| biochemical model reactions indicative of inflammatory processes. activities of extracts from fraxinus excelsior and populus tremula. | all processes of oxygen activation include very reactive intermediates. therefore, aerobic cells must cope with--and to some extent also adapt to--oxidative stress provoked for example by infections or intoxications, where these reactive intermediates accumulate. all inflammatory processes include such oxygen activating processes where reactive oxygen species (ros) are produced. dependent on the strength of these impact(s), several symptoms indicate the deviation from normal, steady-state metabo ... | 2000 | 10800635 |
| expression of a conifer glutamine synthetase gene in transgenic poplar | the assimilation of ammonium into organic nitrogen catalyzed by the enzyme glutamine synthetase (gs; ec 6.3.1.2) has been suggested to be the limiting step for plant nitrogen utilization (h-m. lam et al. 1995, plant cell 7: 887-898). we have developed a molecular approach to increase glutamine production in transgenic poplar by the overexpression of a conifer gs gene. a chimeric construct consisting of the cauliflower mosaic virus 35s promoter fused to pine cytosolic gs cdna and nopaline synthet ... | 1999 | 10592028 |
| responses of foliar photosynthetic electron transport, pigment stoichiometry, and stomatal conductance to interacting environmental factors in a mixed species forest canopy. | we studied limitations caused by variations in leaf temperature and soil water availability on photosynthetic electron transport rates calculated from foliar chlorophyll fluorescence analysis (u) in a natural deciduous forest canopy composed of shade-intolerant populus tremula l. and shade-tolerant tilia cordata mill. in both species, there was a positive linear relationship between light-saturated u (umax) per unit leaf area and mean seasonal integrated daily quantum flux density (ss, mol per s ... | 1999 | 10562401 |
| air-pollutant dispersal patterns and vegetation damage in the vicinity of three aluminium smelters in norway. | dispersal patterns for fluoride and damage to vegetation was studied near three aluminium smelters in norway. leaf samples from three broad-leaved species (betula pubescens ehrh., salix caprea l. and sorbus aucuparia l.) were collected and leaf injury and the plants overall vitality were evaluated systematically in areas with different distance and direction from the emission sources. both dispersal patterns and the distribution of damages were mainly determined by the predominant wind direction ... | 1999 | 10535145 |
| variability in leaf morphology and chemical composition as a function of canopy light environment in coexisting deciduous trees. | morphology, chemical composition, and photosynthetic capacity of leaf laminas were investigated in populus tremula l. and tilia cordata mill. along a canopy light gradient. variables determining the thickness of boundary layer for heat and water exchange at a given wind speed-effective leaf width (ww) and length (wd)-scaled positively with daily integrated quantum flux density averaged over the season (qint, mol m-2 d-1) in t. cordata, but wd decreased and ww was constant with increasing qint in ... | 1999 | 10506464 |
| [pharmacological and clinical effectiveness of a fixed phytogenic combination trembling poplar (populus tremula), true goldenrod (solidago virgaurea) and ash (fraxinus excelsior) in mild to moderate rheumatic complaints]. | besides the well-known nonsteroidal antiinflammatory drugs (nsaid) for the treatment of rheumatic pain herbal medicine can also be applied successfully. plants with antirheumatic efficacy include fraxini cortex, populi cortex/folia and solidaginis herba. this review focuses on pharmacological and clinical efficacy of a combination of fraxinus cortex, populus cortex/folia and solidago herba. antiinflammatory and analgetic properties were shown in pharmacological tests. clinical studies conducted ... | 1999 | 10483692 |
| gene stability in transgenic aspen (populus). i. flanking dna sequences and t-dna structure. | the stability of transgenes in the genome of transformed plants depends strongly on their correct physical integration into the host genome as well as on flanking target dna sequences. for long-lived species like trees, however, no information is available so far concerning inactivation or loss of transgenes due to gene silencing or somatic genome rearrangement events. in this study, four independently transformed 35s-rolc transgenic hybrid aspen plants (populus tremula l. x tremuloides michx.), ... | 1999 | 9928937 |
| molecular characterisation of a novel plant homeobox gene expressed in the maturing xylem zone of populus tremula x tremuloides. | in trees, wood is produced from the vascular cambium. however, little is known about how differentiation of the cambial derivatives is controlled at the molecular level. hybrid aspen, populus tremula x tremuloides, is a fast-growing, wood-forming plant from which an efficient transformation and regeneration protocol has been developed. we use this species as a model to study xylem cell differentiation. in a cross-section of the stem, cells in the cambial region at different stages of development ... | 1998 | 9881151 |
| structural alterations of lignins in transgenic poplars with depressed cinnamyl alcohol dehydrogenase or caffeic acid o-methyltransferase activity have an opposite impact on the efficiency of industrial kraft pulping | we evaluated lignin profiles and pulping performances of 2-year-old transgenic poplar (populus tremula x populus alba) lines severely altered in the expression of caffeic acid/5-hydroxyferulic acid o-methyltransferase (comt) or cinnamyl alcohol dehydrogenase (cad). transgenic poplars with cad or comt antisense constructs showed growth similar to control trees. cad down-regulated poplars displayed a red coloration mainly in the outer xylem. a 90% lower comt activity did not change lignin content ... | 1999 | 9880356 |
| gene discovery in the wood-forming tissues of poplar: analysis of 5, 692 expressed sequence tags. | a rapidly growing area of genome research is the generation of expressed sequence tags (ests) in which large numbers of randomly selected cdna clones are partially sequenced. the collection of ests reflects the level and complexity of gene expression in the sampled tissue. to date, the majority of plant ests are from nonwoody plants such as arabidopsis, brassica, maize, and rice. here, we present a large-scale production of ests from the wood-forming tissues of two poplars, populus tremula l. x ... | 1998 | 9789088 |
| manipulation of glutathione and amino acid biosynthesis in the chloroplast | poplars (populus tremula x populus alba) were transformed to overexpress escherichia coli gamma-glutamylcysteine synthetase (gamma-ecs) or glutathione synthetase in the chloroplast. five independent lines of each transformant strongly expressed the introduced gene and possessed markedly enhanced activity of the gene product. glutathione (gsh) contents were unaffected by high chloroplastic glutathione synthetase activity. enhanced chloroplastic gamma-ecs activity markedly increased gamma-glutamyl ... | 1998 | 9765532 |
| immunolocalization of cinnamyl alcohol dehydrogenase 2 (cad 2) indicates a good correlation with cell-specific activity of cad 2 promoter in transgenic poplar shoots. | cinnamyl alcohol dehydrogenase 2 (cad 2) localization and the cell-specific activity of the eucalyptus cad 2 promoter were investigated by cad 2 immunogold localization and promoter beta-glucuronidase (gus) histochemistry in apical and mature parts of stable transformed poplar (populus tremula x p. alba) stems. both cad 2 protein and gus activity were found to be confined in the same types of cells in the shoot apices, particularly in the determined meristematic cells in leaf axils and shell zon ... | 1998 | 9684367 |
