pH induced elastic modulus of guard cell wall in stomatal movement

Guard cell wall properties are important in stomatal movement. Previous research focused on the structure and anatomy of guard cell walls, but little is known about the physical changes that take place within the walls during stomatal opening and closure. In this work, we investigate the volumetric elastic modulus (ε) of the guard cell wall at different pH values during stomatal opening in Vicia faba epidermal strips using a cell pressure probe. The volumetric elastic modulus of the guard cell wall decrease...     

SLAC1 is required for plant guard cell S-type anion channel function in stomatal signalling

Stomatal pores, formed by two surrounding guard cells in the epidermis of plant leaves, allow influx of atmospheric carbon dioxide in exchange for transpirational water loss. Stomata also restrict the entry of ozone--an important air pollutant that has an increasingly negative impact on crop yields, and thus global carbon fixation and climate change. The aperture of stomatal pores is regulated by the transport of osmotically active ions and metabolites across guard cell membranes. Despite the vital role of guard cells in controlling plant water loss, ozone sensitivity and CO2 supply, the genes encoding some of the main regulators of stomatal movements remain unknown. It has been proposed that guard cell anion channels function as important regulators of stomatal closure and are essential in mediating stomatal responses to physiological and stress stimuli. However, the genes encoding membrane proteins that mediate guard cell anion efflux have not yet been identified. Here we report the mapping and characterization of an ozone-sensitive Arabidopsis thaliana mutant, slac1. We show that SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1) is preferentially expressed in guard cells and encodes a distant homologue of fungal and bacterial dicarboxylate/malic acid transport proteins. The plasma membrane protein SLAC1 is essential for stomatal closure in response to CO2, abscisic acid, ozone, light/dark transitions, humidity change, calcium ions, hydrogen peroxide and nitric oxide. Mutations in SLAC1 impair slow (S-type) anion channel currents that are activated by cytosolic Ca2+ and abscisic acid, but do not affect rapid (R-type) anion channel currents or Ca2+ channel function. A low homology of SLAC1 to bacterial and fungal organic acid transport proteins, and the permeability of S-type anion channels to malate suggest a vital role for SLAC1 in the function of S-type anion channels.     

细胞内部扰动对钙振荡的维持

研究了由于体系内部随机扰动而产生的内噪音对有限尺寸钙离子体系的影响．结果表明内噪音可以在确定性体系不存在振荡的区域诱导出随机钙离子振荡．随着细胞体积的变化,振荡会在某个体积下显示最佳的行为,表明出现了体系尺寸共振．     

胀果甘草气孔振荡实测结果的解析表达及计算机模拟

给出了反映胀果甘草气孔振荡规律的解析表达式，它为Ｊ＝Ａ０＋Ａ１ｃｏｓ（ωｔ＋ψ１）＋Ａ２ｅ＾－ｔＡ３ｃｏｓ（ω＋ψ３）ｃｏｓ（ωｔ＋ψｗ）。由实测结果确定各待常数后，计算机模拟作出的图象与实测图极其吻合。     

Effects of the disaggregation of high—polymerized particles in guard cell vacuoles on osmoregulation of stomatal aperture（stomata opening）

Observation under an electron microscope reveals that in closed and open stomata of V.faba,the average volume of particles in guard cell vacuoles(GCV) reduces about 3 orders in magnitude,while the distribution density of the particles increases about 2 orders of magnitude.By using the method of the ration of fluorescent emissions with laser scanning confocal microscopy,the monitoring to stomata opening shows that during 10 to 30 s before the first distinguishable aperture of stomata,there is a change of pH in GCV about-0.5 units.A quick stomatal opening immediately follows the changes of pH in GCV to reach a steady aperture about 12μm in 100-200s.This work proposes a model for the osmoregulation in GCV for stomatal opening.The proposed osmoregulation is related to the disaggregation of some polymerized particles inside GCV,which is probably induced by a-ΔpH in the vacuole.This model describes a process of osmoregulation that avoids the massive energy consuming transportation across cell membranes,which is a foundation of the current chemiosmotic hypothesis.This model is a supplement to the multiple controlling hypothesis for the stomatal movement,which widens research principle ideas for other quick movements in plants.     

壳梭孢素促进蚕豆气孔开放与保卫细胞H2O2的关系

研究了壳梭孢素(FC)诱导蚕豆气孔开放与保卫细胞过氧化氢(H2O2)水平的关系.结果证明,FC、H2O2清除剂抗坏血酸(ASA)和H2O2合成抑制剂二苯基碘(DPI)均能于暗中诱导气孔开放.另外,FC和ASA不仅阻止外源H2O2诱导气孔关闭,而且促进暗诱导已关闭气孔重新开放,但DPI无此效应.将上述结果联系起来考虑,表明FC通过清除降低保卫细胞内源H2O2水平进而促进气孔开放.     

Regulation of the inward K+-channels in stomatal guard cells by cytoskeletal microtubules

Patch clamp techniques were applied to investigating the regulation of the inward K⁺-channels inVicia stomatal guard cells by cytoskeletal microtubules. The intracellular addition of either microtubule-disassembling reagent amprophos-methyl (APM) or microtubule-stabilizing reagent taxol resulted in significant inhibition of the inward K⁺-currents across the plasma membranes ofVicia stomatal guard cells. The results suggest that the activation of the inward K⁺-channels in stomatal guard cells requires proper dynamic organization of cytoskeletal microtubules. The regulation of the inward K⁺-channels in guard cells by microtubules may mediate the regulation of stomatal movements by cytoskeleton.     

