Water Flow Through Vessel Perforation Plates--The Effects of Plate Angle and Thickness for Liriodendron tulipifera

The effects of scalariform perforation plate thickness and anglewithin vessel elements of Liriodendron tulipifera were studiedwith a computational fluid dynamical model. The pressure gradientand hence resistance to flow through the plate increased asthe perforation plate increased in thickness. Increasing theangle of the plate relative to the axis of the vessel (samenumber of pores) also increased the pressure gradient alongthe modelled cell. For the model matching the actual vesselelement, the plate contributed 8% to the flow resistance ofthe vessel element. This contribution increased only to 11%for doubled plate thickness, and to 14% for a plate at an angleof 60° to the vessel axis. The perforation plate alteredthe velocity profile across the vessel element, but to a differentextent depending on the angle of the plate. A plate at an acuteangle to the vessel axis has little effect on the paraboloidprofile as found upstream from the plate, while obtuse angleplates change the flow profile such that fluid through poresnear the wall is accelerated to a greater velocity than foundin the centre of the cell. Key words: Conductance, perforation plate, vessel, water flow     

Water flow through a 20-pore perforation plate in vessels of Liquidambar styraciflua

The flow of water through perforation plates of Liquidambar styraciflua vessels was studied through a computational fluid dynamics approach together with a large-scale physical model of the perforation plate. For the computational approach, a finite elements model was constructed of a 20-pore perforation plate and the region around the plate. Solutions of this model describe pressures and velocities for points within the model. The pressure gradient within the pores of the plate was about 40-fold greater than for regions away from the plate. However the influence of the plate on flow extends for only a very short distance before and after the plate. Overall, the perforation plate in this model was calculated to account for 23% of the total resistance to flow encountered along the vessel. Calculations from the physical model provided a similar estimate of 21% for the contribution of the perforation plate to flow resistance.      

Water Flow in Vessels with Simple or Compound Perforation Plates

Hydraulic conductance of vessels was studied in young stem internodesand petioles of five species of dicotyledons that have simpleor compound perforation plates. Measured conductances of Clematisdioscoreifolia, Hardenbergia violacea, and Olea europaea, whichhave simple perforation plates, ranged from 92 to 106% of predictedvalues based on Hagen-Poiseuille flow through ideal capillaries.Petioles of Liquidambar styraciflua and Liriodendron tulipifera,which have compound perforation plates, had measured hydraulicconductances in spring-collected material that matched predictedconductances, but values averaged 60% of predicted in materialfrom late summer, suggesting blockage of vessels with time.An analog model of a vessel with and without compound perforationplates was developed from tygon tubing and steel pins to determinethe effect of obstruction by bars, which produced little flowreduction. Likewise, calculations based on the observed geometryof a scalariform perforation plate suggested that the platetypically reduced flow by only 1%. These data suggest that flowrates in vessels with simple as well as compound perforationplates are essentially equal to flows in ideal capillaries ofthe appropriate diameters. Clematis dioscoreifolia, Hagen-Poiseuille, Hardenbergia violacea, hydraulic conductance, Liquidambar styraciflua, Liriodendron tulipifera, Olea europaea, xylem     

凹叶厚朴细弱枝与粗壮枝导管分子的比较研究

对凹叶厚朴粗壮枝和细弱枝的次生木质部进行离析研究,发现其导管穿孔板有两种类型,即单穿孔板和梯状穿孔板。在细弱枝中,具不同类型穿孔板的导管分子有八种类型,即一端为单穿孔板的导管分子,另一端为梯状穿孔板的导管分子;只有一端为单穿孔板的导管分子;只有一端为梯状穿孔板的导管分子;两端均为单穿孔板的导管分子;两端均为梯状穿孔板的导管分子;具三个单穿孔板的导管分子;两端具单穿孔板的导管分子,中间具多个梯状穿孔板的导管分子;具多个梯状穿孔板的导管分子。粗壮枝除了无具多个梯状穿孔板的导管分子外,其它细弱枝的导管分子的类型都具有。细弱枝的导管分子宽而长,粗壮枝导管分子窄而短。     

