Formation of Metachromatic Granules Following Phosphate Uptake by Mycelial Hyphae of an Ectomycorrhizal Fungus

Summary Abundant metachromatic granules, presumed to contain polyphosphate, were present in mycelial hyphae of Paxillus involutus (Batsch. ex Fr.) Fr. grown in phosphate‐rich medium, but were absent when the medium lacked phosphate. Phosphorus‐starved hyphae placed into phosphate‐containing solutions developed granules within 3 to 4 h. Most of this period was required for synthesis of granule materials, since phosphate uptake occurred within minutes. Both phosphate uptake and granule formation are active processes, affected by low temperature and respiratory inhibitiors. No special importance seemed to attach to the presence of any of the following cations: Ca2+; Mg2+; K+; or Na+; and two different isolates of P. involutus, one calcifuge and one calcicole, showed no differential effects regarding granule formation in the presence and absence of Ca2+ and Mg2+.