【作者】 王玉清；

【导师】 朱祝军；

【作者基本信息】 浙江大学 ， 蔬菜学， 2005， 硕士

【摘要】 一氧化氮（nitric oxide, NO）是生物体内的重要活性分子。NO参与了动物体内血管松弛、神经传递及免疫防御反应等一系列生理功能而被认为是可扩散的多功能第二信使。在植物体内NO也是一种广泛存在的信号分子,参与植物生长发育的许多重要的生理过程,如种子萌发、下胚轴伸长、叶扩展、根生长、侧根形成、细胞程序性死亡以及植物抗逆反应等。但NO在植物体内的来源及其作用方式仍不明确,最近的研究表明,NO可以提高小麦、玉米、水稻、羽扇豆及芦苇等的耐盐性,但国内有关NO对黄瓜耐盐性影响的研究甚少,NO对作物耐盐性及其机制仍不清楚。本研究通过对根际施加外源NO供体硝普钠（sodium nitroprusside, SNP）,初步探讨了盐胁迫下NO处理对黄瓜幼苗生理生化的影响,为提高植物的抗盐性提供一定的理论依据。主要研究结果如下: 1.盐胁迫抑制黄瓜幼苗生长,NO处理明显提高黄瓜幼苗地上部和根系干重,增加了叶片可溶性蛋白含量。NO处理显著降低了盐胁迫下黄瓜幼苗叶片电解质渗漏率,减少了H₂O₂和MDA的累积;NO处理提高了盐胁迫下黄瓜叶片抗氧化酶SOD、GPX、CAT和APX的活性。因此,可以推论,盐胁迫下NO处理黄瓜幼苗叶片中较高SOD、GPX、CAT和APX活性,较低的电解质渗漏率、H₂O₂和MDA含量与NO提高了黄瓜幼苗的耐盐性有关。说明NO提高了黄瓜叶片的抗氧化能力,减轻了盐胁迫诱导的膜脂过氧化损伤。NO可能参与了植物的代谢或生理活动。 2.盐胁迫显著降低叶片叶绿素含量、净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）和光系统Ⅱ光合电子传递量子效率（ΦPSⅡ）,NO处理提高了盐胁迫下黄瓜幼苗叶片叶绿素含量、Pn、Tr、Gs以及叶绿素荧光参数ΦPSⅡ、Fv/Fm、qP和NPQ。盐胁迫显著增加叶片细胞间隙CO₂浓度（Ci）,NO处理叶片的Ci值显著小于不加NO处理。盐胁迫下黄叶片中脯氨酸和可溶性糖含量显著增加,NO处理提高了盐胁迫下黄瓜幼苗叶片中脯氨酸含量,降低了可溶性糖含量。说明NO有利于黄瓜对光能的捕获和转化,明显促进植物的生长,降低盐胁迫对黄瓜的抑制作用。更多还原

【Abstract】 Nitric Oxide (NO) is an important active molecule in biology. It is firstly described as a diffusible multifunctional second messenger in animals since it plays various functions including the relaxation of blood vessels, neurotransmission and defense during immune response etc. It is now being evident that NO is also a ubiquitous signal molecule in plant kingdom. It was proved to participate in many key physiological processes such as seed germination, hypocotyls elongation, leaf expansion, root growth, lateral root initialation, programmed cell death, and stress tolerance. However, its disease-resistant physiological mechanisms in plants are still vague at present. Recently, it has been reported that the addition of NO increased the salt tolerance of crops in experiments within wheat (Triticum aestivum), maize (Zea mays) and rice (Oryza sativa), lupin (Lupinus luteus), reed (Phragmites communis trin.). However, information is still lacking regarding the effects of NO on salt tolerance of cucumber (Cucumis sativus L.) and its mechanism. Therefore, the effects of NO donor on the physiological and biochemical mechanisms in hydroponic cucumber seedlings under salt stress were investigated, in order to clarify the possible mechanisms of enhancing salt-tolerance in plants. The main results were presented as follows:1. The cucumber (Cucumis sativus L.) plants were grown in a hydroponics culture system for the investigation of exogenous NO on plant growth and the activities of major antioxidation enzymes [ superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), dehydroascorbate reductase (DR) and glutathione reductase (GR) ] in seedling leaves under salt stress. The results showed that salt stress significantly decreased plant growth and soluble protein content, and increased electrolytic leakage percentage, H2O2 and MDA contents in leaves of cucumber seedlings, while NO treatment significantly decreased electrolytic leakage percentage, H2O2 and MDA contents under salt stress. Compared with the plants treated with salt alone, NO treatment significantly enhanced the activities of SOD, GPX, CAT and APX in salt-stressed cucumber leaves. It could be concluded that higher activieties of SOD, GPX, CAT, APX更多还原