The Ecological Secondary Xylem Anatomy of 7 Desert Species of Leguminosae

The wood anatomy of 7 species (Ammopiptanthus mongolicus, Amorpha fruticosa, Halimodendron halodendron, Hedysarum mongolicum. Hedysarum scoparium, Lespedeza bicolor and Robinia pseudoacacia)of Leguminosae, which grow in desert regions of Northern China, is described in details. A comparative study on the quantitative wood anatomical characters among the species is made. Except some anatomical characters in A. fruticosa were larger in vessel diameter, thin walled in vessels and libriform fibres, all the rest six species showed a general similarities:vessel frequency/sq, mm very numerous and percentage of multiple vessels high; vessel elements very short, perforations simple and in almost horizontal end walls, intervessel bordered pits alternate and vestured; libriform fibres very short, and usually with thickened walls, and with simple pits; average ray height very low, and with multiseriate as well as uniseriate. However, there are differences in other characters, e. g. vessel distribution, percentage of solitary vessels; spiral thickenings present or absent; amount of axial parenchyma and distribution; ray frequency and type; crystals present or absent, and crystal distribution, if present. According to these anatomical diversities, a key to the identification of the 7 species is given. In this article, the relation between the structure of wood and the environmental influences has been discussed.     

四合木属四合木(蒺藜科)的木材解剖学研究

在光学显微镜和扫描电子显微镜下观察了蒺藜科四合木属四合木(Tetraena mongolica Maim.)木材结构.其导管分子直径小,管壁厚,分布密度高,分子短,端壁几乎水平,具单穿孔;管间纹孔为对列或互列的具缘纹孔;韧性纤维短、壁厚、壁上有较少的单纹孔;同型单列射线、分布密度高;轴向薄壁组织散生或傍导管生.这些表明四合木的木材解剖特征是与干旱环境条件是相适应的.     

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.     

Anatomical Studies on Secondary Xylem and Secondary Phloem of Dipentodon sinicus

The anatomy of secondary xylem and secondary phloem in Dipentodon sinicus Dunn a precious and protected plant in China was studied, and compared with the wood anatomy of 8 other genera in Celastraceae. The main characteristics of this genus were described as follows: vessel members length were relatively long with scalariform perforations in oblique end walls, which were formed by 14 (9--28) bars. Intervessel pits possessed scalariform pattern. Libriform fibres and tracheid-fibres were septate. The sieve tube elements of the secondary phloem were relatively shorter, with simple sieve plates in the slightly inclined to almost horizontal end walls. There was no obvious boundary between the functional and non-functional phloem. In the Baileyan sense, the secondary xylem possessed a lower level of specialization, and displayed an obviously primitive and conservative character. In contrast, the secondary phloem possessed a higher level of specialization and displayed advanced characters. Therefore, the phylogenetic evolution between xylem and phloem was not synchronous in this genus. The result provided a novel pattern in the development of xylem and phloem structure which has not been noticed before.     

Wood structure of Aegiceras corniculatum and its ecological adaptations to salinities

We describe the wood structure of Aegiceras corniculatum and its differences under various soil salinities. This species had diffuse-porous wood with poorly defined growth rings. Vessels which had single perforations occurred abundantly and in multiples and were storeyed. Intervascular pits between contiguous vessels were alternate bordered ones while half-bordered pit-pairs existed between both vessel-ray and vessel-parenchyma. Homogenous xylem rays were multiseriate and uniseriate. Fiber-tracheids with bordered pits often had thinner walls. Xylem parenchyma cells were scant and distributed diffusely and paratracheally. Differences in the structural and quantitative characters of vessels, xylem rays and fiber-tracheids under diverse soil salinities are described. This revised version was published online in August 2006 with corrections to the Cover Date.     