| characterization of acetylated 4-o-methylglucuronoxylan isolated from aspen employing 1h and 13c nmr spectroscopy. | water-soluble hemicelluloses were extracted from milled aspen wood (populus tremula) employing microwave oven treatment at 180 degrees c for 10 min. the final ph of this extract was 3.5. from this extract oligo- and polysaccharides were isolated and subsequently fractionated by size-exclusion chromatography. the structures of the saccharides in three of the fractions obtained were determined by 1h and 13c nmr spectroscopy, using homonuclear and heteronuclear two-dimensional techniques. the polys ... | 2000 | 11125823 |
| modification of thiol contents in poplars (populus tremula x p. alba) overexpressing enzymes involved in glutathione synthesis. | the hybrid poplar (populus tremula x p. alba) was transformed to express the escherichia coli gene for gamma-glutamylcysteine synthetase (ec 6.3.2.2: gamma-ecs) in the cytosol. four transformed lines of poplar were obtained. these were phenotypically indistinguishable from untransformed poplars. three lines, ggs28 (noctor et al. 1996, plant physiol 112: 1071-1078), ggs11 and ggs5 possessed high levels of bacterial gene transcripts. line ggs17 had lower transcript levels. antisera were prepared a ... | 1997 | 9431683 |
| [an experimental study of the anti-ulcer properties of an extract of poplar bark]. | marked antiulcerative properties of a populus tremula bark extract were demonstrated in experiments on mice and rats with stress-, reserpine-induced, and acetylsalicylic ulcers. the gastroprotective activity of the extract was expressed in decrease in the number of animals with mucosal ulcers and in marked decrease in the number of ulcers. it exceeded similar parameters of alanton, plantaglucide, and hippopheae oil. | 1997 | 9376756 |
| molecular cloning and biochemical characterization of carbonic anhydrase from populus tremula x tremuloides. | a leaf cdna library from hybrid aspen, populus tremula x tremuloides, was constructed. from this two different cdna clones, denoted ca1a and ca1b, encoding a chloroplastic carbonic anhydrase (ca) were isolated and dna sequenced. analysis of the deduced amino acid sequences showed that the isolated cas belong to the beta-ca family, and have identities around 70% to other dicotyledonous plant cas. the two hybrid aspen cdna clones display a high nucleotide sequence identity, only 12 nucleotides dif ... | 1997 | 9247540 |
| effects of extracts from populus tremula l., solidago virgaurea l. and fraxinus excelsior l. on various myeloperoxidase systems. | extracts from populus tremula, solidago virgaurea and fraxinus excelsior are used as anti-inflammatory drugs. the effects of these extracts on myeloperoxidase (mpo), an enzyme liberated by activated granulocytes and known to produce the destructive agent hypochloric acid, were investigated. populus and fraxinus inhibited this enzyme, solidago was without effect. these results were obtained concordantly with four different mpo-assays (h2o2/mpo; x/xod/mpo; activated pmn; and elastase/alpha 1-pi-mp ... | 1996 | 9125284 |
| overexpression of glutathione reductase but not glutathione synthetase leads to increases in antioxidant capacity and resistance to photoinhibition in poplar trees. | a poplar hybrid, populus tremula x populus alba, was transformed with the bacterial genes for either glutathione reductase (gr) (gor) or glutathione synthetase (gs) (gshii). when the gor gene was targeted to the chloroplasts, leaf gr activities were up to 1000 times greater than in all other lines. in contrast, targeting to the cytosol resulted in 2 to 10 times the gr activity. gr mrna, protein, and activity levels suggest that bacterial gr is more stable in the chloroplast. when the gshii gene ... | 1995 | 8552710 |
| cinnamrutinoses a and b, glycosides of populus tremula. | the cinnamylrutinosides, cinnamrutinoses a and b, were isolated along with known phenolic glucosides, from the stem bark of populus tremula infected with the pathogenic fungus hypoxylon mammatum. the structures were determined from spectroscopic and chemical evidence. | 1994 | 7764484 |
| antioxidative properties of alcoholic extracts from fraxinus excelsior, populus tremula and solidago virgaurea. | aqueous-ethanolic extracts from fraxinus excelsior, populus tremula and solidago virgaurea inhibit biochemical model reactions representing inflammatory situations to various extents. these model reactions include xanthine oxidase, diaphorase in the presence of the autoxidizable quinone juglone, lipoxygenase and photodynamic reactions driven by riboflavin or rose bengal. the tested extracts are the components of the phytomedicine phytodolor n (abbreviated as pd) which possesses antipyretic, anal ... | 1995 | 7710443 |
| inhibition of dihydrofolate reductase activity by alcoholic extracts from fraxinus excelsior, populus tremula and solidago virgaurea. | aqueous-ethanolic extracts of fraxinus excelsior, populus, tremula and solidago virgaurea in a combination of 1: 3: 1 (v/v/v) are the components of the plant drug phytodolor n (abbreviated as pd), which exhibits antipyretic, analgesic and antirheumatic activity. similar to a broad variety of synthetic non-steroidal anti-inflammatories the mentioned plant extracts inhibit dihydrofolate reductase. the following concentrations as percentage in the test volumes represent the individual i50-values: f ... | 1995 | 7710442 |
| a combination of populus tremula, solidago virgaurea and fraxinus excelsior as an anti-inflammatory and antirheumatic drug. a short review. | anti-inflammatory properties of populus tremula are mainly deduced from its components, the well investigated salicylates. solidago extracts have spasmolytic, antihypertensive and diuretic effects. fraxinus excelsior itself has hardly been investigated, but its coumarin components proved to have a variety of pharmacological properties, i.e. inhibition of t-cell activation and of the arachidonic acid cascade. phytodolor n (abbreviated as pd) is a combination of the above mentioned plants. various ... | 1995 | 7710441 |
| the separation of phenolic glucosides and carbohydrates from the bark of populus tremula by gel filtration. | | 1968 | 5659008 |
| [anti-inflammatory, analgesic and antipyretic effect of various plant extracts and their combinations in an animal model]. | antiinflammatory, analgesic and antipyretic effects of various plant extracts and a combination thereof in animal models. the three main components comprising the efficacy of non-steroidal antiinflammatory drugs could be demonstrated for stw 1 in different animal models. the phytotherapeutic preparation, containing three individual plant extracts (populus tremula, solidago virgaurea, fraxinus excelsior) produced dose-dependent antiinflammatory, analgesic and antipyretic effects which were simila ... | 1989 | 2476136 |
| an alternative approach for gene transfer in trees using wild-type agrobacterium strains. | micropropagated shoots of three forest tree species, poplar (populus tremula x p. alba), wild cherry (prunus avium l.) and walnut (juglans nigra x j. regia), were inoculated each with six different wild-type agrobacterium strains. poplar and wild cherry developed tumors that grew hormone-independently, whereas on walnut, gall formation was weak. on poplar and wild cherry, tumors induced by nopaline strains developed spontaneously shoots that had a normal phenotype and did not carry oncogenic t-d ... | 1991 | 1653060 |
| study of the anti-inflammatory activity of populus tremula, solidago virgaurea and fraxinus excelsior. | aqueous/alcoholic extracts of populus tremula, solidago virgaurea and fraxinus excelsior (components of phytodolor n) were tested individually and in 3 different combinations for anti-inflammatory activity using carrageenan induced edema and/or adjuvant induced arthritis of the rat paw. the tested combinations as well as the individual extracts significantly reduced the paw edema to varying degrees and also dose dependently inhibited the arthritic paw volume. the anti-inflammatory activity of th ... | 1992 | 1497695 |
