浙江大学学报 (农业与生命科学版)  2017, Vol. 43 Issue (2): 192-202
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 紫萼玉簪种子和幼苗对酸雨与镉复合污染的生理生态响应 [PDF全文]

1. 四川农业大学风景园林学院，成都 611130;
2. 四川农业大学园林研究所，成都 611130

Physio-ecological responses of seeds and seedlings of Hosta ventricosa to combined pollution of simulated acid rain and cadmium
LUO Liangxu1, GAO Suping1,2 , WANG Chengcong1, LEI Ting1,2, WEN Jinyan1, LUO Yan1
1. College of Landscape Architecture, Sichuan Agricultural University, Chengdu 611130, China;
2. Landscape Research Institute, Sichuan Agricultural University, Chengdu 611130, China
Summary: The combined pollution of acid rain and cadmium (Cd) has been an important component of soil interacted with atmospheric pollution in China. The combined pollution posed harmful impact on human beings, and threatened the habitats of other creature, such as the urban garden plants. Therefore, it is important to investigate the effect of complicated pollution on plant growth, extension of plant population and ecosystem balance. The seed germination is the origin of the plant' s life cycle, which is the key link affecting extension of plant population. The stress resistance was bad in the seeding stage, especially poorer resistance to single and combined pollution compared to seedling stage. Therefore, the seeding period became the key to accomplish extension of plant population under habitat destruction. Previous studies on Hosta ventricosa focused on single pollution of Cd or acid rain; recently H. ventricosa was found to have tolerance against combined pollution of Cd and acid rain. Therefore, it is potential for phytoremediation of Cd polluted soil in acid rain area. In this study, H. ventricosa was selected as test material, to investigate the physico-ecological responses under combined pollution of simulated acid rain and Cd. The tolerance of H. ventricosa was examined under both seed germination and seedling periods, to provide science evidence for selection of urban plants with strong stress resistance under combined pollution. A completely random scheme of two factors (simulated acid rain and Cd) and five levels was used. The simulated acid rain was set at five pH levels (6.5, 5.5, 4.5, 3.5 and 2.5), and the Cd treatment fluids were set at five different Cd2+ concentrations (0, 10, 30, 50 and 100 mg/L). Both normal and abnormal germination rates were measured in each group. Meanwhile, after the seedling of H. ventricosa grew up to 10 to 15 cm height, the contents of chlorophyll, malondialdehyde (MDA) and H2O2, the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) were measured in each group to investigate the physico-ecological responses. Results showed that the combined pollution of acid rain and Cd had significant higher impact on seed germination and seedling growth of H. ventricosa than single pollution. The interaction of acid rain and Cd posed obviously synergistic effect, especially in high strength pollution (Cd2+ concentration ≥30 mg/L). Seed germination and seedling growth of H. ventricosa showed tolerance under stress of low concentration Cd2+ (10 mg/L) and low intensity acid rain, and the seed germination was even promoted by low concentration Cd2+ of 10 mg/L. The tolerance of seedling under Cd stress was weaker than mature seedling, and the critical tolerance value was believed to be 30 mg/L. The CAT activity was more sensitive than POD and SOD activites under the Cd stress, especially under the combined pollution of Cd and acid rain, and the peak value of the CAT activity was observed under 30 mg/L Cd2+. Therefore, the ability of CAT to eliminate reactive oxygen species (ROS) decreased under high concentration of Cd stress (≥30 mg/L). The production of H2O2 was faster than scavenging by antioxidant enzyme systems, so the seedling would completely lose the self-defensive ability. In conclusion, the seed germination and seedling growth can complete the self-update under the combined pollution of low intensity acid rain (pH≥5.5) and low concentration Cd2+ (≤10 and 30 mg/L), respectively, but high intensity of the combined pollution will significantly affect seed germination and seedling growth, which can provide reference for phytoremediation of combined polluted soil environment.
Key words: cadmium    acid rain    combined pollution    ecological stress    resistant physiology    Hosta ventricosa

