安徽大别山木本植物幼树小枝薄壁组织组成特征初探

木本植物次生木质部轴向薄壁组织和射线薄壁组织在物质存储和转运等功能中起着重要的作用,剖析次生木质部薄壁组织组成有助于深入探究其功能,而小枝木质部薄壁组织组成特征还缺乏研究。该研究以天马国家级自然保护区内的18种木本植物幼树为研究对象,测算了各物种小枝木质部薄壁组织的组成含量并检测了其谱系信号,结合有关树干薄壁组织含量数据集,初步探讨木本植物小枝木质部薄壁组织含量特征。研究结果表明:(1) 18种木本植物幼树小枝的薄壁组织总含量为9.96%–18.56%,平均为14.80%;其中射线薄壁组织含量为7.74%–15.45%,高于轴向薄壁组织的含量(1.13%–7.49%);(2)小枝中薄壁组织总含量呈低于树干的趋势,其中小枝射线薄壁组织含量低于树干,而轴向薄壁组织含量高于树干,这可能是由器官差异和生活史阶段差异造成的;(3)轴向薄壁组织的含量具有显著的谱系信号,即物种亲缘关系越近其含量越相近。该研究初步验证了木本植物次生木质部薄壁组织的谱系信号,同时暗示了器官和生活史阶段差异对薄壁组织含量具有重要影响。     

软枣猕猴桃茎次生维管组织的解剖研究

本文对长白山的软枣猕猴桃(Actinidia arguta(Sieb et Zucc.)Planch ex Miquel)茎的次生维管组织进行了比较详细的解剖研究。结果表明其木材为半环孔材,次生木质部中导管底壁倾斜具梯状穿孔板;木薄壁组织丰富,发现其中不仅有离管型,而且也有傍管型。这就为猕猴桃科(Actini-diaceae)植物的木薄壁组织增添了一种新类型。木射线为异形Ⅰ及异形Ⅱ,并具连接木射线。经研究确认其次生韧皮部的筛管属典型的双子叶木本植物型,其特征为筛管具复筛板,无伴胞。同时本文与本属的其它种也作了比较分析,为其营养繁殖时不定根、不定芽的产生提供了理论依据,同时也为野生果树资源研究者提供一份有关软枣猕猴桃茎次生维管组织研究的新资料。     

8种木本旱生植物的木质部解剖学特性研究

从生态学角度对8种旱生植物木材的次生木质部结构进行了对比研究.结果表明,8树种次生木质部结构的共同特点为:生长轮分界明显(霸王和四合木的年轮有时不连续),半环孔材,单穿孔,导管壁间纹孔互列,木纤维无横隔膜,联合傍管轴向薄壁组织丰富,导管壁上呈现螺纹加厚,都具有异型射线;它们主要差异在于射线和导管的数量化指标:四合木异型射线1~2列,霸王、白刺、沙冬青和胡枝子射线2~5列,柽柳、柠条和花棒大型射线4~10列;导管分子长度和纤维长度在树种间和同一树种个体间差异较明显.四合木和沙冬青导管频率较大,导管管孔较小,因此Vulnerability和Mesomorphy值也较小,更能适应干旱环境.     

水松的次生韧皮部解剖及其系统位置的讨论

在光学显微镜和扫描电子显微镜下观察,水松茎次生韧皮部的主要特征为：韧皮部由轴向系统和径向系统组成。轴向系统由筛胞、韧皮薄壁组织细胞、蛋白细胞和韧皮纤维组成,径向系统由韧皮射线组成。在横切面上,轴向系统的各组成分子以单层切向带交替有规律的排列,其排列顺序为：筛胞－韧皮薄壁组织细胞－韧皮纤维-筛胞。筛胞的径向壁上嵌埋有草酸钙结晶,韧皮纤维仅一种类型,韧皮射线同型、单列。根据水松茎次生韧皮部的解剖研究,并与杉科其它各属的有关资料进行比较,我们认为：水松属与水杉属和落羽杉属有较近的亲缘关系。     

