| Popis: |
A riparian zone with its water level fluctuating annually between 145m and 175m above sea level(ASL) has been created around the impoundment since the Three Gorges Dam was built,,turning the terrestrial ecosystem into wetland with winter flooding every year,and most of the original plant species has diminished due to the dramatic environmental changes.Therefore,it is important to examine the recovery dynamic and ecophysiological mechanisms involved in post-submerged plants for vegetative restoration in this reservoir fluctuation zone(RFZ) of the Three Gorges Reservoir,as the recovery ability is critical for plants to survive the periodic flooding and to inhabit the RFZ. In a field experiment,we examined the activity dynamics of antioxidant enzymes in Cynodon dactylon and Hemarthria altissima after a 6-month long flooding over winter.Superoxide dismutase(SOD),ascorbate peroxidase(APX) and catalase(CAT) were analyzed in root tissue of both species grown in the sites of 158m(re-aeration from flooding) and 175m(never flooded) ASL in the RFZ.Samples were taken every 8 days from the day before exposure(0 day) to the 24th day after drainage. At the beginning of post-flooding period,SOD and APX of both species maintained their high activity induced by flooding,indicating that severe oxidative stress occurred after re-aeration.In contrast,CAT activities were at low level at the end of flooding and increased to the control level rapidly after re-aeration.Oxidative stress was relieved on 24th day after re-aeration,showing that there was no significant difference in enzyme activity between the sites of 158m and 175m ASL. Our results suggest that the capacity for scavenging reactive oxygen species accumulated after re-aeration could be taken as one of the key factors underlying the recovery ability for the RFZ plants.Furthermore,re-aerated plants showed close associations among antioxidant enzyme activity,which might be due to the attempt to maintain redox homeostasis in plant cell. |
