【作者】 燕辉；

【导师】 康绍忠；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2012， 博士

【摘要】 在西北干旱荒漠区营造防风固沙林，是遏制荒漠化进程，保障绿洲农业生产不受风沙危害的有效途径。但由于该地区天然降雨量少，仅依靠天然降雨很难满足幼龄人工林对水分的需求。为保证人工林的顺利成活，必须在人工林幼龄期进行补充灌溉。而该地区的淡水资源严重匮乏，补充灌溉只能依赖于地下苦咸水。由于苦咸水含有较高的盐分，利用苦咸水进行灌溉往往会对植物造成一定的生理伤害。要合理利用含有较高盐分的苦咸水进行幼龄林灌溉，首先就要研究盐胁迫条件下植物的耐盐机理。在深入认识盐胁迫对植物生理特性影响的基础上，才能进一步制定幼龄人工林灌溉方案，以提高林分成活率。为深入认识盐胁迫对典型沙生植物柠条与梭梭生理特性的影响，本论文对NaCl胁迫下柠条叶片、梭梭同化枝光合特性、离子积累、抗氧化酶活性、游离氨基酸代谢、内源激素含量进行了研究。并进一步对盐胁迫下非盐生植物柠条与盐生植物梭梭生理特性变化进行了比较，为揭示柠条与梭梭抗盐性差异提供了理论基础。本研究主要获得以下成果：1、轻度与中度NaCl胁迫下，柠条叶片gs降低。进入细胞间隙的CO2不能满足光合碳同化的需求，气孔因素成为降低柠条叶片Pn的主要原因。随着盐胁迫的加剧，300mM NaCl胁迫18d后，各种非气孔因素对光合碳同化的抑制能力增强，非气孔因素成为柠条Pn降低的主要原因。而整个试验过程中，梭梭同化枝Pn、gs与Ci同步降低，表明梭梭Pn降低的主要原因一直是气孔限制。2、NaCl处理导致柠条叶片与梭梭同化枝Na⁺含量升高，但NaCl处理未降低柠条叶片与梭梭同化枝K⁺含量。这种盐胁迫下柠条（梭梭）的K⁺、Na⁺吸收不相竞争现象证实了长期适应盐环境的沙生植物体内可能存在着独特的非竞争K⁺的Na⁺吸收通道。NaCl处理下柠条叶片Na⁺/K⁺超出了0.6（非盐生植物维持最佳代谢效率的阈值），表明长期高盐胁迫下柠条叶肉细胞生理代谢发生了严重紊乱。在整个试验过程中，柠条叶片Ca²⁺、Mg²⁺含量呈现降低趋势，而梭梭同化枝Ca²⁺、Mg²⁺含量维持稳定。3、盐胁迫导致柠条叶片与梭梭同化枝产生氧化损伤。柠条叶片O·2-产生速率、H2O2含量、以及膜质过氧化的产物MDA含量增加幅度明显高于梭梭同化枝。为降低盐胁迫造成的生理伤害，低浓度NaCl胁迫下，柠条叶片SOD、POD、CAT活性呈现升高趋势，这有利于清除过量自由基与活性氧；但高浓度NaCl长期胁迫时，柠条叶片酶活性降低；而整个试验过程中，梭梭同化枝SOD、POD、CAT活性随胁迫加剧持续升高，这表明梭梭较柠条具有更强的耐盐性。4、柠条叶片与梭梭同化枝17种单个游离氨基酸中，Pro、Ser、Glu、Asp、Ala与Thr等六种游离氨基酸在对照与胁迫叶片（同化枝）总游离氨基酸中占的比例最大，而其余11种仅占对照与胁迫叶片（同化枝）总游离氨基酸含量的20%左右。NaCl胁迫下，氨基酸含量升高总是发生在一定的胁迫阶段之后，这表明植物体内存在耐盐阈值。NaCl胁迫未达到耐盐阈值时，叶片（同化枝）游离氨基酸含量维持稳定；NaCl胁迫超过耐盐阈值后，叶片（同化枝）游离氨基酸大量积累。5、NaCl处理会导致柠条叶片与梭梭同化枝ABA含量不同程度的升高，但相同胁迫条件下梭梭同化枝ABA含量较柠条叶片稳定。伴随着盐胁迫的加剧，柠条叶片生长促进型激素表现为降低趋势；而梭梭同化枝IAA、GA与ZR含量维持稳定或显著升高。在整个试验过程中，柠条叶片IAA/ABA、GA/ABA、ZR/ABA以及（IAA+GA+ZR）/ABA的值随着盐胁迫加剧呈现降低趋势；而梭梭同化枝生长促进型激素与ABA的比值基本稳定。表明盐胁迫下梭梭能够更好地调节体内激素平衡，以适应不良盐环境。更多还原

