In order to determine the effects of water stress on the physiological and biochemical characteristics of Paeonia suffruticosa, two varieties ( Luoyanghong and Huhong) , that were cultivated under controlled soil water regimes in the pots, were comparatively studied. The results showed that under water stress condition, the net photosynthetic rate(Pn) and soluble protein content in leaves of two peony varieties significantly decreased, while the total amino acids, soluble sugar and free proline content, production rate of superoxide anion radical ( 02 ) , and relative permeability of cell membrane of the leaves significantly increased. The decrease in Pn, soluble protein content and the rate of increase of Oj, relative permeability of cell membrane of leaves in Huhong was slower than those of Luoyanghong, while the increase in total amino acids content, soluble sugar content and free proline content of leaves in Huhong was faster than those of Luoyanghong. Under soil water saturation condition, these changes were reverse. Under drought condition, Superoxide Dismudase (SOD) activity of leaves significantly decreased in the two peony varieties, and the decreased degree of Huhong was less than that of Luoyanghong. Peroxidase ( POD ) activity of leaves increased in the two peony varieties, with Huhong increased more than Luoyanghong. Catalase (CAT) activity of leaves decreased in Luoyanghong, while the activity increased in Huhong. Under soil water saturation condition, the activities of SOD, POD, CAT of leaves decreased in two peony varieties with bigger decreased degree for Huhong than Luoyanghong. These results indicated that Huhong had stronger resistance to drought than Luoyanghong did, but the latter was more resistant to waterlogging than the former.%@@牡丹(Paeonia suffructicosa),芍药科,芍药属,是我国的传统名花,有数千年的自然生长和2000多年的人工栽培历史,具有重要的观赏价值、药用价值、食用价值和商品价值(王莲英,1997;李嘉钰,1998).
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