红树族植物次生木质部附物纹孔的电镜观测

应用扫描电子显微镜详细观察了红树族4属、10种、1变种植物次生木质部管状分子附物纹孔的分布和形态, 应用Carnoy 2.0软件和扫描电镜下采集的照片, 测定了管间梯状附物纹孔丰富度指标和管间梯状纹孔数量特征指标。结果显示, 红树族植物次生木质部管状分子侧壁具附物纹孔。所观察的植物附物纹孔的分布和形态变化大。附物纹孔丰富度指标与管间梯状纹孔数量特征指标的逐步回归分析表明, 导管侧壁附物纹孔丰富度随纹孔口面积百分比的增大而增大。据此推测, 红树族植物附物纹孔丰富度与纹孔几何构造及数量特征有关。附物纹孔是红树族植物稳定存在的一个木材解剖性状。综合生态-系统演化的观点, 红树族植物具附物纹孔可能是受系统演化关系控制的生态适应结果。     

PRESENCE OF VESSELS IN WOOD OF SARCANDRA (CHLORANTHACEAE); COMMENTS ON VESSEL ORIGINS IN ANGIOSPERMS

Sarcandra is the only genus of Chloranthaceae hitherto thought to be vesselless. Study of liquid-preserved material of S. glabra revealed that in root secondary xylem some tracheary elements are wider in diameter and have markedly scalariform end walls combined with circular pits on lateral walls. Examination of these wider tracheary elements with scanning electron microscope (SEM) demonstrated various degrees of pit membrane absence in the end walls. Commonly a few threadlike fibrils traverse the pits (perforations); these as well as intact nature of pit membranes in pits at ends of some perforation plates are evidence that lack of pit membranes does not result from damage during processing. Some perforations lack any remnants of pit membranes. Although perforation plates and therefore vessels are present in Sarcandra roots, no perforations were observed in tracheary elements of stems or lignotubers. Further, stem tracheids do not have the prominently scalariform end walls that the vessel elements in roots do. Presence of vessels in Sarcandra removes at least one (probably several) hypothetical events of vessel origin that must be postulated to account for known patterns of vessel distribution in angiosperms, assuming that they are primitively vesselless. Seven (perhaps fewer) vessel origin events in angiosperms could account for these patterns; two of those events (Nelumbo and monocotyledons) are different from the others in nature. Widely accepted data on trends of vessel specialization in woody dicotyledons yield an unappreciated implication: vessel specialization has happened in a highly polyphyletic manner in dicotyledons, and therefore multiple vessel origins represent a logical extension backward in time. If a group of vesselless dictyoledons ancestral to other angiosperms existed, they can be hypothesized to have had a relatively homogeneous floral plan now that Sarcandra-like plants no longer need be imagined within that group. Sarcandra and other Chloranthaceae show that the borderline between vessel absence and presence is less sharp than generally appreciated.     

Discovery of vessels in Tetracentron (Trochodendraceae) and its systematic significance

Through SEM observation, we found that there are vessels as well as tracheids in the secondary wood of Tetracentron sinense Oliv. The vessel elements are as narrow and as long as or slightly shorter than the tracheids and generally have 1 to 3 very long, or sometimes relatively short and oblique end-wall perforation plates; such perforation plates are also present on the lateralwalls. The perforation plates of the vessels include scalariform and reticulate-scalariform types, with various degrees of membrane remnants present in the end walls.     

慈姑不定根中导管分子的观察

慈姑导管仅在根中出现。根的后生木质部中央导管由顶端平截、单穿孔的网纹导管分子连接组成;周围较小的导管分子和管胞有从梯纹管胞向导管分子演化的各种过渡类型;有一至多个梯形穿孔或单穿孔发生在导管分子的端壁或侧壁,并有分枝型导管分子存在,特别在根与主茎连接处尤为明显。管胞亦有分枝与不分枝的类型。     

国产胡桃科次生木质部导管分子的比较解剖及其系统位置的讨论

通过对国产胡桃科6属13种植物所做的次生木质部导管分子的长度,弦径,端壁斜度,穿孔板类型,管孔形状及其排列,导管密度及其在分类中作用的解剖学研究,证实了从导管分子来看黄杞属和青钱柳属是相当原始的属,而化香树属,山核桃属是最进化的属,并根据导管分子的解剖学特征探讨了胡桃科各属间的进化顺序。     