栽培太子参块根的发育解剖学研究

应用石蜡制片技术研究了栽培太子参纺锤状块根的发育过程。结果表明,栽培太子参的块根是由其不定根发育而成。太子参不定根的初生结构与次生结构的发育可分为4个阶段:原分生组织阶段、初生分生组织阶段、初生结构与次生结构阶段,类似一般草本双子叶植物根的发育。其特点是初生结构的皮层细胞大,仅3 ~4层,内皮层细胞具凯氏带;初生木质部多为三原型,少数为二原型、四原型与五原型。次生结构中次生木质部约占根面积80 %,主要为薄壁组织细胞,导管呈稀疏的放射状分布其中。由不定根发育成块根过程中,根据从根头至根尾不同距离的各组成部分的面积及细胞层数分析,从上向下其维管形成层活动强度不同,从而根的直径大小不同,使根发育成上粗下细的纺锤状肉质块根。高碘酸-Schiff反应显示,在成熟的块根中次生韧皮部的薄壁组织细胞和次生木质部射线间的木薄壁组织细胞内富含淀粉粒,在有些木薄壁组织细胞中还含有草酸钙簇晶。     

美登木根的显微结构及其内生真菌的分布

本文采用石蜡永久制片和光学显微摄像的方法对美登木(Maytenus confertiflorus)根的显微结构及其内生真菌的分布进行了研究。结果表明, 美登木根的次生结构由周皮和维管组织构成; 周皮由木栓层、木栓形成层和栓内层组成, 其中木栓层由5～6 列长形细胞组成; 维管组织中次生韧皮部所占根径的比例达46%, 其薄壁细胞中内含物较丰富, 次生木质部中分布有导管和木射线及少量木薄壁组织; 在美登木木栓层和次生韧皮部中分布有菌丝片段、膨大的菌丝、菌丝团及分生孢子; 内生真菌只在一定区域的皮层和次生韧皮部细胞中分布。     

乌苏里鼠李茎叶的解剖结构及其生态适应性

为探究乌苏里鼠李（Rhamnus ussuriensis）茎叶的解剖结构对环境的适应性机理,采用石蜡切片及扫描电镜技术,对乌苏里鼠李叶片、茎的解剖结构进行研究。结果表明：乌苏里鼠李叶片为典型异面叶,表皮毛和气孔均分布在下表皮,气孔指数为39.04%;栅栏组织由2层薄壁组织细胞组成,结构紧密,海绵组织排列疏松。叶片主脉发达,维管束呈环状排列,木质部导管数量较多,直径较大,维管束周围薄壁组织细胞后含物丰富。在茎的初生结构中,表皮细胞角质层较厚,皮层薄壁组织细胞内含有晶簇,维管束为外韧无限维管束,髓部发达;茎的次生结构中年轮显明,为典型的环孔材,有凹下的皮孔,次生木质部发达,导管以螺纹导管与孔纹导管居多,导管分子多为复管孔;射线以单列射线为主,偶见双列射线。乌苏里鼠李叶片、茎的解剖结构具有明显的抗逆特性,能够较好的适应干旱、寒冷环境。     

华北低山丘陵区常用树种木质部解剖特征及水其力学抗旱性

木本植物木质部解剖特征与水分运输和干旱适应策略密切相关,但目前对华北低山丘陵区常用树种这方面的研究仍然不足。为研究这一地区植物木质部解剖特征与抗旱性的关系,研究以抗旱树种和非抗旱树种各5种为研究对象,通过测定与木质部横截面导管、薄壁组织相关的大量解剖学性状和非结构性碳浓度,比较两类树种木质部解剖特征的差异和解剖性状间的关联,以探究这些树种水力学的干旱适应策略差异。结果显示:1)10个树种的16个木质部性状均有较大变异性;2)两类树种间的平均导管直径和导管密度无显著差异,但抗旱树种导管壁厚度、最大导管直径、旁管薄壁组织比例和轴向薄壁组织比例以及非结构性碳(NSC)浓度显著大于非抗旱树种;3)抗旱树种的导管壁厚度与平均导管直径、最大导管直径和潜在最大导水率均呈显著正相关关系,最大导管直径与潜在最大导水率呈显著正相关关系,但非抗旱树种不存在这些关系。本研究抗旱树种同时具有较大的最大导管直径和较厚的导管壁,在保证较高的水分运输效率的同时又具备一定的抗栓塞能力,较多的旁管薄壁组织和NSC也为抗旱树种提供了更大的木质部水储存和栓塞修复能力。     

