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

Abstract

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.

Keywords:

• Festuca arundacea; CO₂ fumigation
• oxidative stress

Additional information

Funding

The authors wish to thank the National Natural Science Foundation of China [No. 21876014].