Cu、Zn在黑藻叶片中的富集及其毒理学分析

BIOACCUMULATION AND TOXICITY OF Cu AND Zn IN HYDRILLA VERTICILLATA(LINN.F.) ROYLE

本文以分布广泛的沉水植物———黑藻为研究对象,在人工模拟的含不同浓度的Cu、Zn污水中培养7d,研究了Cu、Zn在黑藻体内的富集及部分毒理学影响。研究表明:黑藻对Cu和Zn都有较强的富集作用,黑藻叶片中的Cu、Zn含量都随介质中金属浓度的增大而呈增长趋势,统计分析都达到极显著正相关(RCu=0.9875,P<0.01;RZn=0.9990,P<0.01)。但黑藻对Cu、Zn吸收和积累能力(以富集系数表示)不同:对Cu的富集系数为571—1328;对Zn的富集系数为346—830。这表明黑藻对Cu的吸收能力大于Zn,而富集系数随外界浓度的增大而下降,则说明较低处理浓度更有利于黑藻对金属元素的吸收。逐步提取法分析表明黑藻体内Cu是2%醋酸提取态最多,而Zn是以1mol/L的NaCl溶液提取态占优势。各结合形态的含量多少依次为:Cu:FHAc>FHCl>FNaCl>FWater>FEthanol>FResidue;Zn:FNaCl>FHAc>FHCl>FEthanol>FResidue>FWater。激光共聚焦扫描显微镜观察结果显示Cu、Zn污染后黑藻叶片自发荧光范围变窄,峰值变小,平均强度减小。扫描电镜和透射电镜观察发现,黑藻叶细胞形态和结构发生了较明显的变化,主要表现为:细胞壁扭曲,细胞变形;细胞核核仁解体,染色质凝集,核膜断裂;叶绿体类囊体膨胀,被膜破裂;线粒体嵴数目减少,线粒体呈空泡状。结果表明,Cu、Zn在黑藻叶中富集得越多,造成的毒害越重,剂量效应非常明显。

In the present study, Hydrilla verticillata （Linn. f. ） Royle, a submerged macrophyte widely distributed in China was used as experimental material. Cu and Zn, essential elements for the normal development and growth of plants were selected as the stress factors. H. verticillata was cultivated in water containing elevated concentrations of Cu and Zn （up to 10 mg/L） for 7d under lab condition. The bioaccumulation of Cu and Zn were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry （ICP） and their environmental toxicology in H. verticillata was studied. The results suggested that contents of Cu and Zn in H. verticillata were nearly in linear increase with rise of metal concentration in solution, and statistical analysis indicated that they all reached significant positive levels （RCu = 0.9875, P 〈 O. O1 ;RZn = O. 9990, P 〈 0.01 ）. It was found that H. verticillata fronds were able to absorb and accumulate Cu and Zn differently, and the bioaccumulation factor ranged from 571 to 1328 and 346 to 830, respectively. The absorption capability of H. verticillata to Cu was better than to Zn and low heavy metal concentration was good for absorption. Sequential extraction indicated that the ratio of different Cu and Zn chemical forms were different markedly, of which NaCl extractable Zn,2 % HAc extractable Cu were predominated as compared with the other 5 forms; which could be seen in the following order： Cu： FHAc 〉 FHCl〉 FNaCl 〉 Fwater 〉 FEthanol 〉 FResidue; Zn： FNaCl 〉 FHAc 〉 FHCl 〉 FEthanol 〉 FResidue 〉 Fwater. Auto fluorescent range narrowed; both peak value and average intensity decreased in leaf of H. verticillata under Cu and Zn stress. Scanning and transmission electron microscope observation indicated that Cu and Zn imposed injury action on morphological structure and uhrastructure of leaf cells, such as distortion of cell wall and cell shape, disaggregation of nucleolus, agglutination and disappearance of chromatin of nucleus, disruption of nuclear membrane, swelling of thylakoids and breakage of chloroplast envelope, decreasing of cristae quantity and vacuolization of mitochondria. The conclusion was that there was a significant doseeffect between bioaccumulation and toxicity. Namely, the more the pollutant contents in H. verticillata,the severer the toxicity to the plant.