Mobilization and transfer of nutrients from litter to tree seedlings via the vegetative mycelium of ectomycorrhizal plants

Abstract

The ability of the mycorrhizal fungus Paxillus involutus to mobilize nitrogen and phosphorus from discrete patches of beech (Fagus sylvatica), birch (Betula pendula) and pine (Pinus sylvestris) litter collected from the fermentation horizon of three forest soils, and to transfer the nutrients to colonized B. pendula Roth seedlings, was investigated in transparent observation chambers. The mycelium of P. involutus foraged intensively in all three types of litter, leading to a significant decline in their phosphorus contents after 90 d. Over the same period only one of the litter types, beech, showed more than a 10 % loss of its N contents. Exploitation of the litter led to invigoration of the vegetative mycelium of the fungus throughout the chambers as well as to significant increases of biomass production and leaf area in seedlings grown in the plus litter (jL) relative to those in minus litter (kL) systems. The yield increases were associated with gains in whole plant tissue content and concentration of P, but in content only in the case of N. Calculations suggest that a major proportion of the phosphorus lost from litter originated in its organic fraction. The possible basis of the discrepancy between values of N loss from litter and gain by the plant is discussed and the extent to which the distinctive pattern of nutrient mobilization is a feature peculiar to this fungus-plant combination is considered. It is concluded that nutrient mobilization from natural organic substrates in the fermentation horizon of forest soils may be a key function of the vegetative mycelium of mycorrhizal systems. The need for experimental analyses of a greater range of fungus-plant partnerships is stressed.

Enzyme secretion by ECM fungi and exploitation of mineral nutrients from soil organic matter

“…In addition, enzymes involved in the degradation of plant cell wall components are important to get access to nutrients enclosed in dead plant tissues (Leake et al 2002;Perez-Moreno and Read 2000). To attack plant cell walls, a number of enzymes are needed: cellulases, hemicellulases, pectinases, and possibly lignin degrading enzymes.…”

Stratégie saprophyte ou symbiotique durant le développement d’ascocarpes de truffes dans une truffière à chêne vert. Une réponse basée sur l’abondance naturelle du 13C et du 15N

“…Trenching completely prevented fruit body formation of ectomycorrhizal fungi. However, some ectomycorrhizal fungi may mobilise organic polymers of nitrogen, increasing their availability to host plants (Perez-Moreno and Read, 2000;Read and Perez-Moreno, 2003). Similarly, ectomycorrhizal fungi, even if they depend on their host for carbon allocation, can also express extracellular enzyme activities in the soil.…”

Identification of Genes Differentially Expressed in Extraradical Mycelium and Ectomycorrhizal Roots during Paxillus involutus-Betula pendula Ectomycorrhizal Symbiosis

“…In addition, nutrient mobilization from natural organic substrates in the fermentation horizon of forest soils may be a function of the vegetative mycelium of mycorrhizal systems. An increase in the activities of nutrient-mobilizing enzymes in P. involutus colonizing birch litter and a significant decline in the nutrient contents of the colonized litter were demonstrated (4,37). Moreover, mycorrhizal roots act as greater sinks for newly fixed 14 C-photosynthates than do nonmycorrhizal roots (NMR) in Eucalyptus pilularis-Pisolithus sp.…”

“…One therefore needs to consider an intact ectomycorrhizal system providing ideal natural simulations for determining mycorrhizosphere-driven nutrient cycling in forest soils by allowing the formation of EM. Such a system was developed by Read and coworkers with mycorrhizal pine and birch seedlings (4,17) and was used to study nutrient translocation within a symbiotic association as described before (14,16,37).…”