土壤水分和磷营养对小麦根系生长生理特性的影响

采用小偃６号小麦品种,在模拟田间原状土容重的条件下土培,研究了土壤水分和磷营养对小麦根系生长生理特性的效应。结果表明：在土壤相对含水量为４０％─７０％范围内,土壤水分亏缺,小麦根系生长受到限制,根系比表面积（ＲＡ）、根呼吸速率（Ｒｐ）、根水势（Ｒψｗ）和叶片蒸腾强度（ＥＩ）明显降低,根系干物重（ＲＤＷ）减少;轻度干旱有利于根系的延伸生长;在土壤干旱条件下,磷营养可以提高根系ＲＡ,降低根系Ｒｐ,提高Ｒψｗ、增加叶面ＥＩ,促进根系延伸生长,扩大小麦根系对土壤深层水分的吸收和利用,进而促进地下部生长,提高ＲＤＷ。磷除作为一种营养物质促进作物根系生长发育外,在水分胁迫条件下,磷营养可明显改善植株体内的水分关系,增强对干旱缺水环境的适应能力,提高作物抗旱性。促进根系生长,提高水分利用的有效方法是根据土壤水分状况调节磷的用量。     

模拟喀斯特不同土壤生境下黑麦草对水分胁迫的生长和光合生理响应

以多年生草本黑麦草为对象,模拟喀斯特生境土壤特征设置浅而宽(Shallow and wide, SW:30×30×5 cm~3)和深而窄(Deep and narrow, DN:10×10×45 cm~3)两种土壤容器,以正常降水量为对照供水(W100%),设减水50%(W50%)和减水70%(W30%)共3种水分处理进行盆栽实验,探究了两种不同土壤生境中土壤水分变化对黑麦草生长及光合生理的影响,以进一步理解喀斯特地区植物的适应对策。结果显示:(1)SW生境对水分变化敏感,随供水减少土壤含水量显著下降。轻度减水下植物叶面积增大,光合速率提高,地上部分生长得到促进,但水分严重减少对其生长和光合生理有抑制作用,但地上质量分数和水分利用效率却显著升高;(2)DN生境保水能力较好,随供水减少土壤水分含量下降较为平缓。叶片相对含水量、气孔导度和比叶面积在各水分处理之间差异不显著,但严重减水条件下总生物量、地上质量分数和水分利用效率均有回升。研究表明:浅而宽生境中植物倾向于通过提高地上部分的生长,保持较高的光合速率,并向地上部分分配较多生物量来应对水分胁迫;而深而窄生境中植物会充分利用土壤空间条件,促进根系的生长来提高对水分的吸收,从而维持植物的生长。     

土壤水分和氮磷营养对冬小麦根系生长及水分利用的调节

模拟试验研究结果表明：在土壤相对含水量为４０％￣７０％范围内,水分亏缺严重,根水势和蒸腾蒸发量显著降低,根系生长严重受阻,根长变短,根干重降低,随着土壤水分趋于良好,根水势和蒸腾蒸发量显著增加,根干重在土壤相对含水量为５５％￣６２％之间时最大,而土壤相对含水量在５５％上下时根长达最长;土壤水分趋于轻度干旱有利根系下扎,土壤水分趋于良好利于根量增长。氮磷营养对小麦根系生长具有明显的调节作用。磷营养可     

