The symbiotic recapture of nitrogen from dead mycorrhizal and non-mycorrhizal roots of tomato plants

Abstract

Aims The aim was to quantify the nitrogen (N) transferred via the extra-radical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices from both a dead host and a dead non-host donor root to a receiver tomato plant. The effect of a physical disruption of the soil containing donor plant roots and fungal mycelium on the effectiveness of N transfer was also examined. Methods The root systems of the donor (wild type tomato plants or the mycorrhiza-defective rmc mutant tomato) and the receiver plants were separated by a 30 μm mesh, penetrable by hyphae but not by the roots. Both donor genotypes produced a similar quantity of biomass and had a similar nutrient status. Two weeks after the supply of 15 N to a split-root part of donor plants, the shoots were removed to kill the plants. The quantity of N transferred from the dead roots into the receiver plants was measured after a further 2 weeks. Results Up to 10.6 % of donor-root 15 N was recovered in the receiver plants when inoculated with the arbuscular mycorrhizal fungus (AMF). The quantity of 15 N derived from the mycorrhizal wild type roots clearly exceeded that from the only weakly surface-colonised rmc roots. Hyphal length in the donor rmc root compartments was only about half that in the wild type compartments. The disruption of the soil led to a significantly increased AMF-mediated transfer of N to the receiver plants. Conclusions The transfer of N from dead roots can be enhanced by AMF, especially when the donor roots have been formerly colonised by AMF. The transfer can be further increased with higher hyphae length densities, and the present data also suggest that a direct link between receiver mycelium and internal fungal structures in dead roots may in addition facilitate N transfer. The mechanical disruption of soil containing dead roots may increase the subsequent availability of nutrients, thus promoting mycorrhizal N uptake. When associated with a living plant, the external mycelium of G. intraradices is readily able to re-establish itself in the soil following disruption and functions as a transfer vessel.

Phosphorus and Nitrogen Regulate Arbuscular Mycorrhizal Symbiosis in Petunia hybrida

“…The predominant nutrient element acquired through AM is phosphorus (P), which is delivered to the plant in its inorganic oxidized form phosphate (P i ) [10] . Furthermore, nitrogen (N) can be transferred to mycorrhizal plants through the fungal symbiont [11] – [14] , involving a complex pathway that has been elucidated in considerable detail in recent years [15] – [17] . Apart from these central macronutrients, sulfur (S) [18] , [19] and several micronutrients can be delivered to plants through AM fungi [20] , [21] .…”

Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production

“…For instance, Zhang et al [ 45 ] reported similar data, i.e ., higher canopy radius/biomass in M. sativa (alfalfa) plants grown in AM soil as compared to plants grown in fungicide-treated (non-mycorrhized) soil. The growth stimulation can be explained by the increase of P and N content found in AM plants [ 46 – 49 ]. In this study, the content of N, P and C was also enhanced at 3 wpi in the shoots of AM- when compared to the control plants ( S1 Table ).…”

Lifespan and functionality of mycorrhizal fungal mycelium are uncoupled from host plant lifespan

“…Accordingly, Müller et al . 33 found significant translocation of 15 N from dead donor roots to receiver plants in mycorrhizal tomato. Such findings represent evidence of the persistence of ERM viability and functionality in dead root systems, recorded over short periods of time, 2 and 6 weeks, respectively.…”