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), orni-thine 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.