采煤塌陷影响下土壤含水量变化对柠条气孔导度、蒸腾与光合作用速率的影响

采煤塌陷引起的土壤环境因子的变化对矿区植物生长的影响越来越受到人们的关注,气孔导度、蒸腾与光合作用作为环境变化响应的敏感因子,研究植物气孔导度、蒸腾与光合作用的变化是揭示荒漠矿区自然环境变化及其规律的重要手段之一。研究采煤塌陷条件下植物光合生理的变化是探究煤炭开采对植物叶片水分蒸腾散失和CO_2同化速率影响的关键环节,是探讨采煤塌陷影响下植物能量与水分交换动态的基础,而采煤矿区植物叶片气孔导度、蒸腾与光合作用速率对采煤塌陷影响下土壤含水量变化的响应如何尚不清楚。选取神东煤田大柳塔矿区52302工作面为实验场地,以生态修复物种柠条为研究对象,对采煤塌陷区和对照区柠条叶片气孔导度、蒸腾和光合作用速率以及土壤体积含水量进行监测,分析了采煤塌陷条件下土壤含水量的变化以及其对柠条叶片气孔导度、蒸腾与光合作用速率的影响。结果显示:(1)煤炭井工开采在地表形成大量裂缝,破坏了土体结构,潜水位埋深降低,土壤含水量均低于沉陷初期,相对于对照区,硬梁和风沙塌陷区土壤含水量分别降低了18.61%、21.12%;(2)柠条叶片气孔导度、蒸腾和光合作用速率均与土壤含水量呈正相关关系;煤炭开采沉陷增加了地表水分散失,加剧了土壤水分胁迫程度,为了减少蒸腾导致的水分散失,柠条叶片气孔阻力增加,从而气孔导度降低,阻碍了光合作用CO_2的供应,从而导致柠条叶片光合作用速率的降低,蒸腾速率也显著降低。     

大棚甜瓜蒸腾规律及其影响因子

研究大棚甜瓜的蒸腾规律和影响因子,可以为大棚甜瓜水分优化管理提供理论依据。利用大棚盆栽试验,设定了4个水分梯度,定量分析了大棚甜瓜蒸腾规律及蒸腾量与植株生理特性、气象环境因子、土壤水分含量的关系。结果表明:(1)各水分处理条件下甜瓜蒸腾强度日变化曲线均呈"双峰型",有明显的"午休"现象。(2)甜瓜生理需水系数与叶面积指数、有效积温关系显著,分别呈线性和抛物线函数关系。(3)甜瓜全生育期累计蒸腾量呈现出"慢—快—慢"的变化规律,可以用Logistic函数进行模拟。(4)甜瓜叶面积指数、日平均空气温度、日平均空气相对湿度、日太阳辐射累积、土壤相对含水量均与单株日蒸腾量呈显著性相关关系;甜瓜叶面积指数对蒸腾的综合作用最大,是决策变量;土壤水分含量是限制变量,主要通过对其他因子的影响间接作用于蒸腾。(5)气象环境因子对甜瓜蒸腾量的影响力很大程度上取决于土壤水分含量;气象环境因子与蒸腾量的相关性随土壤水分含量的增大而增大,在土壤相对含水量为70%—80%范围内达到最高值,当土壤含水量接近田间持水量时,与各因子的相关系数逐渐下降。(6)甜瓜水分胁迫指数与土壤相对有效含水量关系显著,二者呈现线性关系。     

根源信号参与调控气孔行为的机制及其农业节水意义

在土壤干旱情况下,根源信号一方面向植物地上部分的长距离传输,为地上部分提供了土壤水分获取能力的测度,另一方面调控气孔开度,抑制蒸腾作用并提高植物的水分利用效率．文中综述了根源信号参与调控植物水分利用的生理机制和理论模型,指出该模型与根系吸水模型、气孔导度模型耦合,能够更好地反映植物叶片对土壤干旱以及大气干旱的响应、评述了在根源信号参与调控植物水分关系的基础上发展的调亏灌溉(RDI)、部分根系干旱(PRD)和控制性交替灌溉(CAI)等有效灌溉手段,有助于合理配置根系层供水量,通过根土相互作用和信号物质的传输,降低蒸腾和提高水分利用效率、另外,根源信号在调控根系生长发育、延缓地上部分生长以调节根冠比例,优化资源分配以利于生殖生长等方面均有所为,为全面提高农田水分利用效率提供节水生理基础。     