美登木根的显微结构及其内生真菌的分布

本文采用石蜡永久制片和光学显微摄像的方法对美登木（Maytenus confertiflorus）根的显微结构及其内生真菌的分布进行了研究.结果表明,美登木根的次生结构由周皮和维管组织构成;周皮由木栓层、木栓形成层和栓内层组成,其中木栓层由5～6列长形细胞组成;维管组织中次生韧皮部所占根径的比例达46%,其薄壁细胞中内含物较丰富,次生木质部中分布有导管和木射线及少量木薄壁组织;在美登木木栓层和次生韧皮部中分布有菌丝片段、膨大的菌丝、菌丝团及分生孢子;内生真菌只在一定区域的皮层和次生韧皮部细胞中分布.     

乌拉尔甘草根与根状茎发育解剖学研究

应用常规石蜡切片方法,对乌拉尔甘草根和根状茎的结构及其发育进程进行研究.结果显示:(1)乌拉尔甘草根的发育包括原分生组织、初生分生组织、初生生长和次生生长4个发育阶段.原分生组织由3层原始细胞组成,具有典型分生组织细胞的特征;初生分生组织由根冠原、表皮原、皮层原和中柱原组成;初生结构包括表皮、皮层和中柱,初生木质部为4原型,偶见3原型,内皮层细胞具凯氏带;次生生长依靠维管形成层和木栓形成层活动完成,维管形成层源于初生木质部和初生韧皮部之间的薄壁细胞,而木栓形成层由中柱鞘细胞脱分化产生;次生结构由次生维管组织和周皮共同组成,根中央不具髓.(2)根状茎发育过程与地上茎类似,包括原分生组织、初生分生组织、初生生长和次生生长4个发育阶段.原生分生组织由原套和原体组成,其衍生细胞分化成由原表皮、基本分生组织和原形成层组成的初生分生组织;初生结构包括表皮、皮层、外韧维管束、髓和髓射线,维管束呈环形排列;位于维管束中的原形成层细胞恢复活动产生次生木质部和次生韧皮部,束间形成层产生射线细胞;靠近维管束内侧的皮层薄壁组织细胞脱分化产生木栓形成层,以后形成周皮.周皮、次生维管束、射线和髓共同构成根状茎的次生结构.     

杜仲次生木质部分化和脱分化过程中酸性磷酸酶的超微细胞化学定位

杜仲（EucommiaulmoidesOliv．）次生木质部分化过程中,在形成层刚衍生的木薄壁细胞中,酸性磷酸酶（APase）主要分布于核膜边缘和高尔基体;在分化程度较高的木薄壁细胞中,APase散布于整个核中,进而,在各种细胞器残体上聚集;在成熟的木薄壁细胞中,APase沿细胞壁内侧分布。在未成熟导管分子中,核、质膜及纹孔上明显存在APase聚集,进而,核解体;在即将分化成熟的导管分子中,APase主要集中于初生壁;在已分化成熟的导管分子中,APase集中于次生壁。脱分化过程中,只在细胞质中可见分散的APase活性,而细胞核和细胞壁上未见此酶的分布;更深层的即将分化成熟和已分化成熟的导管分子,未见有细胞分裂,其上APase的分布与剥皮前相同。通过比较分化和脱分化过程中APase的分布,推测不同的APase同工酶可能分别参与了次生木质部细胞程序性死亡过程中原生质体的解体和次生壁的建成。APase的聚集程度可能是决定细胞能否脱分化的一个重要特征。     

Protoxylem: the deposition of a network containing glycine-rich cell wall proteins starts in the cell corners in close association with the pectins of the middle lamella

Antibodies were used to localise polysaccharide and protein networks in the protoxylem of etiolated soybean (Glycine max L.) hypocotyls. The deposition of glycine-rich proteins (GRPs) starts in the cell corners between protoxylem elements and xylem parenchyma cells. Finally, the GRPs form a network between two mature protoxylem elements. The network also interconnects the ring- and spiral-shaped secondary wall thickenings, as well as the thickenings with the middle lamellae of living xylem parenchyma cells. In addition to the GRP network, a polysaccharide network composed mainly of pectins is involved in the attachment of the secondary wall thickenings to the middle lamellae of xylem parenchyma cells.     

