【作者】 罗永忠；

【导师】 成自勇；

【作者基本信息】 甘肃农业大学 ， 水土保持与荒漠化防治， 2011， 博士

【摘要】 本研究选取新疆大叶苜蓿苜蓿(Medicago sativa.L.cv.Xinjiang Daye)为实验材料,分别对其进行四种水分处理即:充分供水(TA)(土壤含水量为最大田间持水的80-90%)、轻度土壤水分胁迫(TB)(土壤含水量为最大田间持水的70-80%)、中度土壤水分胁迫(TC)(土壤含水量为最大田间持水的60-70%)和重度土壤水分胁迫(TD)(土壤含水量为最大田间持水的50-60%),在苗期、分枝期、开花期分别测定了不同土壤水分条件下新疆大叶苜蓿的各项水分指标、光合指标、生化指标和形态特征指标,旨在揭示新疆大叶苜蓿在土壤水分胁迫下的适应性,并为该品种抗旱节水栽培提供科学指导。主要结果如下:1、土壤水分胁迫下新疆大叶苜蓿的自由水(Va)含水量下降,束缚水(Vs)含量及束缚水/自由水Vs/Va上升。叶片相对含水量下降,水分饱和亏上升;叶水势下降,叶片保水力增强。分枝期与苗期相比各处理的Va分别下降了17.1%,27.6%,34.0%,44.8%;Vs分别上升了16.9% ,17.5%,25.5%,25.7%;Vs/Va分别上升了41.1%,62.4%,90.0%,127.6%,胁迫越严重,Va下降幅度越大,Vs和Vs/Va上升幅度也越大。苗期叶片相对含水量RWC的大小顺序依次为:充分供水>轻度土壤水分胁迫>中度土壤水分胁迫>重度土壤水分胁迫;水分饱和亏WSD的变化规律与相对含水量RWC正好相反。分枝期、开花期RWC的变化规律相同,大小顺序依次为:轻度土壤水分胁迫最大,中度土壤水分胁迫次之,充分供水和重度土壤水分胁迫RWC最小。叶水势日变化均表现出明显的“W”曲线的特征,且随着土壤水分的降低而降低,叶水势显著降低。2、土壤水分胁迫下新疆大叶苜蓿的蒸腾速率、光合速率下降;气孔限制值LS和胞间二氧化碳浓度Ci升高,水分利用率升高。随着土壤水分胁迫的加剧,新疆大叶苜蓿的蒸腾速率表现出不同程度的下降趋势。苗期,轻度土壤水分胁迫、中度土壤水分胁迫和重度土壤水分胁迫呈明显的双峰曲线,充分供水呈单峰曲线。分枝期,各处理均呈明显的双峰曲线。到开花期各处理均呈单峰曲线。随着土壤水分胁迫的加剧,蒸腾速率呈现明显下降趋势。各处理的光合日进程为双峰曲线,具有“午休"现象。水分胁迫越严重,其Pn越小。从苗期到分枝期,充分供水和重度水分胁迫下的光合速率下降的主要原因表现出从气孔限制因素向非气孔限制因素过渡的趋势。开花期,对各种处理来说其光合速率下降的主要因素都是由非气孔限制因素引起的。在四种土壤水分条件下,WUE的日变化平均值在全生育期的大小顺序为:重度土壤水分胁迫>中度土壤水分胁迫>轻度土壤水分胁迫>充分供水,即土壤水分胁迫越严重,新疆大叶苜蓿的水分利用效率反而越高。3、土壤水分胁迫下新疆大叶苜蓿的细胞膜相对透性增加,丙二醛含量增加,Pro和WSS积累增加;SOD、POD活性呈上升趋势,叶绿素含量减少。随着土壤含水量的下降,细胞相对透性出现不同程度的增加趋势。随胁迫强度的加重和时间的延长,Pro和WSS积累愈多。在中度和重度胁迫下,Pro积累量较多,且在重度胁迫下积累量达到最大。随着水分胁迫的加剧叶绿素含量下降,充分供水条件下的叶绿素含量比苗期下降了48%,轻度水分胁迫比苗期下降了56%,中度水分胁迫比苗期下降了64%,重度水分胁迫比苗期下降了72%。4、土壤水分胁迫下新疆大叶苜蓿的生长发育受阻、生物量降低、根茎比增加。各处理苗高和地径的生长量大小依次为:轻度土壤水分胁迫>中度土壤水分胁迫>充分供水>重度土壤水分胁迫。土壤水分胁迫使新疆大叶苜蓿生长受限,胁迫越重,生长速度越慢,生长量越小。随胁迫强度的加重和时间的延长,除轻度土壤水分胁迫外,叶片数、分枝数和侧根数减少,重度土壤水分胁迫下主根最长。随着土壤水分胁迫的加重,新疆大叶苜蓿根茎比逐渐增大,充分供水条件下,新疆大叶苜蓿地下部分和地上部分的鲜生物量和干生物量之比分别为0.81和0.63;轻度土壤水分胁迫分别为0.92和0.81、中度土壤水分胁迫下为1.09和0.91、重度土壤水分胁迫下为1.34和1.31。更多还原