基于δD和δ18O的青海湖流域芨芨草水分利用来源变化研究

水分条件是限制干旱半干旱地区植物生长重要的生态因子,为了揭示青海湖流域典型生态系统下芨芨草植物的水分利用来源及其如何响应水分条件的变化,选择了自然和干旱控制条件下芨芨草植物,通过测定芨芨草植物茎水和各潜在水源(土壤水、地下水及降水)中δD、δ~(18)O组成,并利用直接比较分析法和多源混合模型计算芨芨草植物对土壤水的利用比例。研究结果表明:表层土壤水分和土壤水中δD、δ~(18)O值表征出较大波动范围,其直接受降水和蒸发作用影响,土壤蒸发线的斜率和截距明显小于大气水线斜率和截距,表明土壤水中同位素组成经历了强烈的蒸发分馏过程,而芨芨草茎水中δD、δ~(18)O值都集中分布土壤水蒸发线附近,说明芨芨草根系主要利用不同深度的土壤水。自然条件下芨芨草在生长季初期(6月)利用表层土壤水(0—10cm,45.1%),8—9月份大降水事件影响土壤含水量和同位素组成,降水入渗深度较深且芨芨草根系对土壤水分吸收的比例相差不大,表明根系在土壤含水量较高时均能吸水不同深度土壤水。在干旱控制条件下芨芨草在7月初主要利用表层土壤水(0-30cm),随着表层土壤水分的减少,根系吸收深度转向较深土壤层,而灌溉后表层土壤水分明显增加,其吸收深度又转向表层,表明芨芨草根系吸收深度能敏感地响应土壤水分的变化。另外还发现芨芨草在生长季内并未直接利用地下水。     

CO2浓度升高和干旱对春小麦生长和水分利用的生态效应

利用开顶式气室对春小麦进行了一个生长季的CO2倍增盆栽实验,土壤水分控制为3个水平(分别为田间持水量(FWC)的80%、60%、40%).结果显示,CO2倍增显著提高小麦的光合速率.但在相同的CO2测定浓度下, 生长在加倍CO2浓度下的小麦的光合速率比当前CO2浓度下小麦低22%.高CO2浓度显著促进小麦生长,相对增加幅度在适宜水分下最大,为14.8%.80%FWC水分条件下高CO2使植株的干重/高度比增加15.7%.高CO2条件下,小麦的蒸腾速率降低、累积耗水量减少、水分利用效率(WUE)提高,WUE的提高幅度在适宜水分下最大,为30%.干旱(40%FWC)使小麦地上干重和WUE在当前CO2条件下分别降低72%和19%,加倍CO2条件下降低幅度较大,分别为76%和23%.根据以上结果得出结论: (1) 高CO2条件下, 小麦的光合速率、地上生物量和水分利用效率提高;(2) 植物长期生长于高CO2浓度导致光合能力降低;(3) 高CO2对植物侧向生长的促进作用大于垂直生长,即高CO2下植株将相对粗壮;(4) 高CO2对植物的生态效应依赖于土壤水分,在适宜水分下相对较大;(5) 在未来高CO2条件下,干旱引起的减产和水分利用效率减低幅度将会更大.     

用Minirhizotrons观测柠条根系生长动态

 Minirhizotrons是一种非破坏性、定点直接观察和研究植物根系的新方法。该文介绍了用Minirhizotrons测定植物根系的方法,并同根钻取原状土样法进行了比较;探讨了根系生长动态同土壤含水量间的关系。试验于2004年植物生长季在沙坡头沙漠试验研究站的水分平衡观测场的人工柠条(Caragana korshinskii)林进行,结果表明：Minirhizotrons 管埋入土壤后需要10个月时间允许柠条根系在其周围定居,其观测图片中的根系代表了管子周围2.6 mm土层的根系。柠条根系生长动态和土壤水分变化相关,含水量的升高导致根系的大量繁殖,而根系吸水及蒸发散又导致含水量的减少;在2004年植物生长季,土壤水分和根系的这种相互作用出现了两次,但根系生长高峰比土壤含水量高峰滞后20 d左右。     

3种禾草苗期生长和水分利用对土壤水分变化的反应

采用5种不同的水分处理,于室内生长箱内盆栽条件下对引种禾草柳枝稷(Panicum virgatum)、乡土禾草白羊草(Bothriochloa ischaemum)和栽培禾草谷子(Setaria italica)等苗期根冠生长和水分利用特征进行了比较分析.结果显示:(1)充分供水下3种禾草的苗期生物量和蒸腾效率均显著高于其它4种水分处理,而高水与低水处理下各自的根冠比无显著差异;(2)各水分处理下谷子苗期总生物量、蒸腾效率和耗水量均显著大于白羊草和柳枝稷;(3)在5种水分处理下,苗期根冠比谷子均最小,柳枝稷最大;(4)低降复水后,3种禾草生物量和蒸腾效率较低水处理分别显著提高16.7%-98.7%和28.2%-118.2%,显示出补偿效应,以白羊草增幅最大.结果表明,白羊草、谷子和柳枝稷在不同土壤水分处理下的苗期生物量、根冠分配比例以及水分利用效率差异反映了野生种、栽培种和引进种禾草苗期对半干旱环境条件水分生态适应性的异同.     

