A 31P nuclear magnetic resonance study of phosphate levels in roots of ectomycorrhizal and nonmycorrhizal plants of Castanea sativa Mill.

Abstract

31 P-Nuclear Magnetic Resonance (NMR) was used to assess phosphate distribution in ectomycorrhizal and nonmycorrhizal roots of Castanea sativa Mill. as well as in the mycorrhizal fungus Pisolithus tinctorius in order to gain insight into phosphate trafficking in these systems. The fungus P. tinctorius accumulated high levels of polyphosphates during the rapid phase of growth. Mycorrhizal and nonmycorrhizal roots accumulate orthophosphate. Only mycorrhizal roots presented polyphosphates. The content in polyphosphates increased along the 3 months of mycorrhiza formation. In mycorrhizal roots of plants cultured under axenic conditions, the orthophosphate pool decreased along the culture time. In nonmycorrhizal roots the decrease in the orthophosphate content was less pronounced. The level of orthophosphate in mycorrhizal roots was significantly lower than in nonmycorrhizal ones, which indicates that this system relies upon the fungal polyphosphates as a major source of phosphate. & k w d :

Ectomycorrhizal fungi: the symbiotic route to the root for phosphorus in forest soils

“…This, however, does not necessarily lead to enhanced host P status, since much of the P may be retained in fungal hyphae rather than being transferred directly to the host (Malajczuk et al 1975;Rousseau and Reid 1991;Colpaert and Verstuyft 1999;Colpaert et al 1999). The relative amounts of P transferred to the host and retained in fungal tissue vary with factors that include P availability and the relative growth rates of the host and ECM fungal partner, but as much as 90% of absorbed P can be retained in the fungal tissues of excised ECM root tips, mainly in the form of polyphosphates McCready 1952, 1981;Martins et al 1999).…”

The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and 31P NMR spectroscopy study

“…S2). Signal identification was carried out according to chemical shifts reported in other ectomycorrhizal fungi (Gerlitz & Werk ; Martins et al ). We also used the spectra of H. cylindrosporum perchloric extracts obtained from P‐starved and P‐sufficient mycelia without and after P‐resupply (experiment 3, Supporting Information Fig.…”

In vitro Mycorrhization of Micropropagated Plants: Studies on Castanea sativa Mill

“…Mycorrhizal symbiosis is frequently associated with increased photosynthetic rates of mycorrhizal plants (Harley and Smith, 1983;Reid et al, 1983;Bougher et al, 1990;Dosskey et al, 1990;Rousseau and Reid, 1990;Guehl and Garbaye, 1990;Jones et al, 1990;Martins, 1992;Martins et al, 1997;Smith and Read, 1997). ECM may influence the assimilation capacity for CO 2 in two distinct forms: increased absorption of P and N in mycorrhizal plants influence the photosynthetic rates, as observed for forestry species when amended with P; the other resulting from enhanced flux of carbon compounds to the roots, promoted by mycorrhizal associations (Martins et al, 1997;1999). This hypothesis considers that the increased photosynthetic rates are related with the fungus necessity of carbon compounds and is named source-sink concept (Dosskey et al, 1990;1991) although this seems to be just one of mechanism involved in photosynthetic increment in mycorrhizal plants (Martins et al, 1997;1999).…”