Water Flow Through Vessel Perforation Plates--A Fluid Mechanical Approach

The effect of scalariform perforation plates on the flow ofwater through plant vessels remains poorly understood. In thisstudy, a new computational tool based on finite element methodsolutions to the Navier-Stokes equation was applied to modellingfluid flow through these structures in plant vessels. Modelsdeveloped for Liriodendron tulipifera vessel elements were solvedfor cells with and without the perforation plate to study effectsof the plate on the pressure drop along the cell. Results indicatethat the pressure gradient was 5-fold greater through the platethan for regions before and after the plate. However, the perforationplate in this species accounts for only about 8% of the resistanceto flow through typical vessels because the plate influencesflow for only a short distance along the cell relative to itslength. Details of the flow characteristics through pores ofthe perforation plate are also described. Key words: Conductance, finite element method, perforation plate, vessel, water flow     

Aporphine alkaloids and lignans in heartwood of Liriodendron tulipifera

The following compounds were isolated from heartwood of Liriodendron tulipifera: glaucine, dehydroglaucine, asimilobine, N-acetylnornuciferine, norushinsunine, liriodenine, O-methylatheroline, (+)-syringaresinol, (+)-syringaresinol dimethyl ether and syringaldehyde. The occurrence of 1-benzyltetrahydroisoquinoline alkaloids also has been indicated by mass spectroscopy. Some characteristic spectral properties of these aporphine alkaloids and their probable biosynthetic pathways are discussed.     

Lignans and aporphine alkaloids in bark of Liriodendron tulipifera

Lirionol, a novel tetracyclic lignan, has been isolated from the bark of Liriodendron tulipifera and its structure determined by spectroscopic analysis. In addition, syringic acid methyl ester, (+)-pinoresinol, (+)-syringaresinol, N-(2-hydroxy-2-phenylethyl)benzamide and O-methyl-N-norlirinine have also been isolated. The structures of lirinine and related compounds isolated from the leaves of this tree-species by Yunusov et al. are also discussed.     

Effects of Partial Defoliation on the Growth of Liriodendron tulipifera L. Seedlings

Partial defoliation of Liriodendron tulipifera L. by removalof leaflets as they emerged from the protective buds affecteda variety of growth parameters. Reductions occurred in totaldry weight production, the percentage of new growth devotedto foliage, leaf area ratio, and the increment of leaf areaper unit of leaf weight increment. Increases occurred in unitleaf rate and the rate of production of new leaves. Weight ofleaves near the base of the seedlings was unaffected by treatmentbut leaves developing at the end of the growing season werelarger on defoliated plants. The net effect of removing one-thirdand two-thirds of the developing leaflets was to reduce totaldry weight production by 14 and 42 per cent respectively.     

维管植物导管及其穿孔板的研究进展

介绍了导管及其穿孔板的研究进展,包括导管的特征(穿孔板的类型、多穿孔板与侧壁穿孔板、纹孔膜残留),导管的起源与穿孔板的演化,蕨类植物、裸子植物与被子植物导管的比较,并就导管进化与穿孔板演化．导管的二型性现象、侧壁穿孔板、多穿孔板与穿孔中纹孔膜．生态对导管进化的影响等方面以及对今后的研究作了展望。     

台湾青枣导管分子及其穿孔板研究

运用细胞图象分析系统及显微照相的方法对台湾青枣Z iziphus mauritiana次生木质部导管分子进行了观察研究。在台湾青枣的次生木质部导管分子中存在着许多不同的样式,并且导管分子穿孔板存在着3种类型:两端均为一个单穿孔板;一端为一个单穿孔板,另一端为梯状穿孔板;具纤毛的单穿孔板。分别对其进行了描述,并从导管分子个体发育与系统发育的角度进行了讨论,认为3种类型的穿孔板为导管分子穿孔板的系统演化提供了新的证据。     

Generation of a large-scale genomic resource for functional and comparative genomics in Liriodendron tulipifera L.

