【作者】 吴芹；

【导师】 张光灿；

【作者基本信息】 山东农业大学 ， 森林培育， 2013， 博士

【摘要】 水分是影响植物生长、分布和生态修复的主要限制因子。水分时空分布不均是我国水资源的主要特点，尤其是我国北方半干旱黄土丘陵地区水分匮乏严重，生态脆弱。本文针对我国干旱半干旱区干旱缺水的主要特征，以山杏（Prunus sibirica）、沙棘（Hippophaerhamnoides）、油松（Pinus tabulaeformis）3个树种为试验试料，采用盆栽试验和自然干旱处理的方法测定了3个树种在土壤干旱逐渐加剧过程中各气体交换参数的光响应过程和CO₂响应过程，以及不同生理生化指标的响应过程及变化规律。阐明了土壤干旱逐渐加剧过程中净光合速率（Pn）、蒸腾速率（Tr）、水分利用效率（WUE）、胞间CO₂浓度（Ci）、气孔导度（Gs）等气体交换参数的光响应过程，揭示光合生理光响应过程发生变化的机理和机制，明确3个树种光合特征生理参数发生明显变化的土壤水分临界点及这种变化与土壤水分的定量关系，确定维持不同树种较高Pn和WUE的土壤水分范围；阐明了土壤干旱逐渐加剧过程3个树种CO₂响应过程及其特征参数对土壤水分的响应及其发生显著变化的机制，确定了3树种光合作用CO₂响应过程与土壤水分的定量关系。采用直角双曲线模型、非直角双曲线模型、指数方程和直角双曲线修正模型对3个树种的光响应过程和CO₂响应过程及光合作用生理参数进行拟合分析，探讨了不同模型在拟合分析不同土壤水分下3个树种光响应过程和CO₂响应过程及其特征参数的适用性。测定了3个树种在土壤干旱逐渐加剧过程中8个生理生化指标的变化，明确3个树种在土壤干旱过程中主要生理生化指标水平的变化过程及其差别，探索3个树种抗旱能力及其生理生化指标与土壤水分的定量关系。通过对3个树种光响应、CO₂响应过程和生理生化指标随着土壤水分的连续降低的变化过程及响应特征的研究，为深入了解3个树种的水分生理生态特征和抗旱机理，为指导3个树种在干旱缺水地区的物种配置、合理栽培及系统构建提供一定的理论依据，同时为不同光合作用模型的适用性评价提供试验证据。主要研究成果如下：（1）3个树种叶片气体交换参数对土壤水分和光强具有明显的阈值响应根据光合速率、蒸腾速率和水分利用效率等气体交换参数与土壤水分的关系分析结果，初步明确了3个树种以提高光合生产力与水分利用效率为核心的适宜土壤水分条件、土壤水分最大亏缺及适宜的光照强度范围。①山杏、沙棘和油松生长适宜的土壤水分范围分别为：52.3%～84.8％、50.2%～84.6%、44.3%～83.6%。适宜的光照强度范围分别为：500～1300、300～1500、300～1500μmol·m-2·s-1。土壤水分最大亏缺值越低，表明植物在干旱胁迫条件下对干旱的忍耐能力越强。由3个树种的土壤水分最大亏缺值可以看出他们的抗旱性从高到低依次为：油松、沙棘、山杏。②3个树种的表观量子效率（Φ）、暗呼吸速率（Rd）和光补偿点（LCP）受土壤水分含量的影响显著，对土壤水分具有明显的阈值响应特征。3个树种对弱光的利用能力由高到低依次为：油松、山杏、沙棘。（2）土壤水分显著影响植物叶片光合作用-CO₂响应过程及其生理参数维持山杏、沙棘和油松叶片具有较高光合速率（Pn）及羧化效率（CE）的土壤相对含水量（RWC）分别为46.3%～81.9%、42.8%～83.5%和35.3%～84.2%范围内；当RWC超出此范围，土壤水分升高或降低均明显降低山杏、沙棘和油松叶片的光合能力（Pnmax）、CE和CO₂饱和点（CSP）。山杏、沙棘和油松光合作用-CO₂响应适宜的土壤水分范围分别在46.3%～81.9%、42.8%～83.5%和35.3%～84.2%之间。3个树种对低的CO₂的同化能力由大到小依次为：油松、沙棘、山杏。（3）不同土壤水分条件下的3个树种的光合作用的光响应过程和CO₂响应过程及其生理特征参数的模型模拟①用直角双曲线模型、非直角双曲线模型、指数方程和直角双曲线修正模型对3个树种光响应数据的模拟效果在不同土壤水分下具有明显差别。当山杏RWC在52.3%～84.8%、沙棘在50.2%～84.6%和油松在44.3%～83.6%范围内时，4个模型均能较好地拟合3个树种的光响应过程及其特征参数如表观量子效率（Φ）、光补偿点（LCP）和暗呼吸速率（Rd）。其中，以非直角双曲线模型拟合值与实测值最为接近；当RWC超出3个树种生长适宜范围时，只有直角双曲线修正模型可以较好地拟合3个树种的光响应过程及其特征参数。②当山杏、沙棘和油松土壤水分范围分别在46.3%～81.9%、42.8%～83.5%和35.3%～84.2%之间时，直角双曲线模型、非直角双曲线模型、指数方程和直角双曲线修正模型均能较好地拟合3树种光合作用的CO₂响应过程及其特征参数CE、CO₂补偿点（CCP）和光呼吸速率（Rp），对CE、CCP和Rp的拟合精度以非直角双曲线模型＞直角双曲线修正模型＞指数方程＞直角双曲线模型；当土壤水分含量超出正常生长范围时，只有直角双曲线修正模型能较好地拟合3树种CO₂响应过程及其特征参数。（4）不同土壤水分下3个树种叶片生理生化指标的变化及其与土壤水分的定量关系随着干旱程度加剧，3个树种叶片相对含水量（LRWC）及叶绿素（Chl）含量持续下降，细胞膜透性逐渐增大；其中，以山杏和沙棘变化幅度较大，油松最小；3个指标发生显著变化的土壤相对含水量（RWC）临界值，油松为61.3%、山杏和沙棘分别为52.3%和54.3%。丙二醛（MDA）含量先升高后降低，轻度干旱胁迫时MDA含量的降低与保护酶活性升高有关，极度干旱胁迫时MDA含量的降低与MDA自身的降解有关；3个树种超氧化物歧化酶（SOD）与过氧化物酶（POD）两种抗氧化酶活性，随RWC降低先升高后降低，SOD活性、POD活性对干旱胁迫的响应程度和防御作用存在差异，即在抵御轻、中度干旱胁迫时SOD发挥着重要作用，干旱胁迫加剧时POD活性作用更大；维持较高抗氧化酶活性的RWC范围，油松为34.6%⁸5.6%、山杏和沙棘分别为52.3%⁸7.2%和39.9%⁸7.7%；在不同土壤干旱程度下，油松的抗氧化酶活性水平高于沙棘和山杏。3个树种两种渗透调节物质脯氨酸（Pro）与可溶性糖（Ss）的含量随RWC降低而增加，油松的增加幅度大于山杏和沙棘；Pro含量的增加速度大于Ss含量。3个树种可通过渗透调节、抗氧化酶活性升高等途径增强对干旱逆境的耐受性和适应性；通过模糊隶属函数值法对3个树种的抗旱能力进行了综合评价，3个树种的抗旱能力为油松＞沙棘＞山杏。更多还原

【Abstract】 Water is the main factor which limited plant growth, distribution and ecologicalrestoration. The main features of water resources is that the distribution is uneven in time andspace in our country. Especially in northern China semi-arid loess hilly area, water scarcity issevere and ecology is fragile. In this paper according to the main features of China’s arid andsemi-arid drought and water shortage, we used Prunus sibirica、Hippophae rhamnoides andPinus tabulaeformis as the test samples, using potted experiment and natural drought method,light response process and CO₂response process of gas exchange parameters were determined,as well as response process and change rules of eight physiological and biochemical indexeswere determined.Light response process of gas exchange parameters, such as net photosynthetic rate（Pn）、transpiration rate（Tr）、water use efficiency （WUE）、intercellular CO₂concentration（Ci）、stomatal conductance（Gs）in three tree species and the mechanisms of thephotosynthetic physiological light response process were revealed in the process