Continual pH lowering and manganese dioxide solubilization in the rhizosphere of the Mn-hyperaccumulator plant Chengiopanax sciadophylloides(Plant Nutrition)

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The Japanese woody plant Chengiopanax sciadophylloides is well known for its extraordinary accumulation of manganese (Mn), and is used as a model for studying Mn uptake and utilization by plants. To clarify the role of manganese dioxide (MnO_2) solubilization for Mn acquisition and further Mn hyperaccumulation in this plant, we examined the lowering of pH in the rhizosphere and Mn accumulation of this plant using regenerated plants. Plants regenerated from C. sciadophylloides calli lowered the pH of the culture broth continuously and simultaneously solubilized MnO_2 added to the medium. The Mn content of the plant increased up to 1,300 mg kg^<-1> within 4 weeks of culture. Release of protein or specific organic acid from the roots was not observed. The medium used for plant culture maintained MnO_2 solubilization ability after removal of the plant; however, this ability was lost by adjustment to the same medium pH of pre-culture conditions. In addition, pH lowering and MnO_2 solubilization were suppressed by adding 1 mmol L^<-1> of the plasma H^+-ATPase inhibitor Na_3VO_4 to the medium, and completely inhibited when 5 mmol L^<-1> of Na_3VO_4 was added. These results suggested that H^+ leaking from plasma H^+-ATPase plays an important role in MnO_2 solubilization in the rhizosphere of C. sciadophylloides and in Mn accumulation in this plant.
社団法人日本土壌肥料学会の論文