Pisolithus arhizus Inoculation Enhances Mercury Tolerance and Growth of Trifolium repens in Mining Soils
Highlights What are the main findings? Inoculation with the ectomycorrhizal fungus Pisolithus arhizus significantly enhanced the growth, biomass production, and mercury (Hg) tolerance of Trifolium repens (white clover) in contaminated mining soils. Mycorrhized plants achieved a 9.53% mercury removal rate from the soil, compared to a 4.33% removal rate in non-mycorrhized treatments. Inoculated plants successfully accumulated nearly 9% of soil Hg, yielding a Bioconcentration Factor (BCF) of 0.939, which classifies T. repens as an Hg low accumulator under these experimental conditions. What are the implications of the main findings? The study demonstrates that mycorrhizal symbiosis functions as a “metabolic buffer,” offering a viable, nature-based strategy to mitigate the phytotoxic effects of heavy metals and support more sustainable land rehabilitation practices in mining-impacted areas. The delayed growth recovery observed in contaminated treatments highlights that the symbiotic benefit is contingent upon the establishment of an extensive extraradicular mycelial network, identifying P. arhizus as a critical bio-amendment for ecosystem restoration. Abstract While mining provides critical raw materials for modern infrastructure and the energy transition, it leaves behind severe environmental damages, such as soil mercury (Hg) contamination. In the present study, we present the first study evaluating the relationship of the ectomycorrhizal fungus Pisolithus arhizus with Trifolium repens (white clover) as a novel nature-based mycoremediation strategy for mercury-stressed soils. Through a controlled 2 × 2 factorial experiment over six months, we demonstrate that P. arhizus significantly enhances both plant biomass and heavy-metal tolerance. Inoculation achieved a 9.53% reduction in soil Hg and drove a dramatic 53% increase in stem growth under Hg stress (compared to 36% in non-contaminated conditions) once the extraradicular mycelial network was established. Furthermore, we report novel soil-chemistry dynamics under Hg stress, including a 16% shift in electrical conductivity alongside unexpected increases in the available potassium (+9%) and phosphorus (+3%). These findings present first results for a novel approach of mycoremediation by incorporating P. arhizus into T. repens co-cultivation as a viable remediation strategy, prior to field-scale remediation.