| differential localization of arabinan and galactan side chains of rhamnogalacturonan 1 in cambial derivatives. | the development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen (populus tremula l. x p. tremuloides michx.) using biochemical and immunocytochemical methods. comparisons were also made between active and resting tissues. active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. use of antibodies raised against arabinan side chains of rhamnogalacturonan 1 (lm6), as well as biochemical ... | 2000 | 10805444 |
| cambial-region-specific expression of the agrobacterium iaa genes in transgenic aspen visualized by a linked uida reporter gene. | the level of indole-3-acetic acid (iaa) was locally modified in cambial tissues of transgenic aspen (populus tremula l. x populus tremuloides michx.). we also demonstrate the use of a linked reporter gene to visualize the expression of the iaa genes. the rate-limiting bacterial iaa-biosynthetic gene iaam and the reporter gene for beta-glucuronidase (gus), uida, were each fused to the cambial-region-specific agrobacterium rhizogenes rolc promoter and linked on the same t-dna. in situ hybridizatio ... | 2000 | 10859183 |
| increased gibberellin biosynthesis in transgenic trees promotes growth, biomass production and xylem fiber length. | in most tree-breeding programs worldwide, increasing the trees' growth rates and stem volumes and shortening their rotation times are important aims. such trees would yield more biomass per unit area. here we show that overexpressing a key regulatory gene in the biosynthesis of the plant hormone gibberellin (ga) in hybrid aspen (populus tremula x p. tremuloides) improves growth rate and biomass. in addition, these transgenic trees have more numerous and longer xylem fibers than unmodified wild-t ... | 2000 | 10888850 |
| cell-specific and conditional expression of caffeoyl-coenzyme a-3-o-methyltransferase in poplar. | caffeoyl coenzyme a-3-o-methyltransferase (ccoaomt) plays an important role in lignin biosynthesis and is encoded by two genes in poplar (populus trichocarpa). here, we describe the expression pattern conferred by the two ccoaomt promoters when fused to the gus-coding sequence in transgenic poplar (populus tremula x populus alba). both genes were expressed similarly in xylem and differentially in phloem. in xylem, expression was preferentially observed in vessels and contact rays, whereas expres ... | 2000 | 10889235 |
| lignification in transgenic poplars with extremely reduced caffeic acid o-methyltransferase activity. | transgenic poplars (populus tremula x populus alba) were obtained by introduction of a sense homologous transgene encoding caffeic acid o-methyltransferase (comt) under the control either of the cauliflower mosaic virus double 35s promoter or of the eucalyptus cinnamyl alcohol dehydrogenase promoter. although these constructs conferred a moderate overexpression of comt in some lines, a transgenic line with the double 35s promoter was found where comt activity in woody tissues was close to zero d ... | 2000 | 10938354 |
| leaf age-dependent differences in sulphur assimilation and allocation in poplar (populus tremula x p. alba) leaves. | 35s-sulphate was flap-fed to poplar leaves of different leaf development stages - young developing, expanding, mature, and old mature poplar leaves. (35)s-sulphate was taken up independent of the leaf development stage. whereas young development leaves did not export the (35)s taken up, export increased with increasing leaf development stage. expanding leaves allocated the exported (35)s mainly into apical tree parts (73-87%) and only to a minor extent (13-27%) in basipetal direction. neither lo ... | 2000 | 10948235 |
| radial distribution pattern of pectin methylesterases across the cambial region of hybrid aspen at activity and dormancy. | biochemical microanalysis combined with tangential cryosectioning was used to visualize the distribution of pectin methylesterases (pmes) across the cambial region in active and dormant hybrid aspen (populus tremula l. x populus tremuloides michx). these novel techniques allowed us to relate activity and isoforms of pmes to specific tissues and developmental stages of the stem to get more information on the physiological function of pmes in cambial growth. isoelectrofocusing analysis revealed nu ... | 2000 | 10982434 |
| regulation of sulfur nutrition in wild-type and transgenic poplar over-expressing gamma-glutamylcysteine synthetase in the cytosol as affected by atmospheric h2s. | this study with poplar (populus tremula x populus alba) cuttings was aimed to test the hypothesis that sulfate uptake is regulated by demand-driven control and that this regulation is mediated by phloem-transported glutathione as a shoot-to-root signal. therefore, sulfur nutrition was investigated at (a) enhanced sulfate demand in transgenic poplar over-expressing gamma-glutamylcysteine (gamma-ec) synthetase in the cytosol and (b) reduced sulfate demand during short-term exposure to h2s. h(2)s t ... | 2000 | 10982459 |
| essential role of caffeoyl coenzyme a o-methyltransferase in lignin biosynthesis in woody poplar plants. | caffeoyl coenzyme a o-methyltransferase (ccoaomt) has recently been shown to participate in lignin biosynthesis in herbacious tobacco plants. here, we demonstrate that ccoaomt is essential in lignin biosynthesis in woody poplar (populus tremula x populus alba) plants. in poplar stems, ccoaomt was found to be expressed in all lignifying cells including vessel elements and fibers as well as in xylem ray parenchyma cells. repression of ccoaomt expression by the antisense approach in transgenic popl ... | 2000 | 11027707 |
| activation of cdk-activating kinase is dependent on interaction with h-type cyclins in plants. | cdnas encoding cyclin h homologs were isolated from poplar (populus tremula x tremuloides) and rice (oryza sativa) plants, and were designated pt;cych;1 and os;cych;1, respectively. the deduced amino-acid sequences showed 40-60% similarity to human cyclin h and schizosaccharomyces pombe mcs2, with higher similarity in the cyclin box region. while pt;cych;1 and os;cych;1 were expressed in all tissues examined, the transcripts accumulated abundantly in dividing cells. expression of os;cych;1 was a ... | 2000 | 11029700 |
| [effect of the dry aspen bark extract on the gastric secretory function]. | dry aspen (populus tremula l.) bark extract exhibits antiulcerogenic activity as demonstrated by the results of experiments using the models of gastric ulcers in rats according to h. shay. the cytoprotective action of the dry aspen bark extract was also demonstrated in experiments on dogs with fistula according to basov. | 2000 | 11109522 |
| microautoradiographic localization of phosphate and carbohydrates in mycorrhizal roots of populus tremula x populus alba and the implications for transfer processes in ectomycorrhizal associations. | microautoradiographic studies were carried out to examine the distribution and exchange of phosphate and labeled carbohydrates in mycorrhizal roots of populus tremula x populus alba l. following application of 33p-orthophosphate (pi) and 14co2. labeled pi was not homogeneously distributed along the mycorrhizal longitudinal axis. the fungal sheath and the hartig net contained more 33pi in the median parts of the root than in the apical or basal root zones, indicating that uptake and transfer of p ... | 2001 | 11303640 |
