Combination of elevated CO2 levels and soil contaminants’ stress in wheat and rice

Abstract

Elevated CO2 levels and the increase in heavy metals in soils through pollution are serious problems worldwide. Whether elevated CO2 levels will affect plants grown in heavy-metal-polluted soil and thereby influence food quality and safety is not clear. Using a free-air CO2 enrichment (FACE) system, we investigated the impacts of elevated atmospheric CO2 on the concentrations of copper (Cu) or cadmium (Cd) in rice and wheat grown in soil with different concentrations of the metals in the soil. In this 2-year study, the interactive effects of CO2 on Cu and Cd uptake in rice and wheat leaves were examined. The activities of antioxidant enzymes—catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and superoxide dismutase (SOD)—in rice and wheat leaves were used to assess the combined stress. Elevated CO2 levels led to lower Cu concentrations and higher Cd concentrations in shoots and grain of both rice and wheat grown in the respective contaminated soil. Elevated CO2 levels lowered the pH of the soil and led to changes in the availability of Cu and Cd in the soil. This study indicates that elevated CO2 alters the distribution of contaminant elements in soil and plants, thereby impacting food quality and safety.