Elevated atmospheric CO2 enhances the phytoremediation efficiency of tall fescue (Festuca arundinacea) in Cd-polluted soil

With the economic development of society, concentrations of atmospheric CO2 and heavy metals in soils have been increasing. The physiological responses of plants to the interaction between soil pollution and climatic change need to be understood. Pot experiments were designed to assess variations in Festuca arundinacea dry weight, leaf type, chlorophyll content, antioxidase activities, and Cd accumulation ability, under different atmospheric CO2 treatments. The results showed that the total dry weights increased with increasing CO2, and Cd concentrations in falling leaf tissues increased with raised atmospheric CO2, before reaching a peak at 600 ppm, above which they remained constant. Compared with the control (400 ppm), 600, 650, and 700 ppm CO2 treatments increased the proportions of the falling tissues by 1.7%, 3.3%, and 4.5%, respectively. Antioxidant enzyme activities in plant leaves increased with increasing atmospheric CO2 levels. The concentration of H2O2 in leaf tissues increased with increasing CO2, reaching a peak at 600 ppm, and then decreased significantly as the CO2 content increased further, to 700 ppm. The results in this study suggest that F. arundinacea could be regarded as a potential candidate for phytoremediation of Cd-polluted soil; especially if senescent and dead leaf tissues could be harvested, and that raised atmospheric CO2 levels could improve its soil remediation efficiency. Novelty statement Extrapolation of results from experiments of environmental impacts in greenhouse to real scale field requires to be considered cautiously. External factors such as water, temperature, humidity, and pollution are variable in real field. Plants will face a lot of beneficial or detrimental conditions which will influence the magnitude of the results. However, the elevation of CO2 is an inevitable phenomenon in future. Therefore, findings from experiments under artificial conditions are sometime a good choice to obtain knowledge about elevated CO2 related impacts on phytoremediation efficiency of a specific plant. The final goal of this work is to find a suitable CO2 fumigation strategy optimized for soil remediation. We report on that elevated atmospheric CO2 can increase the phytoremediation efficiency of Festuca arundinacea for Cd. This is significant because the combined influences of elevated atmospheric CO2 and metal pollution in terms of biomass yield, pollutant uptake, and phytoremediation efficiency would be more complex than the effects of each individual factor.