Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
|---|
| structural evidence for the evolution of xyloglucanase activity from xyloglucan endo-transglycosylases: biological implications for cell wall metabolism. | high-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (gh16) endo-xyloglucanases tm-nxg1 and tm-nxg2 from nasturtium (tropaeolum majus) have been solved by x-ray crystallography. key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the gh16 xyloglucan-active enzymes were identified by structure-function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo- ... | 2007 | 17557806 |
| analysis of codon usage between different poplar species. | codon usage is the selective and nonrandom use of synonymous codons to encode amino acids in genes for proteins. the analysis of codon usage may improve the understanding of codon preferences between different species and allow to rebuild the codons of exogenous genes to increase the expression efficiency of exogenous genes. here, codon dna sequence (cds) of four poplar species, including populus tremuloides michx., p. tomentosa carr., p. deltoides marsh., and p. trichocarpa torr. & gray., is us ... | 2007 | 17601615 |
| reconciling divergent interpretations of quaking aspen decline on the northern colorado front range. | ecologists have debated over the past 65 years whether quaking aspen (populus tremuloides michx.) has or has not declined in abundance, vigor, or regeneration in western north america. many studies have provided divergent interpretations of the condition of aspen forests, leading to difficulty in translating this ecological information into management recommendations. to reconcile these contrasting conclusions and to test the hypothesis that multiple types of aspen decline and persistence occur ... | 2007 | 17708209 |
| data integration in plant biology: the o2pls method for combined modeling of transcript and metabolite data. | the technological advances in the instrumentation employed in life sciences have enabled the collection of a virtually unlimited quantity of data from multiple sources. by gathering data from several analytical platforms, with the aim of parallel monitoring of, e.g. transcriptomic, metabolomic or proteomic events, one hopes to answer and understand biological questions and observations. this 'systems biology' approach typically involves advanced statistics to facilitate the interpretation of the ... | 2007 | 17931352 |
| extrafloral nectaries in aspen (populus tremuloides): heritable genetic variation and herbivore-induced expression. | a wide variety of plants produce extrafloral nectaries (efns) that are visited by predatory arthropods. but very few studies have investigated the relationship between plant genetic variation and efns. the presence of foliar efns is highly variable among different aspen (populus tremuloides) genotypes and the efns are visited by parasitic wasps and predatory flies. the aim here was to determine the heritability of efns among aspen genotypes and age classes, possible trade-offs between direct and ... | 2007 | 17951361 |
| atmospheric co2 and o3 alter the flow of 15n in developing forest ecosystems. | anthropogenic o3 and co2-induced declines in soil n availability could counteract greater plant growth in a co2-enriched atmosphere, thereby reducing net primary productivity (npp) and the potential of terrestrial ecosystems to sequester anthropogenic co2. presently, it is uncertain how increasing atmospheric co2 and o3 will alter plant n demand and the acquisition of soil n by plants as well as the microbial supply of n from soil organic matter. to address this uncertainty, we initiated an ecos ... | 2007 | 18027765 |
| relationships between stand composition and ectomycorrhizal community structure in boreal mixed-wood forests. | we investigated the community structure of ectomycorrhizal fungi under varying overstory tree compositions in the southern mixed-wood boreal forest of quebec. sampling took place at two locations of differing postfire ages and nine 100-m2 plots were sampled per location. the dominant overstory tree species in the plots were trembling aspen (populus tremuloides michx.), white birch (betula papyrifera marsh.) or white spruce [picea glauca (moench) voss], and balsam fir [abies balsamea (l.) mill.]. ... | 2006 | 16699911 |
| distinct roles of cinnamate 4-hydroxylase genes in populus. | cinnamate 4-hydroxylase (c4h) catalyzes the conversion of cinnamate into 4-hydroxy-cinnamate, a key reaction of the phenylpropanoid pathway which leads to the biosynthesis of several secondary metabolites. c4h genes exist as a multigene family in various plant species. in order to understand the roles of individual c4h members, four c4h cdnas (ptrec4h) were isolated from populus tremuloides and three c4h loci (ptric4h) were identified in the p. trichocarpa genome. the ability of populus c4h isof ... | 2006 | 16720648 |
| age-related shifts in leaf chemistry of clonal aspen (populus tremuloides). | developmental changes in plant structure and function can influence both mammalian and arthropod feeding preferences for many woody plant species. this study documents age-related changes that occur in the leaf chemistry of trembling aspen (populus tremuloides michx., salicaceae) and discusses implications for the herbivore community and ecosystem processes. we collected leaves from replicate ramets from six age classes (1-25+ yr) in each of seven aspen clones growing in south central wisconsin, ... | 2006 | 16724272 |
| mortality gradients within and among dominant plant populations as barometers of ecosystem change during extreme drought. | understanding patterns of plant population mortality during extreme weather events is important to conservation planners because the frequency of such events is expected to increase, creating the need to integrate climatic uncertainty into management. dominant plants provide habitat and ecosystem structure, so changes in their distribution can be expected to have cascading effects on entire communities. observing areas that respond quickly to climate fluctuations provides foresight into future e ... | 2006 | 17002765 |
