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Title: Ectomycorrhizal fungi enhance pine growth by stimulating iron‐dependent mechanisms with trade‐offs in symbiotic performance

Iron (Fe) is crucial for metabolic functions of living organisms. Plants access occluded Fe through interactions with rhizosphere microorganisms and symbionts. Yet, the interplay between Fe addition and plant–mycorrhizal interactions, especially the molecular mechanisms underlying mycorrhiza‐assisted Fe processing in plants, remains largely unexplored.

We conducted mesocosms inPinusplants inoculated with different ectomycorrhizal fungi (EMF)Suillusspecies under conditions with and without Fe coatings. Meta‐transcriptomic, biogeochemical, and X‐ray fluorescence imaging analyses were applied to investigate early‐stage mycorrhizal roots.

While Fe addition promotedPinusgrowth, it concurrently reduced mycorrhiza formation rate, symbiosis‐related metabolites in plant roots, and aboveground plant carbon and macronutrient content. This suggested potential trade‐offs between Fe‐enhanced plant growth and symbiotic performance. However, the extent of this trade‐off may depend on interactions between host plants and EMF species. Interestingly, dual EMF species were more effective at facilitating plant Fe uptake by inducing diverse Fe‐related functions than single‐EMF species. This subsequently triggered various Fe‐dependent physiological and biochemical processes inPinusroots, significantly contributing toPinusgrowth. However, this resulted in a greater carbon allocation to roots, relatively reducing the aboveground plant carbon content.

Our study offers critical insights into how EMF communities rebalance benefits of Fe‐induced effects on symbiotic partners.

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New Phytologist
Medium: X
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National Science Foundation
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