【Abstract】 Medicago sativa L.cv.Xinjiang Daye as experimental materials were treated by 4 treatments,namely: Fully water supply (TA)(water content is 80-90% of the maximum field water-holding capacity);Light soil water stress (TB)(water content is 70-80% of the maximum field water-holding capacity);Medium soil water stress (TC) (water content is 60-70% of the maximum field water-holdingcapacity);severe soil water stress (TD)( water content is 50-60% of the maximum fieldwater-holding capacity),this study mainly measured some water indices, photosynthesis indices, biochemical indices and morphological indices characteristics of Medicago sativa L.cv.Xinjiang Daye under different soil water condition at seedling period,branching period and flowering period. The author expects to discover the adaptability of Medicago sativa L.cv.Xinjiang Daye under different soil water stress conditions and wants to provide the science instruction for saving water cultivation. The research result shows:1 Under water stress,free water (Va) content of Medicago sativa L.cv.Xinjiang Daye decreased,while the bound water(Vs) content and Vs/Va increased. RWC decreased and WSD increased,the leave water potential of Medicago sativa L.cv.Xinjiang Daye and its water-holding capacity increased.Va decreased17.1%,27.6%,34.0%,44.8%, respectively,while the Vs increased 16.9% ,17.5%,25.5%,25.7% and Vs/Va increased 41.1%,62.4%,90.0%,127.6% at branching period than it at seedling period, respectively.The more severe the water stress was,the biger the decreasing scale of Va and the increasing scale of Vs/Va were.At seedling period, the changing rule of RWC was fully water supply >light water stress>medium water stress>severe water stress;and the changing rule of WSD was fully water supply <light water stress<medium water stress<severe water stress.During the branching and flowering periods , the changing rule of RWC was light water stress>medium water stress> fully water supply >severe water stress.With the decreasing of soil water content,the daily course of leave water potential appeares an obvious characteristic of“W”curve and the leave water potential decreased rapidly at the same time.2.Under soil water stress conditions, the transpiration rate and the photosynthetic rate of Medicago sativa L.cv.Xinjiang Daye declined .the LS and ci raised and the WUE raisedWith the decling of soil water content , the transpiration rate declined .At seedling period, The daily course of transpiration rate of light,medium and severe water stress appeared an obvious characteristics of bimodal curve except fully water supply,while at the branching period, they all became bimodal curve and they have unimodal curves characteristics at flowering period.Along with the soil water stress’s aggravating, the photosynthetic rate presents the obvious declining trend. The daily courses of photosynthetic rate of all treatments were bimodal curves,they all had“midday rest”phenomenon. the severer the water stress was ,the lower the value of photosynthetic rate was .From seedling period to branching period,the main reason of the decling of photosynthetic rate was the transform from the stomatal restriction to the non-stomatal restriction,at flowering period,the main reason of the decling of photosynthetic rate was the non-stomatal restriction.Under soil water stress conditions, the order of average daily WUE under four soil water stress was severe water stress>medium water stress> light water stress >fully water supply;that is to say ,the more severe the water stress was ,the higher the WUE of Medicago sativa L.cv.Xinjiang Daye was.3 Under soil water stress conditions, the Epicyte Permeability and MDA content of Medicago sativa raised, Proline and WSS content increased and the activity of SOD and POD raised,while the chlorophyll content decreased.With the decling of soil water content,the Epicyte Permeability raised differently. With the enhancement and lasting of water stress,the Proline and WSS content increased.The Pro concent was more under medium and severe water stress and it was the maxium under severe water stress.With the lasting of soil water stress,The chlorophyll content under all treatments declined,the chlorophyll content flowering period decrease48%,56%,64%,and 72% than it at seedling,respectively.4 Under soil water stress, The growth was limited and the biomass of Medicago sativa L.cv.Xinjiang Daye reduced. The ratio between root and stem increased.The order of growthing quantity of seedling height and basic diameter was that light water stress>medium water stress>fully water supply>severe water stress, The growth was limited by water stress,the more severe the stress was,the more slowly the Medicago sativa L.cv.Xinjiang Daye growed .With the enhancement and lasting of water stress,except light water stress,leaves、branch and Lateral root reduced and the main root was the longest under severe water stress.With the enhancement of water stress, the ratio becomes higher. the ratio between root and stem of fresh weight and dry weight under all kinds of treatments was 0.81and0.63,0.92 and 0.81,1.09 and 0.91,1.34 and 1.31.更多还原