| diversity of the small subunit ribosomal rna gene of the arbuscular mycorrhizal fungi colonizing clintonia borealis from a mixed-wood boreal forest. | arbuscular mycorrhizal fungi (amf) communities in clintonia borealis roots from a boreal mixed forests in northwestern québec were investigated. roots were sampled from 100 m2 plots whose overstory was dominated by either trembling aspen (populus tremuloides michx.), white birch (betula papyrifera marsh.), or mixed white spruce (picea glauca (moench) voss) and balsam fir (abies balsamea (l.) mill.). part of the 18s ribosomal gene of the amf was amplified and the resulting pcr products were clone ... | 2006 | 17064264 |
| competition- and resource-mediated tradeoffs between growth and defensive chemistry in trembling aspen (populus tremuloides). | costs of defense are thought to maintain genetic variations in the expression of defense within plant populations. as with many plant species, aspen exhibits considerable variation in allocation to secondary metabolites. this study examined the independent and interactive effects of genotype, soil fertility and belowground competition on defensive chemistry and growth in trembling aspen (populus tremuloides). four aspen genotypes were grown with high and low soil fertility, and with and without ... | 2006 | 16411958 |
| signals controlling root suckering and adventitious shoot formation in aspen (populus tremuloides). | we determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (populus tremuloides michx.). the greatest number of root suckers (67.9 +/- 8.5 per plant) emerged after excision of the entire shoot. defoliated and debudded stems were the major source of inhibitory agents for root suckering, although axillary buds and developing new leaves also ex ... | 2006 | 16452082 |
| genotype and environment determine allocation to and costs of resistance in quaking aspen. | although genetic variability and resource availability both influence plant chemical composition, little is known about how these factors interact to modulate costs of resistance, expressed as negative correlations between growth and defense. we evaluated genotype x environment effects on foliar chemistry and growth of quaking aspen (populus tremuloides) by growing multiple aspen genotypes under variable conditions of light and soil nutrient availability in a common garden. foliage was analyzed ... | 2006 | 16468055 |
| fungal community composition and metabolism under elevated co(2) and o(3). | atmospheric co(2) and o(3) concentrations are increasing due to human activity and both trace gases have the potential to alter c cycling in forest ecosystems. because soil microorganisms depend on plant litter as a source of energy for metabolism, changes in the amount or the biochemistry of plant litter produced under elevated co(2) and o(3) could alter microbial community function and composition. previously, we have observed that elevated co(2) increased the microbial metabolism of cellulose ... | 2006 | 16205953 |
| phylogeny and taxonomy of the north american clade of the ceratocystis fimbriata complex. | ceratocystis fimbriata is a widely distributed, plant pathogenic fungus that causes wilts and cankers on many woody hosts. earlier phylogenetic analyses of dna sequences revealed three geographic clades within the c. fimbriata complex that are centered respectively in north america, latin america and asia. this study looked for cryptic species within the north american clade. the internal transcribed spacer regions (its) of the rdna were sequenced, and phylogenetic analysis indicated that most i ... | 2005 | 16596958 |
| evolution of the isoprene biosynthetic pathway in kudzu. | isoprene synthase converts dimethylallyl diphosphate, derived from the methylerythritol 4-phosphate (mep) pathway, to isoprene. isoprene is made by some plants in substantial amounts, which affects atmospheric chemistry, while other plants make no isoprene. as part of our long-term study of isoprene synthesis, the genetics of the isoprene biosynthetic pathway of the isoprene emitter, kudzu (pueraria montana), was compared with similar genes in arabidopsis (arabidopsis thaliana), which does not m ... | 2005 | 15653811 |
| structural and kinetic basis for substrate selectivity in populus tremuloides sinapyl alcohol dehydrogenase. | we describe the three-dimensional structure of sinapyl alcohol dehydrogenase (sad) from populus tremuloides (aspen), a member of the nadp(h)-dependent dehydrogenase family that catalyzes the last reductive step in the formation of monolignols. the active site topology revealed by the crystal structure substantiates kinetic results indicating that sad maintains highest specificity for the substrate sinapaldehyde. we also report substantial substrate inhibition kinetics for the sad-catalyzed reduc ... | 2005 | 15829607 |
| chemical composition and antibacterial activity of propolis collected by three different races of honeybees in the same region. | the chemical analysis and antibacterial activity of three types of propolis collected three different races of apis mellifera bee in the same apiary were investigated. propolis samples were investigated by gc/ms, 48 compounds were identified 32 being new for propolis. the compounds identified indicated that the main plant sources of propolis were populus alba, populus tremuloides and salix alba. the antimicrobial activity against staphylococcus aureus, escherichia coli, pseudomonas aeruginosa an ... | 2005 | 15848022 |
| clarification of cinnamoyl co-enzyme a reductase catalysis in monolignol biosynthesis of aspen. | cinnamoyl co-enzyme a reductase (ccr), one of the key enzymes involved in the biosynthesis of monolignols, has been thought to catalyze the conversion of several cinnamoyl-coa esters to their respective cinnamaldehydes. however, it is unclear which cinnamoyl-coa ester is metabolized for monolignol biosynthesis. a xylem-specific ccr cdna was cloned from aspen (populus tremuloides) developing xylem tissue. the recombinant ccr protein was produced through an escherichia coli expression system and p ... | 2005 | 15870094 |
