【作者】 王文；

【导师】 蒋文兰； 张德罡；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2013， 博士

【摘要】 唐古特白刺（Nitraria tangutorum）是北方内陆盐碱地区荒漠植被的优势种或建群种之一，为我国特有植物种，具有沙生植物和盐生植物的多重特性。本研究以唐古特白刺为对象，通过根系分布、根际土壤水分、幼苗盐胁迫下生理指标变化、盐离子吸收运输及分布、光响应及叶绿素荧光变化、光合日变化等的观测，对其资源特征及耐盐生理特性进行了研究，以期对其资源利用及盐碱干旱环境生态保护提供理论依据，取得如下主要研究结果：1．根际土壤水分变化规律明显，0～40cm土层含水量变幅较大，40～80cm土层含水量最高，80cm以下随土层加深而递减，160～300cm土层含水量没有明显变化。平均根长100cm，根幅300cm。主根较粗，入土浅，根长为株丛高的1.32倍，侧根发达，扩展范围较广，根幅为冠幅的3.23倍，地上生物量为根系生物量的1.46倍；有效根系主要分布于0～40cm土层，为吸收和利用水分的重要区域，在0～20cm、20～40cm土层中，有效根重分别占总有效根重的58.69％、22.96％，有效根长分别占总有效根长的59.65％、23.20％。根系的水平走向和浅层大范围分布，有利于及时有效吸收利用因降水而补充的地表水分，是其在干旱荒漠地区大面积分布的重要生存策略之一。2．NaCl胁迫10d、20d、30d后，幼苗叶片抗氧化物酶活性均随NaCl浓度的增大呈相似的变化规律，超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性均在低浓度(25～100mmol·L^-1)胁迫时上升，高浓度(200～400mmol·L^-1)盐胁迫时下降；丙二醛（MDA）、脯氨酸（Pro）含量均随NaCl浓度增大持续上升，在相同NaCl浓度下，胁迫10d时上升幅度较大，胁迫20d、30d时上升幅度较小；可溶性蛋白（SP）含量随NaCl浓度增大呈现整体下降趋势；可溶性糖（SS）在低NaCl浓度时上升，高NaCl浓度时下降。表明随NaCl浓度增大，幼苗的膜脂过氧化程度加大，保护酶在低NaCl浓度下对清除活性氧起到主要作用，并且Pro是维持幼苗渗透压平衡的主要物质，而SS、SP对渗透压平衡具有辅助调节作用。3．根系对盐分离子的吸收比以K⁺最大，其次为Cl^-、Na⁺；运输比以Ca²⁺最大，其次为Cl^-、Na⁺。由于土壤介质Cl^-、Na⁺的基数远大于其他离子，所以Cl^-、Na⁺的吸收和运输总量最大，其后依次为K⁺、Ca²⁺、Mg²⁺。在NaCl胁迫下，以叶片优先吸收并积累大量盐分离子为适应特征，茎叶和根系中Cl^-、Na⁺及总离子含量随NaCl浓度的增大而上升。叶片对Cl^-、Na⁺和总无机离子的积累量高于茎和根部，叶片和茎部能够大量积累盐分离子，维持组织细胞的高渗透压和原生质胶体的高亲水性，增大地上部和根部的渗透势差，促进水分向地上部运输。4．NaCl胁迫下，幼苗的净光合速率（P_n）和蒸腾速率（T_r）变化趋势一致，其顺序为：25＞CK＞50＞100＞200＞400mmol·L^-1；水分利用效率（WUE）在200、400mmol·L^-1NaCl浓度下显著高于CK和其他处理。随NaCl浓度增大，幼苗的表观量子效率（a）、暗呼吸速率（R_d）、最大光合速率(P_nmax)、光饱和点（LSP）和光补偿点（LCP）均呈下降趋势，在25mmol·L^-1NaCl浓度下其P_nmax、LSP、LCP显著高于其它处理。随着NaCl浓度的增大，唐古特白刺幼苗对弱光的利用能力增强，对强光的利用能力下降，25mmol·L^-1NaCl浓度下光合同化潜力最大，400mmol·L^-1NaCl浓度下光合同化潜力最小。随NaCl浓度增大，幼苗的初始荧光（F_o）呈增大趋势，最大荧光（F_m）、PSⅡ原初光能转化效率（F_v/F_m）、PSⅡ潜在光化学效率（F_v/F_o）、光化学淬灭系数（qP）、非光化学淬灭系数（NPQ）、PSⅡ实际光合效率（ФPSⅡ）均呈下降趋势。说明NaCl胁迫下幼苗的PSⅡ光反应中心受到的破坏程度随NaCl浓度增大而加重，这也是其P_n下降的主要原因。5．幼苗P_n日变化呈现单峰趋势，峰值出现在上午10:00，之后随光合有效幅射（PAR）的增大而持续下降，无光合“午休”现象；Tr在8:00～10:00随PAR的增加呈现较大幅度上升，10:00-16:00有相对平稳的小幅升降变化，16:00开始下降；WUE的日变化整体表现为8:00-14:00快速下降，14:00以后稳定或小有上升；气孔限制值（L_s）在8:00-14:00整体表现为平稳上升趋势，14:00以后下降。多元回归显示，PAR偏回归系数显著大于其他环境因子，说明PAR与Pn的相关性最大。通径分析结果显示，除800mmol·L^-1外，各环境因子与P_n的通径系数趋势为：PAR＞大气CO2浓度（C_a）＞空气相对湿度（RH）＞大气温度（T_a），表明PAR对P_n的贡献最大。不同NaCl浓度下PAR的通径系数随NaCl浓度的上升先升高后降低，环境因子对P_n的效应在100mmol·L^-1NaCl浓度下最显著，此浓度下PAR和C_a的利用效率最高，在800mmol·L^-1NaCl浓度下，PAR的利用效率最低。更多还原

【Abstract】 Nitraria tangutorum is one of dominant or constructive plant species of desert vegetation innorthwest inland saline area and it is also one of the endemic plant species in China with featuresof psammophytes and halophytes. The study on resource characteristics and salt resistance ofNitraria tangutorum was conducted through measuring the microelement content, root systemdistribution, soil moisture in rhizosphere, physiological index variation of seedling under saltstress, salt ion absorb-transportation and distribution, light response and chlorophyll fluorescencechange, daily variation of photosynthesis in order to