The biology of mycorrhiza in the Ericaceae

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Abstract
SUMMARY: The effect of mycorrhizal infection on the uptake and distribution of iron in Calluna vulgaris was examined when plants were grown in sand supplied with different concentrations of calcium as CaC12 or CaCO3. Infection consistently caused highly significant increases in Fe concentration of Calluna shoots in CaCl2 treatments. A similar effect was obtained with CaCO3 but only in the lowest Ca treatments. Iron concentrations in roots followed the same pattern, being particularly high in all CaCl2 and in the three lowest CaCOa treatments.Total iron contents of shoots were increased by 225% with infection in CaCl2 treatments. In the presence of CaCO3 the average increase in Fe content in shoots of infected plants was 77%, enhancement being restricted to the lowest Ca treatments (0‐50μg ml−1). In roots, the patterns were similar except that since the total Fe contents were higher than in shoots, the proportional differences between infected and uninfected plants were greater.Mycorrhizal infection caused a significant overall increase in specific absorption rate of iron in CaCl2 treatments. In CaCO3 the specific absorption rates of mycorrhizal plants were approximately double those of uninfected plants at the four lowest Ca concentrations but at higher concentrations of the salt the reverse situation was obtained.The nutritional implications of the results are explored, special emphasis being placed upon the possible role of mycorrhizal infection in soils of high calcium content and in situations where iron is present in sparingly soluble mineral combination with phosphates.