| the genome sequence of black cottonwood (populus trichocarpa) reveals 18 conserved cellulose synthase (cesa) genes. | the genome sequence of populus trichocarpa was screened for genes encoding cellulose synthases by using full-length cdna sequences and ests previously identified in the tissue specific cdna libraries of other poplars. the data obtained revealed 18 distinct cesa gene sequences in p. trichocarpa. the identified genes were grouped in seven gene pairs, one group of three sequences and one single gene. evidence from gene expression studies of hybrid aspen suggests that both copies of at least one pai ... | 2005 | 15940463 |
| jasmonic acid induces rapid changes in carbon transport and partitioning in populus. | here, we tested whether rapid changes in carbohydrate transport and partitioning to storage organs would be induced by jasmonic acid (ja), a plant-produced signal of herbivore attack known to induce resistance. carbon-11, introduced as (11)co(2), was used to track real-time carbohydrate transport and partitioning nondestructively in populus species before and 12 h after application of ja to a single leaf. jasmonic acid resulted in more rapid [(11)c]-photosynthate export from both local and syste ... | 2005 | 15948830 |
| gene expression patterns of trembling aspen trees following long-term exposure to interacting elevated co2 and tropospheric o3. | expression of 4600 poplar expressed sequence tags (ests) was studied over the 2001-2002 growing seasons using trees of the moderately ozone (o(3))-tolerant trembling aspen (populus tremuloides) clone 216 exposed to elevated co(2) and/or o(3) for their entire 5-yr life history. based on replication of the experiment in years 2001 and 2002, 238 genes showed qualitatively similar expression in at least one treatment and were retained for analysis. of these 238 genes, 185 were significantly regulate ... | 2005 | 15948836 |
| allelic and population variation of microsatellite loci in aspen (populus tremuloides). | to develop a robust basis for inferences about population genetics and evolution, this work assayed 192 aspens (populus tremuloides) from 11 sites in wisconsin, usa, for allelic and population variation at 16 microsatellite loci distributed across the populus genome. frequency distributions of fluorochrome-labeled alleles resolved by capillary electrophoresis were analyzed for relationships to repeat size and number. population-level statistics were compared with those of other studies, especial ... | 2005 | 15948838 |
| induced resistance in the indeterminate growth of aspen (populus tremuloides). | studies of induction in trees have examined rapid induced resistance (rir) or delayed induced resistance (dir), but have not examined induction that occurs in leaves produced by indeterminately growing trees subsequent to, but in the same season as, damage. we refer to induction that occurs during this time period as intermediate-delayed induced resistance (idir). we assessed the influences of genetic and environmental factors, and their interactions, on temporal and spatial variation in inducti ... | 2005 | 15959818 |
| does lignin modification affect feeding preference or growth performance of insect herbivores in transgenic silver birch (betula pendula roth)? | transgenic silver birch (betula pendula roth) lines were produced in order to modify lignin biosynthesis. these lines carry comt (caffeate/5-hydroxyferulate o-methyltransferase) gene from populus tremuloides driven by constitutive promoter 35s camv (cauliflower mosaic virus) or ubb1 (ubiquitin promoter from sunflower). the decreased syringyl/guaiacyl (s/g) ratio was found in stem and leaf lignin of 35s camv-ptcomt transgenic silver birch lines when compared to non-transformed control or ubb1-ptc ... | 2005 | 15971066 |
| impacts of greenhouse gases on epicuticular waxes of populus tremuloides michx.: results from an open-air exposure and a natural o3 gradient. | epicuticular waxes of three trembling aspen (populus tremuloides michx.) clones differing in o3 tolerance were examined over six growing seasons (1998-2003) at three bioindicator sites in the lake states region of the usa and at facts ii (aspen face) site in rhinelander, wi. differences in epicuticular wax structure were determined by scanning electron microscopy and quantified by a coefficient of occlusion. statistically significant increases in stomatal occlusion occurred for the three o3 bioi ... | 2005 | 16005768 |
| clone identification and clonal structure of the european aspen (populus tremula). | the european aspen (populus tremula) is thought to reproduce mostly asexually. thus aspen forms clones, in which several ramets belong to one genetically defined genet. we compared the clonal structure of aspen in old-growth and managed forests in southern and northeastern finland. clones were identified using morphological characters and nine microsatellite loci originally developed for populus tremuloides. there were more clones identified by microsatellites than morphotypes both in old-growth ... | 2005 | 16029483 |
| sep-class genes in populus tremuloides and their likely role in reproductive survival of poplar trees. | one of the most important processes to the survival of a species is its ability to reproduce. in plants, sepallata-class mads-box genes have been found to control the development of the inner whorls of flowers. however, while much is known about floral development in herbaceous plants, similar systems in woody trees remain poorly understood. populus tremuloides (trembling aspen) is a widespread north american tree having important economic value, and its floral development differs from that of w ... | 2005 | 16040208 |
