Arbuscular mycorrhizal fungi increase the tolerance to excess zinc of a tropical legume grown in iron-ore mining waste

Abstract

Arbuscular mycorrhizal fungi (AMF) might amend the toxicity of trace elements and improve the nutritional status of plants, but little is known about these responses in tropical native plants in iron-ore-impacted sites with excess zinc (Zn). We evaluated how the association with AMF contributes to the resistance capacity of Stryphnodendron adstringens to high Zn concentrations in mining waste. Seeds were sown in pots containing iron-ore mining waste with different concentrations of Zn (0, 100, 200, 400 and 600 mg L⁻¹) and two conditions (inoculated or not with AMF). The biomass accumulation and physiological processes were severely impacted in the mining waste with Zn concentration above 100 mg L⁻¹. The relative growth rate (RGR) and the concentration of phosphorus (P) in the shoot were higher in the AMF-inoculated plants, mainly when cultivated without Zn excess. Non-inoculated plants presented the lowest net photosynthetic rate (An) mainly due to impairment in light use efficiency, especially under Zn excess. The treatments did not change stomatal conductance, transpiration, Rubisco carboxylation rate, triose-phosphate utilization and respiration rate. The AMF improved the plant resistance capacity in mining waste substrate by promoting decreased oxidative damage, ameliorated P nutrition, higher RGR, root biomass and An.

Keywords:

• AMF
• heavy metals
• oxidative damage
• phosphorus
• photosynthesis
• stryphnodendron adstringens
• zinc

Authors’ contributions

EGP: Funding acquisition and resources, project administration, supervision, conceptualization, formal analysis, writing-reviewing, and editing. LS: conceptualization, investigation, formal analysis, writing-original draft. MMP: investigation, writing-reviewing and editing. MCMK and MCSS: formal analysis, writing-reviewing, and editing. All authors approved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Additional information

Funding

This work was supported by the Foundation for Research Development of Minas Gerais State (FAPEMIG) and the Coordination for the Improvement of Higher Education Personnel (CAPES). E. G. Pereira and M. C. M. Kasuya are supported by the National Council for Scientific and Technological Development (CNPq) with a research productivity grant.