夏玉米叶片气体交换参数对干旱过程的响应

目前已经开展了大量的干旱对作物叶片气体交换参数影响的研究,但关于作物叶片气体交换参数对干旱过程的响应及其关键阈值的研究仍较少。基于夏玉米七叶期开始的5个初始水分梯度的长时间持续干旱模拟实验资料,分析了不同强度持续干旱过程中夏玉米叶片气体交换参数(净光合速率Pn,气孔导度Gs,蒸腾速率Tr,胞间CO_2浓度Ci和气孔限制值Ls)的变化规律及其关键阈值。结果表明,玉米的净光合速率(Pn),蒸腾速率(Tr)和气孔导度(Gs)在干旱发生初期呈大幅度下降,但随着干旱持续会出现一定的适应性。利用统计容忍限方法确定了夏玉米拔节期Pn,Tr和Gs响应干旱的临界土壤相对湿度(0—30cm)分别为53%,51%和48%,对应的临界叶含水率分别为81.8%,81.3%和81.2%。夏玉米光合作用由气孔限制向非气孔限制转换的0—30cm土壤相对湿度均为44%±2%,对应的叶含水率均为77.6%±0.3%。研究结果可为夏玉米干旱发生发展过程的监测预警提供依据。     

液压信号与植物水分胁迫信号传递研究（综述）

植物根部受到干旱胁迫时,由茎部产生的液压信号使茎部作出反应.液压传递根到茎之间的水分胁迫信号.土壤干旱引起茎中场所产生液压反应,然后产生ABA信号,引起气孔关闭.在不同植物中,减弱液压反应,阻止干旱信号的长距离传导,气孔不能关闭.     

整树水力导度协同冠层气孔导度调节森林蒸腾

冠层气孔导度决定森林的蒸腾效率,它对驱动水汽移动的水汽应力的响应受树木水力结构的影响,并随水汽压亏缺上升和水力导度下降而降低,维持水势在最低阈值之上,避免出现水力灾变,调控冠层蒸腾。由于叶形和树冠结构的特点,部分脱耦联反映了湿润地区阔叶林冠层与大气的水汽交换特征,单纯以气孔导度的变化难以完整描述水分通量的调节规律,因而,需要考虑冠层气孔导度与水力导度协同控制冠层蒸腾的潜在机理。通过整合叶片气孔气体交换、树干液流、冠层微气象和其他环境因子的野外观测值,估测不同时间尺度的森林冠层气孔导度与大气的脱耦联系数和变异范围,以基于树干液流的冠层蒸腾,结合叶片/土壤水势梯度计算的水力导度,分析水力导度影响冠层气孔导度响应水汽压亏缺的敏感性,可以揭示和阐明水力导度和冠层气孔导度联合调节森林蒸腾的机理,对准确估测全球变化背景下森林对水资源利用的潜在生态效应有明显的理论意义。     

脱落酸调节植物抵御水分胁迫的机制研究

干旱、盐渍、低温等均可导致植物可利用水分的亏缺,表现为水分胁迫。植物感受到水分胁迫,诱导脱落酸（abscisic acid,ABA）生物合成。ABA可通过促使气孔关闭或抑制气孔开放,使作物尽可能地降低蒸腾失水,以抵御水分胁迫。该文就植物激素ABA及其下游信号过氧化氢（hydrogenperoxide,H2O2）、一氧化氮（nitric oxide,NO）以及Ca2＋等在植物气孔运动调节方面的研究进展进行概述,以构建水分胁迫下ABA调节植物气孔运动的可能模式。     

华南荷木林冠层气孔导度对水汽压亏缺的响应

冠层气孔导度(Gs)是量化气孔在冠层尺度水平上表现的参数,能够表征森林冠层表面水汽和能量交换的动态.本研究利用Granier树干液流测定系统,连续监测华南地区荷木林的树干液流,通过尺度转换和扩展获得冠层蒸腾速率,结合微气象观测值,以Pen-man-Monteith公式计算了Gs,并比较不同土壤水分条件下Gs对水汽压亏缺的响应.结果显示,Gs与气孔气体交换方法实测的叶片气孔导度(gs)日变化相似,单位转换数值大小与实测gs数量级一致.Gs对水汽压亏缺的响应在干季和湿季有明显差别:(1)在土壤水分充足的湿季(土壤含水量θ ＞33％),Gs对水汽压亏缺的响应更敏感(偏相关系数-0.316),而在干季(θ＜23％)则对光合有效辐射的响应更敏感(偏相关系数0.885).(2)荷木林冠层-大气脱耦联系数(Ω)在湿季接近l,干季则较湿季小,说明湿季叶片的界面层较厚,水汽压亏缺对Gs影响较小,而光合有效辐射是控制Gs的主要环境因子.     