| fine root chemistry and decomposition in model communities of north-temperate tree species show little response to elevated atmospheric co2 and varying soil resource availability. | rising atmospheric [co2] has the potential to alter soil carbon (c) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. because fine root turnover constitutes a large fraction of annual npp, changes in fine root decomposition are especially important. these responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. we evaluated the effects of elevated atm ... | 2005 | 16041614 |
| elevated atmospheric co2 alters soil microbial communities associated with trembling aspen (populus tremuloides) roots. | global atmospheric co(2) levels are expected to double within the next 50 years. to assess the effects of increased atmospheric co(2) on soil ecosystems, cloned trembling aspen (populus tremuloides) seedlings were grown individually in 1 m(3) open bottom root boxes under either elevated (720 ppm, elev) or ambient co(2) (360 ppm, amb). after 5 years, soil cores (40 cm depth) were collected from the root boxes and divided into 0-20 cm and 20-40 cm fractions. elev treatment resulted in significant ... | 2005 | 16052378 |
| clonal and spatial genetic structures of aspen (populus tremuloides michx.). | to portray aspen clonal and spatial genetic structures, we mapped and genotyped trees in two 1-ha plots, each containing three aspen cohorts originating from fire or subsequent secondary disturbances. we used four microsatellite loci to identify aspen clones and increment core analysis to determine tree age. clonal dimensions were measured by the maximum distance between two ramets and the number of ramets per genet. standard normal deviate (snd) was used to assess the spatial distribution of as ... | 2005 | 16101767 |
| prolonged herbicide-induced vegetation changes in a regenerating boreal aspen clearcut. | a soil-active herbicide (hexazinone) was applied (0, 2, and 4 kg/ha of active ingredient) in a 3-year-old regenerating boreal populus tremuloides michx. (aspen) clearcut to determine its effect on the compositional and structural development of the vegetation. woody stem densities and plant foliar cover were evaluated prior to and 2, 6, and 17 years after treatment. herbicide treatment at the 2 and 4 kg/ha rates reduced tree and total woody stem densities relative to the 0 kg/ha level. the 4 kg/ ... | 2005 | 16102889 |
| effects of elevated concentrations of atmospheric co2 and tropospheric o3 on decomposition of fine roots. | rising atmospheric carbon dioxide (co2) concentration ([co2]) could alter terrestrial carbon (c) cycling by affecting plant growth, litter chemistry and decomposition. how the concurrent increase in tropospheric ozone (o3) concentration ([o3]) will interact with rising atmospheric [co2] to affect c cycling is unknown. a major component of carbon cycling in forests is fine root production, mortality and decomposition. to better understand the effects of elevated [co2] and [o3] on the dynamics of ... | 2005 | 16137936 |
| effects of elevated concentrations of atmospheric co2 and tropospheric o3 on leaf litter production and chemistry in trembling aspen and paper birch communities. | human activities are increasing the concentrations of atmospheric carbon dioxide ([co2]) and tropospheric ozone ([o3]), potentially leading to changes in the quantity and chemical quality of leaf litter inputs to forest soils. because the quality and quantity of labile and recalcitrant carbon (c) compounds influence forest productivity through changes in soil organic matter content, characterizing changes in leaf litter in response to environmental change is critical to understanding the effects ... | 2005 | 16137937 |
| mycorrhiza formation enhances adaptive response of hybrid poplar to drought. | mycorrhized and nonmycorrhized plants of hybrid poplar (populus tremula l. x populus tremuloides mich) were cultivated in petri dishes until the amount of water became limiting (detected by a decrease of photosynthetic yield). rna was isolated from both main and fine roots and used for analysis of water channel (aquaporin) gene expression by semiquantitative rt-pcr. for three of five investigated aquaporin genes, expression did not differ between mycorrhized and nonmycorrhized plants. however, e ... | 2005 | 16154985 |
| long-term effects of defoliation on quaking aspen in relation to genotype and nutrient availability: plant growth, phytochemistry and insect performance. | this research tested the long-term effects of defoliation on aspen chemistry and growth in relation to genotype and nutrient availability. we grew saplings of four aspen genotypes in a common garden under two conditions of nutrient availability, and subsequently subjected them to two levels of artificial defoliation. artificial defoliation suppressed plant growth, and saplings of the four genotypes did not show evidence of genetic variation in tolerance to defoliation. phenolic glycoside concent ... | 2004 | 14740291 |
| time of flight secondary ion mass spectrometry studies of the distribution of metals between the soil, rhizosphere and roots of populus tremuloides minchx growing in forest soil. | time of flight secondary ion mass spectroscopy has been used to study the metal distribution at the soil/root interface of tree roots extracted from smelter-impacted soils. the results, augmented by scanning electron microscopy, show that the technique is capable of resolving metal distributions at the cellular level. in addition, the distribution of metals between the root plaque and the root interior may be useful in interpreting local metal transport mechanisms. | 2004 | 14664840 |
| 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 |
