Rice (Oryza sativa L.) seedlings enriched with zinc or manganese: Their impacts on cadmium accumulation and expression of related genes

Cadmium (Cd) contamination in paddy soils means that the rice produced there may be unsafe for human consumption. A hydroponic study was conducted to enrich rice seedlings with zinc (Zn) or manganese (Mn), and the uptake and transport characteristics of Cd in these Zn- and Mn-rich seedlings were subsequently investigated using a greenhouse pot trial. The results showed that hydroponic cultivation in 10-50 mu mol L-1 Zn (ZnSO4 center dot 7H(2)O) or 50-250 mu mol L-1 Mn (MnSO4 center dot H2O) for 30 d had no significant impact on rice growth, while the accumulation of Zn and Mn was 7.31-18.5 and 25.4-47.7 times higher, respectively, than in the control (no Zn or Mn addition). The accumulation of Cd in the Zn- and Mn-rich rice plants was 26.3%-38.6% and 34.4%-44.5% lower than that in the control, respectively, and the translocation factors of Cd from roots to shoots also decreased by 23.3%-41.3% and 25.3%-37.0%, respectively, after transplanting to Cd-contaminated soils. Furthermore, the relative expression levels of OsIRT1 (Oryza sativa iron-regulated transporter 1) were downregulated by 40.1%-59.3% and 16.0%-25.9%, respectively, in the Zn- and Mn-rich seedling roots. This downregulation may indicate a possible mechanism contributing to the reductions in Cd absorption. Field experiments confirmed that the Zn- and Mn-rich seedlings produced brown rice (unpolished rice grains) with significantly decreased concentrations of Cd (34.2%-44.4%). This study provides an innovative method for reducing the food safety risks from rice grown on slightly to moderately Cd-contaminated paddy soils.

Automated summary

The study enriched rice seedlings with zinc and manganese through hydroponic cultivation, effectively reducing the accumulation of Cd in rice plants. Field experiments confirmed the success of this innovative method in reducing food safety risks associated with rice grown on slightly to moderately Cd-contaminated paddy soils.