ericaceous plant Vaccimium macrocarpon in the presence (M) or absence (NM) of ericoid mycorrhizal inoculum when provided with orthophosphate (Ortho-P) or nutrients supplied in the form of nuclei. Data from Myers and Leake (1996).

In soils in which most of the nutrients are in the form of organic compounds, nitrogen is not the only nutrient that becomes scarcely available for plant growth. In these soils, Phosphorus is also complexed within organic compounds and can be released through the action of a variety of phosphatase enzymes. Ericoid mycorrhizae are capable of producing phosphatase enzymes (Pearson and Read, 1975; Mitchell and Read, 1981; Straker and Mitchell 1985). In these low-pH soils, heavy metals are often more available than in other soils. Concentrations of iron and aluminum greater than 100 mg l−1 were shown to be inhibitory to phosphatase production by the ericoid mycorrhizal fungus Hymenoscyphus ericae (Shaw and Read, 1989). In low-pH soils, however, ericoid mycorrhizal associations have been said to “detoxify” the ecosystem by assimilation of phenolic and aliphatic acids (Leake and Read, 1991) and complexing toxic metal ions (Bradley et al., 1982). This ability allows the establishment of the host plant in extreme environmental conditions. (See Chap. 6.) The importance of ericoid mycorrhizae, their role in the acquisition of nutrients, and their tolerance of heavy metals may be of great importance to those ericaceous plant species that have been brought into cultivation. There is little documented evidence of the role of ericoid mycorrhizae in these cultivated forms (Goulart et al., 1993), in which the extent of root colonization is much higher than expected, based on their survey of native and cultivated blueberry (Vaccinium corymbosum) in the United States.