Transfer of symbiotically fixed nitrogen from berseem (Trifolium alexandrinum L.) to maize via vesicular—arbuscular mycorrhizal hyphae

Abstract

SUMMARYIn order to examine wbetber bypbae of VA mycorrbizal fungi may aid tbe transfer of symbiotically fixed nitrogen from a legume to a non-legume, tbe roots of berseem plants inoculated with the VAM fungus Glomus intraradices and Rhizobium leguminosarum biovar. trifolii (strain RCR 5) were separated by a 2 cm root-free zone from tbe roots of maize plants. A 40 (xm pore size nylon net allowed VAM bypbae to pass tbrougb tbe root-free zone but prevented root penetration. Replacement of tbis net by a 0-45 ixm pore size membrane prevented penetration of VAM bypbae to tbe root-free compartment. Wben tbe berseem plants were 63 d old, tbe plant chambers were sealed in plastic bags to allow tbe roots of tbe plants to be exposed to a ^"N2-enriched atmospbere for 5 d.Berseem plants tbat were exposed to a ^''Ng-enricbed atmospbere fixed more ^^N tban did berseem plants maintained under air at natural ^"N abundance. Tbe total '^N excess content of berseem was similar wbetber or not tbe mycorrhiza bad access to tbe maize roots. Plant mass (dry weight) of maize was not affected by tbe mycorrbizal fungus, but total nitrogen content tended to be bigber in VAM-colonized maize tban in non-colonized maize. Furtbermore, botb atom % ^^N excess and ^^N excess content of mycorrbizal maize were significantly increased as compared witb non-mycorrbizal maize or witb maize controls witbout berseem. Tbe amounts of ^^N transferred were small, accounting for less tban 4% of tbe ^^N in tbe Ng-fixing plant.In spite of tbe 2 cm root-free separating zone, tbe presence of tbe mycorrbizal fungus in tbe non-legume increased tbe transfer of symbiotically fixed nitrogen from berseem to maize plants tbat were physiologically younger. Tbe implications of tbese results for nitrogen transfer from a legume to an accompanying non-legume via VAM bypbae are discussed.

Effect of the arbuscular mycorrhizal fungus Glomus fasciculatum on the uptake of amino nitrogen by Lolium perenne

“…Previous work has demonstrated that both ectoand endomycorrhizas are able to mediate N-transfer between plants (Haystead, Malaczuk & Grove, 1988; Barea, Azcon & Azcon-Aguilar, 1989;Bethlenfalvay etal., 1991 ;Arnebrant e( a/., 1993;Frey & Schuepp, 1994). However, Hamel et a!.…”

Transport of 15N from a soil compartment separated by a polytetrafluoroethylene membrane to plant roots via the hyphae of arbuscular mycorrhizal fungi

“…Nevertheless, the mycorrhizal contribution to the N nutrition of plants in the field might be substantial, especially in dry soils as shown by Tobar et al (1994) or in acid soils, where N occurs mainly in the less-mobile ammonium form. Investigations on AMF-mediated N transfer from an N-fixing plant species to a nonfixing plant species is another potential field of application (Bethlenfalvay et al, 1991 ;Frey & Schu$ epp, 1992 ;Tomm et al, 1994). To avoid problems in the calculations of N transfer due to N mineralized during the experiment, we suggest that only quartz sand should be used as a plant growth substrate, not a mixture that includes field soil (Frey et al, 1998).…”

Bi-directional transfer of phosphorus between red clover and perennial ryegrass via arbuscular mycorrhizal hyphal links

“…The one exception that did not contain the tracer was a non-mycorrhizal plant species. Transfer of phosphorus (P) and nitrogen (N) between plants via hyphal links has also been reported for many plants in pot culture and in glasshouse conditions [7][8][9][10]. Most of the experiments were designed to investigate transfer in one direction despite the possible occurrence also of transfer in the opposite direction.…”