Effects of elevated CO2 on growth, photosynthesis, elemental composition, antioxidant level, and phytochelatin concentration in Lolium mutiforum and Lolium perenne under Cd stress

The objective of this study was to investigate combined effects of Cd and elevated CO2 on growth, physiological and physiochemical characteristics, elemental compositions in Lolium mutiforum and Lolium perenne grown in soils amended with three Cd concentrations (0, 25, 100 mg kg−1) under two CO2 levels (375, 810 μL L−1). Elevated CO2 increased net assimilation rate and internal CO2 concentration, and consequently increased total plant biomass by 51 to 31%. At same spiked Cd level, malondialdehyde content in leaves was lower under elevated than under ambient CO2, whereas superoxide dismutase activity was higher. Elevated CO2 decreased Cd, S, and phytochelatin concentrations in roots and shoots to a various degree, depending on plant species and element, but the PC–Cd ratio was not affected. It was concluded that elevated CO2 ameliorated Cd toxicity in both Lolium species under Cd stress, and that the increase of plant biomass and the alleviation of Cd toxicity with elevated CO2 for the Lolium species may be more dependent on increased photosynthesis and enhanced antioxidant capacity. Results of the study may provide insights into the interaction between soil Cd contamination and atmospheric CO2 concentration with regard to plant ability to grow and remove the Cd from soils.