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Taking aseptic seedlings of P.crispus as the experimental material,the effect of different concentrations of Cu2+(0,1,2,4,8,12 μmol/L) on the metabolism of polyamine(PAs) and reactive oxygen were investigated.With the increasing of Cu2+ concentration,the results indicated that:(1) Superoxide dismutase(SOD) activity increased markedly,while the activities of peroxidase(POD) and catalase(CAT) increased progressively followed by a decline.(2) The generation rate of O·-2and the content of H2O2 and MDA increased,while soluble protein content decreased.(3) Free putrescine(Put) content first enhanced and then reduced notably.However,the content of free spermidine(Spd) decreased gradually and spermine(Spm) increased significantly.Therefore,the ratio of free(Spd+Spm)/Put promptly increased under high concentrations of Cu2+ stress.The changes of total PAs content were similar to those on free PAs.Perchloric acid soluble conjugated(PS-conjugated) Put and Spm changed in the same pattern as free PAs.While PS-conjugated Spd content increased slightly.In addition,the content of perchloric acid insoluble bound(PIS-bound) Put and Spd first increased and then decreased,but they were still higher than those in the control.Moreover,PIS-bound Spm content declined.(4) With the increase of Cu2+ concentration,the activity of arginine decarboxylase(ADC) sharply decreased after a transient increase,while the activity of ornithine decarboxylase(ODC) did not change significantly.Polyamine oxidase(PAO) and diamine oxidase(DAO) activities increased gradually,followed by a decrease.Our results suggested that Cu2+ stress induced obvious oxidative damage on aseptic seedlings of P.crispus.The up-regulation of antioxidant enzymes activities and Spm content,the changes of Put into Spd and Spm as well as the conversion between different forms of polyamines played a key role in the adaptation mechanism of aseptic seedlings of P.crispus under Cu2+ stress.

Sterile seedlings of Potamogeton crispus were cultured by tissue culture technique,and used as experimental materials.In this study,different concentrations of Ni2+(0,0.05,0.10,0.15 and 0.20 mmol/ L) on contents of hydrogen peroxide(H2O2),superoxide anion(O.-2) and malondialdehyde(MDA),antioxidant defense system and proline metabolism were investigated.The results indicated that(1) Ni2+ stress triggered the generation of reactive oxygen species(ROS) as evidenced by a substantial accumulation of H2O2 and O.-2,accompanied by the increased MDA content with the increasing of Ni2+ concentration;(2) Activities of superoxide dismutase(SOD),peroxides(POD) and catalase(CAT),as well as contents of reduced glutathione(GSH) and non-protein thiols(NP-SH) increased at first and then decreased,while no outstanding changes were observed in ascorbate(AsA) content,and level of phytochelatins(PCs) increased significantly;(3) Analysis of enzyme activities showed that the accumulation of proline induced by Ni2+ stress is due to the increases of ornithine-δ-aminotransferase(OAT) at 0.05-0.10 mmol/L and pyrroline-5-carboxylate synthetase(P5CS) activity at 0.15-0.20 mmol/ L,respectively,but there was not a statistically significant difference in ProDH activity.Our results demonstrated that Ni2+ induced the enhancement of reactive oxygen species level,aggravated lipid peroxidation and interfere with intrinsic balance of antioxidant defense system.In addition,proline accumulation is mediated by increased biosynthesis from ornithine at low concentrations(0.05 and 0.10 mmol/L),while glutamate pathway,instead of the ornithine pathway,plays a vital role when exposed to higher concentrations of Ni2+.

Sterile seedlings of Potamogeton crispus L.were cultured by tissue culture technique.They were exposed to 0,5,10,15,20μmol/L Hg2+ respectively for 3 days and analyzed with reference to its toxic impact on total chloroplyll content,chloroplyll autofluorescence,the ATPase activity and mineral nutrition absorption under lab conditions.Results revealed that with increasing Hg2+ concentration,the intensity of chloroplyll autofluorescence and chlorophyll decreased gradually.The content of soluble protein increased under 5μmol/L Hg2+ stress,and then followed by a decline in the present of higher concentration of Hg2+,which was the same as the change of Ca2+Mg2+-ATPase activity.Na+K+-ATPase also decreased with the rise of Hg2+ concentration.The absorption of Na,K,Ca,Mg was affected under Hg2+ stress.It was concluded that photo system and normal physiological metabolism were disordered.

Callus of Alternanthera philoxeroides,as experimental material,was cultured by tissue culture technique.In this study,the calluses were subjected to different concentrations of Cr6+(0,0.1,0.3,0.6 and 0.9 mmol/L) and the impacts on contents of putrescine(Put),spermidine(Spd),spermine(Spm)and proline(Pro),activities of arginine decarboxylase(ADC),ornithine decarboxylase(ODC),polyamine oxidase(PAO) and Diamine Oxidase(DAO) were investigated.Results indicated that,with the increasing of Cr6+ concentration,(1) the contents of three free PAs increased at first and then decreased,and reached their peak values at 0.6 mmol/L Cr6+ treatments;(2) the content of PS-conjugated Put reached its peak value at 0.1 mmol/L Cr6+ treatment and then decreased slowly,while the contents of PS-conjugated spermidine(Spd) and spermine(Spm) increased significantly;(3) the peak values of PIS-conjugated Put and Spd were present at 0.6 mmol/L Cr6+ treatment;meantime the peak value of PIS-conjugated Spm was present at 0.1 mmol/L Cr6+ treatment;(4)the activities of ADC and ODC increased gradually,while PAO and DAO activities decreased sharply after a transient increase;(5) the level of Pro increased at 0.1-0.3 mmol/L Cr6+ treatments and decreased at 0.6-0.9 mmol/L Cr6+ treatments.These results suggested that Cr6+ stress disturbed metabolic balance of polyamines and increased the level of PAs.Obviously,the changes of PAs levels might be essential to Cr6+ adaption of cells.