| expression of a glycine decarboxylase complex h-protein in non-photosynthetic tissues of populus tremuloides. | the gly decarboxylase complex (gdc) is abundant in mitochondria of c3 leaves and functions in photorespiratory carbon recovery. however, expression of gdc component proteins has generally been less evident in non-green tissues. here we report an aspen (populus tremuloides michx.) ptgdch1 gene, encoding a gdc subunit h-protein that is phylogenetically distinct from previously characterized photorespiratory h-proteins. strong expression of ptgdch1 in root tips and developing xylem suggests that gd ... | 2004 | 14984933 |
| component and whole-system respiration fluxes in northern deciduous forests. | we measured component and whole-system respiration fluxes in northern hardwood (acer saccharum marsh., tilia americana l., fraxinus pennsylvanica marsh.) and aspen (populus tremuloides michx.) forest stands in price county, northern wisconsin from 1999 through 2002. measurements of soil, leaf and stem respiration, stem biomass, leaf area and biomass, and vertical profiles of leaf area were combined with biometric measurements to create site-specific respiration models and to estimate component a ... | 2004 | 14996654 |
| molecular cloning of ten distinct hypervariable regions from the cellulose synthase gene superfamily in aspen trees. | recent molecular genetic data suggest that cellulose synthase (cesa) genes coding for the enzymes that catalyze cellulose biosynthesis (cesas) in arabidopsis and other herbaceous plants belong to a large gene family. much less is known about cesa genes from forest trees. to isolate new cesa genes from tree species, discriminative but easily obtainable homologous dna probes are required. hypervariable regions (hvrii) of cesa genes represent highly divergent dna sequences that can be used to exami ... | 2004 | 14996658 |
| cloning and characterization of cellulose synthase-like gene, ptrcsld2 from developing xylem of aspen trees. | genetic improvement of cell wall polymer synthesis in forest trees is one of the major goals of forest biotechnology that could possibly impact their end product utilization. identification of genes involved in cell wall polymer biogenesis is essential for achieving this goal. among various candidate cell wall-related genes, cellulose synthase-like d (csld) genes are intriguing due to their hitherto unknown functions in cell wall polymer synthesis but strong structural similarity with cellulose ... | 2004 | 15032825 |
| changes in root water flow properties of solution culture-grown trembling aspen (populus tremuloides) seedlings under different intensities of water-deficit stress. | to study the effects of water-deficit stress on root water flow properties in trembling aspen (populus tremuloides michx.), seedlings were grown in solution culture and subjected to water-deficit stress by placing their roots in sealed high humidity chambers. after 17 h of stress treatment, seedlings showed mild stress (ms) symptoms with a decline in shoot water potentials. within 20 h, shoot water potentials rapidly declined, and severe stress (ss) symptoms were present. root hydraulic conducti ... | 2004 | 15086816 |
| 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 |
| 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 |
| suppression subtractive hybridization-mediated transcriptome analysis from multiple tissues of aspen (populus tremuloides) altered in phenylpropanoid metabolism. | a pcr-based suppression subtractive hybridization (ssh) technique was used to identify differentially expressed genes in developing tissues of control and transgenic aspen (populus tremuloides michx.) with down-regulated 4cl1 (4-coumarate:coenzyme a ligase) expression and enhanced growth. a total of 11,308 expressed sequence tags (ests) representing 5,028 non-redundant transcripts encoding 4,224 unique proteins was obtained from shoot apex, young stem, young leaf and root tip ssh libraries. puta ... | 2004 | 15146331 |
| 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 |
| differential expression patterns of two new primary cell wall-related cellulose synthase cdnas, ptrcesa6 and ptrcesa7 from aspen trees. | based on elegant molecular genetic analyses, distinct classes of cellulose synthase (cesa) genes have been associated with either primary or secondary cell wall development in arabidopsis. here, we report on cloning of two new cesa cdnas, ptrcesa6 and ptrcesa7 involved in the primary cell wall development in aspen (populus tremuloides) trees. both these distinct cdnas, isolated from a developing xylem cdna library, share only 60-67% identities with each other as well as with five other previousl ... | 2004 | 15256257 |
| differential expression patterns of two cellulose synthase genes are associated with primary and secondary cell wall development in aspen trees. | the quality and quantity of cellulose deposited in the primary and secondary cell walls of plants vary in accordance with their biological function. however, the molecular basis of such cellulose heterogeneity has so far remained unclear. since enrichment of better-quality cellulose, in terms of increased degree of polymerization and crystallinity, is one of the goals of forest biotechnology, our main objective is to decipher the roles of distinct cellulose synthase (cesa) genes in tree developm ... | 2004 | 15278458 |
| 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 |
| north american populations of entoleuca mammata are genetically more variable than populations in europe. | entoleuca mammata (syn. hypoxylon mammatum) is a damaging pathogen of populus tremuloides and p. grandidentata in north america and p. tremula in europe, where the fungus occurs only sporadically in alpine regions and scandinavia. it has been hypothesized that e. mammata was introduced to europe from north america. in this study, e. mammata isolates collected from europe and north america were compared by a sequence analysis of two dna markers derived from dna fingerprints. the objective of the ... | 2004 | 15446709 |
