秋华柳抗氧化酶系统对镉胁迫的响应
Response of the Antioxidant Enzyme System of Salix variegata Franch to Cadmium Stress

采用水培方式，研究了秋华柳在不同的镉（Cd）质量浓度梯度：0 mg/L（CK），2 mg/L（T1），10 mg/L（T2），20 mg/L（T3），50 mg/L（T4）下的氧化胁迫程度及其叶片抗氧化酶系统对Cd胁迫的响应特征.结果表明：1）秋华柳叶片MDA质量分数与Cd胁迫质量浓度呈显著正相关关系，胁迫12 d后MDA质量分数极显著增加，表明植物生理功能早期出现暂时性修复后细胞膜损伤程度显著增加.2）不同质量浓度和时间的Cd胁迫下，植物抗氧化酶活性表现出不同的变化规律，不同酶活性存在不同的阈值.3）SOD和CAT酶活性随着Cd处理时间的延长和质量浓度的增加均呈先上升后下降的趋势，与对照相比始终保持着高活性状态；在氧化胁迫前期，APX酶具有较高的酶活性，在Cd解毒前期中起主要作用；随着Cd胁迫程度的增加，GR酶活性升高，与Cd胁迫质量浓度呈极显著正相关关系.4）秋华柳叶片中POD酶活性与Cd处理质量浓度间无统计学意义.5）在耐受Cd的阈值内，秋华柳叶片抗氧化酶系统通过活性变化的协同作用，共同应对Cd胁迫.表明秋华柳抗氧化酶系统对Cd既具有解毒功能，也是Cd毒性的作用位点.
The degree of oxidative stress can be determined through the amount of malondialdehyde (MDA) present within the leaf, while information about the anti-oxidative defense systems within the leaf can be obtained through the abundance of super oxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). A hydroponic experiment with different cadmium treatments (Cd²⁺ 0, 2, 10, 20 and 50 mg/L) was conducted over 18 days in order to investigate the effects of cadmium on oxidative stress and the response of the anti-oxidative defense systems in the leaf of Salix variegata to cadmium stress. The concentrations of MDA and the aforementioned enzymes were then analyzed once the experiment was completed. A significant positive correlation was shown to exist between MDA content in the leaf of S. variegata and cadmium concentration, MDA content being significantly higher after 12 days of treatment, which implied that the degree of oxidative stress increased significantly after a temporary repair of the plant physiological function. The enzymes that made up the anti-oxidative defense system in the leaf played different roles when S. variegata was under cadmium stress. This implied that different enzymes of the anti-oxidative defense system had different thresholds. The activities of the SOD and CAT showed a similar trend in change:they first increased with increasing Cd treatment concentration and time, followed then by a decline, always maintaining a relatively high activity in comparison with the CK. In the early stage of the oxidative stress, the activity of APX maintained relatively high activities, suggesting an important role in defending against the toxicity of cadmium. The activity of GR in the leaf of S. variegata increased steadily with increasing cadmium stress, exhibiting a highly significant positive correlation between them. No significant correlation was detected between POD activity and cadmium