土壤水分亏缺条件下根源信号ABA参与作物气孔调控的数值模拟

建立了根系吸水模型和根源ABA参与作物气孔调控过程相耦合的气孔导度模型,该模型在根源信号ABA的产生项中考虑了根系吸水影响函数和根系密度分布函数.利用该耦合模型模拟大田状况下根源ABA参与玉米气孔行为调控过程,结果表明,由于充分考虑了根区土壤水势和土壤中根长密度分布对根系吸水的影响,较好地反映了土壤不同层次根系吸水强度,更为确切地描述了当土壤水分亏缺时,根系合成ABA的量、各层根系蒸腾流中ABA浓度、木质部ABA浓度以及最终ABA参与对气孔行为的调控作用.     

黄土高原地区春小麦对有限灌溉的反应及其生理生态基础

从对黄土高原地区有限灌溉条件下作物生理生态反应的众多研究中得出：（1）水分轻度亏缺时,作物可通过根信号物质ABA调节叶片的气孔导度。非水力根信号作用太强,可因降低光合作用而减少干物质生产和影响干物质分配模式而影响产量和水分利用效率,故削弱非水力根信号的作用将有利于提高产量。（2）浅层根系占根系总量比值越高,对干旱越敏感,表现为根信号能力增强;深层根系所占比例越高,越有利于土壤深层水分利用,并可削弱根信号,同理,给土壤中下层补水或采用播种前灌溉,可因为减少了无效蒸发,且削弱根信号而提高水分利用率。（3）本地区有限灌溉的最佳时期由于降水变率较高而变得较为复杂,不同降水年型,最佳灌溉时期差异很大,对有限灌溉进行科学管理还需要做更多的研究工作。     

干旱胁迫下冠菌素对玉米幼苗光合参数和内源激素含量的影响

采用沙培称重法研究冠菌素对玉米幼苗光合参数及内源激素系统影响的结果表明,干旱胁迫下,0.01μmol·L-1冠菌素显著增加玉米幼苗茎基部粗、根长、干鲜重、光合速率、蒸腾速率和气孔导度,降低胞间二氧化碳浓度,提高幼苗的ABA和1-氨基环丙烷-1-羧酸(ACC)含量。叶片与根中ABA/GA3大时耐旱性增大。     

羊草叶片气体交换参数对温度和土壤水分的响应

 采用生长箱控制的方法研究了羊草(Leymus chinensis)幼苗叶片光合参数对5个温度和5个水分梯度的响应和适应。结果表明：轻度、中度土壤干旱并没有限制羊草叶片的生长,对气体交换参数亦无显著影响,反映了羊草幼苗对土壤水分胁迫的较高耐性。叶片生物量以26 ℃时最大,其它依次为23 ℃、20 ℃、29 ℃和32 ℃。温度升高使气孔导度和蒸腾速率增加, 却使光合速率和水分利用效率降低。水分和温度对叶片生物量、光合速率、气孔导度和蒸腾速率存在显著的交互作用,表明高温加强了干旱对叶片生长和气体交换的影响, 降低了羊草对土壤干旱的适应能力。高温和干旱的交互作用将显著减少我国半干旱地区草原的羊草生产力。     

干旱胁迫与ABA 的信号转导

植物经历干旱胁迫时,ABA被普遍认为是一种干旱信号而传递干旱信息。在干旱信号ABA的转导过程中,从ABA的被感知到保卫细胞发生变化引起气孔关闭以及ABA诱导的基因表达都经历了复杂的变化。本文对ABA的信号转导过程进行了综述。     

Comparing contributions of soil versus root colonization to variations in stomatal behavior and soil drying in mycorrhizal Sorghum bicolor and Cucurbita pepo

In prior studies we learned that colonization of soil can be as important as colonization of roots in determining mycorrhizal influence on the water relations of host plants. Here we use a path analysis modeling approach to test (a) whether quantity of hyphae in soil contributes to variations in stomatal behavior and soil drying, and (b) whether soil colonization or root colonization has a stronger influence on these stomatal and soil drying responses. Experiments were performed on Sorghum bicolor and Cucurbita pepo, with soils and roots colonized by a mixture of Glomus intraradices and Gigaspora margarita. Soil colonization generally made more significant contributions to stomatal conductance than did root colonization. Soil colonization did not make significant direct contributions to soil water potential measures (soil water potential at stomatal closure or soil drying rate), whereas root colonization did contribute a potentially important path to each. The findings further support a role for mycorrhization of the soil itself in contributing to the regulation of stomatal behavior of host plants.     

Is stomatal conductance in a tomato crop controlled by soil or atmosphere?