Elemental sulfur improves growth and phytoremediative ability of wheat grown in lead-contaminated calcareous soil

Little is known about the effect of elemental sulfur on lead uptake and its toxicity in wheat. A pot experiment was conducted with the purpose to examine the impact of sulfur on improving Pb solubility in soil, and uptake and accumulation in wheat plants. The effect of three levels of lead (0, 50, and 100 mg/kg soil) and sulfur (0, 150, and 300 mmol/kg soil) was tested in all possible combinations. Root dry matter, straw, and grain yields, and the photosynthetic and transpiration rates decreased significantly with increase in the concentration of Pb in the soil. However, sulfur fertilization in the presence of Pb improved the photosynthetic and transpiration rates and consequently increased the straw and grain yields of wheat. It also enhanced Pb accumulation in roots, its translocation from roots to shoot, and accumulation in grain. S and Zn contents of different plant parts were also enhanced. Thus, by mitigating the toxic effect of Pb and improving wheat growth, sulfur enhances Pb accumulation by the aboveground plant parts and hence the phytoextraction capacity of wheat. However, total accumulation of Pb shows that wheat plant cannot be considered as a suitable candidate for phytoremediation.     

耕作播种方式对稻茬小麦根系发育、土壤水分和硝态氮含量的影响

2016—2018年,以深旋耕播种模式为对照,研究了浅旋耕播种和免耕带旋播种模式对稻茬小麦根系发育、土壤水分和硝态氮含量的影响。结果表明: 孕穗期以前免耕带旋播种和浅旋耕播种处理耕层土壤含水量高于深旋耕播种处理,而硝态氮含量低于深旋耕播种处理。拔节和开花期根重密度和根表面积密度处理间差异不显著。2016—2017年,3种耕播方式的产量和地上部分氮吸收量无显著差异;2017—2018年,免耕带旋播种和浅旋耕播种处理的产量较深旋耕播种分别增加10.9%和10.5%,地上部分氮吸收量分别增加17.5%和12.0%。与深旋耕播种和浅旋耕播种处理相比,免耕带旋播种处理播种效率高、断垄率低。综上,免耕带旋播种处理可提高稻茬小麦的播种质量,增强土壤保墒能力,降低氮淋溶风险,促进产量和环境效益的协同提升。     

全膜微垄沟穴播对春小麦土壤水热环境的影响及其光合和产量效应

减弱春季寒旱生境限制是提高甘肃中东部旱地春小麦产量的关键要素之一。本研究于2016—2018年在甘肃中部半干旱旱作区开展大田试验,以‘陇春35号’为供试品种,设置全膜微垄沟穴播(PRF)、全膜覆土穴播(PMS)和露地穴播(CK)3个处理,测定春小麦不同生育期0～300 cm土层的土壤含水量、0～25 cm土壤温度、叶片生物量、叶片叶绿素(SPAD)、光合速率、蒸腾速率和作物产量,从土壤水热-冠层发育-产量角度揭示PRF处理对土壤水热环境、水分利用效率(WUE)和产量的影响。结果表明: 与CK相比,PRF和PMS处理0～25 cm土层的土壤温度在苗期分别提高2.8和2.5 ℃,灌浆-成熟期分别降低1.4和0.9 ℃;0～300 cm土壤贮水量在播前-苗期分别增加59.7和41.8 mm;0～300 cm耗水量在苗期-灌浆期分别提高46.1和39.8 mm。与PMS处理相比,PRF处理的小麦苗期温度提高0.3 ℃,灌浆-成熟期降低0.5 ℃;播前-苗期0～300 cm土壤贮水量增加18.0 mm,拔节-成熟期耗水量提高13.0 mm。基于对土壤水热条件的优化,PRF和PMS处理的叶片生物量、SPAD值、苗期-灌浆期叶片净光合速率、蒸腾速率均显著高于CK,且PRF处理均显著高于PMS处理。PRF处理比PMS处理和CK分别增产9.1%和36.5%,WUE分别提高5.9%和30.8%。因此,PRF处理能提高苗期地温,降低灌浆-成熟期地温,促进春小麦苗期-灌浆期的耗水,提高了春小麦叶片SPAD值和生物量,增强春小麦苗期-灌浆期旗叶的光合功能,从而实现增产和水分高效利用,而且这一优势在欠水年份(2016和2017年)更加明显。     