东北刺人参茎次生木质部结构植物学研究

东北刺人参为五加科植物,本文对其茎次生木质部进行结构植物学研究,发现其为环孔材,射线为异形Ⅱ型。在离析材料中,发现其导管分子穿孔板有单穿孔板和梯状穿孔板2种。具不同穿孔板的导管分子可分为8种。还有维管管胞、纤维管胞和韧型木纤维。8种导管分子是只有中央具1个单穿孔的导管;中央有2个穿孔的导管,其中一个孔是单穿孔,另一个是梯状穿孔;一端是梯状穿孔板,另一端为孔纹增厚的导管;一端是单穿孔。另一端是孔纹增厚的导管;一端为单穿孔板。另一端为梯状穿孔板的导管;两端都是梯状穿孔板的导管;侧壁具有3个穿孔的导管;两端都具单穿孔的导管。在东北刺人参的个体发育中重演了系统发育过程中导管分子穿孔板的演化过程。     

Distribution of scalariform and simple perforation plates within the vessel network in secondary xylem of Araliaceae and its implications for wood evolution

The distribution of scalariform and simple perforation plates along vessels in Arthrophyllum otopyrenum, Meryta tenuifolia, and Polyscias multijuga (Araliaceae) is examined. In all three species, most vessels bear simple perforation plates only, but the combination of simple and scalariform perforation plates in variable ratios also occurs. Aggregated arrangement of scalariform perforation plates along the vessels was statistically confirmed in some vessel portions. The scalariform perforation plates occur mostly in narrow vessels that are grouped in multiples. Within the clade represented by Polyscias and Arthrophyllum, the evolutionary transition from scalariform to simple perforation plates is realized as the gradual elimination of vessels or vessel portions with scalariform perforation plates, but is not accompanied by a gradual decrease of the number of bars per perforation plate. The narrow vessels that are grouped in vessel multiples are likely to retain the ability to develop scalariform plates, which could promote the evolution from simple to scalariform perforation plates as is the case within Meryta.     

Resistances to fluid flow of model xylem vessels with simple and scalariform perforation plates

The resistances of xylem vessel walls and perforation plates has been investigated using 18 large-scale physical models made of plastic tubing into which scale models of plates were inserted. Flow of water through vessels was modelled using glycerol instead of water to keep the Reynolds number below 0.1. The technique proved easy, cheap and reliable.Results showed that perforation plate resistance is low compared with the resistance of the walls, whatever the plate morphology; plates only provided 0.6-18.6% extra resistance. Simple plates provided less resistance than scalariform plates, but because they are arranged closer together in vessels, resistance values (1.7-5.1%) overlap with those of scalariform plates. The resistance of scalariform plates varied in a systematic way with their morphology. For a given plate angle, increasing the number of bars increased resistance. For a given bar number, increasing the angle of the plate to the vessel axis also increased the resistance. However, for a given gap between bars, increasing the angle of the plate to the vessel axis decreased resistance. These results are discussed in the light of theories about the function of perforation plates.Keywords: Flow, xylem vessel, perforation plate, models.      

国产五味子科植物导管分子的比较解剖

对五味子科 2属 1 9种植物导管分子的结构进行了比较观察。结果表明 :2属均以具缘纹孔导管为主 ,少有梯纹和螺纹导管 ,南五味子属多数种还有梯孔纹导管 ;2属导管长度和宽度差异很小 ,长 /宽比值有差异 ;根据穿孔板的结构可分为 2种形式 :( 1 )单穿孔板 ,这类穿孔板较普遍存在 ;( 2 )梯形穿孔板 ,发现 2属中的红花五味子 (Schisandrarubriflora)、五味子 (S .chinensis)、翼梗五味子 (S .henryi)、铁箍散 (S .propinquavar.sinensis)和黑老虎 (Kadsuracoccinea) 5种植物的导管分子具有此类穿孔板。其中五味子属中的五味子导管分子只具有梯形穿孔板 ,无单穿孔板 ,但横条较少 ,多为 2～ 3条。     

细枝木麻黄导管分子及穿孔板解剖学研究

运用细胞图象分析系统和显微照相的方法对细枝木麻黄(CasuarinacunninghamianaMiq.)次生木质部导管分子进行了观察研究。细枝木麻黄次生木质部导管分子有3种类型,即两端具尾导管、一端具尾导管和无尾导管。导管分子穿孔板有4种类型:两端均为梯状穿孔板、一端为单穿孔板,另一端为梯状穿孔板、两端均为单穿孔板、一梯状穿孔板与一单穿孔板位于同一端壁两侧相互对应以及一些过渡类型穿孔板。根据观察结果,分析了各类型穿孔板之间的演化关系。     

