| This thesis studied the growth of Skeletonema costatum under Cd2+ stress and Cu2+ stress and the changes of MDA and polyamines contents.The activity of SOD, DAO, PAO extracted from Skeletonema costatum were also determined. In order to explore the physiological role of polyamines under heavy metal stress, all the physiological indexes were measured after adding free Put, Spd, Spm under Cd2+ stress and Cu2+ stress respectively. All the results are as follows:Cd2+ stress inhibited the growth of Skeletonema costatum, and the greater the concentration was, the stronger the inhibition would be. With the enhancement of Cd2+ stress, MDA content in the Skeletonema costatum cell increased slightly, SOD activity reduced significantly(P<0.001) and DAO, PAO activity enhanced respectively. As the effect of Cd2+ stress strengthen, the contents of free putrescine(Put), spermidine(Spd) and spermine(Spm) decreased firstly and increased subsequently; conjugated Put, Spd and Spm contents increased at first and then decreased. However, bound Put, Spm and Spd as well as total Put and total Spm kept increasing. It suggested that Cd2+ stress caused oxidation damage to Skeletonema costatum cells. Meanwhile, the enhancement of DAO and PAO activity as well as the increment of free Put, bound Spd and Spm, total Put and total Spm would strengthen the resistance ability of Skeletonema costatum against Cd2+ stress.Under Cd2+ stress, the relative growth rate of Skeletonema costatum declined(P<0.05), while adding Spd, Spm to the culture medium containing excess Cd2+, the relative growth rate of algae increased. It suggests that Cd2+ stress inhibit the growth of Skeletonema costatum, while exogenous application of Spd, Spm can mediate the inhibition to the growth of algae cells. The content of MDA in Skeletonema costatum cell increased under the Cd2+ stress comparing with the control group, leading to a certain degree of oxidation injury. In the contrary, in the groups of adding Spd, Spm, the contents of MDA decreased compared with the Cd2+ stress group, and the activity of SOD enhanced, possibly because exogenous Spd, Spm mediated the oxidation injury through scavenge the reactive oxide species. After applying Spd, Spm, the contents of bound Put, Spd, Spm increased in contrast with Cd2+ stress, and the contents of bound Put increased by 4 folds and 14.5 folds respectively than the group of Cd2+ stress(P<0.01). This shows exogenous polyamines enhance the resistibility to Cd2+ stress by bound Put, Spd, Spm.In the condition of Cu2+ stress, the relative growth rate of Skeletonema costatum declined, the content of MDA in the algae cells increased slightly; and the activity of SOD, DAO, PAO extracted from Skeletonema costatum enhanced respectively; the contents of bound Put and conjugated Spm increased as the rise of Cu2+ concentration. It indicates that Cu2+ stress can inhibit the growth of Skeletonema costatum, and cause oxidation injury to algae cell. The enhancement of SOD, DAO, PAO activity and the increment of bound Put and conjugated Spm contents can strengthen the tolerance of Skeletonema costatum to Cu2+ stress.Cu2+ stress reduced the relative growth rate of Skeletonema costatum compared with the control group; while the application of exogenous Put, Spd, Spm can alleviate the growth inhibition. The content of MDA in algae cells increased under Cu2+ stress, however, adding Put, Spd, Spm lowered the content of MDA, and elevated the activity of SOD. These results indicate that polyamines can prevent Cu-induced lipid peroxidation. In addition, the activities of DAO, PAO in the groups of adding Spd, Spm groups enhanced compared with the Cu2+ stress. For polyamines, under Cu2+ stress, the contents of conjugated Put, Spd, Spm decreased, while adding Put, Spd or Spm to the culture medium, the contents of conjugated Put, Spd, Spm showed rising trends. It demonstrated that conjugated polyamines play a significant role for Skeletonema costatum in resisting Cu2+ stress. |
PDF Full Text Request