Background Screening and restoration of artificial vegetation is one of the important measures to control the ecological environment of the water-level-fluctuating zone of the Three Gorges Reservoir Area. In order to select more flood-resistant species suitable for vegetation construction and temporal spatial replacement, 4 indigenous herbaceous plants, Houttuynia cordata, Rumex acetosa, Kalimeris indica and Xanthium sibiricum) from the Three Gorges Reservoir (Wanzhou section), surviving in the recession period were taken to our experimental station for investigating their response mechanisms to short-term submerging stress.

Methods Above 4 plants were treated for pot submerging and restoring experiment lasting 30 d. The plants were randomly divided into 3 groups of each 10 pots, CK group was under nature outside and no more adding water, the submerged group was watering until the top of plants, and the submerged + restored group was first 15 d submerged and later 15 d under natural outside condition. Morphological, photosynthetic and physiological and biochemical indices were measured at first day, 15 d, and 30 d respectively. The result data were processed by SPSS19.0 and One-way ANOVA.

Results 1) The aboveground parts of H. cordata and K. indica were successively necrotic after 15 d of submerging, the aboveground parts of R. acetosa and X. sibiricum were survived for about 22 d, and the root length of X. sibiricum increased significantly in the environment of submerging and restoring. 2)After 15 d of submergence, the contents of proline (Pro), superoxide dismutase (SOD), catalase (CAT) and root activity(TTC content)of R. acetosa increased significantly compared to CK. After 15 d of restoring, net photosynthetic rate (P_n), transpiration rate (T_r), malondialdehyde (MDA), TTC, soluble sugar content and antioxidant enzyme activity increased significantly compared to CK. 3)After 15 d of submergence, MDA content, Pro content, SOD, CAT activity and TTC value of X. sibiricum increased significantly compared to CK, especially the values of Pro and TTC reached a very prominent difference. After 15 d of restoring, P_n, stomatal conductance (G_s), Pro content, SOD, CAT activity and TTC value increased notably. 4)After 15 d of submergence, P_n, intercellular CO₂ concentration (C_i), CAT activity of H. cordata increased compared to CK, but no significant changes were observed after 15 d of restoring. 5)After 15 d of submergence, C_i, G_s, TTC, Pro, CAT of K. indica decreased drastically, MDA and SOD increased significantly.

Conculsions The results indicated that X. sibiricum and R. formosana regulated the submerging stress mainly by enhancing root activity, antioxidant enzymes activity and Pro content, and the photosynthetic indexes and root activity were stimulated and enhanced after restoring, showing they were sensitive to submerging or had high submerging-tolerance. The photosynthetic index of H. cordata decreased significantly and no timely response in physiological aspect after submergence, showing it was insensitive to submerging stress. K. indica maintained energy balance of root system in anoxic environment by reducing root activity, showing it had lower submerging-tolerance.