洋蒲桃次生木质部中导管分子的解剖学

运用细胞图像分析系统和显微照相的方法对洋蒲桃(Syzygium samarangense)次生木质部导管分子进行了观察研究。次生木质部导管分子类型有: 两端具尾导管、一端具尾导管和无尾导管。导管分子穿孔板存在着4种类型: 两端均为具2个单穿孔的复穿孔板;一端为1个单穿孔板, 另1端为具2个单穿孔的复穿孔板;两端均为单穿孔板;两单穿孔板位于同一端壁两侧相互对应以及一些过渡类型穿孔板。根据观察结果, 分析了各类型穿孔板之间的演化关系。     

洋蒲桃次生木质部中导管分子的解剖学

运用细胞图像分析系统和显微照相的方法对洋蒲桃（Syzygium samarangense）次生木质部导管分子进行了观察研究。次生木质部导管分子类型有：两端具尾导管、一端具尾导管和无尾导管。导管分子穿孔板存在着4种类型：两端均为具2个单穿孔的复穿孔板;一端为1个单穿孔板,另1端为具2个单穿孔的复穿孔板;两端均为单穿孔板：两单穿孔板位于同一端壁两侧相互对应以及一些过渡类型穿孔板。根据观察结果,分析了各类型穿孔板之间的演化关系。     

猫儿屎导管分子穿孔板新类型的发现

运用扫描电镜(SEM)对木通科(Lardizabalaceae)猫儿屎属(Decaisnea Hook.f. & Thoms.)植物猫儿屎[Decaisnea insignis (Griff.) Hook.f.et Thoms.]茎的次生木质部导管分子进行观察,以期为该属的系统演化提供依据.结果表明,猫儿屎的导管分子具有多个穿孔板,端壁穿孔板除了梯状以外,还有梯-网、梯-网-单、梯-单混合穿孔板等类型;侧壁穿孔板包括梯状、网状、梯-网混合状穿孔板;穿孔板上纹孔膜的残余有丝状、网状和片状.同时对导管分子的长度、宽度及端壁倾斜度等特征进行统计,并讨论了木通科各类群的穿孔板特征.     

基质盐度对木榄叶柄导管分子形态特征的影响

对温室中培养在不同盐度下一年生木榄[Bruguiera gymnorrhiza(L.)Poil]植株上成熟叶的叶柄离析研究的结果表明：1）木榄叶柄导管分子以梯纹导管为主,其次为螺纹导管及它们之间的过渡类型;随着盐度的升高,螺纹导管及它们之间的过渡类型有增多的趋势;2）而叶柄长度,梯纹导管分子的直径、长度及两端梯状穿孔板的横隔条数都与盐度呈抛物线关系,而它们的最大值出现在20‰-30‰范围内;3）培养于盐度10‰的海水中的木榄叶柄中导管分子一端有出现两个朝向不同的梯状穿孔板现象;4）在低盐条件下,随着基质盐度的提高,导管分子的形态朝着有利于加快水分运输的方向发展,而在高盐环境下,导管分子的形态朝着增加水分运输的安全性方向发展。讨论了叶柄导管分子解剖学特征的适应意义。     

Single‐vessel flow measurements indicate scalariform perforation plates confer higher flow resistance than previously estimated

During vessel evolution in angiosperms, scalariform perforation plates with many slit‐like openings transformed into simple plates with a single circular opening. The transition is hypothesized to have resulted from selection for decreased hydraulic resistance. Previously, additional resistivity of scalariform plates was estimated to be small – generally 10% or less above lumen resistivity – based on numerical and physical models. Here, using the single‐vessel technique, we directly measured the hydraulic resistance of individual xylem vessels. The resistivity of simple‐plated lumens was not significantly different from the Hagen–Poiseuille (HP) prediction (+6 ± 3.3% mean deviation). In the 13 scalariform‐plated species measured, plate resistivity averaged 99 ± 13.7% higher than HP lumen resistivity. Scalariform species also showed higher resistivity than simple species at the whole vessel (+340%) and sapwood (+580%) levels. The strongest predictor of scalariform plate resistance was vessel diameter (r² = 0.84), followed by plate angle (r² = 0.60). An equation based on laminar flow through periodic slits predicted single‐vessel measurements reasonably well (r² = 0.79) and indicated that Baileyan trends in scalariform plate evolution maintain an approximate balance between lumen and plate resistances. In summary, we found scalariform plates of diverse morphology essentially double lumen flow resistance, impeding xylem flow much more than previously estimated.     

