狗牙根与牛鞭草在三峡库区消落带水淹结束后的抗氧化酶活力

三峡水库周期性水淹结束后,消落带植物积极恢复生长的能力有利于其生存和定居,因此,探究影响植物恢复生长的关键生理生态机制对于消落带生态治理具有重要意义。采用野外采样、对比测定的手段,研究了生长于三峡水库消落带的狗牙根和牛鞭草根系在冬季水淹结束后清除活性氧(ROS)的关键酶活力恢复动态。结果表明:与对照相比,经历水淹的植物恢复初期发生明显氧化胁迫,超氧化歧化酶(SOD)、抗坏血酸过氧化物酶(APX)均维持了水淹诱导增加的活力水平。两个物种的过氧化氢酶(CAT)在水淹中活力均较低;出露之后后狗牙根CAT趋向于对照水平,牛鞭草CAT活力迅速上升但未到显著水平。水淹结束后24 d各个酶活力均回复到对照水平,表明氧化胁迫已基本消失。消落带位点植物不同酶活力之间表现出显著的相关关系,这可能是植株维持ROS代谢内稳态的表现。

Dynamics of antioxidant enzyme activities in roots of Cynodon dactylon and Hemarthria altissima recovering from annual flooding

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.