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作 者 ：徐勤松*,计汪栋,杨海燕,王红霞,许晔,赵娟,施国新

期 刊 ：生态学报 2009年 29卷 6期 页码：3019~3027

关键词：槐叶苹；Cd；蓄积；矿质营养；氧化胁迫；超微结构；毒理；

Keywords:Salvinia natans, Cd, bioconcentration, nutrient elements, oxidative stress, ultrastructure, phytotoxicity,

摘 要 ：以分布广泛的浮水蕨类植物——槐叶苹为研究对象，用含不同浓度Cd（2.5，5，7.5 mg/L和10 mg/L）的10% Hoagland营养液培养7d，旨在分析Cd在蕨类植物中的蓄积及其诱导产生的毒理学作用。随着培养液中Cd浓度的增加，(1) 槐叶苹叶片中Cd含量极显著上升；(2) Cd处理造成槐叶苹叶片产生明显的矿质营养失衡症状，主要表现为显著增加了对Ca和降低了对P，K和Na的吸收；(3)叶绿素含量和叶绿素荧光Fv/Fm比值都逐渐降低；(4)抗氧化防御系统活性或含量紊乱，其中超氧化物岐化酶（SOD）活性下降最突出，过氧化物酶（POD）、过氧化氢酶（CAT）、还原型谷胱甘肽（GSH）、抗坏血酸（AsA）和类胡萝卜素（Car）也都先升后降，膜脂过氧化产物MDA含量则显著增多；(5)可溶性蛋白含量一直下降；(6)透射电镜观察发现细胞超微结构损伤明显，主要为叶绿体膨胀和解体、线粒体嵴突减少和空泡化、细胞核核仁解体、核膜破裂、核质消失，并有晶体出现。结果表明槐叶苹虽然对水体Cd有一定的净化作用，但Cd浓度与毒害之间的剂量\|效应关系明显；MDA含量的明显上升以及叶绿素和可溶性蛋白含量的显著下降标志着槐叶苹遭受到明显的氧化损伤；Cd破坏了槐叶苹进行正常生理活动所必需的生理和结构基础；SOD可以作为Cd诱导产生氧化压力的分子生物标志物和水体Cd污染的灵敏生态毒理学指标，Cd的半效应浓度为241mg/L，最大允许浓度为0.241mg/L。

Abstract:Higher aquatic plants are known to accumulation and bioconcentrate heavy metals, while works dealing with fern are still very scarce. In this study, cadmium (Cd) accumulation and its influence on mineral nutrients, photosynthetic pigments and Fv/Fm, enzymatic and non-enzymatic antioxidants, protein content and ultrastructure of Salvinia natans (Linn.) All. plants exposed to 2.5，5，7.5 mg/L and 10 mg/L Cd for 7d were analyzed. It was found that, with the rise of the Cd concentration in culture medium, (1) Cd content increased in a concentration dependent manner. (2) Cd resulted in serious imbalance of nutrient elements, and promoted the adsorption of Ca and prohibited the adsorption of P, K and Na significantly. (3) Chlorophyll content and chlorophyll fluorescence Fv/Fm showed a decreasing trend. (4) Cd treatment led to the disorder of content/activity of antioxidant systems. A significant reduction in SOD activity was observed in Cd treated S. natans, in contrast, an increase was also noted in POD and CAT activity, levels of GSH, AsA and Car followed by a decline. MDA content increased evidently with augment of Cd concentration indicating the occurrence of oxidative stress. (5) Soluble protein content was found to be decreased at all the Cd concentration. (6)TEM observation revealed that Cd impaired the organelle ultrastructure obviously, such as swelling and disorganization of chloroplasts, decrease of cristae quantity and vacuolization of mitochondria, disaggregation of nucleolus, breakage of nuclear envelope, disappearance of karyoplasms, and appearance of crystal. Results suggest that S. natans was able to accumulate Cd, the correlation of dose-effect was significant between the toxicity and concentration, and Cd caused oxidative damage as evidenced by increased lipid peroxidation and decreased chlorophyll and protein contents. Cd pollution destroyed the physiological and ultrastructural foundation essential for normal growth and metabolism of plants. SOD could be served as a molecular biomarker of oxidative pressure imposed by Cd pollutant and a sensitive eco-toxicological indicator to evaluate Cd pollution on water environment, its 50% effective concentration (EC50) for 7 d of exposure was 2.41 mg/L; the maximum permissible concentration (MPC) was 0.241 mg/L.

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