The Influence of Moisture Stress on Liriodendron tulipifera L. Seedlings

A comparison of yellow poplar seedlings subjected to availablemoisture ranging from 100 per cent to 20 per cent of field capacityin two separate experiments (a soil study and a solution study)indicated that total dry matter production, stem height, totalleaf area and area of individual leaves, decreased with increasedmoisture stress. Differences in unit leaf rate (ULR) were primarilyresponsible for final plant size. Leaf area: weight ratio wasaffected by the method of induced stress. As stress increasedthe ratio increased in the soil study but decreased in the solutionstudy. The number of leaves produced was unaffected by stress,except at the most severe stresses. The number of senescentleaves increased as moisture stress increased. The allocationof new growth was unaffected by either moisture stress or timeand decreased in order of root, foliage, stem for the soil grownplants and foliage, root, stem for the solution grown plants.ULR and relative growth rate (RGR) were reduced by both moisturestress and time. A growth simulation of the soil-grown plantsbased on results from the solution moisture stress experimentpredicted the final plant dry weight within 12 per cent andleaf area within 7 per cent of the actual values.     

Growth Responses of Common Ash Seedlings (Fraxinus excelsior L.) to Total and Partial Defoliation

Common ash seedlings, grown in controlled conditions, were completelydefoliated 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 d afterthe completion of stem elongation. Complete defoliation up to80 d after the completion of stem elongation caused renewedgrowth of terminal buds. The buds had changed from a reversiblestate to an irreversible state by 80 d after the cessation ofstem elongation, as shown by the lack of response to defoliation.When leaves were removed before the cessation of stem elongation,rather than after, a similar enhancement of stem growth wasobserved. Partial defoliation experiments indicated that thedegree and location of defoliation play important roles in theplant response. Complete defoliation or complete removal ofleaflets was necessary to obtain 100% budburst. Apical dominancewas altered by partial defoliation treatments such that thebasal axillary buds began to grow out. Partial defoliation,especially before the cessation of stem elongation, was prejudicialto stem elongation. These results suggest that the inductionof compensatory growth mechanisms in ash seedlings require athreshold level of defoliation. Copyright 2000 Annals of BotanyCompany Fraxinus excelsior L., common ash, defoliation, growth, paradormancy     

Le carpelle du Tulipier (Liriodendron tulipifera L.)

Sans résumé     

升温情境中叶损对树木幼苗生长的影响

为探究升温能否在一定程度上抵消虫害叶损造成的负面影响,该研究采用控制变量法比较不同叶损程度下落叶松(Larix gmelinii)、红松(Pinus koraiensis)和冷杉(Abies fabri)幼苗当年的高生长以及来年不同温度下的萌芽情况。结果表明,当叶损程度达到50%时,落叶松幼苗当年的高生长会受到显著影响;而红松和冷杉在叶损程度达到75%时才会受到显著影响。室温下(13℃～18℃)落叶松来年的萌芽物候比20℃和25℃提前且高生长情况较好;红松和冷杉在室温下叶损75%会导致萌芽物候推迟且高生长受到影响,在20℃或25℃时,叶损造成的不利影响则会被削弱。因此,在未来变暖的情境中,推测红松和冷杉因虫害叶损造成的不利影响在一定程度上会被抵消,且对于虫害的抵抗和恢复亦明显高于落叶松。     

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.     

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.     

Ferroxidase activity in a laccase-like multicopper oxidase from Liriodendron tulipifera.

Ferroxidase activity was detected in a laccase-like multicopper oxidase (LMCO) produced in transgenic tobacco cells expressing an LMCO cDNA (Ltlacc2.2) cloned from yellow-poplar (Liriodendron tulipifera). This marks the first report of ferroxidase activity associated with a plant laccase and suggests that some members of this plant enzyme family may have physiological functions based on activities other than their more widely recognized phenoloxidase activity. Recent work with LMCOs from bacteria, yeast and mammals has shown that metal oxidase activities in these enzymes can be important for their primary physiological functions, With respect to ferroxidase activity in certain plant LMCOs, it is proposed that the high levels of LMCO expression in plant vascular tissues may reflect the need for high-efficiency iron uptake pumps in tissues that undergo lignification during normal development. Such iron uptake pumps would function to minimize levels of free iron so that reactive oxygen species do not reach toxic levels when H2O2 is generated for peroxidase-mediated monolignol coupling during lignin deposition.     

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.     

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     

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     

Liriodendronine,an oxoaporphine pigment from discolored sapwood of Liriodendron tulipifera

A new violet oxoaporphine alkaloid. liriodendronine, has been isolated from the discolored sapwood of Liniodendron tulipifera and its structure determined by spectroscopic methods and by conversion into a corunnine-type compound, 2-O,N-dimethylliriodendronine. UV studies demonstrated that the compound exists primarily as a quinone-methide in a neutral medium, a dianion in base, an isoquinolinium ion in weak acid, and as an antiaromatic conjugate acid in conc H₂SO₄.     

二氢血根碱对莴苣幼苗根生长及其细胞分裂的影响

以莴苣幼苗为受体,用培养皿法检测从细果角茴香中分离得到的二氢血根碱对莴苣幼苗根生长和根毛发育的影响,并采用根尖细胞有丝分裂检测和单细胞凝胶电泳法对其可能的作用机制进行了初步研究.结果显示:较低浓度(25、50μmol/L)二氢血根碱能显著促进莴苣根的生长,较高浓度(200、300μmol/L)二氢血根碱显著抑制根的生长;二氢血根碱(10、20、30、40、50μmol/L)对莴苣幼苗根毛发育有极显著的抑制作用,且两者均表现了浓度依赖性.较低浓度(25、50μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著增加,而对根尖细胞DNA没有显著影响;较高浓度(200、300μmol/L)二氢血根碱使根尖细胞有丝分裂指数显著下降,同时根尖细胞DNA受到显著性损伤.研究发现,低浓度的二氢血根碱对莴苣幼苗根生长的促进作用主要是由于根尖细胞有丝分裂活力增加所致;而高浓度二氢血根碱对莴苣幼苗根的抑制作用极可能是由于根尖细胞DNA受到损伤,使得细胞分裂活力降低,分裂期细胞数目减少,从而导致根生长受到抑制.     

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.     

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.