| Using rice seedlings at two-leaf stage as tested materials, the free proline content and activities of en-zymes involved in proline metabolism were studied under water stress induced by 15%PEG. The results showed that the proline content increased obviously under stress, reached the maximum after 24 h and then decreased. The activities of △1-pyroline-5-carboxylate synthetase (P5CS ) and ornithine- δ-aminotransferase (δ-0AT)， the key enzymes of proline accumulation, increased sigificantly and then declined; while the activity of proline dehydrogenase (ProDH)， a key en-zyme of proline degradation, declined significantly and then increased. |