonas palustris RESULTS IN MUTUAL INHIBITION AND LOWER ARSENIC ACCUMULATION OF Nicotiana tabacum L. IN AN ARSENIC CONTAMINATED SOIL

摘要

A greenhouse experiment was undertaken to investigate the effects of an AM fungus Glomus caledonium and a photoheterotrophic purple nonsulfur bacterium (PNSB) Rhodopseudomonas palustris inoculated alone or in combination on the growth and arsenic (As) uptake of tobacco (Nicotiana tabacum L.) in an As-contaminated soil. Mutual inhibition between G. caledonium and R. palustris was observed, which was revealed by the reduction in both mycorrhizal colonization rate and R. palustris abundance in the dual inoculation treatment. The interaction between two tested inoculants was associated with the decreased levels of biomass and P uptake of tobacco and acid phosphatase activity in rhizosphere soil, but related to the increased levels of pH and As concentration of the in-situ soil solution at three sampling dates as compared to the single inoculation. Furthermore, amounts of three rhizosphere soil As fractions and the As concentrations in root and the whole plant were considerably reduced by the G. caledonium and R. palustris inoculated alone as well as in combination. In conclusion, despite mutual inhibition between G. caledonium and R. palustris this interaction did not impair their observed plant As uptake suppression, but further experiments need to be carried out to reveal the mechanisms involved in these responses.