Elevated atmospheric CO enhances the phytoremediation efficiency of tall fescue in Cd-polluted soil.

With the economic development of society, concentrations of atmospheric CO 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 dry weight, leaf type, chlorophyll content, antioxidase activities, and Cd accumulation ability, under different atmospheric CO treatments. The results showed that the total dry weights increased with increasing CO, and Cd concentrations in falling leaf tissues increased with raised atmospheric CO, before reaching a peak at 600 ppm, above which they remained constant. Compared with the control (400 ppm), 600, 650, and 700 ppm CO 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 CO levels. The concentration of HO in leaf tissues increased with increasing CO, reaching a peak at 600 ppm, and then decreased significantly as the CO content increased further, to 700 ppm. The results in this study suggest that 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 CO levels could improve its soil remediation efficiency. 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 CO is an inevitable phenomenon in future. Therefore, findings from experiments under artificial conditions are sometime a good choice to obtain knowledge about elevated CO related impacts on phytoremediation efficiency of a specific plant. The final goal of this work is to find a suitable CO fumigation strategy optimized for soil remediation. We report on that elevated atmospheric CO can increase the phytoremediation efficiency of for Cd. This is significant because the combined influences of elevated atmospheric CO and metal pollution in terms of biomass yield, pollutant uptake, and phytoremediation efficiency would be more complex than the effects of each individual factor.