干旱胁迫对条墩桑生物量分配和光合特性的影响

以1年生红皮花桑为材料,采用盆栽的方法,研究了不同水分条件下条墩桑幼苗的生物量、荧光参数、净光合速率、气孔导度、蒸腾速率及水分利用效率的变化.结果表明： 随着干旱胁迫程度的增加,植株地上部分的生物量和总生物量逐渐降低,但光合产物向根部的分配比例逐渐增大,根冠比逐渐增加;叶片的荧光参数F_o、F_v和F_v/F_m逐渐降低;气孔导度、蒸腾速率、净光合速率和水分利用效率逐渐下降.     

水分亏缺和施氮对冬小麦生长及氮素吸收的影响

利用管栽试验研究了不同生育期,水分亏缺和施氮对冬小麦生长及氮素吸收的影响.结果表明：任何生育期水分亏缺都会影响冬小麦的株高、叶面积、干物质累积及对氮素的吸收.冬小麦对水分亏缺的敏感期为拔节期,其次为开花期、灌浆期和苗期.苗期干旱后复水对后期生长有显著的补偿效应,开花期适度干旱后复水对生物量形成和氮素吸收有一定的补偿作用,拔节期干旱对小麦的生长影响明显.相同氮肥处理下, 与不亏水处理比较, 苗期水分亏缺、拔节期水分亏缺、开花期水分亏缺、灌浆期水分亏缺的根系氮素积累量分别平均降低25.82%、55.68%、46.14%和16.34%,地上部氮素积累量分别平均降低33.37%、51.71%、27.01%和2.60%.在相同水分处理下冬小麦含氮量、累积吸收氮量都表现为高氮处理（0.3 g N·kg^-1FM）>中氮处理（0.2 g N·kg^-1FM）>低氮处理（0.1 g N·kg^-1FM）.水分逆境条件下施用氮肥对冬小麦植株生长和干物质累积及氮吸收具有明显的调节效应.     

Salt distribution around roots of wheat under different transpiration rates

Summary Magnitude of Na and Cl accumulation around wheat roots was studied under different transpiration conditions in a loamy sand soil salinized with sodium chloride to an electrical conductivity of 4.1 mmho/cm in the saturation extract. A significant correlation was observed between rate of water loss per unit root length and Na and Cl content of the soil closely adhering to the roots. Under high transpiration condition, maximum ion accumulation occurred in the apparent free space of roots followed by the soil closely adhering to the roots. Results indicate that salt concentration at the root surface is markedly altered under the influence of transpiration rate such that under high transpiration conditions, the plant roots may be exposed to a much higher salt concentration than that anticipated from an analysis of the bulk soil samples.Department of Soil and Water EngineeringDepartment of Soils     

土壤水分变化对长白山主要树种蒙古栎幼树生长的影响

选择长白山红松阔叶林主要优势树种蒙古栎为研究对象,人工控制3种施水量研究蒙古栎幼树形态、生物量效应和光合生理特征对土壤含水量变化的响应．结果表明,不同土壤含水量变化显著影响蒙古栎叶片、枝、根的生物量及其分配格局和叶片光合气体交换特征．水分胁迫改变幼树树冠结构,抑制幼树树高、地径、叶片大小、地上和地下生物量;同时,蒙古栎幼树根冠生物量比随着土壤水分含量的减少显著提高;供水量减少对幼树净光合速率、CO2利用率和碳利用率等特征有显著的负向影响;而叶片气孔导度、蒸腾速率和水分利用率对不同土壤含水量反应较复杂,只在土壤含水量较低时,幼树气孔导度、蒸腾速率明显降低,叶片水分利用率升高,表现出蒙古栎树种是干旱可变植物,长期水分胁迫可提高树种的耐旱能力．     