| metabolic profiling of the sink-to-source transition in developing leaves of quaking aspen. | profiles of small polar metabolites from aspen (populus tremuloides michx.) leaves spanning the sink-to-source transition zone were compared. approximately 25% of 250 to 300 routinely resolved peaks were identified, with carbohydrates, organic acids, and amino acids being most abundant. two-thirds of identified metabolites exhibited greater than 4-fold changes in abundance during leaf ontogeny. in the context of photosynthetic and respiratory measurements, profile data yielded information consis ... | 2004 | 15448196 |
| application of controlled mesocosms for understanding mercury air-soil-plant exchange. | whole system elemental mercury (hg0) flux was measured for approximately 1.5 years using two large gas exchange mesocosms containing approximately 100 two-year old aspen trees (populus tremuloides) planted in soil with elevated mercury concentrations (12.3 microg/g). we hypothesized that during leafout, whole mesocosm hg0 flux would increase due to movement of hg0 in the transpiration stream from the soil to the air. this hypothesis was not supported; plants were found to assimilate hg0 from the ... | 2004 | 15573605 |
| morphology and phylogenetic placement of endoconidioma, a new endoconidial genus from trembling aspen. | endoconidioma populi gen. et sp. nov. is described from black subicula on twigs of trembling aspen, populus tremuloides, in alberta, canada. pycnidium-like conidiomata are produced on twigs and in culture, but, unlike pycnidia, conidiomata of e. populi have a closed peridium and a locule filled with conidiogenous cells that form conidia endogenously. these endoconidia are hyaline, unicellular and released by the dissolution of the peridial cell wall. in addition to endoconidia, mostly two-celled ... | 2004 | 21148931 |
| increased mortality of gypsy moth lymantria dispar (l.) (lepidoptera: lymantriidae) exposed to gypsy moth nuclear polyhedrosis virus in combination with the phenolic gycoside salicin. | second instar gypsy moth, lymantria dispar (l.) (lepidoptera: lymantriidae), larvae suffered significantly greater mortality from aerially applied gypsy moth nuclear polyhedrosis virus (gypchek) when the virus was consumed on quaking aspen, populus tremuloides michx., versus red oak, quercus spp. l., foliage. laboratory assays in which various doses of gypchek and salicin (a phenolic glycoside present in aspen foliage) were tested in combination demonstrated that salicin significantly increased ... | 2003 | 14977101 |
| model-based assessment of aspen responses to elk herbivory in rocky mountain national park, usa. | in rocky mountain national park (rmnp), aspen (populus tremuloides michx.) has been observed to be declining on elk (cervus elaphus nelsoni) winter range for many decades. to support elk management decisions, the savanna ecosystem model was adapted to explore interactions between elk herbivory and aspen dynamics. the simulated probability of successful vegetative regeneration for senescent aspen stands declines sharply when elk densities reach levels of 3-5 elk/km2, depending on model assumption ... | 2003 | 14703920 |
| reduction of soil carbon formation by tropospheric ozone under increased carbon dioxide levels. | in the northern hemisphere, ozone levels in the troposphere have increased by 35 per cent over the past century, with detrimental impacts on forest and agricultural productivity, even when forest productivity has been stimulated by increased carbon dioxide levels. in addition to reducing productivity, increased tropospheric ozone levels could alter terrestrial carbon cycling by lowering the quantity and quality of carbon inputs to soils. however, the influence of elevated ozone levels on soil ca ... | 2003 | 14562100 |
| characterization of ptm5 in aspen trees: a mads-box gene expressed during woody vascular development. | the vascular component of trees possesses some of the most specialized processes active in the formation of roots, stems, and branches, and its wood component continues to be of primary importance to our daily lives. the molecular mechanisms of wood development, however, remain poorly understood with few well-characterized regulatory genes. we have identified a vascular tissue-specific mads-box gene, populus tremuloides mads-box 5 (ptm5) that is expressed in differentiating primary and secondary ... | 2003 | 14585498 |
| effects of elevated carbon dioxide and ozone on the phytochemistry of aspen and performance of an herbivore. | the purpose of this study was to assess the independent and interactive effects of co(2), o(3), and plant genotype on the foliar quality of a deciduous tree and the performance of a herbivorous insect. two trembling aspen (populus tremuloides michaux) genotypes differing in response to co(2) and o(3) were grown at the aspen face (free air co(2) enrichment) site located in northern wisconsin, usa. trees were exposed to one of four atmospheric treatments: ambient air (control), elevated carbon dio ... | 2003 | 12647186 |
| fluoride inhibits root water transport and affects leaf expansion and gas exchange in aspen (populus tremuloides) seedlings. | the effects of sodium fluoride (0.3, 5 and 10 mm naf) on root hydraulic conductivity, and gas exchange processes were examined in aspen (populus tremuloides michx.) seedlings grown in solution culture. a long-term exposure of roots to naf significantly decreased root hydraulic conductivity (lp) and stomatal conductance ( gs). root absorbed naf significantly affected electrolyte leakage in leaf tissues and substantially restricted leaf expansion. naf did not significantly affect leaf chlorophyll ... | 2003 | 12654037 |
| experimental evidence against diffusion control of hg evasion from soils. | elemental hg (hg(0)) evolution from soils can be an important process and needs to be measured in more ecosystems. the diffusion model for soil gaseous efflux has been applied to modeling the fluxes of several gases in soils and deserves testing with regard to hg(0). as an initial test of this model, we examined soil gaseous hg(0) and co(2) concentrations at two depths (20 and 40 cm) over the course of a controlled environment study conducted in the ecocells at the desert research institute in r ... | 2003 | 12663182 |
