根源ABA参与气孔调节的数学模拟

建立了包括植物体内的水分传输,并有根源ABA参与的气孔调节模型,模拟了饱和水气压差(VPD)、气温、表层土壤含水量(θ_(s1))等环境因子对叶片水势、木质部汁液中ABA浓度([ABA]_x)及气孔导度的影响。结果显示,VPD和气温的变化能够改变叶片水势及气孔导度;[ABA]_x几乎不受VPD和气温变化的影响,却决定着叶片水势及气孔导度对VPD和气温变化的响应幅度;θ_(s1)影响[ABA]_x,并由此影响气孔导度,但相比之下对叶片水势的作用并不显著。     

干旱条件下小麦根系的形态解剖学研究

经历严重干旱危害的冬小麦,返青至拔节期分布于耕层以内密集根系都已枯黄萎缩,其表皮细胞全部剥落,皮层细胞也严重受损,只有内部输导组织仍然健全,表明上层根此时已丧失了吸收功能。而位于深层的根由于所处土层较为湿润,外观为嫩白色,根的表皮和皮层细胞健全,春季降水（≥２０ｍｍ）后,上层已受扣迪的根不能恢复其原有的表皮和皮层组织,但能从分蘖节处产生新的次生根,恢复其吸收功能。     

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。     

香蕉苗期氮素亏缺与补偿对植株生长和根系形态的影响

为探究氮素亏缺及亏缺后补偿供氮对蕉苗生长及其根系形态特征的影响,该研究以主要栽培品种基因组类型(AAA型和ABB型)的香蕉品种为材料,通过石英砂基质培养结合氮素亏缺与补偿处理,分析其株高、叶长、叶宽、新增绿叶数、地上部和根系的鲜重和干物质质量、根长和根表面积及根体积等指标的变化。结果表明：(1)亏缺30 d,香蕉苗呈现明显的缺氮表型症状,株高、叶长、叶宽及新增绿叶数均显著降低,根系干物质积累增加,品种Ⅰ、Ⅱ根系干物质分别提高64.71%、87.50%,根冠比增加,总根表面积分别增加4.38%、11.85%,体积分别增加71.78%、66.55%。(2)亏缺68 d,干物质积累受到明显抑制,品种Ⅰ、Ⅱ全株干物质质量降低33.74%、42.04%,根系干物质质量与常规处理无显著差异,根系形态参数变化趋势与轻度亏缺一致。(3)亏缺后补偿供氮,缺氮症状消失,植株生长指标恢复正常水平;品种Ⅰ、Ⅱ根系干物质质量显著增加51.22%、52.38%,根冠比显著高于常规处理,根系趋向正常形态生长,并且总根体积分别增加61.80%、45.92%;轻度氮素亏缺后适时补偿供氮,缺氮蕉苗可恢复正常生长,根系干物...     

覆膜对旱地麦田土壤水分及氮素平衡的影响

通过大田试验研究了平膜穴播和垄膜沟播等覆膜方式对晋南旱地麦田土壤水分、氮素平衡及产量的影响,以期在当地确立一套适宜的科学覆膜方式,为晋南旱塬地区乃至我国旱作小麦的高产优质提供理论依据。结果表明,垄膜沟播和平膜穴播处理的冬小麦增产效果显著,且以平膜穴播处理的效果最优,较测控施肥处理的籽粒产量和生物产量分别提高22.71%和25.45%。经过冬小麦一个生育期对土壤水分的吸收利用,两种覆膜处理的耗水量较不覆膜处理有较大的提高,而其水分利用率略低于不覆膜处理,但差异不显著。两种覆膜处理也能提高麦田的降水生产效率和休闲效率,较不覆膜处理分别提高9.46%—30.16%和9.95%—39.22%。覆膜有利于氮的矿化,并能促进小麦对氮素的吸收利用,同时也可以在一定程度上降低氮素在土壤中的残留,最终有利于小麦增产。     