Summary The effects of soil water deficits and air vapour pressure deficits on stomatal conductance of tomato leaves were analysed separately under field conditions in central Portugal. Three conditions were created: low soil and air humidity (A), high soil and air humidity (B) and low soil but high air humidity (C). The results show that the effect of air vapour pressure deficit on stomatal behaviour is more important than the effect of soil water deficit when the predawn leaf water potential is above –0.4 MPa.     

Ethylene limits abscisic acid‐ or soil drying‐induced stomatal closure in aged wheat leaves

The mechanism of age‐induced decreased stomatal sensitivity to abscisic acid (ABA) and soil drying has been explored here. Older, fully expanded leaves partly lost their ability to close stomata in response to foliar ABA sprays, and soil drying which stimulated endogenous ABA production, while young fully expanded leaves closed their stomata more fully. However, ABA‐ or soil drying‐induced stomatal closure of older leaves was partly restored by pretreating plants with 1‐methylcyclopropene (1‐MCP), which can antagonize ethylene receptors, or by inoculating soil around the roots with the rhizobacterium Variovorax paradoxus 5C‐2, which contains 1‐aminocyclopropane‐1‐carboxylic acid (ACC)‐deaminase. ACC (the immediate biosynthetic precursor of ethylene) sprays revealed higher sensitivity of stomata to ethylene in older leaves than younger leaves, despite no differences in endogenous ACC concentrations or ethylene emission. Taken together, these results indicate that the relative insensitivity of stomatal closure to ABA and soil drying in older leaves is likely due to altered stomatal sensitivity to ethylene, rather than ethylene production. To our knowledge, this is the first study to mechanistically explain diminished stomatal responses to soil moisture deficit in older leaves, and the associated reduction in leaf water‐use efficiency.     

土壤水分对温室盆栽番茄叶片生理特性的影响及光合下降因子动态

以温室盆栽番茄(Lycopersicon esculentum Mill．)为试验材料,研究了土壤水分对叶水势(LWP)、细胞液浓度(CSC)、气孔导度(Gs)、气孔限制值(Ls)和叶片光合特性的影响,以及引起光合下降的因子动态。结果表明,随着土壤水分胁迫程度的增加,净光合速率(Pn)、蒸腾速率(Tr)、LWP明显下降．Gs具有相同的趋势,而CSC显著升高。土壤水分胁迫和高水分处理的Pn与Tr日变化呈双峰曲线,但在适宜土壤水分下为单峰曲线。随着土壤含水量的增加,光合下降的非气孔限制出现的时间具有滞后现象。本文对非气孔限制出现的临界点动态作了进一步的探讨。     

兰州北山不同坡向刺槐叶脉密度与气孔性状的关联性分析

植物叶脉和气孔性状的关系反映了叶片的水力特性, 对认识它们与植物水分利用有关的生理功能间的关系及其调控作用具有重要意义。该文利用GIS (geographic information system)与实验生态学相结合的方法, 采用标准化主轴估计方法, 研究了兰州市北山不同坡向人工林刺槐(Robinia pseudoacacia)叶脉密度与气孔密度、气孔大小的关系。结果表明: 随着坡向由南坡向东坡、西坡和北坡转变, 植被群落的郁闭度、高度和土壤含水量呈逐渐增加的趋势, 刺槐的净光合速率(P_n)、蒸腾速率(T_r)、光合有效辐射(PAR)、叶脉密度和气孔密度呈逐渐减小的趋势, 气孔与叶面积呈逐渐增大的趋势; 各个坡向的刺槐叶脉密度与气孔密度呈显著正相关关系, 与气孔大小呈显著负相关关系, 且在南坡达到极显著相关关系。生长在南坡的刺槐具有高的叶脉密度和密而小的气孔, 生长在北坡的刺槐具有低的叶脉密度和疏而大的气孔。不同坡向刺槐叶脉密度与气孔特征间的资源分配模式, 反映了植物在异质性生境中根据其功能需求在自身性状之间进行投资权衡机制的优化。     

冬小麦近轴和远轴叶面气孔对土壤水分胁迫反应的敏感性

当根层土壤水分含量不足,作物体内出现水分胁迫时,小麦叶片两面气孔的反应有明显差异。远轴叶面气孔对水分胁迫的反应比近轴叶面气孔敏感。当出现水分胁迫时,远轴叶面气孔首先收缩,且收缩的程度比近轴叶面气孔大。远轴与近轴叶面气孔阻力的比值(r_(ab)/r_(ab))与根层平均土壤水势(Ψ_s)有关,当Ψ_s大于-50 kPa时,r_(ab)/r_(ad)基本稳定在1.5左右,而当Ψ_s小于-50 kPa时,r_(ab )/r_(ab)随Ψ_s降低而明显增加。     

