湿地匍灯藓（Plagiomnium acutum）对Pb胁迫的生物标志物响应

采用浸没培养实验研究了不同浓度Pb胁迫下湿地匍灯藓(Plagiomnium ac utu)的总叶绿素、丙二醛、可溶性糖、游离脯氨酸含量以及抗氧化酶活性等生理生化生物标志物的变化,以探讨Pb胁迫下湿地匍灯藓的受损和耐受机理.结果表明,湿地匍灯藓外表伤害症状与Pb胁迫浓度存在明显的剂量-效应关系；低浓度(20 mg·L-1)Pb胁迫可以显著地促进湿地匍灯藓的总叶绿素含量增加,而中、高浓度(50 ng ·L-1)Pb胁迫则导致总叶绿素含量显著降低.湿地匍灯藓对Pb具有较强的生物富集能力,且藓体Pb的累积量与环境Pb浓度呈显著正相关.湿地匍灯藓体内MDA和游离脯氨酸含量随Pb胁迫浓度的增加表现为显著升高.可溶性糖含量仅在高浓度Pb胁迫下显著升高.可溶性蛋白含量、过氧化物酶(POD)和过氧化氢酶(CAT)活性均随Pb胁迫浓度的增加而显著下降,其中CAT活性的降幅最大,SOD活性随Pb胁迫浓度的增加逐渐显著增加.在高浓度Pb胁迫下,由于细胞膜脂过氧化和蛋白质变性失活所导致的膜保护体系损伤可能是湿地匍灯藓Pb中毒的主要原因,而渗透调节可能是其缓解Pb毒害的一种主要方式,SOD则在清除Pb胁迫产生的活性氧自由基过程中起重要作用.总叶绿素、丙二醛、游离脯氨酸、可溶性蛋白、CAT和SOD可以作为湿地匍灯藓受Pb胁迫的敏感生物标志物.

Biomarker Responses of Plagiomnium acutum to Lead Stress

To investigate the possible negative effects of Pb stress on moss Plagiomnium acutum and the possible mechanisms by which P. acutum can tolerate Pb stress, a submersion experiment was set up and the changes in biomarkers profiles(i.e. the contents of total chlorophyll, malondialdehyde(MDA), soluble sugar and free proline, as well as the activities of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT)) in P. acutum under Pb stress were characterized. The results showed that there was an obvious dose-response relationship between the visible damages observed in P. acutum and Pb concentrations in the solutions. At low concentration(20 mg·L-1), Pb could cause a significant increase in the content of total chlorophyll in P. acutum; whereas, at high concentrations(>50 mg·L-1), Pb led to significant decreases in the content of total chlorophyll. P. acutum displayed a strong ability to accumulate Pb from the solutions. The concentrations of Pb in P. acutum were significantly positively correlated to the concentrations of Pb in the solutions. The levels of MDA and free proline in P. acutum significantly increased with increasing Pb concentrations in the solutions; however, a significant increase in the content of soluble sugar was only observed in P. acutum treated with the highest Pb concentration. The contents of soluble protein and the activities of POD and CAT significantly decreased with increasing concentrations of Pb in the solutions, with a maximum reduction of the CAT activity. In contrast, the activity of SOD significantly increased with the increasing concentrations of Pb in the solutions. The damage of membrane protection system caused by lipid peroxidation, protein denaturation and inaction might be a primary cause of Pb toxicity in P. acutum. The osmotic regulation might be one of the major processes that are able to mitigate the toxicity of Pb in P. acutum, while SOD seems to play an important role in eliminating ROS under Pb stress. The levels of total chlorophyll, MDA, free proline, soluble protein, CAT, and SOD might be considered as sensitive biomarkers of Pb stress in P. acutum.