of graduallyintensified soil drought, the soil moisture critical point of the photosynthetic characteristicparameters changed significantly and the quantitative relationship of thus change and the soilmoisture were clear, the soil moisture range of the three trees to maintain higher Pnand WUEwere determined.CO₂response process of the three trees and the response of characteristic parameters tosoil water and the mechanisms of the characteristic parameters changed significantly wererevealed, the quantitative relationship of photosynthetic CO₂response process and itscharacteristic parameters were determined in the process of gradually intensified soil drought.The light response process and CO₂response process and the photosyntheticphysiological parameters of the three tree species were fitted by rectangular hyperbolic model,non-rectangular hyperbolic model, exponential equation and modified rectangular hyperbolicmodel, the applicability of different models to fit the photosynthesis process of the three treespecies was discussed in different soil moisture conditions.The variation and the difference of eight physiological and biochemical indexes of thethree tree species were determined in the process of intensified soil drought, droughtresistance of the three tree species and the quantitative relationship of the physiological and biochemical indices and the soil moisture were explored. Through the study of the variationand response characteristics of the light response process and CO₂response process and thephysiological and biochemical indices in the three tree species, a theoretical basis could beprovided to understand the hydrological and ecological characteristics and drought resistancemechanism deeply, to guide species configuration, reasonable cultivationin and systemconstruction in arid areas; at the same time the test evidence could be provide to evaluate theapplicability of different photosynthetic models. The main results are as follows:（1）Leaf gas exchange parameters of the three tree species had obvious thresholdresponses to soil moisture and light intensityAccording to the analysis results of the relation between gas exchange parameters suchas net photosynthetic rate、transpiration rate、water use efficiency and the soil moisture,suitable soil moisture conditions, the biggest soil moisture deficit and suitable light intensityrange of the three tree species to improve photosynthetic productivity and water use efficiencywere clear initially.①The suitable soil moisture ranges for P.sibirica、H. rhamnoides、P. tabulaeformis were52.3%～84.8％、50.2%～84.6%、44.3%～83.6%, respectively. Suitable light intensity rangesfor them were500～1300、300～1500、300～1500μmol·m-2·s-1, respectively. The lower thebiggest soil moisture deficit value, the stronger drought tolerance ability under drought stress.From the biggest soil moisture deficit value we could see that their drought resistance fromhigh to low were in the order of P. tabulaeformis、H. rhamnoides、P. sibirica.②The apparent quantum yield（Φ）、dark respiration rate（Rd）and light compensationpoint（LCP）of the three species were affected significantly by soil moisture contents, they allhad clear threshold response characteristics to the soil moisture. The order from high to low ofthe ability to utilize low light of the three species were P. tabulaeformis、H. rhamnoides、P.sibirica.（2）Soil moisture significantly affected leaf photosynthetic CO₂response process and thephysiological parametersThe suitable soil moisture ranges of photosynthetic CO₂response for P. sibirica、H.rhamnoides、P. tabulaeformis were in the ranges of46.3%～81.9%、42.8%～83.5%and35.3%～84.2%, respectively. When RWC exceeded these ranges, photosynthetic capacity（Pnmax）、CE and CO₂saturation point（CSP）significantly reduced when the soil moistureincreased or reduced. The order of the ability to assimilate low CO₂of the three species from high to low were P. tabulaeformis、H. rhamnoides、P. sibirica.