Rhizosphere nutrient solubilization and phosphate transporter upregulation drive CaCO3-enhanced arsenic accumulation in calcicolous Pteris vittata

Being a calcicolous plant, Pteris vittata grows well and effectively accumulates arsenic (As) in lime-rich substrates. To investigate the underlying mechanisms, P. vittata was grown for 2 months in a contaminated neutral soil containing 100 mg kg –1 As and/or 1% CaCO 3 . Besides As-induced growth promotion, CaCO 3 increased P. vittata biomass by 48% to 11.5 g plant –1 in the As+CaCO 3 vs. As treatment. Consistent with its better growth, P. vittata showed 43–125% better nutrient acquisition, with Ca, Fe and Mn contents in the fronds reaching 9210, 4009 and 68.2 mg kg –1 , respectively. Probably due to the increased root biomass, CaCO 3 enhanced dissolved organic carbon by 123% in P. vittata rhizosphere over bulk soil, while maintaining a neutral pH. Subsequent to the increased rhizosphere solubilization, the P and As contents in P. vittata fronds were enhanced by 81–104% to 3729 and 3942 mg kg –1 in the As+CaCO 3 vs. As treatment, respectively. Correspondingly, the 2.3–3.3 fold upregulation of P-transporters PvPht1;3/1;4 supported the enhanced P and As uptake in P. vittata roots. Overall, CaCO 3 boosts plant growth and As accumulation in P. vittata via Ca/Fe/Mn solubilization and P/As uptake regulation, providing practical strategies for improving phytoremediation of As-contaminated soils.