Organic acids in the rhizosphere of Banksia integrifolia L.f

Water leachates of the proteoid root layer of a mature stand of Banksia integrifolia were analysed for low molecular weight (LMW) organic acids by GC, HPLC and colorimetrie techniques. Large amounts of organic acids (2500 ì g in 100 mL of leachate) were found in the proteoid root layer compared to the surrounding soil and leaf litter (~230 µg in 100 mL of leachate). Citric acid represented approximately 50% of the total organic acids leached, malic acid approximately 18%, and aconitic acid constituted approximately 17%. Concentration of citric acid in the proteoid root layer may enhance the availability of phosphorus for plant uptake.