The biology of mycorrhiza in the Ericaceae

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Abstract
Summary: The effects of the metals, iron and aluminium, on acid phosphatase (P‐NPPase) activity of the ericoid endophyte, Hymenoseyphus ericae (Read) Korf and Kernan were determined. The endophyte was grown in pure culture and then treated with Fe2+ and Al2−over a range of concentrations (0–1000mgl−1), and at two concentrations of inorganic phosphorus (20μ and 200 μM p). Activities of p‐NPPase were determined. Enzyme activity was greatly inhibited at the highest concentration of external P even in the absence of the metal ions. The presence of the metals in the low P treatment had effects determined by their concentration. At the highest concentration used, they precipitated products of acid phosphatase activity (p‐NP), and so invalidated the use of the assay at these metal levels. However, the assay could reliably be used over the concentration range 0–200 mg 1−1 Al2+ and 1–100 mg 1 −1 Fe2+, the upper concentrations in both cases being considerably above those normally found in soil solutions. Over these ranges the presence of Al3+ only slightly inhibited p‐NPPase activity, whereas there was a small increase of activity in the case of Fe2+. The results are discussed in relation to the role of ericoid mycorrhizal infection in the phosphorus nutrition of ericaceous plants in natural ecosystems.