Mechanisms of xylem embolism repair in woody plants: Research progress and questions

To maintain long-distance water transport in woody plants is critical for their survival, growth and development. Water under tension is in a metastable state and prone to cavitation and embolism, which leads to loss of hydraulic conductance, reduced productivity, and eventually plant death. In face to water stress-induced cavitation, plants either reduce frequency of embolism occurrence through cavitation resistance with specialized anatomical struc- ture, or/and form a metabolically active embolism repair mechanism. For the xylem embolism and repair, however, there are controversies regarding the occurring frequency, conditions and underlying mechanisms. In this review paper, we first examined the process, temporal dynamics and frequency of xylem embolism and repair. Then, we summarized hypotheses for the mechanisms of the novel refilling in xylem embolism repair, including the osmotic hypothesis, the reverse osmotic hypothesis, the phloem-driven refilling hypothesis, and the phloem unloading hypothesis. We further compared differences in xylem embolism and repair between conifers and angiosperms tree species, and examined the trade-offs between cavitation resistance and xylem recovery performance. Finally, we proposed four priorities in future research in this field: (1) to improve measuring technology of xylem embolism; (2) to test hypotheses for the mechanisms of the novel refilling in xylem embolism repair and the signal triggering xylem refilling; (3) to explore species-specific trait differences related to xylem embolism and repair and their underlying trade-off relationships; and (4) to enhance studies on the relationship between the involvement of carbon metabolism and aquaporins expression in xylem embolism and repair.     

杨树新梢积累营养贮藏蛋白质的细胞学研究

采用光学显微镜和电子显微镜技术,对杨树新梢中的营养贮藏蛋白质进行了细胞学鉴定。在用戊二醛固定的标本中,营养贮藏蛋白质呈颗粒状,积累在中央大液泡里。在新梢伸长生长时期,新梢茎的基部已积累了营养贮藏蛋白质,在伸长生长刚停止,中上部的叶片近成熟时,整个新梢的茎都有营养贮藏蛋白质的积累,其中,以新梢基部的茎最为丰富。营养贮藏蛋白质优先在次生韧皮部的韧皮薄壁细胞和韧皮射线薄壁细胞中积累,在新梢伸长生长停止后,新梢基部茎的木质部中也积累了相当数量的营养贮藏蛋白质,主要分布在初生木质部和内侧次生木质部的各种生活的薄壁细胞中。新梢较早地积累营养贮藏蛋白质是热带树木和温带树木的一个共同特点,对于树木的氮代谢和树木当年的生长发育可能具有重要的调控作用。     

掌叶大黄根多糖的积累分布特征

采用组织化学方法和苯酚硫酸比色法研究了掌叶大黄（Rheum palmatum）根中大黄多糖的贮藏分布特征和含量变化规律。结果表明：大黄多糖在根内的贮藏是多位点的,在根周皮的栓内层、次生维管组织的薄壁细胞内不同程度地贮藏和积累了一定数量的大黄多糖,次生木质部的木薄壁细胞和次生韧皮部的韧皮薄壁细胞是主要贮藏和积累的部位;不同发育时期根中大黄多糖含量的变化规律为,随着植物的不断成熟,根及其各组织中大黄多糖的总含量表现为逐渐增高的趋势,但在发育的后期略有下降;韧皮薄壁细胞与木薄壁细胞相比,贮藏大黄多糖的含量相对较多,大黄多糖的贮藏积累方式为逐渐累积的方式。     

Xylem parenchyma cells deliver the H<Subscript>2</Subscript>O<Subscript>2</Subscript> necessary for lignification in differentiating xylem vessels

