| Horticulture |
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| 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) |
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Abstract 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, such as the urban garden plants. Therefore, it is important to investigate the effect of complicated pollution on the growth of plants, 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 physicoecological 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.
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Published: 25 March 2017
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Corresponding Authors:
GAO Suping (http://orcid.org/0000-0002-4609-9988)，E-mail: gao_suping@sicau.edu.cn
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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
为了解紫萼玉簪生长初期对酸雨与镉（Cd）复合污染的生理生态响应，探究该物种在复合污染下的自我更新能力，分别以紫萼玉簪种子和幼苗为供试材料，采用2因子5水平完全随机试验，研究不同梯度（pH分别为6.5、5.5、 4.5、3.5、2.5）模拟酸雨与不同质量浓度重金属Cd2+（0、10、30、50、100 mg/L）复合污染胁迫下，该植物种子和幼苗的生理生态指标变化。结果表明：酸雨和Cd复合污染比单一污染对紫萼玉簪种子和幼苗造成的伤害更大，两者之间交互作用显著，表现为协同作用，且这一作用在高强度复合污染下表现得尤为突出；紫萼玉簪种子和幼苗对低强度酸雨和低质量浓度Cd胁迫有一定的耐受性，其中，低质量浓度Cd2+（10 mg/L）处理对种子萌发表现出一定的促进作用。幼苗对Cd胁迫的耐受能力弱于成苗，在本试验条件下，耐受的临界质量浓度值为30 mg/L。过氧化氢酶活性对Cd污染胁迫的敏感性高于超氧化物歧化酶，尤其在与酸雨复合作用下敏感性增加，表现在重金属Cd2+质量浓度为 30 mg/L时就到达峰值，这也进一步导致其在高质量浓度Cd2+污染时对活性氧的清除能力下降，使活性氧的产生速率超过抗氧化酶系统的清除能力，从而使幼苗完全丧失了自我保护的能力。综合各指标结果认为，紫萼玉簪种子萌发和幼苗生长分别在低强酸酸雨（pH≥5.5）与低质量浓度Cd2+（≤10和30 mg/L）污染胁迫下能顺利进行自我更新，而高强度复合污染对种子萌发和幼苗生长极为不利。该研究结果对复合污染地区的土壤环境修复工作具有一定的参考价值。
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