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| 低剂量MC-LR慢性暴露对生菜氮代谢的影响 |
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姜子涵1, 马腾1, 叶凡1, 陈国元1,2, 李青松1,2
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1.厦门理工学院 环境科学与工程学院，福建 厦门 361024;2.厦门市水资源利用与保护重点实验室，福建 厦门 361024
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| 摘要: |
| 【目的】研究微囊藻毒素-LR（MC-LR）慢性暴露对生菜（Lactuca sativa）叶片、根系中氮素分配及氮代谢相关酶活性的影响，为富营养化水体在生菜灌溉中的应用提供理论指导。【方法】以散叶生菜为试验材料，采用土培方法，以灌溉超纯水为对照组，用不同质量浓度（2，4，6，8和10 μg/L）MC-LR的水溶液灌溉生菜45 d，测定不同处理生菜叶片光合生理特性（净光合速率（Pn）、气孔导度（Gs）及胞间CO2浓度（Ci）、1,5 二磷酸核酮糖羧化酶（Rubisco）活性）、土壤全氮和叶片NO-3-N、NH+4-N含量及叶片、根系中氨基酸、可溶性蛋白、还原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）含量，并测定与氮代谢相关酶（硝酸还原酶（NR）、谷氨酰胺合成酶（GS）、谷氨酸合成酶（GOGAT）、谷氨酸脱氢酶（GDH）、谷草转氨酶（GOT）、谷丙转氨酶（GPT））活性的变化，分析Pn与氮含量及氮代谢相关酶活性的相关性。【结果】随着MC-LR质量浓度的增加，生菜叶片Pn、Gs和Rubisco活性总体呈先升高后降低趋势，生菜叶片Ci呈降低趋势；土壤中氮含量呈先下降后升高趋势；生菜叶片中NO-3-N含量呈先升高后降低趋势，NH+4-N含量呈升高趋势；生菜叶片及根系中GSH含量总体呈下降趋势，GSSG含量总体呈升高趋势；生菜叶片、根系中的氨基酸和可溶性蛋白含量以及NR、GS、GOGAT、GDH、GOT、GPT活性总体均呈先升高后降低趋势。与对照组相比，2～6 μg/L MC-LR处理生菜叶片Pn和叶片、根系中的氨基酸、可溶性蛋白、GSSG含量以及NR、GDH、GOT、GPT活性均明显增加，10 μg/L MC-LR处理生菜叶片Pn、Gs、Ci与Rubisco活性及叶片、根系氨基酸、可溶性蛋白、GSH、GSSG含量和GOGAT、GDH 、GOT 、GPT活性均明显下降。相关性分析结果表明，Pn与氨基酸和可溶性蛋白含量及NR、GOGAT、GDH、GOT、GPT活性均呈显著或极显著正相关。【结论 2~8 μg/L MC-LR处理生菜叶片及根系中的可溶性蛋白含量均有一定程度上升，使GSH维持较高含量，从而提高了MC-LR胁迫生菜的抗性；虽然10 μg/L MC-LR处理生菜GSH和氨基酸含量以及氮代谢相关酶活性均降低，但仍然维持较高含量可溶性蛋白。生菜叶片及根系中氮代谢的调节及含氮化合物的分配策略，对生菜应对MC-LR的慢性暴露具有积极意义。 |
| 关键词: 生菜 微囊藻毒素 慢性暴露 氮代谢 含氮化合物 |
| DOI：10.13207/j.cnki.jnwafu.2025.04.011 |
| 分类号: |
| 基金项目:福建省自然科学基金项目（2020J01256）；厦门理工学院研究生科技创新计划基金项目（YKJCX2023183） |
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| Effect of low dose MC-LR chronic exposure on nitrogen metabolism in Lactuca sativa |
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JIANG Zihan1, MA Teng1, YE Fan1, CHEN Guoyuan1,2, LI Qingsong1,2
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1.School of Environment Science and Engineering,Xiamen University of Technology,Xiamen,Fujian 361024,China;2.The Key Laboratory of Water Resources Utilization and Protection of Xiamen,Xiamen,Fujian 361024,China
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| Abstract: |
| 【Objective】This research aimed to study the effects of chronic exposure to microcystin-LR (MC-LR) on nitrogen partitioning and nitrogen metabolism-related enzyme activities in leaves and roots of lettuce (Lactuca sativa),and to provide theoretical guidance for the application of eutrophic water in lettuce irrigation.【Method】With loose-leaf lettuce as experimental material and soil cultivation as the method,lettuce was irrigated with aqueous solutions of MC-LR at different mass concentrations (2,4,6,8 and 10 μg/L) for 45 d.The photosynthetic characteristics (net photosynthetic rate (Pn),stomatal conductance (Gs),intercellular CO2 concentration (Ci),and ribulose-1,5-diphosphate carboxylase (Rubisco) activity) of lettuce leaves were determined.Soil total nitrogen and leaf NO-3-N,NH+4-N contents,and the contents of amino acids,soluble