Contribution by two arbuscular mycorrhizal fungi to P uptake by cucumber (Cucumis sativus L.) from32P-labelled organic matter during mineralization in soil

Abstract

An experiment was set up to investigate the role of arbuscular mycorrhiza (AM) in utilization of P from organic matter during mineralization in soil. Cucumber (Cucumis sativus L.) inoculated with one of two AM fungi or left uninoculated were grown for 30 days in cross-shaped PVC pots. One of two horizontal compartments contained 100 g soil (quartz sand : clay loam, 1:1) with 0.5 g ground clover leaves labelled with 32p. The labelled soil received microbial inoculum without AM fungi to ensure mineralization of the added organic matter. The labelling compartment was separated from a central root compartment by either 37 #m or 700 #m nylon mesh giving only hyphae or both roots and hyphae, respectively, access to the labelled soil. The recovery of 32p from the hyphal compartment was 5.5 and 8.6 % for plants colonized with Glomus sp. and G. caledonium, respectively, but only 0.6 % for the non-mycorrhizal controls. Interfungal differences were not related to root colonization or hyphal length densities, which were lowest for G. caledonium. Both fungi depleted the labelled soil of NaHCO3-extractable P and 32p compared to controls. A 15-25 % recovery of 32p by roots was not enhanced in the presence of mycorrhizas, probably due to high root densities in the labelled soil. The experiment confirms that AM fungi differ in P uptake characteristics, and that mycorrhizal hyphae can intercept some P immobilization by other microorganisms and P-sorbing clay minerals.

Sulfur Transfer through an Arbuscular Mycorrhiza

“…Under conditions of low S availability, an AM symbiosis can increase the percentage of S in pot-grown onions (Cepa allium; Guo et al, 2007) and maize (Zea mays; Banerjee et al, 2003). The ability of mycorrhizal fungi to transfer nitrogen (N) and P from organic compounds (Joner and Jakobsen, 1994;Hawkins et al, 2000;Govindarajulu et al, 2005) also suggests the possibility that mycorrhizal plants might obtain S from organic sources.…”

No Significant Contribution of Arbuscular Mycorrhizal Fungi to Transfer of Radiocesium from Soil to Plants

“…Thus, the mycorrhizal effects on Cs uptake may be confounded by the effects of plant nutrient status, plant size, and root density. To distinguish the contribution of fungal transport, one may employ compartmented growth systems in which Cs is made available only to mycorrhizal hyphae (17). This was recently attempted with soil-free in vitro cultures (6) in a study in which a mycorrhizal fungus was grown in a jellified medium in petri plates containing a symbiotic root organ culture.…”

Contribution of arbuscular mycorrhizal fungi to utilization of organic sources of phosphorus by red clover in a calcareous soil

“…This enhancement effect could be due to both an increase in surface area and phosphatase activity of the extraradical hyphae (Li et al, 1997a;Tarafdar and Marschner, 1994). It is well established that arbuscular mycorrhiza can increase the P uptake of plants through the extraradical hyphae under certain conditions, but most research has dealt with inorganic P and few investigations have considered the utilization of organic P compounds by AM plants (Jayachandran et al, 1992;Joner and Jakobsen, 1994;Cade-Menun and Berch, 1997).…”