| combinatorial modification of multiple lignin traits in trees through multigene cotransformation. | lignin quantity and reactivity [which is associated with its syringyl/guaiacyl (s/g) constituent ratio] are two major barriers to wood-pulp production. to verify our contention that these traits are regulated by distinct monolignol biosynthesis genes, encoding 4-coumarate-coa ligase (4cl) and coniferaldehyde 5-hydroxylase (cald5h), we used agrobacterium to cotransfer antisense 4cl and sense cald5h genes into aspen (populus tremuloides). trees expressing each one and both of the transgenes were p ... | 2003 | 12668766 |
| antioxidants in the midgut fluids of a tannin-tolerant and a tannin-sensitive caterpillar: effects of seasonal changes in tree leaves. | the seasonal decline in foliar nutritional quality in deciduous trees also effects the availability of essential micronutrients, such as ascorbate and alpha-tocopherol, to herbivorous insects. this study first examined whether there are consistent patterns of seasonal change in antioxidant concentrations in deciduous tree leaves. alpha-tocopherol concentrations increased substantially through time in late summer in sugar maple (acer saccharum), red oak (quercus rubra), and trembling aspen (popul ... | 2003 | 12857024 |
| isolation and characterization of a new, full-length cellulose synthase cdna, ptrcesa5 from developing xylem of aspen trees. | cellulose synthases (cesa) represent a group of beta-1,4 glycosyltransferases involved in cellulose biosynthesis. recent molecular studies confirmed that a large cesa gene family encoding various cesa isoforms exists in plants. the isolation and characterization of a new, full-length cesa cdna, ptrcesa5 from an economically important tree, quaking aspen (populus tremuloides) is reported here. the predicted ptrcesa5 protein is highly similar to arabidopsis atcesa3 (88%) involved in primary cell w ... | 2003 | 12867550 |
| foliar quality influences tree-herbivore-parasitoid interactions: effects of elevated co2, o3, and plant genotype. | this study examined the effects of carbon dioxide (co2)-, ozone (o3)-, and genotype-mediated changes in quaking aspen (populus tremuloides) chemistry on performance of the forest tent caterpillar (malacosoma disstria) and its dipteran parasitoid (compsilura concinnata) at the aspen free-air co2 enrichment (face) site. parasitized and non-parasitized forest tent caterpillars were reared on two aspen genotypes under elevated levels of co2 and o3, alone and in combination. foliage was collected for ... | 2003 | 12898383 |
| toxicity and chemistry of aspen wood leachate to aquatic life: field study. | a dark, toxic leachate has been observed around woodpiles of trembling aspen (populus tremuloides michx.) cut in winter for pulp or structural lumber. we measured production of leachate from 18 m3 of harvestable aspen logs stacked in an open field near dawson creek, british columbia, canada. the logpile began producing leachate during the first winter thaw and continued to do so for the duration of the two-year study (mean, 250 l/collection). aspen leachate was characterized by dark color, acidi ... | 2003 | 12959530 |
| assessing the source of mercury in foliar tissue of quaking aspen. | foliar accumulation of mercury has been demonstrated to occur as plants leaf out, yet the primary source of this mercury is not known. using closed-system growth chambers, uptake of mercury by quaking aspen (populus tremuloides) foliage was measured over time as a function of soil mercury concentrations (0.01, 6.2, and 25.6 microg/g) and atmospheric mercury exposure concentrations (1.4, 14.9, and 68.5 ng/m3). foliar mercury concentrations increased as a function of time for all exposures. twice ... | 2003 | 12959539 |
| leaf area dynamics of a boreal black spruce fire chronosequence. | specific leaf area (sla) and leaf area index (lai) were estimated using site-specific allometric equations for a boreal black spruce (picea mariana (mill.) bsp) fire chronosequence in northern manitoba, canada. stands ranged from 3 to 131 years in age and had soils that were categorized as well or poorly drained. the goals of the study were to: (i) measure sla for the dominant tree and understory species of boreal black spruce-dominated stands, and examine the effect of various biophysical condi ... | 2002 | 12359526 |
| differential expression of two distinct phenylalanine ammonia-lyase genes in condensed tannin-accumulating and lignifying cells of quaking aspen. | lignins, along with condensed tannins (cts) and salicylate-derived phenolic glycosides, constitute potentially large phenylpropanoid carbon sinks in tissues of quaking aspen (populus tremuloides michx.). metabolic commitment to each of these sinks varies during development and adaptation, and depends on l-phenylalanine ammonia-lyase (pal), an enzyme catalyzing the deamination of l-phenylalanine to initiate phenylpropanoid metabolism. in populus spp., pal is encoded by multiple genes whose expres ... | 2002 | 12376645 |
| a new cellulose synthase gene (ptrcesa2) from aspen xylem is orthologous to arabidopsis atcesa7 (irx3) gene associated with secondary cell wall synthesis. | we report here the molecular cloning and characterization of a new full-length cellulose synthase (cesa) cdna, ptrcesa2 from aspen (populus tremuloides) trees. the predicted ptrcesa2 protein shows a high degree of identity/similarity (87%/91%) to the predicted gene product of arabidopsis atcesa7 gene that has been associated with secondary cell wall development. previously, a mutation in atcesa7 gene (irx3) was correlated with a significant decrease in the amount of cellulose synthesized (about ... | 2002 | 12383501 |
