PHOSPHATE-SOLUBILIZING BACTERIA ASSOCIATED WITH PROTEOID ROOTS OF SEEDLINGS OF WARATAH [TELOPEA-SPECIOSISSIMA-(SM)-R-BR]

Bacteria isolated from proteoid roots and non-proteoid lateral roots o f Telopea speciosissima (Sm.) R.Br. seedlings were able to acidify the medium and solubilize calcium phosphates when grown in culture in the presence of ammonium salts and an appropriate carbon source. In gener al this activity was not detected when NO3- was substituted for NH4+, and it is proposed that protons were secreted in exchange for ammonium ions. Cation exchange between these protons and calcium in the medium is a possible cause of the calcium phosphate solubilizing activity. T he relevance of these data to phosphate-solubilizing activity in natur al environments is discussed.