Liriodendron tulipifera L., a member of Magnoliaceae in the order Magnoliales, has been used extensively as a reference species in studies on plant evolution. However, genomic resources for this tree species are limited. We constructed cDNA libraries from ten different types of tissues: premeiotic flower buds, postmeiotic flower buds, open flowers, developing fruit, terminal buds, leaves, cambium, xylem, roots, and seedlings. EST sequences were generated either by 454 GS FLX or Sanger methods. Assembly of almost 2.4 million sequencing reads from all libraries resulted in 137,923 unigenes (132,905 contigs and 4,599 singletons). About 50% of the unigenes had significant matches to publically available plant protein sequences, representing a wide variety of putative functions. Approximately 30,000 simple sequence repeats were identified. More than 97% of the cell wall formation genes in the Cell Wall Navigator and the MAIZEWALL databases are represented. The cinnamyl alcohol dehydrogenase (CAD) homologs identified in the L. tulipifera EST dataset showed different expression levels in the ten tissue types included in this study. In particular, the LtuCAD1 was found to partially recover the stiffness of the floral stems in the Arabidopsis thaliana CAD4 and CAD5 double mutant plants, of the LtuCAD1 in lignin biosynthesis. L. tulipifera genes have greater sequence similarity to homologs from other woody angiosperm species than to non-woody model plants. This large-scale genomic resour"HistryDatesce will be instrumental for gene discovery, cDNA microarray production, and marker-assisted breeding in L. tulipifera, and strengthen this species' role in comparative studies.     

The significance of allozyme variation and introgression in the Liriodendron tulipifera complex (Magnoliaceae)

Fifty populations of Liriodendron tulipifera were sampled and scored for electrophoretic variation at 23 loci. The level of genetic polymorphism and population differentiation is greater in L. tulipifera than is usual for an outbreeding species. Since this species exhibits a cline of morphological and ecological variation from north to south, the 50 populations were divided into seven geographically defined regional groupings: three from the Appalachian uplands, three from the southeastern coastal plains, and one from the Florida peninsula. Nei's genetic identity, I, was calculated for all within- and among-population and region comparisons. The populations from the upland regions clustered closely together while the coastal plain populations were similar but measurably separated from the upland ones. The populations from the Florida peninsula were markedly divergent. A principal components analysis of the same data set revealed a nearly identical pattern of population clustering. Two hypotheses were explored to explain the pattern observed: 1) post-Pleistocene differentiation and migration from a single refugium and; 2) sympatry of two previously isolated taxa during glacial maxima, followed by introgression and migration. The weight of evidence best supports the introgression hypothesis which is explained in terms of plant migration events during Pleistocene time. The level and distribution of electrophoretic variation in L. tulipifera is compared to that of other woody taxa in which historical events of the Pleistocene may have contributed to modern levels and patterns of variation.     

利用RAPD标记分析北美鹅掌楸与鹅掌楸种间遗传多样性

利用ＲＡＰＤ标记技术对鹅掌楸属（Ｌｉｒｉｏｄｅｎｄｒｏｎ Ｌ．）２个现存种鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎ ｃｈｉｎｅｎｓｅ （Ｈｅｍｓｌ．）Ｓａｒｇ）和北美鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎ ｔｕｌｉｐｉｆｅｒａ ｌｉｎｎ．）的遗传多样性进行分析,结果表明：２个种都有较高的遗传多样性,但北美鹅掌楸的遗传多样性水平高于鹅掌楸;鹅掌楸的遗传变异主要来自地理种源内,而北美鹅掌楸的遗传变异主要来自地理种源     

两种鹅掌楸繁殖成效的比较

通过交配设计结合花部性状调查对鹅掌楸(Liriodendron chktense Sarg.)与北美鹅掌楸(L.tulipifera Linn.)的繁殖资源分配与繁殖成效进行了比较.结果表明,鹅掌楸通过增加繁殖器官的数目以提高繁殖成效,而北美鹅掌楸则通过提高繁殖器官功效来保障繁殖成效.根据不同交配组合的子代出苗率分析表明,鹅掌楸总体的雄性繁殖成效高于北美鹅掌楸,而雌性繁殖成效低于北美鹅掌楸.     

Characterization and heterologous expression of laccase cDNAs from xylem tissues of yellow-poplar (Liriodendron tulipifera)

Four closely related cDNA clones encoding laccase isoenzymes from xylem tissues of yellow-poplar (Ltlacc2.1–4) were identified and sequenced. The inferred yellow-poplar laccase gene products were highly related to one another (79–91% at the amino acid level) and showed significant similarity to other blue copper oxidases, especially with respect to the copper-binding domains. The encoded proteins had N-terminal signal sequences and 17–19 potential N-linked glycosylation sites. The mature proteins were predicted to have molecular masses of ca. 61 kDa (unglycosylated) and high isoelectric points (pI 9.3–9.5). The canonical copper ligands were conserved, with the exception of a Leu residue associated with the axial position of the Type-1 cupric ion. The residue at this position has been proposed to influence the redox potential of Type-1 cupric ions. Northern blot analysis revealed that the yellow-poplar laccase genes are differentially expressed in xylem tissues. The genes were verified as encoding active laccases by heterologous expression in tobacco cells and demonstration of laccase activity in extracts from transformed tobacco cell lines.     