【Abstract】 Establishing sand break forest in arid areas of northwest China is an effective way tocurb the expansion of land desertification and protect oasis agriculture from the hazardsof sandstorm. Natural rainfall in the area is less and difficult to satisfy the demand of sandbreak forest for water. In order to ensure young sand break forest survival, Supplementaryirrigation with underground brackish water must be performed. However, the young sandbreak forest will be harmed by high salinity brackish water. So, mechanisms of salinitytolerance in plants must be studied firstly before the utility of brackish water irrigation.In order to understand effects of salinity on physiological traits of Caraganakorshinskii Kom and Haloxylon ammodendron Bunge, the two typical sand-fixing plants,in arid areas of northwest China. Leaf photosynthesis, ion content, antioxidant enzymeactivities, free amino acid and endogenous hormones in Caragana korshinskii Kom andHaloxylon ammodendron Bunge exposed to NaCl stress was studied in this paper.Furthermore, differences in physiological traits of Caragana korshinskii Kom andHaloxylon ammodendron Bunge under salt stress were compared. Theoretical basis wasprovided for differences in salt resistance of Caragana korshinskii Kom and Haloxylonammodendron Bunge.This study has obtained the following results.（1） Stomatal conducance of Caragana korshinskii Kom is significantly reduced dueto mild and moderate NaCl stress. CO2which entered cell gap could not satisfy thedemand of photosynthetic carbon assimilation, and stomatal limitation became the majorfactor in reducing the photosynthesis rate. At18days with300mM NaCl treatment, theinhibition of photosynthetic carbon assimilation increased due to non-stomatal factors,and non-stomatal limitation becomes the major factor in reducing the photosynthesis rate.During the entire experiment, photosynthesis rate, stomatal conductance and intercellularCO2concentration of Haloxylon ammodendron Bunge reduced synchronously, whichindicated stomatal limitation was the major factor in reducing the photosynthesis rate.（2） Salt stress increased Na⁺content in leaves of Caragana korshinskii Kom andHaloxylon ammodendron Bunge, but had no effect on K⁺content. The phenomenon of alack of competition between K⁺and Na⁺absorption confirms a unique pathway of Na⁺ absorption in the plants which can grow well under salt environment. The ratio of Na⁺toK⁺in salt-treated leaves of Caragana korshinskii Kom was above0.6（Maximum for anoptimal metabolic efficiency in non-halophytic plants）, suggesting the metabolicdisorders in leaves of Caragana korshinskii Kom occurred. During the entire experiment,Ca²⁺and Mg²⁺contents in leaves of Caragana korshinskii Kom reduced but Ca²⁺andMg²⁺contents in leaves of Haloxylon ammodendron Bunge was almost constant.（3） Oxidative damages to leaves of Caragana korshinskii Kom and Haloxylonammodendron Bunge were observed under salt stress. The increases of production rate ofsuperoxide radical, content of Hydrogen peroxide and content of Maloniedialdehyde inleaves of Caragana korshinskii Kom were significantly higher than Haloxylonammodendron Bunge. To reduce the physiological damages caused by salt stress, SOD,CAT and POD activity in leaves of Caragana korshinskii Kom increased with lowconcentrations of NaCl. It is helpful to eliminate excess free radicals and reactive oxygenspecies. However, with high concentrations of NaCl, enzyme activity in leaves ofCaragana korshinskii Kom reduced. SOD, CAT and POD activity in leaves of Haloxylonammodendron Bunge increased with salt stress. It indicated that Haloxylon ammodendronBunge has greater salt tolerance than Caragana korshinskii Kom.（4） In seventeen free amino acids of Caragana korshinskii Kom and Haloxylonammodendron Bunge leaves, proline, serine, glutamic acid, aspartic acid, alanine andthreonine are most abundant in both salt-treated and control leaves. The rest of elevenfree amino acids only accounting for20%of total amino acids. The increases of freeamino acid always happen after a certain stage of NaCl stress, which indicates theexistence of a critical salinity level in Caragana korshinskii Kom and Haloxylonammodendron Bunge. Free amino acids in salt-stressed leaves slowly accumulated belowthe critical salinity level, but rapidly accumulated when above the level.（5） NaCl treatment would lead to the accumulation of ABA in leaves of Caraganakorshinskii Kom and Haloxylon ammodendron Bunge. But ABA content in leaves ofHaloxylon ammodendron Bunge is more stable than Caragana korshinskii Kom.Endogenous hormones which are able to promote growth in leaves of Caraganakorshinskii Kom decreased with increased salinity, but contents of IAA, GA and ZR inleaves of Haloxylon ammodendron Bunge was constant or increased significantly. Duringthe entire experiment, the ratio of IAA/ABA, GA/ABA, ZR/ABA and （IAA+GA+ZR）/ABA in salt-treated leaves of Caragana korshinskii Kom decreased with the increase ofNaCl stress. While, the ratio of growth-promoting hormones to ABA in leaves ofHaloxylon ammodendron Bunge was constant. It is indicated that Haloxylon ammodendron Bunge could regulate the hormonal balance effectively to adapt theadverse salt environment.更多还原