1 材料与方法 1.1 供试材料

1.2 模拟酸雨溶液配制

1.3 外源Cd溶液配制

1.4 试验方法 1.4.1 种子萌发试验设计

1.4.2 幼苗生理试验设计

1.4.3 数据处理

2 结果与分析 2.1 在复合污染环境中紫萼玉簪种子的萌发情况 2.1.1 对种子发芽率的影响

2.1.2 对种子异状发芽率的影响

2.2 紫萼玉簪在复合污染环境中幼苗的生理变化 2.2.1 对幼苗叶绿素含量的影响

2.2.2 对幼苗叶片质膜过氧化的影响

 图中数据为平均值±标准差，n=3。短栅上的不同大写字母表示不同酸雨处理组间在P < 0.05水平差异有统计学意义，不同小写字母表示不同质量浓度Cd2+处理间在P < 0.05水平差异有统计学意义。 Data shown are means ± standard deviation, n=3. Different capital letters above the bars show statistically significant differences among different simulated acid rain at the 0.05 probability level; different lowercase letters above the bars show statistically significant differences among different Cd2+ concentrations at the 0.05 probability level. 图1 模拟酸雨与Cd复合污染对紫萼玉簪幼苗叶片MDA含量的影响 Fig. 1 Effects of combined pollution of simulated acid rain and Cd on the MDA content in leaves of Hosta ventricosa seedlings

 图中数据为平均值±标准差，n=3。短栅上的不同大写字母表示不同酸雨处理组间在P < 0.05水平差异有统计学意义，不同小写字母表示不同质量浓度Cd2+处理间在P < 0.05水平差异有统计学意义。 Data shown are means ± standard deviation, n=3. Different capital letters above the bars show statistically significant differences among different simulated acid rain at the 0.05 probability level; different lowercase letters above the bars show statistically significant differences among different Cd2+ concentrations at the 0.05 probability level. 图2 模拟酸雨与Cd复合污染对紫萼玉簪幼苗叶片H2O2含量的影响 Fig. 2 Effects of combined pollution of simulated acid rain and Cd on the H2O2 content in leaves of Hosta ventricosa seedlings
2.2.3 对幼苗抗氧化酶活性的影响

 图中数据为平均值±标准差，n=3。短栅上的不同大写字母表示不同酸雨处理组间在P < 0.05水平差异有统计学意义，不同小写字母表示不同质量浓度Cd2+处理间在P < 0.05水平差异有统计学意义。 Data shown are means ± standard deviation, n=3. Different capital letters above the bars show statistically significant differences among different simulated acid rain at the 0.05 probability level; different lowercase letters above the bars show statistically significant differences among different Cd2+ concentrations at the 0.05 probability level. 图3 模拟酸雨与Cd复合污染对紫萼玉簪幼苗叶片抗氧化酶活性的影响 Fig. 3 Effects of combined pollution of simulated acid rain and Cd on the activities of antioxidant enzymes in leaves of Hosta ventricosa seedlings

3 讨论 3.1 复合污染对紫萼玉簪种子萌发的影响

3.2 复合污染对紫萼玉簪幼苗生理指标的影响

SOD、POD和CAT是植物体内抗氧化酶系统的重要组成酶类，三者协同使得植物体内的活性氧（reactive oxygen species, ROS）含量维持在较低水平，从而防止逆境胁迫对植物造成的ROS伤害[24-25]。ROS的产生与抗氧化酶的清除维持着动态平衡。SOD是植物防御机制的第一道防线[26]，能将$\text{O}_{2}^{{\underset{\scriptscriptstyle\centerdot}{-}}}$转化为H2O2，防止其对细胞造成伤害；POD和CAT紧随其后，将SOD生成的H2O2转化为无害的水[27]，使其维持在一个较低的、对细胞无害的浓度。酸雨和Cd胁迫可以改变三者在紫萼玉簪幼苗叶片中的活性。从3种酶活性峰值可以看出，CAT对复合污染的敏感性明显高于POD，而POD对复合污染的敏感性明显高于SOD。在酸雨pH=2.5的各处理组合中，SOD活性呈现出持续增大的趋势，并且远远高于其他处理组合：表明高强度的酸雨能够大大激发SOD的潜在活性，从而有效地清除紫萼玉簪体内过剩的ROS，减少其对植物组织的损伤。这一结果与H2O2含量的提高相互印证。本试验还发现，紫萼玉簪幼苗在酸雨与Cd复合污染强度较小时，其体内产生的ROS会诱导SOD、POD以及CAT活性上升，从而减少ROS含量并防止逆境胁迫伤害[25, 28]。这是因为SOD产生的H2O2刺激了POD和CAT的合成。当胁迫强度持续增大到超过植物的耐受限度时，紫萼玉簪幼苗体内ROS的产生速率超过了抗氧化酶系统的清除能力，对植物体内多种膜系统和酶系统造成破坏，POD和CAT活性开始呈现出下降趋势。这一结果与段文芳等[29]的研究结果一致。

4 结论 4.1

4.2

4.3