干旱胁迫下氮素营养与根信号在气孔运动调控中的协同作用

干旱胁迫下根系与地上部分之间的信息传递可使植物叶片及时感知土壤水势变化,从而使植物在没有真正受到干旱伤害时即可做出主动、快速的抗旱应答反应,而在这一过程中,脱落酸（abscisic acid,ABA）和pH起着关键的作用。本研究表明。干旱胁迫下鸭趾草（Commelina communis L．）、番茄（Lycopersicon esculentum Mill．）和向日葵（Helianthus annuus L．）木质部汁液中pH的变化很不相同,且该pH变化和木质部汁液中硝态氮离子浓度的变化没有直接的关系;然而,饲喂实验表明,无论对于何种植物,蒸腾流中硝态氮离子浓度的增加都可有效地增加气孔对ABA的敏感度;分根实验进一步表明,土壤中硝态氮营养的增加可明显提高气孔对根信号的敏感度。以上结果说明,氮素营养可以和根信号相互作用共同操纵气孔运动。     

干旱胁迫下氮素营养与根信号在气孔运动调控中的协同作用

干旱胁迫下根系与地上部分之间的信息传递可使植物叶片及时感知土壤水势变化, 从而使植物在没有真正受到干旱伤害时即可做出主动、快速的抗旱应答反应, 而在这一过程中, 脱落酸(abscisic acid, ABA)和pH起着关键的作用。本研究表明, 干旱胁迫下鸭趾草(Commelina communis L.)、番茄(Lycopersicon esculentum Mill.)和向日葵(Helianthus annuus L.)木质部汁液中pH的变化很不相同, 且该pH变化和木质部汁液中硝态氮离子浓度的变化没有直接的关系; 然而, 饲喂实验表明, 无论对于何种植物, 蒸腾流中硝态氮离子浓度的增加都可有效地增加气孔对ABA的敏感度; 分根实验进一步表明, 土壤中硝态氮营养的增加可明显提高气孔对根信号的敏感度。以上结果说明, 氮素营养可以和根信号相互作用共同操纵气孔运动。     

不同土壤水分条件下土壤容重对玉米木质部汁液中ABA浓度和气孔导度的影响

受旱玉米植株木质部汁液中的ABA浓度是高水分处理的5倍,土壤容重每增加0.12g·cm-3,木质部液汁中ABA浓度约增加1倍。在相同土壤基质势下,植株的气孔导度和蒸腾速率随土壤容重的增大而下降,而容重对植株的叶水势没有影响。生长在混合容重(一边为1.20g·cm-3,另一边为1.45g·cm-3)土壤上的植株中,ABA浓度和气孔导度与全部根系处在高容重土壤中的植株接近。     

逆境下拟南芥ABA信号途径负调控因子的研究进展

ABA信号途径的主要负调控因子蛋白磷酸酶2C(protein phosphatase 2C,PP2C)是一类丝氨酸/苏氨酸蛋白磷酸酶(protein Ser/Thr phosphatases,PSP),为ABA信号传导途径下游的关键组分.拟南芥中PP2C主要包括ABI1、ABI2、HAB1、AHG3和PP2CA,它们通过改变ABA信号的强弱等调控植物的胁迫应答.该文主要对国内外有关PP2C家族的组成以及在逆境胁迫下负调控ABA信号途径中的调控机制和应答特征等方面的研究进展进行综述.     

长期施肥条件下黑土镉的积累及其趋势分析

以中国科学院海伦农业生态实验站长期田间定位试验为基础,研究了长期定量施用氮磷化肥和猪粪对黑土Cd的积累及其有效性的影响,并对黑土Cd的积累趋势进行了预测.结果表明：在完全不施肥的自然农业生产条件下黑土Cd浓度略有增加;长期定量施用氮磷化肥使黑土Cd浓度显著增加,但不同化肥用量对黑土Cd积累的影响无显著差异;长期施用猪粪可显著增加黑土Cd的积累,且近年来有加速积累的趋势,含Cd饲料添加剂可能是猪粪中Cd的重要来源;施用氮磷化肥对黑土Cd的有效性无显著影响,长期施用猪粪则可显著提高黑土Cd的有效性.     

