Abstract: In order to understand the regulatory mechanism of proline metabolism at the cellular level, Nitraria tangutorum Bobr. callus was used to investigate the effects of exogenous hydrogen peroxide (H₂O₂) treatment on the proline content and the activities of proline-related metabolism enzymes. After treatment with 2 and 10 μmol·L^-1 H₂O₂ for 24 h, proline content was about 112% and 92% of the control value in N.tangutorum Bobr. callus, respectively; at 72 h treatment, the amount of proline increased about 41% and 19% in comparison with the control. Analysis of enzyme activities showed that exogenous H₂O₂ induced remarkable decrease in proline dehydrogenase (ProDH) activity and significant increase in glutamyl kinase (GK) activity, but no significant changes in ornithine aminotransferase activity. In addition, the endogenous H₂O₂ level was increased in exogenous H₂O₂ treated callus. In conclusion, our results indicated that exogenous H₂O₂ treatment resulted in the significant increase of endogenous H₂O₂ content in N.tangutorum Bobr. callus. Here it was also indicated that H₂O₂ induced proline accumulation, which was associated with the reduction of ProDH activity and the elevation of GK activity in N.tangutorum Bobr. callus.

Key words: Nitraria tangutorum Bobr., callus, proline, hydrogen peroxide, proline dehydrogenase