Hydraulic characteristics of water-refilling process in excised roots of Arabidopsis

Plants have efficient water-transporting vascular networks with a self-recovery function from embolism, which causes fatal discontinuity in sap flow. However, the embolism-refilling process in xylem vessel is still unclear. The water-refilling processes in the individual xylem vessels of excised Arabidopsis roots were visualized in this study using synchrotron X-ray micro-imaging technique with high spatial resolution up to 1 μm per pixel and temporal resolution up to 24 fps. In normal continuous water-refilling process, we could observe various flow patterns affected by the morphological structures of the xylem vessels, especially when water passed through perforation plates. A simple criterion based on the variation in dynamic pressure was suggested to evaluate the contribution of individual perforation plates to the water-refilling process. Meanwhile, the water-refilling embolized sections of xylem vessels through radial pathways were also observed. Separated water columns were formed from this discontinuous water-refilling process and the water influx rates through the radial pathways were estimated to be 478 and 928 μm³ s^?1. The dynamic behavior of the separated water columns were quantitatively analyzed from the stoppage of volume growth to the translational phase. These water-refilling processes in excised roots of Arabidopsis may shed light on understanding the water refilling in the embolism vessels of intact plants and the interconnectivity of xylem vessel networks in vascular plants.     

基于不同方法的毛茛族(毛茛科)导管穿孔板比较研究

导管分子的演化与植物的进化相关联.毛茛科是联系基部被子植物和核心真双子叶植物的关键类群,对其导管穿孔板的研究具有重要的系统学意义.为研究毛茛科毛茛族不同属植物导管穿孔板类型及其与环境的相关性,该文利用新的扫描电子显微镜和半薄切片技术,对该族7属8种植物次生木质部导管状分子进行了比较观察.结果表明:木质部管状分子以单穿孔...     

基质盐度对木榄叶柄导管分子形态特征的影响

对温室中培养在不同盐度下一年生木榄[Bruginera gyninorrhiza(L.)Poil]植株上成熟叶的叶柄离析研究的结果表明:1)木榄叶柄导管分子以梯纹导管为主,其次为螺纹导管及它们之间的过渡类型;随着盐度的升高,螺纹导管及它们之间的过渡类型有增多的趋势;2)而叶柄长度,梯纹导管分子的直径、长度及两端梯状穿孔板的横隔条数都与盐度呈抛物线关系,而它们的最大位出现在20‰-30‰,范围内;3)培养于盐度10‰的海水中的木榄叶柄中导管分子一端有出现两个朝向不同的梯状穿孔板现象;4)在低盐条件下,随着基质盐度的提高,导管分子的形态朝着有利于加快水分运输的方向发展,而在高盐环境下,导管分子的形态朝着增加水分运输的安全性方向发展。讨论了叶柄导管分子解剖学特征的适应意义。     

Vessel member length-diameter and perforation plate-vessel member length relations inDioscorea alata L.

The vessel member length-diameter and perforation plate-vessel member length relations inDioscorea alata L. have been investigated. The two types of vessel elements, one with scalariform perforation plate and the other with foraminate perforation plate, have been considered for correlation tests; the variables being vessel member length and diameter, and vessel member length and perforation plate length. Significant positive correlation was found only in the case of perforation plate length and vessel member length for types with scalariform perforation plates.     

余甘子次生木质部导管分子观察研究

运用细胞图象分析系统及显微照相的方法,对余甘子次生木质部导管分子进行观察研究.结果发现,余甘子次生木质部导管分子中存在着许多不同的样式,导管分子大多数具尾;其穿孔板存在着两种类型:(1)两端均为1个单穿孔板;(2)一端为1个单穿孔板另一端为2个单穿孔板;(3)极少数的导管分子具有特殊的内含物;(4)管间纹孔式为互列纹孔式;(5)导管射线间纹孔式为混合型纹孔与横列刻痕状纹孔以及梯状穿孔.     

A Cytochemical Study of Differentiation and Breakdown of Vessel End Walls

A cytochemical approach was used to study the architecture ofthe end wall and its modifications during vessel differentiationin Populus italica and Dianthus caryophyllus. The combinationof cytochemical techniques with selective extractions to removeend wall subunits provides information on the different componentsof the end wall and on the method of perforation. The end wallappears to be formed mainly from pectins and hemicelluloses.No cellulosic components nor lignin were found though the 3,3'-diaminobenzidine assay revealed the presence of peroxidases.That the method of perforation may depend on the species isdiscussed. Dianthus caryophyllus L., carnation, Populus italica, poplar, xylem vessel, cell wall, cytochemistry, vessel differentiation