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

Abstract

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.

Arbuscular mycorrhiza can depress translocation of zinc to shoots of host plants in soils moderately polluted with zinc

“…In compartment cultivation systems, extraradical hyphae increase the soil volume accessible for P acquisition (Li et al, 1991). In addition, P taken up is efficiently transported to plant roots (Cox et al, 1980;Smith and Smith, 1990). As a result, both the P concentration and P uptake of mycorrhizal plants can be much higher, sometimes several times higher, than those of corresponding controls (Chen et al, 2003).…”

Arbuscular Mycorrhizal Symbiosis Requires a Phosphate Transceptor in the Gigaspora margarita Fungal Symbiont

“…Intraradical hyphae can also serve as a potential site for nutrient exchange between host and symbiont (Parniske, 2008), while the septa in hyphae separate the senescent or dead fungal branches from the normal ones (Cox et al, 1980), indicating that the formation of septa impairs the development of AM fungi in roots. To test whether GigmPT function is essential for the hyphal growth of AM fungus within roots, we examined the effect of GigmPT RNAi lines on intraradical hyphae.…”

pH measurement of tubular vacuoles of an arbuscular mycorrhizal fungus, Gigaspora margarita

“…The V-ATPase activity or vacuolar pH might be involved indirectly in the polyphosphate accumulation in vacuoles via regulation of VTC activity. Cytochemical and biochemical reports have described that AM fungi also synthesize polyphosphate and accumulate it in tubular vacuoles (Cox et al 1980;Kuga et al 2008;Tani et al 2009). The vacuoles in which polyphosphate accumulates have pH 6.0, as indicated by the chemical shift of terminal phosphate residues in the polyphosphate chain by in vivo 31 P-NMR spectroscopy (Viereck et al 2004), which is consistent with our pH measurement of tubular vacuoles.…”

“…The P i taken by the extraradical hyphae had been regarded as accumulated in spherical vacuoles as a form of polyphosphate granule and translocated in the aseptate hyphae by cytoplasmic streaming (Cox et al 1980). However, the vacuolar system in living filamentous fungi has been revealed as a complex tubular system, not a simple spherical form (Shepherd et al 1993;Rees et al 1994;Uetake et al 2002;Shoji et al 2006;Ashford and Allaway 2007).…”