Pressure-Induced Water and Solute Flow Through Plant Roots

Water and salt flows through detopped sunflower, tomato andred kidney bean roots under applied pressure were studied usinga pressure chamber. Values of J_v for these root systems weremeasured applying variable pressure on the root medium, andL_p calculated. The K, Na and Cl fluxes under applied pressure were comparedwith those in intact plants at the same water flow rates. Tento 100 times higher Na and Cl fluxes were observed through detoppedroots under pressure as compared to those in the unpressurized,intact plants. It is suggested that the roots under pressureare not completely analogous to intact plant roots, and thatpressure-induced flow may not be a reliable method of determiningcharacteristics of ion flow in roots in relation to water flow. Key words: Volume flow, Hydraulic conductivity, K selectivity     

Response surface optimization of oxalic acid pretreatment of yellow poplar (Liriodendron tulipifera) for production of glucose and xylose monosaccarides

The primary goal of this study was to determine the optimal condition to obtain fermentable monosaccharides (xylose and glucose) from hydrolysates of yellow poplar (Liriodendron tulipifera) by oxalic acid pretreatment as a potential bio-ethanol source. Based on 2(3) factorial design, fifteen operations were performed by varying on acid loading, reaction time and temperature, and the components of the solid and liquid fractions were analyzed. The sugar concentration (g/L) in hydrolysates and xylose solubilization (%) were applied to response surface methodology. The optimal condition for producing sugars was 151 °C, 0.042 g/g (weight of oxalic acid/dry matter), 13 min with predicted yield of 37.4 g/L, and for the xylose solubilization was 158 °C, 0.037 g/g, 13 min yielding 72.0% of the predicted value. Severe conditions generated inhibitors. By measuring the concentrations, the possibility utilizing hydrolysates for fermentation were estimated.     

Tensile growth stress and lignin distribution in the cell walls of yellow poplar, Liriodendron tulipifera Linn.

Five specimens that contained a continuous gradient of wood, from normal to tension wood regions, were collected from an inclined yellow poplar (Liriodendron tulipifera), and the released strain of tensile growth stress was quantified. Ultraviolet (UV) microspectrophotometry was used to examine the relationship between lignin distribution in the cell wall and the intensity of tensile growth stress. The UV absorption of the secondary wall and the cell corner middle lamella decreased with increasing tensile released strain (i.e., tensile growth stress). The UV absorption in the compound middle lamella region remained virtually constant, irrespective of the tensile released strain. The absorption maximum (5_max) remained virtually constant in the secondary wall, the cell corner middle lamella, and the compound middle lamella region at 273-274, 277-278, and 275-278 nm respectively, irrespective of the tensile released strain. The ratios of the UV absorbance at 280 to 260 nm and 280 to 273 nm of the secondary wall decreased with increasing tensile released strain. The ratios in the cell corner and compound middle lamella region remained constant, irrespective of the tensile released strain. The lignin content of the secondary wall decreased, while the syringyl/guaiacyl ratio increased with increasing tensile released strain. Gelatinous fibers were not observed in the tension wood regions, but the secondary wall became gelatinous-layer-like, i.e., the lignin content and microfibrillar angle decreased and the cellulose content increased. A definite gelatinous layer seems to be important for generating greater tensile growth stress. It is concluded that a decrease in lignin and an increase in cellulose microfibrils parallel to the fiber axis in the secondary wall are necessary to produce large tensile growth stress.     

Development of a BAC library for yellow-poplar (Liriodendron tulipifera) and the identification of genes associated with flower development and lignin biosynthesis