Lignification in Zinnia elegans L. stems is characterized by a burst in the production of H₂O₂, the apparent fate of which is to be used by xylem peroxidases for the polymerization of p-hydroxycinnamyl alcohols into lignins. A search for the sites of H₂O₂ production in the differentiating xylem of Z. elegans stems by the simultaneous use of optical (bright field, polarized light and epi-polarization) and electron-microscope tools revealed that H₂O₂ is produced on the outer-face of the plasma membrane of both differentiating (living) thin-walled xylem cells and particular (non-lignifying) xylem parenchyma cells. From the production sites it diffuses to the differentiating (secondary cell wall-forming) and differentiated lignifying xylem vessels. H₂O₂ diffusion occurs mainly through the continuous cell wall space. Both the experimental data and the theoretical calculations suggest that H₂O₂ diffusion from the sites of production might not limit the rate of xylem cell wall lignification. It can be concluded that H₂O₂ is produced at the plasma membrane in differentiating (living) thin-walled xylem cells and xylem parenchyma cells associated to xylem vessels, and that it diffuses to adjacent secondary lignifying xylem vessels. The results strongly indicate that non-lignifying xylem parenchyma cells are the source of the H₂O₂ necessary for the polymerization of cinnamyl alcohols in the secondary cell wall of lignifying xylem vessels.     

宁夏盐池不同坡位旱地紫苜蓿水分来源

紫苜蓿(Medicago sativa)是一种经济和生态价值较高的优良牧草, 但其耗水量大, 在西北半干旱地区仅靠天然降水难以满足紫苜蓿的正常生长发育。宁夏盐池北部地处毛乌素沙地南缘, 地下水埋深较浅, 地下水有可能成为紫苜蓿的潜在水源, 弥补天然降水的不足。本试验在地势平坦的缓坡丘陵梁地和丘间低地, 选择8年生旱地紫苜蓿试验地作为研究对象, 采用稳定同位素技术, 研究了不同海拔的4个坡位(海拔自低到高分别为: 坡1、坡2、坡3和坡4)紫苜蓿的水分来源及其生长生理表现。结果表明: 坡位对0-300 cm土壤剖面含水量有显著影响, 海拔最低的坡1土壤含水量最高。土壤水和植物茎秆水δ ¹⁸O-δD坐标点大部分位于中国西北地区地方大气降水线(LMWL)的右侧, 说明植物利用的水源氢氧同位素组成受到蒸发的影响而发生了富集作用。0-450 cm土壤剖面水δ ¹⁸O值随着海拔高度的增加而增大。同一坡位土壤水δ ¹⁸O值随着土壤深度的增加逐渐下降。深层土壤水δ ¹⁸O值与地下水δ ¹⁸O相近, 说明地下水通过土壤毛细管上升而补充其上层土壤水分。0-40 cm土壤水δ ¹⁸O值随季节波动较大, 270 cm以下土壤水δ ¹⁸O值较为稳定。4、7、8月份坡1紫苜蓿茎秆水δ ¹⁸O值显著低于其他3个坡位(p < 0.001)。在4、6、7三个月, 坡位1紫苜蓿对深层土壤水(270 cm以下)的利用率最高。而在8月份, 坡1、坡3、坡4紫苜蓿主要利用150-270 cm、270-450 cm土层土壤水以及地下水, 坡2对表层(0-20 cm)土壤水利用率最高。坡1紫苜蓿的产量、整株Δ ¹³C值及气孔导度显著高于其他3个坡位。本研究表明: 在平均年降水量只有280 mm的西北半干旱地区种植旱地紫苜蓿要尽量选择地势较低的滩地, 使其能够利用到埋深较浅地下水, 以满足植物生长发育的需要并取得较好的生态和经济效益。     

Anatomical characteristics of xylem in tree rings and its relationship with environments

The anatomical traits of xylem are the characteristics of tree rings at the cellular and subcellular scales, and are often reflection of environmental signals. Studying the relationships between anatomical traits of xylem and environmental change not only provide physiological explanations to the statistics in dendroclimatology, but can also provide a new vision for studying the adaptation process and response strategies of tree growth to climate change. In this paper, with the relationships between the anatomical characteristics of xylem in tree-rings (cell chronology) and climate change as a main thread, we first outline the basic principles and mechanisms of wood anatomical features to record environmental signals, and expounded the basic methods involved in the process of xylem anatomy. Secondly, we discuss the relationship between the anatomical features of xylem and climate factors. We then propose the following as possible directions of future research based on the existing knowledge gap in the topical area: (1) to explore the temporal and spatial variations in the anatomical characteristics of xylem in tree-rings along radial and tangential directions and the relationships with environmental changes; (2) to explore the threshold of tree growth response to environmental plasticity and adaptation processes; (3) to assess the synergistic and antagonistic effects as well as the formation mechanisms of climate response among different tree-ring proxies, and to determine the specific roles and contributions of major climatic factors during different periods of tree-ring formation.     