Vessel dimensions in liana and tree species of Gnetum (Gnetales)

Maximum vessel diameters were examined in the secondary xylem of stems of Gnetum of various sizes. One tree (G. gnemon) and 13 liana species were compared. In three species, vessel length distributions were determined by the latex paint method, and showed many short and fewer long vessels. Latex and compressed air methods, used to find the maximum vessel lengths, showed that maximum vessel lengths were similar for three species of Gnetum. In old stems, mean and maximum vessel diameters tended to be greater in lianas than in the tree species. The skewed distribution of vessel lengths and the trend of wider vessels in lianas as compared to trees were similar to those distributions and trends described previously for angiosperms. In random samples of macerated wood of three species, simple perforation plates were most common in vessel members of all species. Foraminate and modified foraminate perforations were less frequent. Average diameter of vessel members with either foraminate or modified foraminate perforations was less than for those with simple perforations. The resemblance of Gnetum vessels to those of angiosperm trees and vines is most likely a case of convergent evolution (homoplasy) in xylem characteristics.     

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。     

Occurrence of plasmodesmata between differentiating vessels and other xylem cells inSorbus torminalis L. Crantz and their fate during xylem maturation

Summary The development of pit-pairs between differentiating xylem cells has been examined by transmission electron microscopy in young shoots ofSorbus torminalis. In some vessel-to-tracheid pits, as well as in previously studied intertracheid pits, a thickening of the pit membrane containing branched plasmodesmata was observed. A secondary wall-like cap was deposited over the thickening prior to cytoplasmic autolysis; some plasmodesmata, parallel to the plane of section, appeared to perforate the cap. At the end of the cell maturation stage, the central part of the primary wall thickening was hydrolysed, while the cap, including plasmodesmata remnants, appeared unaltered. In half-bordered pit-pairs between a parenchyma cell and a vessel or a tracheid, similar structures could be observed beside the conducting elements. When the vessel or tracheid matured, sealing of the pit membrane plasmodesmata resulted from the formation of a protective layer on the parenchyma-side rather than from the deposition of a cap on the conducting cell-side. These observations provide the first information on the presence of symplasmic connections in pits between differentiating vessels and neighbouring xylem cells. InS. torminalis, xylem differentiation is probably highly coordinated within a symplasmic domain; the persistence of such connections may account for the lack of specialization ofSorbus wood.     

Comparative wood anatomy of epacrids (Styphelioideae,Ericaceae s.L.)

The wood anatomy of 16 of the 37 genera within the epacrids (Styphelioideae, Ericaceae s.l.) is investigated by light and scanning electron microscopy. Several features in the secondary xylem occur consistently at the tribal level: arrangement of vessel-ray pits, distribution of axial parenchyma, ray width, and the presence and location of crystals. The primitive nature of Prionoteae and Archerieae is supported by the presence of scalariform perforation plates with many bars and scalariform to opposite vessel pitting. The wood structure of Oligarrheneae is similar to that of Styphelieae, but the very narrow vessel elements, exclusively uniseriate rays and the lack of prismatic crystals in Oligarrheneae distinguish these two tribes. The secondary xylem of Monotoca tamariscina indicates that it does not fit in Styphelieae; a position within Oligarrheneae is possible. Like most Cosmelieae, all Richeeae are characterized by exclusively scalariform perforation plates with many bars, a very high vessel density and paratracheal parenchyma, although they clearly differ in ray width (exclusively uniseriate rays in Cosmelieae vs. uniseriate and wide multiseriate rays in Richeeae). Several wood anatomical features confirm the inclusion of epacrids in Ericaceae s.l. Furthermore, there are significant ecological implications. The small vessel diameter and high vessel frequency in many epacrids are indicative of a high conductive safety to avoid embolism caused by freeze-thaw cycles, while the replacement of scalariform by simple vessel perforation plates and an increase in vessel diameter would suggest an increased conductive efficiency, which is especially found in mesic temperate or tropical Styphelieae.     