| population genetics of chrysomela tremulae: a first step towards management of transgenic bacillus thuringiensis poplars populus tremula x .p. tremuloides. | many strategies have been proposed for delaying the development of insect resistance to bacillus thuringiensis (bt). the current paradigm for bt resistance management is the high dose-refuge strategy. for this strategy to be successful: (i) heterozygotes must be killed in treated areas, (ii) resistant alleles must be rare (frequency < 10-3), and (iii) there must be a high level of gene flow between populations to ensure random mating. we studied gene flow within and between populations with a vi ... | 2000 | 11338433 |
| a small family of novel cuzn-superoxide dismutases with high isoelectric points in hybrid aspen. | several cuzn-superoxide dismutases (sods; ec 1.15.1.1) were cloned from hybrid aspen (populus tremula l. x tremuloides michx.). two of the cloned genes encode representatives of a novel type of cuzn-sod and we named it hipi-sod because of its high isoelectric point (> or =9). the sods were cloned by screening a cdna library with a probe based on a scots pine (pinus sylvestris l.) cuzn-sod that is predominantly located extracellularly. the expression pattern of hipi-sod was examined using a north ... | 2001 | 11469593 |
| sensitivity of photosynthetic electron transport to photoinhibition in a temperate deciduous forest canopy: photosystem ii center openness, non-radiative energy dissipation and excess irradiance under field conditions. | we used chlorophyll fluorescence techniques to investigate responses of photosystem ii (psii) quantum yield to light availability in the short term (quantum flux density integrated over the measurement day, qd) and in the long term (qd averaged over the season, qs) in a mixed deciduous forest comprising shade-tolerant and water-stress-sensitive tilia cordata mill. in the lower canopy and shade-intolerant and water-stress-resistant populus tremula l. in the upper canopy. in both species, intrinsi ... | 2001 | 11498337 |
| first isolation of an isoprene synthase gene from poplar and successful expression of the gene in escherichia coli. | for the first time, the complete functional gene for isoprene synthase has been isolated from poplar (populus alba x populus tremula). the gene was quite similar to known limonene and other monoterpene synthases, but was found to specifically catalyze the formation of isoprene from the precursor dimethylallyl diphosphate with only a marginal activity for the formation of the monoterpene limonene from geranyl diphosphate as compared with limonene synthases. omitting the part of the gene that puta ... | 2001 | 11506373 |
| cellulose in cyanobacteria. origin of vascular plant cellulose synthase? | although cellulose biosynthesis among the cyanobacteria has been suggested previously, we present the first conclusive evidence, to our knowledge, of the presence of cellulose in these organisms. based on the results of x-ray diffraction, electron microscopy of microfibrils, and cellobiohydrolase i-gold labeling, we report the occurrence of cellulose biosynthesis in nine species representing three of the five sections of cyanobacteria. sequence analysis of the genomes of four cyanobacteria revea ... | 2001 | 11598227 |
| gene stability in transgenic aspen (populus). ii. molecular characterization of variable expression of transgene in wild and hybrid aspen. | in many annual plant species, transgene inactivation occurs most often when multiple incomplete/complete copies of the transgene are present in a genome. the expression of single-copy transgene loci may also be negatively influenced by the flanking plant dna and/or chromosomal location (position effect). to understand transgene silencing in a long-lived tree system, we analyzed several wild (populus tremula l.) and hybrid (p. tremula l. x p. tremuloides michx.) aspen lines transgenic to the rolc ... | 2001 | 11678277 |
| the cytoskeleton facilitates a three-dimensional symplasmic continuum in the long-lived ray and axial parenchyma cells of angiosperm trees. | the microtubule (mt), microfilament (mf) and myosin components of the cytoskeleton were studied in the long-lived ray and axial parenchyma cells of the secondary xylem (wood) and secondary phloem of two angiosperm trees, aesculus hippocastanum l. (horse-chestnut) and populus tremula l. x p. tremuloides michx. (hybrid aspen), using indirect immunofluorescence localisation and transmission electron microscopy. mts and mfs were bundled and oriented axially (parallel to the cell's long axis) within ... | 2001 | 11678287 |
| bacterial disease resistance of transgenic hybrid poplar expressing the synthetic antimicrobial peptide d4e1. | important losses in poplar productivity occur because of susceptibility to microbial pathogens. to enhance disease resistance in susceptible genotypes, the gene coding for d4e1, a synthetic antimicrobial peptide consisting of 17 amino acid residues, was introduced into poplar (populus tremula l. x populus alba l.) via agrobacterium-mediated transformation. four kanamycin-resistant transformants were selected based on significant accumulation of the d4e1 transcript and confirmed by reverse transc ... | 2003 | 12642242 |
| [neural network based on modified simplex method and its application in studying forest self-thinning]. | the mechanism of forest self-thinning is generally nonlinear and dynamic, and the artificial neural network has the characteristic of expressing arbitrary nonlinear mapping. in this paper, the feasibility and limitation of artificial neural network used to simulating forest self-thinning was expounded, and the principle and algorithms of the neural network model based on modified simplex method (bp-msm mixed algorithms) for modeling forest self-thinning were described. its applications in self-t ... | 2000 | 11767515 |
| understanding the role of the cytoskeleton in wood formation in angiosperm trees: hybrid aspen (populus tremula x p. tremuloides) as the model species. | the involvement of microfilaments and microtubules in the development of the radial and axial components of secondary xylem (wood) in hybrid aspen (populus tremula l. x p. tremuloides michx.) was studied by indirect immunofluorescent localization techniques. in addition to cambial cells, the differentiated cell types considered were early- and late-wood vessel elements, axial parenchyma, normal-wood fibers and gelatinous fibers, and contact and isolation ray cells. microfilaments were rare in ra ... | 2002 | 11874720 |
| rate of stomatal opening, shoot hydraulic conductance and photosynthetic characteristics in relation to leaf abscisic acid concentration in six temperate deciduous trees. | correlations between leaf abscisic acid concentration ([aba]), stomatal conductance (gs), rate of stomatal opening in response to an increase in leaf water potential (si), shoot hydraulic conductance (l) and photosynthetic characteristics were examined in saplings of six temperate deciduous tree species: acer platanoides l., padus avium mill., populus tremula l., quercus robur l., salix caprea l. and tilia cordata mill. species-specific values of foliar [aba] were negatively related to the mean ... | 2002 | 11874723 |
| molecular cloning and characterization of a cdna encoding poplar udp-glucose dehydrogenase, a key gene of hemicellulose/pectin formation. | plant udp-glucose dehydrogenase (ugdh) is an important enzyme in the formation of hemicellulose and pectin, the components of newly formed cell walls. a cdna clone (ugdh) corresponding to ugdh was isolated from a cdna library prepared from cambial zone of poplar (populus tremula x tremuloides). within the 1824-nucleotide (nt)-long clone, an open reading frame encoded a protein of 481 amino acids (aa), with a calculated molecular weight of 53.1 kda. the derived aa sequence showed 90% and 63% iden ... | 2002 | 12031484 |