provide the basis for N. tangutorumutilization in ecological protection in saline and arid area. The main results are as follows:1. The soil moisture in rhizosphere showed a remarkable variation pattern. The variationwithin0to40cm soil layer was large and it was small within160to300cm soil layer. The soilmoisture within40to80cm layer was the highest. The root length and diameter of root systemwere100cm and300cm respectively. The root length was1.32times of plant height. Thediameter of root system was3.22times of plant crown. The aboveground biomass was1.46times of underground. And the alive root weight within0to20cm and20to40cm layersaccounted for58.69%and22.96%of the total respectively, and for the alive root length, theywere59.65%and23.20%respectively. Root system distributed horizontally and mainly inuplayer in order to effectively absorb the rainfall to surface and this was the important strategyfor plants growing in desert area to survive.2. The activity of protective antioxidant enzyme in leaf of seedling under NaCl stress for10,20and30days showed a same pattern. The activity of superoxide dismutase （SOD）, catalases（CAT） and peroxidase （POD） increased under the low concentration stress (25to100mmol·L^-1)and decreased under high concentration (200to400mmol·L^-1). The content of malonate （MDA）kept increasing under stress. The proline （Pro） content increased along with the stressconcentration. And the increasing amount was higher within10to20days compared to thatwithin20to30days under same stress concentration. Soluble protein （SP） content showed adecreasing pattern in general. Soluble sugar （SS） content increased under low concentrationstress and decreased under high concentration stress. This might explain that the membrane lipidperoxisome degree of seedling increased along with NaCl concentration and the protective enzyme played an important role for clearing reactive oxygen under low NaCl concentratin. Procould keep seedling osmoregulation balance as the major material, SS and SP behaved as theassistant matter.3. The absorptance of root system for K⁺was the highest, and followed by Cl^-and Na⁺. Thetransportation rate for Ca²⁺was the highest, and followed by Cl^-and Na⁺. The absorbtion andtransportation amount of Cl^-and Na⁺were the highest because of their high proportions in soil,and followed by K⁺, Ca²⁺and Mg²⁺. The leaf priorly absorbed and accumulated a large amountof action for adapting the environment under NaCl stress, and the contents of Cl^-, Na⁺and totalions in leaf, stem and root increased with NaCl concentration. The accumulation amount of Cl^-,Na⁺and total inorganic ions in leaf were higher than those in stem and root, and leaf and stemcould store a large amount of salt ions for maitaining the osmosis pressure and protoplast of highhydrophilic property, increased over ground part and root system osmosis pressure difference,keeping water towards over