Effects of elevated CO(2) levels on root morphological traits and Cd uptakes of two Lolium species under Cd stress.

This study was conducted to investigate the combined effects of elevated CO(2) levels and cadmium (Cd) on the root morphological traits and Cd accumulation in Lolium multiflorum Lam. and Lolium perenne L. exposed to two CO(2) levels (360 and 1 000 μl/L) and three Cd levels (0, 4, and 16 mg/L) under hydroponic conditions. The results show that elevated levels of CO(2) increased shoot biomass more, compared to root biomass, but decreased Cd concentrations in all plant tissues. Cd exposure caused toxicity to both Lolium species, as shown by the restrictions of the root morphological parameters including root length, surface area, volume, and tip numbers. These parameters were significantly higher under elevated levels of CO(2) than under ambient CO(2), especially for the number of fine roots. The increases in magnitudes of those parameters triggered by elevated levels of CO(2) under Cd stress were more than those under non-Cd stress, suggesting an ameliorated Cd stress under elevated levels of CO(2). The total Cd uptake per pot, calculated on the basis of biomass, was significantly greater under elevated levels of CO(2) than under ambient CO(2). Ameliorated Cd toxicity, decreased Cd concentration, and altered root morphological traits in both Lolium species under elevated levels of CO(2) may have implications in food safety and phytoremediation.