| far red end-of-day treatment restores wild type-like plant length in hybrid aspen overexpressing phytochrome a. | shoot elongation in woody plants is modulated by a multitude of light signals, including irradiance, photoperiod and spectral composition, for which the phytochrome system is the probable photoreceptor. in hybrid aspen (populus tremula x tremuloides) overexpression of the oat phytochrome a (phya) prevents growth cessation in response to short photoperiod, and plants exhibit dwarf growth that is related to reduced cell numbers and reduced gibberellin contents. end-of-day far-red treatment signifi ... | 2002 | 12081538 |
| partitioning of nitrate assimilation among leaves, stems and roots of poplar. | plants differ in tissue localization of nitrate reduction and assimilation. some species reduce nitrate primarily in the leaves, whereas other species localize nitrate reduction and assimilation in the roots. we determined how nitrate assimilation is partitioned among leaves, stems and roots of poplar (populus tremula l. x p. alba l.) by comparing tissue differences in in vivo nitrate reductase activity (nra), nitrate reductase abundance and tissue nitrate concentration. compared with stems or r ... | 2002 | 12091153 |
| independent activation of cold acclimation by low temperature and short photoperiod in hybrid aspen. | temperate zone woody plants cold acclimate in response to both short daylength (sd) and low temperature (lt). we were able to show that these two environmental cues induce cold acclimation independently by comparing the wild type (wt) and the transgenic hybrid aspen (populus tremula x populus tremuloides michx.) line 22 overexpressing the oat (avena sativa) phytochrome a gene. line 22 was not able to detect the sd and, consequently, did not stop growing in sd conditions. this resulted in an impa ... | 2002 | 12177476 |
| environmental and auxin regulation of wood formation involves members of the aux/iaa gene family in hybrid aspen. | indole acetic acid (iaa/auxin) profoundly affects wood formation but the molecular mechanism of auxin action in this process remains poorly understood. we have cloned cdnas for eight members of the aux/iaa gene family from hybrid aspen (populus tremula l. x populus tremuloides michx.) that encode potential mediators of the auxin signal transduction pathway. these genes designated as pttiaa1-pttiaa8 are auxin inducible but differ in their requirement of de novo protein synthesis for auxin inducti ... | 2002 | 12220260 |
| a radial concentration gradient of indole-3-acetic acid is related to secondary xylem development in hybrid aspen. | the radial distribution pattern of indole-3-acetic acid (iaa) was determined across the developing tissues of the cambial region in the stem of hybrid aspen (populus tremula l. x populus tremuloides michx). iaa content was measured in consecutive tangential cryo-sections using a microscale mass spectrometry technique. analysis was performed with wild-type and transgenic trees with an ectopic expression of agrobacterium tumefaciens iaa-biosynthetic genes. in all tested trees iaa was distributed a ... | 1997 | 12223825 |
| expression of the agrobacterium rhizogenes rolc gene in a deciduous forest tree alters growth and development and leads to stem fasciation. | we have altered the growth and development of a deciduous forest tree by transforming hybrid aspen (populus tremula x populus tremuloides) with the agrobacterium rhizogenes rolc gene expressed under the strong cauliflower mosaic virus 35s promoter. we demonstrate that the genetically manipulated perennial plants, after a period of dormancy, maintain the induced phenotypical changes during the second growing period. furthermore, mass-spectrometrical quantifications of the free and conjugated form ... | 1996 | 12226405 |
| synthesis of glutathione in leaves of transgenic poplar overexpressing [gamma]-glutamylcysteine synthetase. | internode stem fragments of the poplar hybrid populus tremula x populus alba were transformed with a bacterial gene (gshl) for [gamma]-glutamylcysteine synthetase ([gamma]-ecs) targeted to the cytosol. lines overexpressing [gamma]-ecs were identified by northern analysis, and the transformant with the highest enzyme activity was used to investigate the control of glutathione synthesis. whereas foliar [gamma]-ecs activity was below the limit of detection in untransformed plants, activities of up ... | 1996 | 12226433 |
| red xylem and higher lignin extractability by down-regulating a cinnamyl alcohol dehydrogenase in poplar. | cinnamyl alcohol dehydrogenase (cad) catalyzes the last step in the biosynthesis of the lignin precursors, the monolignols. we have down-regulated cad in transgenic poplar (populus tremula x populus alba) by both antisense and co-suppression strategies. several antisense and sense cad transgenic poplars had an approximately 70% reduced cad activity that was associated with a red coloration of the xylem tissue. neither the lignin amount nor the lignin monomeric composition (syringyl/guaiacyl) wer ... | 1996 | 12226459 |
| altered growth and wood characteristics in transgenic hybrid aspen expressing agrobacterium tumefaciens t-dna indoleacetic acid-biosynthetic genes. | a key regulator of cambial growth is the plant hormone indoleacetic acid (iaa). here we report on altered wood characteristics and growth patterns in transgenic hybrid aspen (populus tremula l. x populus tremuloides michx.) expressing agrobacterium tumefaciens t-dna iaa-biosynthetic iaam and iaah genes. eighteen lines simultaneously expressing both genes were regenerated. of these, four lines, verified to be transgenic by northern blot analysis, were selected and raised under controlled growth c ... | 1995 | 12228661 |
| a novel metabolic pathway for indole-3-acetic acid in apical shoots of populus tremula (l.) x populus tremuloides (michx.). | metabolism of indole-3-acetic acid (iaa) in apical shoots of populus tremula (l.) x populus tremuloides (michx.) was investigated by feeding a mixture of [12c]iaa, [13c6]iaa, and [1[prime]-14c]iaa through the base of the excised stem. hplc of methanolic plant extracts revealed eight major radiolabeled metabolites after a 24-h incubation period. comparison between feeds with [5-3h]iaa and [1[prime]-14c]iaa showed that all detectable metabolites were nondecarboxylative products. the purified radio ... | 1994 | 12232425 |
| the vascular expression pattern directed by the eucalyptus gunnii cinnamyl alcohol dehydrogenase egcad2 promoter is conserved among woody and herbaceous plant species. | cinnamyl alcohol dehydrogenase (cad; ec 1.1.1.195) catalyses the last step in the synthesis of the monomeric precursors of lignin. here, we demonstrate that the vascular expression pattern conferred by the eucalyptus gunnii egcad2 promoter in transgenic poplar (populus tremula x populus alba) is conserved in another perennial woody angiosperm of economic interest (vitis vinifera l.), as well as in a model herbaceous plant (nicotiana tabacum l.). furthermore, promoter deletion analysis performed ... | 2002 | 12369625 |
| root aeration in wetland trees by pressurized gas transport. | tracer gas studies and oxygen uptake measurements have shown that pressurized gas transport improves oxygen supply to roots in the wetland tree species taxodium distichum l. rich. (taxodiaceae), betula pubescens j.f. ehrh. (betulaceae), and populus tremula l. (salicaceae), but not in acer pseudoplatanus l. and ilex aquifolium l., which are found in drier habitats. in the deciduous tree species betula pubescens and populus tremula, pressurized gas transport was most evident during the resting per ... | 1992 | 14969985 |
| characterization of sp1, a stress-responsive, boiling-soluble, homo-oligomeric protein from aspen. | sp1 cdna was isolated from aspen (populus tremula) plants by immunoscreening an expression library using polyclonal antibodies against bspa protein. bspa, which is a boiling-stable protein, accumulates in aspen plants in response to water stress and abscisic acid application (pelah et al., 1995). the sp1 cdna was found to encode a 12.4-kd generally hydrophilic protein with a hydrophobic c terminus, which is different from the bspa protein and was termed sp1 (stable protein 1). northern-blot anal ... | 2002 | 12376651 |