The Vascular System of Maize Stems Revisited: Implications for Water Transport and Xylem Safety

The plexus of vascular bundles in the nodes of grasses is notoriouslycomplex, where long axial bundles pass through a network oftransverse bundles. The xylem pathways for water in maize stemshave been investigated anatomically and with dye and particulatetracers, revealing some of the details of this complexity. Onlyapprox. 3% of axial vessels pass through nodes without beinginterrupted by end walls. Axial bundles at nodes differ fromthose in internodes in having the metaxylem and protoxylem vesselsconnected by small tracheary elements. So it is only at nodesthat exchange of sap occurs between the large vessels withina bundle. End walls, acting as filters for particles and gasbubbles, always separate axial vessels from vessels in transversebundles. The high redundancy of bundle connections in the nodalplexus is interpreted as providing alternative water pathwaysto bypass embolisms and damaged or diseased sections of thexylem. The pores in the filters at the base of nodes and betweenaxial and transverse vessels within nodes are <20 nm in diameter.Where axial vessels connect to transverse vessels, a varietyof unusual shapes of vessel elements mediate two- and three-wayconnections within the plexus.Copyright 2000 Annals of BotanyCompany Zea mays, cryoSEM, maize, node, pits, pit membranes, vessel ends, vessels, xylem embolism, xylem pathogens     

Wood anatomy of Elaeagnaceae, with comments on vestured pits, helical thickenings, and systematic relationships

The secondary xylem of Elaeagnus, Hippophae, and Shepherdia is described and illustrated in detail. Shrubs and small trees of Elaeagnaceae have ring-porous or semi-ring-porous wood with simple perforation plates, vascular tracheids, fiber-tracheids, diffuse or rarely paratracheal axial parenchyma, and uni- or biseriate rays in Hippophae and Shepherdia, but wider rays in Elaeagnus. Walls of vessel elements, especially narrow ones, tracheids, or fiber-tracheids sometimes show helical thickenings; in a few instances these intergrade with small bud-like protrusions associated with pits. Scanning electron microscopy illustrates that small to vestigial vestures are present in all species studied, although nonvestured pits are also common. The analogous nature of vestures and helical thickenings is considered. Comparative wood anatomy suggests a rather isolated position of the family Elaeagnaceae; affinities with Rhamnaceae, Proteaceae, and Thymelaeaceae are discussed.     

秋茄次生木质部的生态解剖学研究

为了探讨秋茄(Kandelia obovata Sheue et al.)次生木质部的形态解剖和数量解剖特征变化对不同红树林生境的生态适应意义,采用光学显微镜(LM)、扫描电镜(SEM)、透射电镜(TEM)和激光共聚焦显微镜(LSCM)对深圳福田红树林自然保护区内7个秋茄种群的次生木质部解剖特征进行观测,并对种群样地的土壤盐分含量、pH值和土壤养分含量进行测定。结果显示,(1)7个秋茄种群的次生木质部具有一些共同形态解剖特征:具纤维状导管和环管管胞;许多导管壁的微观结构(如管壁附物、穿孔板附物和螺旋雕纹等)有利于提高水分输导的高效性和安全性,以适应潮间带生境;(2)应用逐步回归分析法对秋茄次生木质部数量解剖特征和土壤理化因子的关系进行分析发现,随着土壤Na+、土壤全盐量增高,秋茄次生木质部导管分子趋向于"大型化"。"大型化"导管有利于水分输导,但降低了安全性。在土壤盐离子含量越高、秋茄导管分子越大其水分输导安全性越低的情况下,推测可能有其它机制保证秋茄导管水分输导的安全性。     