干旱胁迫下植物根源化学信号研究进展

土壤干旱胁迫诱导植物根系产生根源化学信号,经运输系统长距离传输到地上部分,降低气孔导度,抑制蒸腾作用,从而提高植物的水分利用效率。根源化学信号包括脱落酸(ABA)、细胞分裂素(CTK)、生长素、木质部pH值和钙离子(Ca²⁺)等,其中以ABA为主的植物根源信号通路研究得最为广泛和深入。总结了几种主要的化学根源信号物质的基本性质、主要功能和调节机制,重点对这些信号参与气孔行为、差别基因表达和生长发育方面的研究进展进行了综述。由于干旱条件下植物根源信号反应涉及到从分子到群体的一系列复杂过程,各种信号的生理效应呈现交互作用、耦合发生的特点,今后的热点领域将集中在研究交互网络中合成的的关键物质和揭示这些物质在分子及生理水平上的作用机理上。根源化学信号研究正朝向"以分子和生理研究为基础、不同尺度的结构和功能耦合"的方向发展。     

在大气干旱条件下胀果甘草气孔振荡的RLC电路模拟

建立了植物水分输导和蒸腾的电阻(R)、电感(L)、电容(C)电路模型。实验测定出的胀果甘草气孔振荡发生、持续和衰减的阈值与模型分析结果一致。当蒸腾拉力(F)大于输导阻力(R)时气孔开始振荡并使振幅逐渐加大;当F=R时气孔振荡的振幅和频率不变;当0<(R-F)<2(1/2)/(L/C)时气孔振荡开始减弱;当(R-F)>2(1/2)/(L/C)时气孔不会出现振荡。在本实验条件下胀果甘草的R=3.1×10~9MPa·m~(-3)·s,2(1/2)/(L/C)=3.11-3.64×10~5MPa·m~(-3)·s。     

干旱下植物气孔运动的调控

概述了植物气孔对大气干旱和土壤干旱的反应,认为植物气孔对大气干旱的反应并不是一种反馈机制;并就干旱条件下植物气孔运动的水力学和化学信号调控机制进行了简要论述,认为虽然化学信号调控干旱下气孔运动更为广泛,但ABA不是唯一的化学信号,水分关系影响了信号的产生、运转和气孔对信号的敏感性,干旱条件下水力学和化学信号共同调控着植物的气孔运动。     

Xylem ABA controls the stomatal conductance of field-grown maize subjected to soil compaction or soil drying

Stomatal conductance of individual leaves was measured in a maize field, together with leaf water potential, leaf turgor, xylem ABA concentration and leaf ABA concentration in the same leaves. Stomatal conductance showed a tight relationship with xylem ABA, but not with the current leaf water status or with the concentration of ABA in the bulk leaf. The relationship between stomatal conductance and xylem [ABA] was common for variations in xylem [ABA] linked to the decline with time of the soil water reserve, to simultaneous differences between plants grown on compacted, non-compacted and irrigated soil, and to plant-to-plant variability. Therefore, this relationship is unlikely to be fortuitous or due to synchronous variations. These results suggest that increased concentration of ABA in the xylem sap in response to stress can control the gas exchange of plants under field conditions.     

Abscisic acid (ABA) inhibits light-induced stomatal opening through calcium- and nitric oxide-mediated signaling pathways

Nitric oxide (NO) is an important signaling component of ABA-induced stomatal closure. However, only fragmentary data are available about NO effect on the inhibition of stomatal opening. Here, we present results supporting that, in Vicia faba guard cells, there is a critical Ca2+-dependent NO increase required for the ABA-mediated inhibition of stomatal opening. Light-induced stomatal opening was inhibited by exogenous NO in V. faba epidermal strips. Furthermore, ABA-mediated inhibition of stomatal opening was blocked by the specific NO scavenger cPTIO, supporting the involvement of endogenous NO in this process. Since the raise in Ca2+ concentration is a pre-requisite in ABA-mediated inhibition of stomatal opening, it was interesting to establish how does Ca2+, NO and ABA interact in the inhibition of light-induced stomatal opening. The permeable Ca2+ specific buffer BAPTA-AM blocked both ABA- and Ca2+- but not NO-mediated inhibition of stomatal opening. The NO synthase (NOS) specific inhibitor L-NAME prevented Ca2+-mediated inhibition of stomatal opening, indicating that a NOS-like activity was required for Ca2+ signaling. Furthermore, experiments using the NO specific fluorescent probe DAF-2DA indicated that Ca2+ induces an increase of endogenous NO. These results indicate that, in addition to the roles in ABA-triggered stomatal closure, both NO and Ca2+ are active components of signaling events acting in ABA inhibition of light-induced stomatal opening. Results also support that Ca2+ induces the NO production through the activation of a NOS-like activity.     