| host-associated allozyme variation in tree cambium miners, phytobia spp. (diptera: agromyzidae). | the larvae of the agromyzid flies that belong to the genus phytobia lioy feed by mining in the differentiating xylem just below the cambium of growing forest trees. the genus, which is apparently one of the most primitive groups in the agromyzidae, comprises over 50 currently recognized species. most of the species are mono- or oligophagous, and the host plants belong to numerous genera in about 60 families. thus, phytobia is an attractive candidate for studies on the evolution of insect-plant r ... | 2002 | 12399999 |
| shoot structure and growth along a vertical profile within a populus-tilia canopy. | we investigated shoot growth patterns and their relationship to the canopy radiation environment and the distribution of leaf photosynthetic production in a 27-m-tall stand of light-demanding populus tremula l. and shade-tolerant tilia cordata mill. the species formed two distinct layers in the leaf canopy and showed different responses in branch architecture to the canopy light gradient. in p. tremula, shoot bifurcation decreased rapidly with decreasing light, and leaf display allowed capture o ... | 2002 | 12414376 |
| a transcriptional timetable of autumn senescence. | we have developed genomic tools to allow the genus populus (aspens and cottonwoods) to be exploited as a full-featured model for investigating fundamental aspects of tree biology. we have undertaken large-scale expressed sequence tag (est) sequencing programs and created populus microarrays with significant gene coverage. one of the important aspects of plant biology that cannot be studied in annual plants is the gene activity involved in the induction of autumn leaf senescence. | 2004 | 15059257 |
| poplar potassium transporters capable of controlling k+ homeostasis and k+-dependent xylogenesis. | the cambial k+ content of poplar increases during the growth period in a k+ supply dependent manner. upon k+ starvation or application of tetraethylammoniumchloride (tea+), a k+ channel blocker, the average vessel lumen and expansion zone area were significantly reduced. in search for the molecular basis of potassium-dependent xylogenesis in poplar, k+ transporters homologous to those of known function in arabidopis phloem- and xylem-physiology were isolated from a poplar wood est library. the e ... | 2002 | 12492841 |
| gene expression in autumn leaves. | two cdna libraries were prepared, one from leaves of a field-grown aspen (populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (populus tremula x tremuloides). expressed sequence tags (ests; 5,128 and 4,841, respectively) were obtained from the two libraries. a semiautomatic method of annotation and functional classification of the ests, according to a modified munich institute of pr ... | 2003 | 12586868 |
| crystallization and preliminary x-ray analysis of a xyloglucan endotransglycosylase from populus tremula x tremuloides. | xyloglucan endotransglycosylases (xets) cleave and religate xyloglucan polymers in plant cell walls. recombinant xet from poplar has been purified from a pichia pastoris expression system and crystallized. two different crystal forms were obtained by vapour diffusion from potassium sodium tartrate and from an imidazole buffer using sodium acetate as a precipitant. data were collected from these crystal forms to 3.5 and 2.1 a resolution, respectively. the first crystal form was found to belong to ... | 2003 | 12595718 |
| stoichiometry of foliar carbon constituents varies along light gradients in temperate woody canopies: implications for foliage morphological plasticity. | foliar morphology and chemical composition were examined along a light gradient in the canopies of five deciduous temperate woody species, ranked according to shade-tolerance as populus tremula l. < fraxinus excelsior l. < tilia cordata mill. = corylus avellana l. < fagus sylvatica l. foliar carbon was divided between structural (cell-wall polysaccharides, lignin) and nonstructural (proteins, ethanol-soluble carbohydrates, starch) fractions. foliar morphology of all species was strongly affected ... | 1998 | 12651358 |
| myosin, microtubules, and microfilaments: co-operation between cytoskeletal components during cambial cell division and secondary vascular differentiation in trees. | the immunolocalisation of unconventional myosin viii ('myosin') in the cells of the secondary vascular tissues of angiosperm (populus tremula l. x p. tremuloides michx. and aesculus hippocastanum l.) and gymnosperm (pinus pinea l.) trees is described for the first time and related to other cytoskeletal elements, as well as to callose. both myosin and callose are located at the cell plate in dividing cambial cells, whereas actin microfilaments are found alongside the cell plate; actin and tubulin ... | 2002 | 11925036 |
| mycorrhizal colonization of transgenic aspen in a field trial. | mycorrhizal colonization of genetically modified hybrid aspen (populus tremula x p. tremuloides michx.) was investigated over 15 months in a field experiment. the aspen carried the rolc gene from agrobacterium rhizogenes under control of either the constitutive cauliflower mosaic virus 35s promoter or the light-inducible rbcs promoter. arbuscular mycorrhizas (ams) were rare in all root samples, while fully developed ectomycorrhizas (ems) were found in all samples. no significant differences in t ... | 2002 | 11925050 |
| daylength and spatial expression of a gibberellin 20-oxidase isolated from hybrid aspen (populus tremula l. x p. tremuloides michx.). | physiologically active gibberellins (gas) are key regulators of shoot growth in trees. to investigate this mechanism of ga-controlled growth in hybrid aspen, we cloned cdnas encoding gibberellin 20-oxidase (ga 20-oxidase), a key, highly regulated enzyme in the biosynthesis of gas. clones were isolated from leaf and cambium cdna libraries using probes generated by polymerase chain reaction, based on conserved domains of ga 20-oxidases. upon expression in escherichia coli, the gst-fusion protein w ... | 2002 | 11941469 |
| asymmetric expression of a poplar acc oxidase controls ethylene production during gravitational induction of tension wood. | ethylene is produced in wood-forming tissues, and when applied exogenously, it has been shown to cause profound effects on the pattern and rate of wood development. however, the molecular regulation of ethylene biosynthesis during wood formation is poorly understood. we have characterised an abundant 1-aminocyclopropane-1-carboxylic acid (acc) oxidase gene (pttaco1) in the wood-forming tissues of populus tremula (l.) x p. tremuloides (michx). pttaco1 is primarily expressed in developing secondar ... | 2003 | 12713540 |
| nutrient translocation in the xylem of poplar--diurnal variations and spatial distribution along the shoot axis. | this investigation shows diurnal variations in the xylem sap composition of poplar (populus tremula x p. alba). all major macronutrients reached a maximum concentration in the first half of the light period and decreased to the middle of the night. the relative abundance of the nutrients did not change during the day. the sap flow, which responded very fast to the environmental changes (2.2-fold increase within 10-20 min of illumination), reached a maximum value in the second half of the light p ... | 2003 | 12721678 |
