Metabolomics analysis reveal the molecular responses of rice to elevated CO2 concentration and/or Pb stress

Purpose: To explore the regulatory mechanisms of rice to elevated CO 2 concentration and/or Pb stress. Methods: Rice seedling was exposed to two CO 2 concentrations (400±20 and 800±20 μmol/mol) and three PbNO 3 concentrations (0 µmol/L, 50 µmol/L and 100 µmol/L) for 10 days. Electrical conductivity, MDA content, activities of antioxidant enzymes (SOD, POD and CAT) and metabolomics changes were studied. Results: Elevated CO 2 increased some antioxidant enzymes activities and decreased electrical conductivity. Sugars, polyols, organic acids, amino acid and secondary metabolites contents increased; Pb stress damaged cell membrane system, also increased some antioxidant enzymes activities. Sugar, polyol, amino acid metabolism and fatty acid β-oxidation were all enhanced. Secondary metabolite was increased; Under compound treatments, cell membrane damage was reduced, activities of protective enzymes almost increased compared with only Pb stress. High CO 2 increased TCA cycle intermediate products, also caused fatty acid desaturation under mild Pb stress. Most of the sugars, polyols and amino acids contents increased by elevated CO 2 under severe Pb stress. High CO 2 enhanced secondary metabolite under Pb stress. Conclusion: High CO 2 cause efficient photosynthesis and dark respiration metabolism changes, regulated some secondary metabolites production; Under Pb stress, many metabolisms were enhanced to improve osmotic adjustments, maintaining cell membrane stability, supply energy, nitrogen assimilates and antioxidant capacity; Under compound treatments, high CO 2 played a dominant role, also caused the increase of cells antioxidant capacity and fatty acid desaturation under mild Pb stress. Elevated CO 2 increased osmotic regulatory substances and enhanced the shikimic acid pathway under severe Pb stress.