Seasonal variation of water uptake of a Quercus suber tree in Central Portugal

Hydraulic redistribution (HR) is the phenomenon where plant roots transfer water between soil horizons of different water potential. When dry soil is a stronger sink for water loss from the plant than transpiration, water absorbed by roots in wetter soil horizons is transferred toward, and exuded into dry soil via flow reversals through the roots. Reverse flow is a good marker of HR and can serve as a useful tool to study it over the long-term. Seasonal variation of water uptake of a Quercus suber tree was studied from late winter through autumn 2003 at Rio Frio near Lisbon, Portugal. Sap flow was measured in five small shallow roots (diameter of 3–4 cm), 1 to 2 m from the tree trunk and in four azimuths and at different xylem depths at the trunk base, using the heat field deformation method (HFD). The pattern of sap flow differed among lateral roots as soil dried with constant positive flow in three roots and reverse flow in two other roots during the night when transpiration ceased. Rain modified the pattern of flow in these two roots by eliminating reverse flow and substantially increasing water uptake for transpiration during the day. The increase in water uptake in three other roots following rain was not so substantial. In addition, the flux in individual roots was correlated to different degrees with the flux at different radial depths and azimuthal directions in trunk xylem. The flow in outer trunk xylem seemed to be mostly consistent with water movement from surface soil horizons, whereas deep roots seemed to supply water to the whole cross-section of sapwood. When water flow substantially decreased in shallow lateral roots and the outer stem xylem during drought, water flow in the inner sapwood was maintained, presumably due to its direct connection to deep roots. Results also suggest the importance of the sap flow sensor placement, in relation to sinker roots, as to whether lateral roots might be found to exhibit reverse flow during drought. This study is consistent with the dimorphic rooting habit of Quercus suber trees in which deep roots access groundwater to supply superficial roots and the whole tree, when shallow soil layers were dry.     

Hydraulic redistribution in a stand of <Emphasis Type="Italic">Artemisia tridentata</Emphasis>: evaluation of benefits to transpiration assessed with a simulation model

The significance of soil water redistribution facilitated by roots (an extension of "hydraulic lift", here termed hydraulic redistribution) was assessed for a stand of Artemisia tridentata using measurements and a simulation model. The model incorporated water movement within the soil via unsaturated flow and hydraulic redistribution and soil water loss from transpiration. The model used Buckingham-Darcy's law for unsaturated flow while hydraulic redistribution was developed as a function of the distribution of active roots, root conductance for water, and relative soil-root (rhizosphere) conductance for water. Simulations were conducted to compare model predictions with time courses of soil water potential at several depths, and to evaluate the importance of root distribution, soil hydraulic conductance and root xylem conductance on transpiration rates and the dynamics of soil water. The model was able to effectively predict soil water potential during a summer drying cycle, and the rapid redistribution of water down to 1.5 m into the soil column after rainfall events. Results of simulations indicated that hydraulic redistribution could increase whole canopy transpiration over a 100-day drying cycle. While the increase was only 3.5% over the entire 100-day period, hydraulic redistribution increased transpiration up to 20.5% for some days. The presence of high soil water content within the lower rooting zone appears to be necessary for sizeable increases in transpiration due to hydraulic redistribution. Simulation results also indicated that root distributions with roots concentrated in shallow soil layers experienced the greatest increase in transpiration due to hydraulic redistribution. This redistribution had much less effect on transpiration with more uniform root distributions, higher soil hydraulic conductivity and lower root conductivity. Simulation results indicated that redistribution of water by roots can be an important component in soil water dynamics, and the model presented here provides a useful approach to incorporating hydraulic redistribution into larger models of soil processes.     

杀灭土壤中线虫对小麦生长和吸收N、P的影响

盆栽条件下研究了施用杀线剂(克线磷,67mg·kg^-1干土)和干热(105℃,2h)两种杀线措施对小麦生长和N、P养分吸收的影响。杀线剂对土壤中线虫的平均杀灭率约为80%, 干热处理的杀灭率为100%. 在杀线剂处理中,苗期至抽穗期小麦生物量、拔节期至成熟期植株含N量、全生育期植株吸N量以及抽穗和成熟期吸P量均显着低于对照。土壤干热处理后抽穗和成熟期小麦的生物量、含N量及N、P吸收量也比对照显着降低。两种杀线处理植株地上部生物量和N、P吸收量与相应处理全株变化趋势基本一致。但杀灭线虫对植株含P量影响较小。分析杀线虫后小麦生长和养分吸收受抑主要与土壤有机氮的矿化作用减弱、微生物活动产生的植物生长促进物质降低有关