植物抗旱过程中ABA生理作用的研究进展

植物在长期进化中,对干旱等胁迫从生理,生化和分子水平上产生了适应性变化,从而增加逆境存活机会,在这些响过程中,ABA起着极其重要的作用,本文介绍了近年来研究ABA的植物抗旱中生理作用方面所取得的进展。     

Sequential response of whole plant water relations to prolonged soil drying and the involvement of xylem sap ABA in the regulation of stomatal behaviour of sunflower plants

Sunflower plants ( Helianihus animus cv. Tall Single Yellow} were grown in the greenhouse in drain pipes (100 mm inside diameter and 1 m long) rilled with John Innes No. 2 compost. When the fifth leaf had emerged, half of the plants were left unwatered for 6 days, rewatered for 2 days and then not watered for another 12 days. Measurements of water relations and abaxial stomatal conductance were made at each leaf position at regular intervals during the experimental period. Estimates were also made of soil water potentials along the soil profile and of ABA concentrations in xylem sap and leaves.
Soil drying led to some reduction in stomatal conductance alter only 3 days but leaf turgors were not reduced until day 13 (6 days after rewatering). When the water relations of leaves did change, older leases became substantially dehydrated while high turgors were recorded in younger leaves. Leaf ABA content measured on the third youngest leaf hardly changed over the first 13 days of the experiment, despite substantial soil drying, while xylem ABA concentrations changed very significantly and dynamically as soil water status varied, even when there was no effect of soil drying on leaf water relations. We argue that the highest ABA concentrations in the xylem, found as a result of substantial soil drying, arise from synthesis in both the roots and the older leaves, and act to delay the development of water deficit in younger leases.
In other experiments ABA solutions were watered on to the root systems of sunflower plants to increase ABA concentrations in xylem sap. The stomatal response to applied ABA was quantitatively very similar to that to ABA generated as a result of soil drying. There was a log-linear relationship between the reduction of leaf conductance and the increase of ABA concentration m xylem sap.     

羊草气孔导度的Jarvis-类模型

在干旱半干旱气候条件下,土壤水分状况通常是决定植物气孔导度的重要因素,现有气孔导度模型Jarvis-类和耦合模型(或光合-导度模型)未充分考虑这一因素对气孔导度的影响。本文以Jarvis气孔导度模型为基础,提出一个充分考虑土壤水分状况因素的气孔导度模型。该模型对羊草连续两年(1998~1999)野外实地观测结果拟合良好(R2=0.603),预测能力较线性回归方程(R2=0.361)有明显提高。     

The relations of stomatal closure and reopening to xylem ABA concentration and leaf water potential during soil drying and rewatering

Two tropical tree species, Acacia confusa and Leucaena leucocephala, were used to study the relationships among stomatal conductance, xylem ABA concentration and leaf water potential during a soil drying and rewatering cycle. Stomatal conductance of both A. confusa and L. leucocephala steadily decreased with the decreases in soil water content and pre-dawn leaf water potential. Upon rewatering, soil water content and pre-dawn leaf water potential rapidly returned to the control levels, whereas the reopening of stomata showed an obvious lag time. The length of this lag time was highly dependent not only upon the degree of water stress but also on plant species. The more severe the water stress, the longer the lag time. When A. confusa and L. leucocephala plants were exposed to the same degree of water stress (around –2.0 MPa in pre-dawn leaf water potential), the stomata of A. confusa reopened to the control level 6 days after rewatering. However, it took L. leucocephala about 14 days to reopen fully. A very similar response of leaf photosynthesis to soil water deficit was also observed for both species. Soil drying resulted in a significant increase in leaf and xylem ABA concentrations in both species. The more severe the water stress, the higher the leaf and xylem ABA concentrations. Both leaf ABA and xylem ABA returned to the control level following relief from water deficit and preceded the full recovery of stomata, suggesting that the lag phase of stomatal reopening was not controlled by leaf and/or xylem ABA. In contrast to drying the whole root system, drying half of the root system did not change the leaf water relations, but caused a significant increase in xylem ABA concentration, which could fully explain the decrease of stomatal conductance. After rewatering, the stomatal conductance of plants in which half of the roots were dried recovered more rapidly than those of whole-root dried plants, indicating that the leaf water deficit that occurred during the drying period was related to the post-stress stomatal inhibition. These results indicated that the decrease in stomatal conductance caused by water deficit was closely related to the increase in xylem ABA, but xylem ABA could not fully explain the reopening of stomata after relief of water stress, neither did the leaf ABA. Some unknown physiological and/or morphological processes in the guard cells may be related to the recovery process.