梣属11种植物次生木质部附物纹孔的电镜观测

应用扫描电镜对梣属11种植物次生木质部导管附物纹孔的分布和形态进行了详细的观察,应用Carnoy2.0软件和扫描电子显微镜采集的照片,测定了附物纹孔丰富度指标和纹孔数量特征指标。电镜观察表明,梣属11种研究植物次生木质部导管分子侧壁附物纹孔的分布和形态变化较大,附物纹孔丰富度指标的统计描述进一步证实附物纹孔的分布变化大;3个附物纹孔丰富度指标分别与管间具缘纹孔数量特征指标的逐步回归分析表明,导管侧壁附物纹孔丰富度2个指标,即导管外纹孔口附物频率与导管纹孔腔附物频率随纹孔口面积百分比的增大而增大,推测梣属植物附物纹孔丰富度与纹孔几何构造及数量特征有关。研究认为,附物纹孔在梣属植物稳定存在,是可界定梣属植物的木材解剖性状。     

Anatomy of the vessel network within and between tree rings of Fraxinus lanuginosa (Oleaceae)

The three-dimensional (3-D) arrangement of vessels and the vessel-to-vessel connections in the secondary xylem of the stem of the ring-porous hardwood tree Fraxinus lanuginosa were studied in series of thick transverse sections with epifluorescence microscope and confocal laser scanning microscope. Vessels were traced in sequential sections, and vessel networks were reconstructed in two segments of wood with dimensions of 2 × 1.4 × 21.2 mm(3) and 2 × 1.4 × 5.8 mm(3) (tangential × radial × axial). The arrangement of vessels and intervessel pits were visualized by scanning electron microscopy in low-density polyethylene microcasts and on exposed tangential faces of growth-ring boundaries. The vessels deviated from the stem axis in the tangential direction and, to a lesser extent, in the radial direction. Some neighboring vessels were twisted around each other. Vessels that appeared solitary in single sections were found to be sequentially contiguous with a number of other vessels, forming networks that extended in the tangential direction and across growth-ring boundaries. In the 21.2-mm wood block, all earlywood vessels at the growth-ring boundary made contact with latewood vessels in the previous tree ring. Within a growth ring however, only a single contact was observed between individual earlywood and latewood vessels. Densely arranged intervessel pits were characteristic in the regions where adjacent vessels made contact with each other. Such bordered pits were abundant in the tangential walls of vessel elements adjacent to growth-ring boundaries. Therefore, bordered pits appear to provide the pathway for the radial transport of water via the vessel network across growth-ring borders. Fiber-tracheids, observed as terminal cells in the tree rings, might also contribute to the apoplastic transfer of water across ring borders.     

五味子科比较木材解剖及其系统学意义

在光学显微镜和扫描电镜下观察了南五味子属Kadsura 7种21个样品和五昧子属Schisandra 8种14个样品的木材解剖特征,结果表明次生木质部的导管分子类型、导管一射线间纹孔的排列方式、射线类型、射线细胞形状等性状在科的水平上很稳定,这些共同特征都支持五味子科Schisandraceae是比较自然的类群。在五昧子科中发现木材导管单生、具梯状穿孔板、导管壁具梯形排列的纹孔以及木射线异型等原始性状,支持五味子科在被子植物中的原始地位。此外,该科木材还具有单穿孔板导管、导管次生壁具螺纹加厚、具分隔纤维等较为特化的性状状态,这种性状进化水平的异等级现象,使五味子科表现出不同进化水平性状的镶嵌组合。根据木材解剖性状对五味子科进行UPGMA聚类分析,所得结果显示南五昧子属和五味子属在木材解剖特征方面有一定的交叉和重叠,这与分子系统学的结论一致,表明这两个属关系密切,可能起源于共同的祖先。通过比较五昧子科与八角科Illiciaceae的木材解剖特征,进一步证明两个科的亲缘关系很近,不支持将五味子科从八角目Illiciales中独立出来成立五味子目Schisandrales的观点。