Differential Analysis in the Uptake and Accumulation of Cadmium and Lead by Wheat Varieties with Different Phosphorus Efficiencies.

Objective Soil contamination by cadmium (Cd) and lead (Pb) is a great environmental concern for food safety, and breeding cultivars that can reduce their uptake is one way to grow crops in Cd-and Pb-contaminated soils. In this paper, we experimentally studied how wheat lines with different phosphorus (P) uptake affect their uptake, translocation and accumulation of P, Cd and Pb in the crops. Method The experiment consisted of a lab part and a field part. The lab part considered one factor -- wheat varieties, and the field part was arranged randomly in soil that had been moderately contaminated by Cd and Pb. In both parts, we measured Cd and Pb uptake and their subsequent translocation. Result The average P content in the roots of lines with high P (HP) use efficiency was 7.69 mg/g, significantly lower than that in the lines with low P (LP) use efficiency, which was 8.36 mg/g (P<0.05). The average P content in the shoots of HP varieties was 9.73 mg/g, significantly higher than the 8.19 mg/g in the LP cultivars (P<0.05). The transport coefficient of P in HP varieties was 1.45, significantly higher than the 1.19 of the LP varieties (P<0.05). The kinetic uptake of Cd and Pb by roots and their translocation to shoots followed Michaelis- Menten equation (R2>0.94), with the maximum absorption rates (Vmax) and the Michaelis constants (Km) differing significantly between varieties (P<0.05). The Vmax of the roots of HP varieties was 23.9 and 411 μg/(g·d), respectively, for Cd and Pb, in comparison with 80.0 and 835 μg/(g·d) (P<0.01) for the LP lines. In contrast, Vmax for Cd and Pb in the shoots of the HP varieties was much higher than that for the LP varieties. The difference in Km between the HP and LP varieties was consistent with their difference in Vmax. Correlation analysis showed that the transport coefficients of both Cd and Pb were negatively correlated with root P content (r=-0.638 and -0.714, respectively) at significant level. The transport coefficient of Cd was positively correlated with P transport coefficient (r=0.671, P<0.01). The Pb transport coefficient was also positively correlated with P transport coefficient though not at significant level (r=0.391, P>0.05). The increase in root P content helps reduce the translocation of Cd and Pb; an increase in translocation coefficient of P did not show a noticeable impact on Pb translocation, but significantly boosted Cd transport from roots to the shoots. Conclusion The roots of LP varieties showed high uptake but low translocation of P, Cd and Pb, as opposed the HP varieties which showed a low uptake but high translocation. This suggests that LP varieties are more suitable for growing in soils contaminated by Cd and/or Pb. [ABSTRACT FROM AUTHOR]