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作 者 ：李清明,刘彬彬,艾希珍*

期 刊 ：生态学报 2010年 30卷 22期 页码：6063~6071

关键词：黄瓜；CO2浓度倍增；干旱胁迫；膜脂过氧化；抗氧化系统；

Keywords:cucumber, doubled CO2 concentration, drought stress, lipid peroxidation, antioxidant system,

摘 要 ：为了探明CO2浓度倍增对干旱胁迫下黄瓜幼苗氧化损伤的缓解机理，为未来大气CO2浓度升高或温室CO2施肥以及干旱、半干旱地区水分亏缺等逆境胁迫下黄瓜的优质高效栽培提供理论依据和技术参数，以温室专用黄瓜品种津优1号（Cucumis sativus L. var. Jinyou No. 1）为试材，采用裂区设计，主区因素为CO2浓度处理，设2个CO2浓度水平：大气CO2浓度（≈380 μmol/mol，表示为Ambient $$CO2$$ ）和倍增CO2浓度（（760±20） μmol/mol，表示为Doubled $$CO2$$ ）；裂区因素为水分处理，用PEG 6000模拟根际干旱胁迫，设3个水分处理水平：对照（营养液，表示为C）、中度干旱胁迫（含5% PEG 6000的营养液，相当于水势ψw = -0.05MPa，表示为M）和重度干旱胁迫（含10% PEG 6000的营养液，相当于水势ψw = -0.15MPa，表示为S），研究了CO2浓度倍增对干旱胁迫条件下黄瓜幼苗叶片渗透调节物质含量、膜脂过氧化及抗氧化系统的影响，结果表明：（1）干旱胁迫导致黄瓜幼苗活性氧积累，质膜透性增大，丙二醛含量升高，同时幼苗叶片脯氨酸、可溶性蛋白质和可溶性总糖含量显著增加，抗氧化酶活性（SOD、POD、CAT、APX和GR）显著提高，抗坏血酸（AsA）和还原型谷胱甘肽（GSH）含量显著升高；（2）CO2浓度倍增不仅有利于促进干旱胁迫条件下黄瓜叶片渗透调节物质的积累，而且能够促进干旱胁迫条件下黄瓜叶片抗氧化酶（SOD、POD、CAT、APX和GR）活性的表达，减轻干旱胁迫下活性氧的积累，使膜脂过氧化程度下降，质膜相对透性降低，丙二醛含量减少，对防止植物的氧化损伤具有一定的保护作用。综上所述，推测温室CO2施肥或未来CO2浓度升高可在一定程度上增强黄瓜幼苗的抗旱性和缓解干旱胁迫的负效应。

Abstract:Carbon dioxide (CO2) is the most important anthropogenic greenhouse gas, the global atmospheric CO2 concentration ( $$CO2$$ ) has increased from a pre-industrial value of about 280 to 379 mol/mol in 2005, which was directly resulted from human activities. With the ongoing rise in world population and economic activity, atmospheric $$CO2$$ is expected to double its current level at the end of 21st century and will reach to 730-1020 μmol/mol in 2100. The doubled atmospheric $$CO2$$ and a rise of other greenhouse gases could lead to available soil water shortage in many areas of the world. Thus it is important to consider both elevated CO2 concentrations and different water conditions in order to assess the possible effects of climate change on plants. This study aimed to explore the effect and its mechanism of doubled CO2 concentration on oxidative damage of cucumber seedlings under drought stresses, and then provide theoretical basis and technical parameters for the high quality and efficient cultivation of cucumber. Osmolates, lipid peroxidation and antioxidant system of hydroponic cucumber seedlings (Cucumis sativus L. var. Jinyou No.1) were investigated under atmospheric and doubled CO2 concentration (760±20 μmol/mol), companied with drought stresses simulated by PEG 6000. Split-plot design was employed in the experiment, the main treatment was CO2 concentration including two levels (Ambient $$CO2$$ ≈380 μmol/mol and Doubled $$CO2$$ =760±20 μmol/mol), the subplot treatment was drought stress treatment including three levels (control was Yamazaki cucumber nutrient solution indicated as C; moderate drought stress was Yamazaki cucumber nutrient solution + 5% PEG 6000, water potential ψw=-0.05MPa, indicated as M; severe drought stress was Yamazaki cucumber nutrient solution + 10% PEG 6000, water potential ψw = -0.15MPa, indicated as S). The results showed that: (1) drought stresses induced the accumulation of reactive oxygen species, subsequently resulted in the increase of MDA content and permeability of cell membrane as well as osmoticum (proline, soluble protein and soluble carbohydrate) content. Meanwhile, the antioxidative enzymes (SOD, POD, CAT, APX and GR) activities, AsA and GSH contents increased significantly with the aggravation of drought stress; (2) under the condition of severe drought stress, doubled $$CO2$$ remarkably increased proline content; under the conditions of both moderate and severe drought stress, doubled $$CO2$$ significantly enhanced soluble protein and soluble carbohydrate content; (3) doubled $$CO2$$ markedly reduced permeability of cell membrane by 17.1% under severe drought stress and reduced MDA content significantly by 94% and 16.4% under moderate and severe drought stress, respectively; (4) doubled $$CO2$$ increased activities of SOD, POD, APX and GR under moderate drought stress, while increased the all antioxidative enzymes activities significantly under severe drought stress by 17.6%, 15.5%, 10.6%, 11.4% and 8.8%, respectively; (5) doubled $$CO2$$ increased AsA content significantly by 37.7% under severe drought stress, and there was no significant difference for GSH content between ambient and doubled $$CO2$$ . In conclusion, not only did doubled CO2 concentration promote osmolates accumulate, but also enhanced the activities of antioxidative enzymes and increased the content of AsA and GSH in cucumber seedlings under drought stresses condition, and then reduced the accumulation of ROS, decreased lipid peroxidation and cytomembrane permeability as well as MDA content. Based on the above results, we speculate that increasing CO2 concentration can enhance the resistance of cucumber seedlings to drought stress and mitigate the negative effects of drought stress to some extent.

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