（3）Model simulation of photosynthetic light response process and CO₂response processand their characteristic parameters①Effect of light response data fitted by rectangular hyperbola model、non-rectangularhyperbola model、exponential equation and modified rectangular hyperbola model hadsignificant differences under different soil moisture conditions. The photosynthetic lightprocess and its characteristic parameters such as the apparent quantum yield（Φ）、darkrespiration rate（Rd）and light compensation point （LCP）were well fitted by the4modelswhen RWC of P. sibirica were from52.3%to84.8%、that of H. rhamnoides were from50.2%to84.6%、that of P. tabulaeformis were from44.3%to83.6%，and the values fitted bynon-rectangular hyperbola model were the most close to measured values. Only the modifiedrectangular hyperbola model could well fit the light response process and its characteristicparameters when RWC were ouside of the above ranges.②The photosynthetic CO₂response process and its characteristic parameters CE、CO₂compensation point （CCP） and light respiration rate （Rp） were well fitted by rectangularhyperbola model、non-rectangular hyperbola model、exponential equation and modifiedrectangular hyperbola model when RWC of P. sibirica were from46.3%to81.9%、that of H.rhamnoides were from42.8%to83.5%、that of P. tabulaeformis were from35.3%to84.2%，the fitting precision was that non-rectangular hyperbola model> modified rectangularhyperbola model> exponential equation> rectangular hyperbola mode. Only the modifiedrectangular hyperbola model could well fit the photosynthetic CO₂response process and itscharacteristic parameters when the soil moisture content exceeded the above ranges.（4）Changes of physiological and biochemical indexes in the three species and thequantitative relationship of the changes and the soil moisture under different soil moistureconditionsLeaf relative water content （LRWC） and the chlorophyll （Chl） content decreased whilethe cell membrane permeability increased gradually in the three tree species following therelative water content （RWC） of soil reduced. The changes of the tested responses in P.sibirica and H. rhamnoides were bigger than those in P. tabulaeformis．LRWC, Chl contentand the cell membrane relative permeability changed significantly when the soil RWC werelower than61.3%,52.3%, and54.3%for P. tabulaeformis, P. sibirica and H. rhamnoides,respectively．The content of malondidehyde （MDA） increased and then declined, the decrease of MDA content under light drought stress condition was related with the protective enzymeactivity increase, and the decrease under severe drought stress condition was related withMDA itself degradation．The activity of SOD and POD in the three tree species increased firstand then decreased following the soil water reduced．The response time and the defensive roleof SOD and POD to drought stress were different. SOD played an more important role in theearly drought stress and POD played a bigger role in the late drought stress when droughtstress was intensified．The soil RWC required to maintain higher enzyme activity were34.6%⁸5.6%,52.3%⁸7.2%and39.9%⁸7.7%for P. tabulaeformis, P. sibirica, and H.rhamnoides, respectively. The Pro content and the Ss content increased following the soilwater reduced, with the higher level in P. tabulaeformis. The Pro increased faster than Ss. Sowe conclude that the three tree species enhance their tolerance and adaptability to droughtstress by osmotic adjustment and protective enzyme system．The comprehensive evaluationwas made about the drought-resistant capability of the three tree species by using the subjectfunction method. The order was P. tabulaeformis＞H. rhamnoides＞P. sibirica．更多还原