| differential effects of elevated ozone on two hybrid aspen genotypes predisposed to chronic ozone fumigation. role of ethylene and salicylic acid. | the role of ethylene (et) signaling in the responses of two hybrid aspen (populus tremula l. x p. tremuloides michx.) clones to chronic ozone (o(3); 75 nl l(-1)) was investigated. the hormonal responses differed between the clones; the o(3)-sensitive clone 51 had higher et evolution than the tolerant clone 200 during the exposure, whereas the free salicylic acid concentration in clone 200 was higher than in clone 51. the cellular redox status, measured as glutathione redox balance, did not diffe ... | 2003 | 12746525 |
| activation tagging of a dominant gibberellin catabolism gene (ga 2-oxidase) from poplar that regulates tree stature. | we identified a dwarf transgenic hybrid poplar (populus tremula x populus alba) after screening of 627 independent activation-tagged transgenic lines in tissue culture, greenhouse, and field environments. the cause of the phenotype was a hyperactivated gene encoding ga 2-oxidase (ga2ox), the major gibberellin (ga) catabolic enzyme in plants. the mutation resulted from insertion of a strong transcriptional enhancer near the transcription start site. overexpression of the poplar ga2ox gene (ptaga2 ... | 2003 | 12857810 |
| anaerobic induction of the maize gapc4 promoter in poplar leaves requires light and high co2. | the maize (zea mays l.) glyceraldehyde-3-phosphate dehydrogenase gene 4 ( gapc4) promoter confers anaerobic gene expression in tobacco (nicotiana tabacum l.), potato (solanum tuberosum l.) and arabidopsis thaliana (l.) heynh. here we have investigated its expression in hybrid poplar (populus tremula x p. alba). our results show that the promoter is not expressed in leaves and stems under normoxic conditions while anaerobiosis induces reporter gene expression in leaves up to a level observed for ... | 2003 | 12883886 |
| genetics of resistance to transgenic bacillus thuringiensis poplars in chrysomela tremulae (coleoptera: chrysomelidae). | the area under genetically engineered plants producing bacillus thuringiensis (bt) toxins is steadily increasing. this increase has magnified the risk of alleles conferring resistance to these toxins being selected in natural populations of target insect pests. the speed at which this selection is likely to occur depends on the genetic characteristics of bt resistance. we selected a strain of the beetle chrysomela tremulae fabricius on a transgenic bt poplar clone populus tremula l. x populus tr ... | 2004 | 15279291 |
| significant increases in pulping efficiency in c4h-f5h-transformed poplars: improved chemical savings and reduced environmental toxins. | the gene encoding ferulate 5-hydroxylase (f5h) was overexpressed in poplar (populus tremula x populus alba) using the cinnamate-4-hydroxylase (c4h) promoter to drive expression specifically in cells involved in the lignin biosynthetic pathway and was shown to significantly alter the mole percentage of syringyl subunits in the lignin, as determined by thioacidolysis. analysis of poplar transformed with a c4h-f5h construct demonstrated significant increases in chemical (kraft) pulping efficiency f ... | 2003 | 14518941 |
| what affects mrna levels in leaves of field-grown aspen? a study of developmental and environmental influences. | we have analyzed the abundance of mrnas expressed from 11 nuclear genes in leaves of a free-growing aspen (populus tremula) tree throughout the growing season. we used multivariate statistics to determine the influence of environmental factors (i.e. the weather before sampling) and developmental responses to seasonal changes at the mrna level for each of these genes. the gene encoding a germin-like protein was only expressed early in the season, whereas the other tested genes were expressed thro ... | 2003 | 14563929 |
| antifungal activity of stilbenes in in vitro bioassays and in transgenic populus expressing a gene encoding pinosylvin synthase. | the effect of two stilbene compounds, pinosylvin and resveratrol, on the growth of several fungi was evaluated in plate tests. wood decay tests were carried out with birch and aspen samples impregnated with the two stilbenes. in plate experiments, resveratrol had an enhancing effect on growth at concentrations where pinosylvin was already enough to prevent the growth of most fungi studied. pinosylvin impregnated at 0.2% (w/w) concentration significantly reduced the decay caused by all fungi exce ... | 2004 | 14714142 |
| condensed lignins are synthesized in poplar leaves exposed to ozone. | poplar (populus tremula x alba) trees (clone inra 717-1-b4) were cultivated for 1 month in phytotronic chambers with two different levels of ozone (60 and 120 nl l(-1)). foliar activities of shikimate dehydrogenase (ec 1.1.1.25), phenylalanine ammonia lyase (ec 4.3.1.5), and cinnamyl alcohol dehydrogenase (cad, ec 1.1.1.195) were compared with control levels. in addition, we examined lignin content and structure in control and ozone-fumigated leaves. under ozone exposure, cad activity and cad rn ... | 2004 | 14730080 |
| characterization of bspa, a major boiling-stable, water-stress-responsive protein in aspen (populus tremula). | we identified a novel 66 kda boiling-stable protein (bspa) in cultured shoots of aspen (populus tremula l.) which was highly expressed in response to gradual water stress. the bspa protein, which was highly expressed as early as 1 h after initiation of a drought treatment, accumulated during progressive water stress, decreased on rehydration, and was expressed in response to abscisic acid (aba) application, as detected by sds-page protein analysis and western blotting. anti-bspa antibodies also ... | 1995 | 14966001 |
| enhancement of the endogenous cytokinin concentration in poplar by transformation with agrobacterium t-dna gene ipt. | the agrobacterial isopentenyltransferase (ipt) gene, under the control of its native promoter, was transferred to poplar (populus tremula x p. alba) by an agrobacterium co-cultivation method. the ipt-transformed stem explants developed calli that regenerated many buds in the absence of exogenous cytokinins. microcuttings of the ipt transformants exhibited frequently branching shoots with short internodes that were unable to root. in this material, the concentrations of zeatin, zeatin riboside an ... | 1994 | 14967631 |
| poplar peroxiredoxin q. a thioredoxin-linked chloroplast antioxidant functional in pathogen defense. | peroxiredoxins are ubiquitous thioredoxin- or glutaredoxin-dependent peroxidases, the function of which is to destroy peroxides. peroxiredoxin q, one of the four plant subtypes, is a homolog of the bacterial bacterioferritin comigratory proteins. we show here that the poplar (populus tremula x populus tremuloides) protein acts as a monomer with an intramolecular disulfide bridge between two conserved cysteines. a wide range of electron donors and substrates was tested. unlike type ii peroxiredox ... | 2004 | 14976238 |
| regulation of sulphate assimilation by glutathione in poplars (populus tremula x p. alba) of wild type and overexpressing gamma-glutamylcysteine synthetase in the cytosol. | glutathione (gsh) is the major low molecular weight thiol in plants with different functions in stress defence and the transport and storage of sulphur. its synthesis is dependent on the supply of its constituent amino acids cysteine, glutamate, and glycine. gsh is a feedback inhibitor of the sulphate assimilation pathway, the primary source of cysteine synthesis. sulphate assimilation has been analysed in transgenic poplars (populus tremula x p. alba) overexpressing gamma-glutamylcysteine synth ... | 2004 | 15020643 |
| crystal structures of a poplar xyloglucan endotransglycosylase reveal details of transglycosylation acceptor binding. | xyloglucan endotransglycosylases (xets) cleave and religate xyloglucan polymers in plant cell walls via a transglycosylation mechanism. thus, xet is a key enzyme in all plant processes that require cell wall remodeling. to provide a basis for detailed structure-function studies, the crystal structure of populus tremula x tremuloides xet16a (pttxet16a), heterologously expressed in pichia pastoris, has been determined at 1.8-a resolution. even though the overall structure of pttxet16a is a curved ... | 2004 | 15020748 |