Liriodendron tulipifera L., a member of the Magnoliaceae, occupies an important phylogenetic position as a basal angiosperm that has retained numerous putatively ancestral morphological characters, and thus has often been used in studies of the evolution of flowering plants and of specific gene families. However, genomic resources for these early branching angiosperm lineages are very limited. In this study, we describe the construction of a large-insert bacterial artificial chromosome (BAC) library from L. tulipifera. Flow cytometry estimates that this nuclear genome is approximately 1,802 Mbp per haploid genome (±16 SD). The BAC library contains 73,728 clones, a 4.8-fold genome coverage, with an average insert size of 117 kb, a chloroplast DNA content of 0.2%, and little to no bacterial sequences nor empty vector content clones. As a test of the utility of this BAC library, we screened the library with six single/low-copy genic probes. We obtained at least two positive clones for each gene and confirmed the clones by DNA sequencing. A total of 182 paired end sequences were obtained from 96 of the BAC clones. Using BLAST searches, we found that 25% of the BAC end sequences were similar to DNA sequences in GenBank. Of these, 68% shared sequence with transposable elements and 25% with genes from other taxa. This result closely reflected the content of random sequences obtained from a small insert genomic library for L. tulipifera, indicating that the BAC library construction process was not biased. The first genomic DNA sequences for Liriodendron genes are also reported. All the Liriodendron genomic sequences described in this paper have been deposited in the GenBank data library. The end sequences from shotgun genomic clones and BAC clones are under accession DU169330–DU169684. Partial sequences of Gigantea, Frigida, LEAFY, cinnamyl alcohol dehydrogenase, 4-coumarate:CoA ligase, and phenylalanine ammonia-lyase genes are under accession DQ223429–DQ223434. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Foliar physiology of yellow-poplar ( Liriodendron tulipifera L.) exposed to O3 and elevated CO2 over five seasons.

The chronic effects of ozone (O₃) alone or combined with elevated carbon dioxide (CO₂) on the foliar physiology of unfertilized field-grown yellow-poplar ( Liriodendron tulipifera L.) seedlings were studied from 1992 to 1996. Within open-top chambers, juvenile trees were exposed to the following: charcoal-filtered air (CF); 1× ambient ozone (1XO₃); 1.5× ambient ozone (1.5XO₃); 1.5× ambient ozone plus 700 ppm carbon dioxide (1.5XO₃+CO₂); or chamberless open-air (OA). Seasonal 24-h mean ambient O₃ concentrations ranged from 32 to 46 ppm over the five seasons. Averaged over 5 years, midseason net photosynthesis at saturating light ( A _sat) was reduced by 14% ( P =0.029) and stomatal conductance ( g _s) was reduced, albeit non-significant, by 13% ( P =0.096) in upper canopy foliage exposed to 1.5XO₃-air relative to CF controls. There were no significant differences over the 5 years in A _sat and g _s between trees grown in 1XO₃- and 1.5XO₃-air. Our results support the hypothesis that the magnitude of O₃ effects on A _sat and g _s decreases as saplings age. When averaged over the five seasons of exposure, total chlorophyll concentration ( chl) was not significantly affected by exposure to elevated O₃; however, in 1.5XO₃+CO₂-air, foliar chl was reduced by 33% relative to all others ( P <0.001). In 1.5XO₃+CO₂-air, A _sat was 1.4–1.9 times higher ( P <0.001) and g _s was 0.7 times lower ( P =0.022) than all others. O₃ uptake in juvenile trees exposed to elevated O₃ plus elevated CO₂ (1.5XO₃+CO₂-air) was most comparable to trees exposed to ambient air (1XO₃) throughout the study. These findings suggest that elevated CO₂ may minimize the negative effects of O₃ by reducing O₃ uptake through decreased stomatal conductance.     

Petiole mechanics, leaf inclination, morphology, and investment in support in relation to light availability in the canopy of Liriodendron tulipifera

To determine the role of leaf mechanical properties in altering foliar inclination angles, and the nutrient and carbon costs of specific foliar angle variation patterns along the canopy, leaf structural and biomechanical characteristics, biomass partitioning into support, and foliar nitrogen and carbon concentrations were studied in the temperate deciduous species Liriodendron tulipifera L., which possesses large leaves on long petioles. We used beam theory to model leaf lamina as a uniform load, and estimated both the lamina and petiole flexural stiffness, which characterizes the resistance to bending of foliar elements at a common load and length. Petiole and lamina vertical inclination angles with respect to horizontal increased with increasing average daily integrated photon flux density (Q_int). Yet, the light effects on lamina inclination angle were primary determined by the petiole inclination angle. Although the petioles and laminas became longer, and the lamina loads increased with increasing Q_int, the flexural stiffness of both lamina and petiole increased to compensate for this, such that the lamina vertical displacement was only weakly related to Q_int. In addition, increases and decreases in the petiole inclination angle with respect to the horizontal effectively reduced the distance of lamina load from the axis of rotation, thereby reducing the bending moments and lamina inclination due to gravity. We demonstrate that large investments, up to 30% of total leaf biomass, in petiole and large veins are necessary to maintain the lamina at a specific position, but also that light has no direct effect on the fractional biomass investment in support. However, we provide evidence that apart from light availability, structural and chemical characteristics of the foliage may also be affected by water stress, magnitude of which scales positively with Q_int.