ground part transportation.4. The variation of net photosynthetic rate （P_n） and transpiration rate （T_r） of seedling underNaCl stress with different concentrations showed a same pattern and the order of P_n was25>CK>50>100>200>400mmol·L^-1. The water use efficiency （WUE） under treatments of200and400mmol·L^-1NaCl was higher that other treatments and CK.With NaCl concentration increased, the apparent quantum yield （a）, dark respiratory rate（R_d）, maximum photosynthesis rate (P_nmax), light saturation point （LSP） and light compensationpoint （LCP） of seedling performed a decreasing trend. And its P_nmax, LSP and LCP were thehighest under25mmol·L^-1stress out of all treatment concentrations. The weak light utilizationability of seedling was increased along with the NaCl stress concentration and meanwhile thestrong light utilization ability was decreased. The photosynthesis assimilatory potential ofseedling reached the highest under25mmol·L^-1NaCl concentration and the lowest under400mmol·L^-1NaCl concentration.With NaCl concentration increasing, the minimal fluorescence （F_o） of seedling showed anincreasing trend, however, the maximal fluorescence （F_m）, maximal quantum yield ofPSⅡ（F_v/F_m）, PSⅡLatent photosynthesis efficiency （F_v/F_o）, photochemical quench coefficient（qP）, non photochemical quench coefficient （NPQ）, PSⅡreality photosynthesis efficiency（ФPSⅡ） decreased. It could be concluded that the PSⅡlight reaction center was damaged by NaCl stress and it was also the cause of P_n decreace.5. The P_n daily change of seedling showed a single peak pattern and the peak valueappeared at10:00, and then it decreased along with the increase of photosynthesis activeradiation. No photosynthesis noon break phenomenon was found. T_r increased greatly from8:00to10:00along with PAR increase and it steadily increased from10:00to16:00, and then it beganto decrease. The daily change of WUE showed the following pattern: it rapidly decreased from8:00to14:00and was stable after14:00or a small amount of increasing. The stomata limitationvalue （L_s） from8:00to14:00was rising in general and dropping after14:00.Multiple regression indicated that PAR partial regression coefficient was notable largerthan other environment factor, and it suggested that PAR greatly correlated to P_n. Pathanalysis showed that the order of path coefficient of environmental factors was PAR> airCO₂concentration （C_a）> air relative humidity （RH）> air temperature （T_a） except800mmol·L^-1treatment, and this meant that the contribution of PAR to P_n was the largest. PARpath coefficient under stress of different NaCl concentrations increased first and thendecreased along with the increase of NaCl concentration. And it suggested that the impact ofenvironmental factors on P_n was most significant under100mmol·L^-1and PAR and C_autilization efficiency were the highest, however, they were the lowest under800mmol·L^-1.更多还原