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Fig. 2. Effect of Zn on the growth of rhizobia isolated from nodules present on indigenous clover growing in both low and high metal soil, or from nodules of the plants used to determine the most probable number (MPN) of rhizobia in the high metal soil. Each point represents the average of three different measures of metal tolerance for each individual isolates. Identical results were observed for the three metal tolerance determinations, explaining the lack of error bars on both figures.
