Translocation and Transfer of Nutrients in Vesicular‐arbuscular Mycorrhizas. Iii. Polyphosphate Granules and Phosphorus Translocation

Summary X‐ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm‐3) of cytochemically‐demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high‐voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra‐matrical mycelium in soil measured in the light microscope were around 12·6 cm h‐1. From these data a flux rate of about 2·7 × 10‐8 mol P cm‐2 s‐1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.