proteins,glutathione (GSH),glutathione disulfide (GSSG) in leaves and roots were measured.The activities of nitrogen metabolism-related enzymes (nitrate reductase (NR),glutamine synthetase (GS),glutamate synthase (GOGAT),glutamate dehydrogenase (GDH),glutamic-oxaloacetic transaminase (GOT),and glutamic-pyruvic transaminase (GPT)) were measured,and the correlation between Pn and nitrogen content and nitrogen metabolism-related enzyme activities was analyzed.【Result】With the increase of MC-LR mass concentration,the Pn,Gs and Rubisco activities of lettuce leaves showed a general trend of increasing and then decreasing,and the Ci of lettuce leaves showed a decreasing trend;the nitrogen content of soil showed a trend of decreasing and then increasing;the NO-3-N content of lettuce leaves showed a trend of increasing and then decreasing,and the NH+4-N content showed a trend of increasing;the GSH content of lettuce leaves and roots showed a general trend of decreasing,and the GSSG content showed a general trend of increasing;the amino acid and soluble protein contents,as well as NR,GS,GOGAT,GDH,GOT and GPT activities in lettuce leaves and roots showed a general trend of increasing.GSSG content in lettuce leaves and roots showed a general trend of increasing and then decreasing;amino acid and soluble protein content as well as NR,GS,GOGAT and GDH,GOT and GPT activities in lettuce leaves and roots showed a general trend of initial increasing and then decreasing.Compared with the control group, Pn,amino acid,soluble protein,GSSG content,and NR,GDH,GOT and GPT activities in leaves and roots of the lettuce treated with 2-6 μg/L MC-LR were significantly increased,and Pn,Gs,Ci,and Rubisco activities,as well as amino acid,soluble protein,GSH,GSSG content,and GOGH,GOT and GPT activities in leaves and roots of the lettuce treated with 10 μg/L MC-LR were significantly increased.GSSG content and the activities of GOGAT,GDH,GOT and GPT were all significantly decreased.The results of correlation analysis showed that Pn was significantly or highly significantly positively correlated with amino acid and soluble protein contents and NR,GOGAT,GDH,GOT and GPT activities.【Conclusion】The soluble protein content in leaves and roots of lettuce treated with 2-8 μg/L MC-LR increased to a certain extent,which resulted in the maintenance of high GSH content,thus improving the resistance of lettuce to MC-LR stress;although the GSH,and amino acid contents,and the activities of nitrogen metabolism-related metabolizing enzymes of lettuce treated with 10 μg/L MC-LR were reduced,the high content of soluble protein still maintained.The regulation of nitrogen metabolism and the allocation strategies of nitrogen-containing compounds in lettuce leaves and roots had positive implications for lettuce to cope with chronic exposure to MC-LR. |
| Key words: lettuce microcystin chronic exposure nitrogen metabolism nitrogen-containing compound |
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