Aluminium toxicity and multiplication of Rhizobium trifolii in a defined growth medium |
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| Authors: | M Wood JE Cooper |
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| Institution: | 1. Department of Agricultural and Food Bacteriology, The Queen''s University of Belfast, Belfast BT9 5PX, Northern Ireland;2. Agricultural and Food Bacteriology Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, Northern Ireland |
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| Abstract: | The responses of six strains of R. trifolii to pH, Ca, Al and phosphate were studied in the defined medium of Munns and Keyser (1981) supplemented with vitamins. Wild-type strains responded in the same way as rifampicin-resistant mutant strains. Multiplication was inhibited by acidity alone at pH4.3, and by 50 μM Al at pH 5.5 (despite the precipitation of Al). This inhibitory effect of Al was overcome by increasing the pH above 6.0, or by increasing the phosphate concentration from 10 to 100 μm. Ca concentration had no effect, nor did holding the medium at 22°C for 36 weeks before inoculation. There was variation between strains in their responses to concentrations of A1 < 50 μM. These responses indicate that the defined medium is a satisfactory model for the white clover rhizosphere.Results from these studies and from chemical analyses indicate that the inhibitory effect of Al under partially-neutralized conditions is not due to a direct effect of monomeric A1, nor to an indirect effect of polymeric A1 in reducing the concentration of phosphate, but is due to a direct effect of polymeric A1. |
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