电磁场对胞内钙振荡的影响

目的 研究细胞钙振荡的周期与IP3受体浓度的关系以及外加电磁场对细胞钙振荡的影响.方法 从单个肝细胞内钙离子振荡的动力学模型出发,以细胞膜上IP3受体浓度作为作用因子,数值分析电磁场频率对胞内钙离子浓度的影响.结果 给出了胞浆内钙离子浓度随时间变化的关系.结论 钙振荡的周期与IP3受体的浓度成非线性关系,外加电磁场频率影响胞内钙振荡的周期.     

Reversible inactivation of K+ channels of Vicia stomatal guard cells following the photolysis of caged inositol 1,4,5-trisphosphate

RECENT investigations suggest that cytoplasmic D-myo-inositol 1,4,5-trisphosphate (InsP3) functions as a second messenger in plants, as in animals, coupling environmental and other stimuli to intracellular Ca2+ release. Cytoplasmic levels of InsP3 and the turnover of several probable precursors in plants are affected by physiological stimuli--including light, osmotic stress and the phytohormone indoleacetic acid--and InsP3 activates Ca2+ channels and Ca2+ flux across plant vacuolar and microsomal membranes. Complementary data also link changes in cytoplasmic free Ca2+ to several physiological responses, notably in guard cells which regulate gas exchange through the stomatal pores of higher plant leaves. Recent evidence indicates that guard cell K+ channels and, hence, K+ flux for stomatal movements may be controlled by cytoplasmic Ca2+. So far, however, direct evidence of a role for InsP3 in signalling in plants has remained elusive. Here we report that InsP3 released from an inactive, photolabile precursor, the P5-1-(2-nitrophenyl)ethyl ester of InsP3 (caged InsP3) reversibly inactivates K+ channels thought to mediate K+ uptake by guard cells from Vicia faba L. while simultaneously activating an apparently time-independent, inward current to depolarize the membrane potential and promote K+ efflux through a second class of K+ channels. The data are consistent with a transient rise in cytoplasmic free Ca2+ and demonstrate that intact guard cells are competent to use InsP3 in signal cascades controlling ion flux through K+ channels.     

油菜素内酯诱导蚕豆气孔关闭与过氧化氢和一氧化氮的关系

研究了油菜素内酯(BR)对蚕豆气孔运动的效应及其与过氧化氢和一氧化氮的关系。结果表明,BR能显著诱导气孔关闭,其最适处理浓度和时间分别为5μmol/L和3h。H2O2清除剂抗坏血酸和过氧化氢酶、NO清除剂c-PTIO和血红蛋白、过氧化氢产生酶NADPH氧化酶抑制剂二苯基碘和NO产生酶一氧化氮合酶(NOS)抑制剂L-NAME均显著抑制BR诱导的气孔关闭,显示NADPH氧化酶催化产生的H2O2和NOS催化产生的NO参与BR诱导气孔关闭。BR有显著抑制ABA诱导气孔关闭的效应。     

A cell surface receptor mediates extracellular Ca(2+) sensing in guard cells

Extracellular Ca(2+) (Ca(2+)(o)) is required for various physiological and developmental processes in animals and plants. In response to varied Ca(2+)(o) levels, plants maintain relatively constant internal Ca(2+) content, suggesting a precise regulatory mechanism for Ca(2+) homeostasis. However, little is known about how plants monitor Ca(2+)(o) status and whether Ca(2+)(o)-sensing receptors exist. The effects of Ca(2+)(o) on guard cells in promoting stomatal closure by inducing increases in the concentration of cytosolic Ca(2+) ([Ca(2+)](i)) provide a clue to Ca(2+)(o) sensing. Here we have used a functional screening assay in mammalian cells to isolate an Arabidopsis complementary DNA clone encoding a Ca(2+)-sensing receptor, CAS. CAS is localized to the plasma membrane, exhibits low-affinity/high-capacity Ca(2+) binding, and mediates Ca(2+)(o)-induced [Ca(2+)](i) increases. CAS is expressed predominantly in the shoot, including guard cells. Repression of CAS disrupts Ca(2+)(o) signalling in guard cells, and impairs bolting (swift upward growth at the transition to seed production) in response to Ca(2+) deficiency, so we conclude that CAS may be a primary transducer of Ca(2+)(o) in plants.     

窄坡口MAG焊摆动参数对焊缝成形的影响

为了解决窄坡口侧壁熔合问题,改善焊缝成形,采用窄坡口高速摆动MAG焊枪,进行了不同摆动宽度和摆动频率的焊接试验。通过测量焊缝宏观金相获得焊缝截面尺寸,对焊缝截面尺寸随摆动宽度、摆动频率的变化趋势进行曲线拟合,研究了高速摆动电弧窄坡口MAG焊摆动参数对焊缝成形的影响规律。结果表明,增加摆动宽度和频率都能减小焊缝熔深,增加侧壁熔深,当焊枪摆动宽度使侧间距大于-0.5mm、小于1mm时会获得好的焊缝成形,摆动频率增加到5Hz以上时,能消除焊缝指状熔深,但是当摆动频率高于9Hz时,增加摆动频率,焊缝截面尺寸的变化不明显。获得的这些摆动参数对焊缝成形的影响规律能够为焊接工艺参数的选择提供指导。     

血细胞生成模型的数值振动性分析

考虑一个描述血细胞生成模型的非线性延迟微分方程的数值振动性,建立了一些数值解振动的条件,证明了每一个非振动的数值解都趋近于原方程的唯一正平衡点.为了验证理论结果,给出了几个数值例子.论文的结论在数值方面推广了文献中已有的结果.