分根区施保水剂对玉米气孔导度和单叶WUE的影响

盆栽条件下,研究了陕单9号玉米(zea mays L．)在根区不施保水剂(对照)、分根区施保水剂和根区全施保水剂3种处理下,叶片气孔导度、CO2吸收和H2O蒸腾的变化。结果表明,在75％土壤饱和持水量下,各指标在3种处理之间没有明显差别;在50％土壤饱和持水量下,分根区施保水剂显著降低了叶片气孔导度,叶片CO2吸收量和H2O蒸腾量也同时降低,但H2O蒸腾量下降幅度更大;在两种水分条件下,分根区施保水剂均能提高玉米单叶水分利用效率(water use efficiency,WUE)。     

Correlation analysis between vein density and stomatal traits of Robinia pseudoacacia in different aspects of Beishan Mountain in Lanzhou

AimsThe relationship between leaf venation and stomatal traits reflects leaf water potential of plants, and is fundamental to probe the relationship between physiological functions and water use. Our objective was to study the changes in the relationship between venation density and stomatal traits (stomatal density and stomatal length) in Robinia pseudoacacia with the changes in slope aspects.MethodsIn Beishan Mountain of Lanzhou in Gansu Province, China, 20 transects were laid out horizontally along the contour at intervals of 50 m from an elevation of 1550-1750 m in four different slope aspects, and 12 plots were set up along each transect at intervals of 5 m. A handed GPS (global positioning system) was used to measure latitude, longitude and altitude at each plot. Community characteristics, including crown density, tree height and soil moisture, were investigated. Robinia pseudoacacia within all plots were sampled and used for measurements of individual leaf area, venation density, stomatal density and stomatal length in laboratory in each plot. The 240 plots were categorized into groups of southern, eastern, western and northern aspects, and the standardized major axis (SMA) estimation method was then used to examine the relationship between the stomatal density, stomatal length and vein density.Important findings The results showed that with a change of the aspect from south to east, west, and north, the crown density, average tree height and soil moisture of the plant community increased, while leaf net photosynthetic rate (P_n), transpiration rate (T_r), photosynthetically active radiation (PAR), vein density and stomatal density decreased. In addition, stomatal length and individual leaf area increased. Venation density of each aspect of R. pseudoacacia was positively correlated with stomatal density (p < 0.05) and negatively with stomatal length (p < 0.05). These correlations were strongest in south slope (p < 0.01).     

不同生境下入侵种假臭草叶片的气孔特征

【背景】探讨入侵种假臭草不同生境下气孔的变化规律,揭示假臭草种群在不同生境下所采取的生长对策及适应机制,可为入侵生物的防治提供参考。【方法】采取光学显微镜系统观察桉树林、木薯地、弃耕地、公路边4种生境下假臭草叶片的气孔特征。【结果】光照和土壤肥、水条件对假臭草叶片的气孔孔径（横轴方向和纵轴方向）、单个气孔器面积、气孔器总面积、气孔密度及气孔指数的影响显著。低光照及肥沃、湿润土壤生境与高光照及贫瘠、干旱土壤相比,假臭草的气孔孔径（横轴方向和纵轴方向）、单个气孔器面积、气孔器总面积较大,气孔密度及气孔指数较小。【结论与意义】假臭草叶片气孔特征表现可塑性,说明其对异质环境具有一定的生态适应能力。     

Hormonal Interactions and Stomatal Responses

Both environmental and hormonal factors and their interactions affect stomatal behavior. Methodologies for identifying hormonal interactions affecting stomatal function are reviewed. Although there is abundant evidence that abscisic acid (ABA) closes stomata, evidence that the other classical plant hormones (auxins, cytokinins, ethylene, gibberellins) in isolation alter stomatal response often comes from exogenous applications to detached epidermes and leaves, rather than correlation of endogenous concentrations with stomatal conductance (g_s). Evidence for hormonal interactions comes from isolated tissues with exogenous hormones supplied at nonphysiological concentrations, or from variation in stomatal response to xylem ABA concentration in planta. The roles of hormonal changes in causing stomatal closure following changes in soil environment are considered. Although soil drying induces multiple changes in xylem sap composition, analysis of stomatal responses suggests a dominant role for increased endogenous ABA concentrations and relatively little evidence of roles for other hormones. A similar picture emerges from studies of soil compaction. Although soil flooding decreases ABA export from the root system, there is some evidence that apoplastic ABA accumulation elicits stomatal closure. Stomatal closure following nitrogen deprivation does not appear to involve ABA and may provide a suitable experimental system to investigate roles for other hormones. The availability of mutant or transgenic lines with altered hormone homeostasis or sensitivity provides opportunities to screen for altered stomatal behavior in response to different environments, and may provide new evidence that hormonal interactions are important in the control of stomatal behavior.