Effects Of High Concentration CO₂ And/or Cd Stress On Endogenous Hormones And Organic Acids Contents In Rice Seedlings

Based on global CO₂ concentration increases and Cd pollution stress in the soil,the rice seedlings?Oryza sativa L.?were studied,three gradients?0?mol/L,50?mol/L,150?mol/L?of Cd stress were performed simultaneously at the atmospheric CO₂ concentration conditions?400±20?mol/mol?and at high CO₂ concentration conditions?800±20?mol/mol?.Treatment was divided into six groups:control group?AC?,high concentration CO₂ treatment?EC?,different concentration Cd treatment?L,H?,high concentration CO₂ and Cd combined treatment?EC+L,EC+H?.Growth,endogenous hormones and organic acids contents of rice seedling under elevated CO₂ and/or Cd stress were studied,which provided theoretical basis for future rice production under the double environmental impacts of atmospheric CO₂ changes and Cd stress.The results showed as follow:1.Compared with AC,under EC treatment,dry weight of above-ground was promoted significantly;Gibberellin?GA₃?,auxin?IAA?,zeatin?ZT?contents in leaves increased significantly,abscisic acid?ABA?and tartaric acid,malic acid,lactic acid,succinic acid contents in leaves decreased significantly;GA₃,IAA and ZT contents in roots increased significantly,salicylic acid?SA?,jasmonate?JA?content in roots decreased significantly;Succinic acid content of roots exudation decreased significantly.It shows that high concentration CO₂ can increase growth-promoting hormones contents and decrease growth-inhibiting hormones contents to promote the growth and development of rice seedlings.2.Compared with AC,single Cd stress inhibited the growth of rice seedlings,height,root length,fresh weight and dry weight decreased,and with the increase of stress level,the inhibitory effect becomes greater.Under L treatment,JA,ABA contents in leaves increased significantly,GA₃ content in leaves decreased significantly;JA,SA and malic acid,lactic acid,acetic acid contents in roots increased significantly;Oxalic acid,malic acid,acetic acid,citric acid,succinic acid contents of roots exudation increased significantly.Under H treatment,ABA,JA and acetic acid contents in leaves increased significantly;SA and malic acid,lactic acid,acetic acid contents in roots increased significantly;Oxalic acid,malic acid,succinic acid contents of roots exudation increased significantly.By decreasing growth-promoting hormones contents and increasing growth-inhibiting hormones contents,plant growth and development are negative,and by increasing organic acids contents to alleviate Cd toxicity.3.Compared with L,under EC+L treatment,fresh weight and dry weight of above-ground,root length of rice seedlings was promoted significantly;ZT,GA₃,IAA contents in leaves increased significantly,ABA and tartaric acid contents in leaves decreased significantly;ZT,GA₃,IAA contents in roots increased significantly,SA,JA content in roots decreased significantly;Malic acid and succinic acid contents of roots exudation decreased significantly.Compared with H,under EC+H treatment,fresh weight and dry weight,root length of rice seedlings were promoted significantly;ZT,GA₃,IAA contents in leaves increased significantly,ABA and tartaric acid contents in leaves decreased significantly;ZT,GA₃,IAA contents in roots increased significantly,SA,lactic acid content in roots decreased significantly;Oxalic acid,malic acid,succinic acid contents of roots exudation decreased significantly.It shows that high concentration CO₂ canincrease growth-promoting hormones contents and decrease growth-inhibiting hormones contents,the damage of Cd stress on plant growth and metabolism are alleviated to some extent.