Alleviation of antimonate (SbV) toxicity in maize by silicon (Si)

• Antimonate did not influence root biomass but retarded root growth and architecture.
• Si mitigated the negative Sb effect on root morphology and enhanced root aerenchyma.
• Si did not affect root Sb concentrations but modified Sb translocation to the shoot.
• The interactions between Sb and Si occurred through different types of mechanisms.

Silicon (Si) has often been found to alleviate phytotoxic effects of trace elements. Here, we investigated whether it can also mitigate negative effects of the metalloid antimony (Sb) on plant growth. Young maize seedlings (Zea mays, hybrid Valentina) were hydroponically grown in the presence of various antimonate Sb(OH)6− concentrations (0–30 mg kg−1) and one concentration of Si (2.5 mM). Antimonate did not influence root biomass but retarded root growth, leading to shorter and thinner roots. The increase in root mass density was in line with a decrease in root cortical aerenchyma. Silicon addition mitigated the negative Sb effects on root growth and architecture and enhanced aerenchyma formation. It did not affect root Sb concentrations, but with increasing Sb exposure level it first increased and then reduced the small fraction of Sb that was translocated into the shoots. In turn, antimonate reduced Si accumulation by the roots, but did not inhibit root-to-shoot translocation of Si. The simultaneous occurrence of positive and negative interactions between Sb and Si indicates that they involved multiple mechanisms.