| branch growth and leaf gas exchange of populus tremula exposed to low ozone concentrations throughout two growing seasons. | during two consecutive growing seasons, the same potted individuals of european aspen (populus tremula), grown from root cuttings of one clone, were fumigated with either ambient air or ozone concentrations of 0 (control), 0.05 or 0.1 microlitre litre(-1). structure and biomass of the annually formed branches were analysed after excision at the end of each season. only at 0.1 microlitre litre(-1) was branch weight reduced, and crooked axes occurred in each season. during the second season, branc ... | 1993 | 15091906 |
| density patterns of gall mites (acarina:eriophyidae) in a polluted area. | trends in the densities of six species of gall mites on european aspen (populus tremula) and on two birch species (betula pubescens and b. pendula) were compared in an air pollution gradient from the harjavalta copper-nickel smelter, sw finland. the densities of gall mites on both birch species decreased towards the smelter and were negatively correlated with the levels of copper and nickel in the birch leaves. in contrast, the densities of aspen mites correlated neither with distance from the p ... | 1996 | 15093531 |
| potassium-dependent cambial growth in poplar. | to study the involvement of potassium in wood formation, poplar plants ( populus tremula l. x populus tremuloides michx.) were grown over a period of one growing season, under different potassium regimes. seasonal changes in cambial potassium content, osmotic potential, and cambial activity correlated strongly throughout the season, increasing from spring to summer and decreasing from summer to autumn. moreover, changing the potassium supply during the growing season affected the seasonal change ... | 2004 | 15095132 |
| liquid phase fluorescence in situ rt-pcr analysis for gene expression analysis in woody stems. | we explore a rapid in situ rt-pcr protocol for gene expression studies in woody stem tissues. in situ rt-pcr was performed using fluorescent dye-conjugated nucleic acid and the fluorescence signals derived from target rnas were detected using confocal laser scanning microscopy. the signal to background ratio was greatly enhanced by performing two rounds of pcr reactions, first without the fluorescent dye and second with the dye. using this protocol, we obtained strong gene-specific signals in se ... | 2004 | 15095134 |
| fluorescent proteins in poplar: a useful tool to study promoter function and protein localization. | the jellyfish (aequorea victoria) green fluorescent protein (gfp) and its variants (cfp [cyan] and yfp [yellow]) were successfully used as a vital marker system for the transformation of hybrid poplar (populus tremula x p. alba). our results show that, in this woody plant, fluorescent proteins can be expressed: (i) transiently in protoplasts after peg-mediated transformation, as well as in leaf cells after particle bombardment, and (ii) stably in callus cells and plants after agrobacterium-media ... | 2004 | 15095136 |
| an analysis of light effects on foliar morphology, physiology, and light interception in temperate deciduous woody species of contrasting shade tolerance. | maximum rubisco activities (v(cmax)), rates of photosynthetic electron transport (j(max)), and leaf nitrogen and chlorophyll concentrations were studied along a light gradient in the canopies of four temperate deciduous species differing in shade tolerance according to the ranking: populus tremula l. < fraxinus excelsior l. < tilia cordata mill. = corylus avellana l. long-term light environment at the canopy sampling locations was characterized by the fractional penetration of irradiance in the ... | 1998 | 12651418 |
| biomass investment in leaf lamina versus lamina support in relation to growth irradiance and leaf size in temperate deciduous trees. | foliar biomass investment in support and assimilative compartments was studied in four temperate deciduous tree species along a natural light gradient across the canopy. the species ranked according to shade tolerance as betula pendula roth. < populus tremula l. < fraxinus excelsior l. < tilia cordata mill. long-term light conditions at sampling locations were characterized as seasonal mean integrated quantum flux density (q(int), mol m(-2) day(-1)) estimated by a method combining hemispherical ... | 1999 | 12651556 |
| seasonal embolism and xylem vulnerability in deciduous and evergreen mediterranean trees influenced by proximity to a carbon dioxide spring. | we investigated how proximity to natural co(2) springs affected the seasonal patterns of xylem embolism in quercus ilex l., quercus pubescens willd., fraxinus ornus l., populus tremula l. and arbutus unedo l., which differ in leaf phenology and wood anatomy. xylem embolism was evaluated in both artificially dehydrated branches and in hydrated apical branches collected at monthly intervals during a 20-month sampling period. initial specific hydraulic conductivity was also evaluated. we found spec ... | 1999 | 12651570 |
| cloning and overproduction of gibberellin 3-oxidase in hybrid aspen trees. effects on gibberellin homeostasis and development. | to broaden our understanding of gibberellin (ga) biosynthesis and the mechanism whereby ga homeostasis is maintained in plants, we have investigated the degree to which the enzyme ga 3-oxidase (ga3ox) limits the formation of bioactive gas in elongating shoots of hybrid aspen (populus tremula x populus tremuloides). we describe the cloning of a hybrid aspen ga3ox and its functional characterization, which confirmed that it has 3beta-hydroxylation activity and more efficiently converts ga9 to ga4 ... | 2004 | 15122019 |
| patterns of auxin distribution during gravitational induction of reaction wood in poplar and pine. | gravistimulation of tree stems affects wood development by unilaterally inducing wood with modified properties, called reaction wood. commonly, it also stimulates cambial growth on the reaction wood side. numerous experiments involving applications of indole-3-acetic acid (iaa) or iaa-transport inhibitors have suggested that reaction wood is induced by a redistribution of iaa around the stem. however, in planta proof for this model is lacking. therefore, we have mapped endogenous iaa distributio ... | 2004 | 15122024 |
| transgenic poplar characterized by ectopic expression of a pine cytosolic glutamine synthetase gene exhibits enhanced tolerance to water stress. | physiological responses to water stress in hybrid poplar (inra 7171-b4, populus tremula l. x p. alba l.) lines transformed to overexpress a pine cytosolic glutamine synthetase (gs1) gene were compared with those of non-transgenic plants. before, during and after a drought treatment, net photosynthetic rates (anet) were higher in transgenic than in non-transgenic plants. stomatal conductance (gs) was higher in transgenic than in non-transgenic plants before, but not after exposure to drought. bef ... | 2004 | 15123444 |
| expansins abundant in secondary xylem belong to subgroup a of the alpha-expansin gene family. | differentiation of xylem cells in dicotyledonous plants involves expansion of the radial primary cell walls and intrusive tip growth of cambial derivative cells prior to the deposition of a thick secondary wall essential for xylem function. expansins are cell wall-residing proteins that have an ability to plasticize the cellulose-hemicellulose network of primary walls. we found expansin activity in proteins extracted from the cambial region of mature stems in a model tree species hybrid aspen (p ... | 2004 | 15247397 |