Phytochelatin synthesis in response to elevated CO2 under cadmium stress in Lolium perenne L.

The increasing atmospheric CO2 and heavy metal contamination in soil are two of the major environmental problems. Knowledge of the Cd stress coping mechanisms is needed to understand the regulation of the plants’ metabolism under the increasing atmospheric CO2 levels. Lolium perenne L. was grown hydroponically under two concentrations of atmospheric CO2 (360 and 1000 μL L−1) and six concentrations of cadmium (0–160 μmol L−1) to investigate Cd uptake, Cd transportation, and variations in phytochelatin (PC) concentration. Cd concentrations in roots and shoots were decreased, but transport index (Ti) was increased under elevated CO2 compared to ambient CO2. Regardless of CO2 concentrations, Cd and PC concentrations, especially the concentrations of high molecular weight PCs (PC4, PC5, PC6) were higher with increasing Cd concentration in growth media and longer Cd exposure time. Under the elevated CO2, more high molecular weight PCs (PC4, PC5, PC6) in shoots and roots were synthesized compared to ambient CO2, with higher SH:Cd ratio in roots as well. These results indicate that under elevated CO2, L. perenne may be better protected against Cd stress with higher biomass, lower Cd concentration and better detoxification by phytochelatins.