Living cells in wood. 1. Absence,scarcity and histology of axial parenchyma as keys to function

The diversity of expression in axial parenchyma (or lack of it) in woods is reviewed and synthesized with recent work in wood physiology, and questions and hypotheses relative to axial parenchyma anatomy are offered. Cell shape, location, abundance, size, wall characteristics and contents are all characteristics for the assessment of the physiological functions of axial parenchyma, a tissue that has been neglected in the consideration of how wood histology has evolved. Axial parenchyma occurrence should be considered with respect to mechanisms for the prevention and reversal of embolisms in tracheary elements. This mechanism complements cohesion–tension‐based water movement and root pressure as a way of maintaining flow in xylem. Septate fibres can substitute for axial parenchyma (‘axial parenchyma absent’) and account for water movement in xylem and for the supply of carbohydrate abundance underlying massive and sudden events of foliation, flowering and fruiting, as can fibre dimorphism and the co‐occurrence of septate fibres and axial parenchyma. Rayless woods may or may not contain axial parenchyma and are informative when analysing parenchyma function. Interconnections between ray and axial parenchyma are common, and so axial and radial parenchyma must be considered as complementary parts of a network, with distinctive but interactive functions. Upright ray cells and more numerous rays per millimetre enhance interconnection and are more often found in woods that contain tracheids. Vesselless woods in both gymnosperms and angiosperms have axial parenchyma, the distribution of which suggests a function in osmotic water shifting. Water and photosynthate storage in axial parenchyma may be associated with seasonal changes and with succulent or subsucculent modes of construction. Apotracheal axial parenchyma distribution often demonstrates storage functions that can be read independently of osmotic water shifting capabilities. Axial parenchyma may serve to both enhance mechanical strength or, when parenchyma is thin‐walled, as a tissue that adapts to volume change with a change in water content. Other functions of axial parenchyma (contributing resistance to pathogens; a site for the recovery of physical damage) are considered. The diagnostic features of axial parenchyma and septate fibres are reviewed in order to clarify distinctions and to aid in cell type identification. Systematic listings are given for particular axial parenchyma conditions (e.g. axial parenchyma ‘absent’ with septate fibres substituting). A knowledge of the axial parenchyma information presented here is desirable for a full understanding of xylem function. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 291–321.     

Phenylcoumaran benzylic ether reductase, a prominent poplar xylem protein, is strongly associated with phenylpropanoid biosynthesis in lignifying cells

 It has previously been shown (D.R. Gang et al., 1999, J Biol Chem 274: 7516–7527) that the most abundant protein in the secondary xylem of poplar (Populus trichocarpa cv. `Trichobel') is a phenylcoumaran benzylic ether reductase (PCBER), an enzyme involved in lignan synthesis. Here, the distribution and abundance of PCBER in poplar was studied at both the RNA and protein level. The cellular expression pattern was determined by immunolocalization of greenhouse-grown plants as well as of a field-grown poplar. Compared to other poplar tissues, PCBER is preferentially produced in the secondary xylem of stems and roots and is associated with the active growth period. The protein is present in all cells of the young differentiating xylem, corresponding to the zone of active phenylpropanoid metabolism and lignification. In addition, PCBER is located in young differentiating phloem fibers, in xylem ray parenchyma, and in xylem parenchyma cells at the growth-ring border. Essentially the same expression pattern was observed in poplars grown in greenhouses and in the field. The synthesis of PCBER in phenylpropanoid-synthesizing tissues was confirmed in a bending experiment. Induction of PCBER was observed in the pith of mechanically bent poplar stems, where phenylpropanoid metabolism is induced. These results indicate that the products of PCBER activity are synthesized mainly in lignifying tissues, suggesting a role in wood development. Received: 28 September 1999 / Accepted: 15 March 2000