Abstract: In this paper, the changes in plant morphology, photosynthetic characteristics, antioxidase and osmotic regulation substance of peony (Paeonia suffruticosa cv. Wulongpengsheng) under flooding of four degrees were measured to study the response of peony to flooding stress. The results showed that light flooding had no significant influence on the morphology of peony plants. The peony plants became wilting quickly under severe flooding stress and then suffered a serious damage. There was no obvious change in the chlorophyll contents of peony leaves under light flooding stress, however, the contents of chlorophyll a and (a+b) of leaves under severe flooding stress decreased gradually over time. The net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) of leaves kept decreasing, while the intercellular CO₂ concentration (C_i) increased over time. The content of MDA and the activities of POD and APX increased over time. The activities of SOD, CAT, GR and the contents of soluble sugar and proline gradually increased in plants under light flooding stress, but increased at first and then decreased in plants under severe flooding stress. These results suggested that the growth and photosynthetic apparatus of peonies were damaged to a certain degree under severe flooding stress. The accumulation of antioxidation enzymes and osmotic adjustment substances could improve the resistance and adaptation of peonies to flooding stress.

Key words: spatial response, rice, climate change, Northeast China., crop spatial allocation model