| altered performance of forest pests under atmospheres enriched by co2 and o3. | human activity causes increasing background concentrations of the greenhouse gases co2 and o3. increased levels of co2 can be found in all terrestrial ecosystems. damaging o3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are predicted to affect fully 60% by 2100 (ref. 3). although individual effects of co2 and o3 on vegetation have been widely investigated, very little is known about their interaction, and long-term studies on mature trees and higher t ... | 2002 | 12459738 |
| naphthenic acids inhibit root water transport, gas exchange and leaf growth in aspen (populus tremuloides) seedlings. | effects of sodium naphthenates (nas) on root hydraulic conductivity (lp) and gas exchange processes were examined in aspen (populus tremuloides michx.) seedlings grown in solution culture. exposure of roots to nas for 3-5 weeks significantly decreased lp and stomatal conductance. root-absorbed nas also decreased leaf chlorophyll concentration, net photosynthesis and leaf growth. short-term (< or = 2 h) exposure of excised roots to nas significantly decreased root water flow (qv) with a concomita ... | 2002 | 12464580 |
| molecular analysis of herbivore-induced condensed tannin synthesis: cloning and expression of dihydroflavonol reductase from trembling aspen (populus tremuloides). | in order to study condensed tannin synthesis and its induction by herbivory, a dihydroflavonol reductase (dfr) cdna was isolated from trembling aspen (populus tremuloides). bacterial overexpression demonstrated that this cdna encodes a functional dfr enzyme, and southern analysis revealed that dfr likely is a single-copy gene in the aspen genome. aspen plants that were mechanically wounded showed a dramatic increase in dfr expression after 24 h in both wounded leaves and unwounded leaves on woun ... | 2002 | 12472686 |
| differential substrate inhibition couples kinetically distinct 4-coumarate:coenzyme a ligases with spatially distinct metabolic roles in quaking aspen. | 4-coumarate:coenzyme a ligase (4cl) activates hydroxycinnamates for entry into phenylpropanoid branchways that support various metabolic activities, including lignification and flavonoid biosynthesis. however, it is not clear whether and how 4cl proteins with their broad substrate specificities fulfill the specific hydroxycinnamate requirements of the branchways they supply. two tissue-specific 4cls, pt4cl1 and pt4cl2, have previously been cloned from quaking aspen (populus tremuloides michx.), ... | 2002 | 11842147 |
| ethylene enhances water transport in hypoxic aspen. | water transport was examined in solution culture grown seedlings of aspen (populus tremuloides) after short-term exposures of roots to exogenous ethylene. ethylene significantly increased stomatal conductance, root hydraulic conductivity (l(p)), and root oxygen uptake in hypoxic seedlings. aerated roots that were exposed to ethylene also showed enhanced l(p). an ethylene action inhibitor, silver thiosulphate, significantly reversed the enhancement of l(p) by ethylene. a short-term exposure of ex ... | 2002 | 11891251 |
| photosynthetic acclimation of overstory populus tremuloides and understory acer saccharum to elevated atmospheric co2 concentration: interactions with shade and soil nitrogen. | we exposed populus tremuloides michx. and acer saccharum marsh. to a factorial combination of ambient and elevated atmospheric co2 concentrations ([co2]) and high-nitrogen (n) and low-n soil treatments in open-top chambers for 3 years. our objective was to compare photosynthetic acclimation to elevated [co2] between species of contrasting shade tolerance, and to determine if soil n or shading modify the acclimation response. sun and shade leaf responses to elevated [co2] and soil n were compared ... | 2002 | 11960756 |
| responses of deciduous broadleaf trees to defoliation in a co2 enriched atmosphere. | relatively little is known about the implications of atmospheric co2 enrichment for tree responses to biotic disturbances such as folivory. we examined the combined effects of elevated co2 concentration ([co2]) and defoliation on growth and physiology of sugar maple (acer saccharum marsh.) and trembling aspen (populus tremuloides michx.). seedlings were planted in the ground in eight open-top chambers. four chambers were ventilated with co2-enriched air (ambient + 283 micromol mol-1) and four ch ... | 2002 | 11986047 |
| coarse and fine root respiration in aspen (populus tremuloides). | coarse and fine root respiration rates of aspen (populus tremuloides michx.) were measured at 5, 15 and 25 degrees c. coarse roots ranged from 0.65 to 4.45 cm in diameter, whereas fine roots were less than 5 mm in diameter. to discriminate between maintenance and growth respiration, root respiration rates were measured during aboveground growing periods and dormant periods. an additional measurement of coarse root respiration was made during spring leaf flush, to evaluate the effect of mobilizat ... | 2002 | 12091154 |
| 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 |
| effects of soil temperature on parameters of a coupled photosynthesis-stomatal conductance model. | to examine the effects of soil temperature on a coupled photosynthesis-stomatal conductance model, seedlings of trembling aspen (populus tremuloides michx.), jack pine (pinus banksiana lamb.), black spruce (picea mariana (mill.) b.s.p.) and white spruce (picea glauca (moench) voss) were exposed to soil temperatures ranging from 5 to 35 degrees c for 4 months. light and co(2) response curves of foliar gas exchange were measured for model parameterization. the effects of soil temperature on four k ... | 2002 | 12184971 |
| 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 |
| does clonal integration improve competitive ability? a test using aspen (populus tremuloides [salicaceae]) invasion into prairie. | many clonal plants consist of many connected individual ramets, allowing them to share water and nutrients via physiological integration. integration among ramets may also improve the ability of clonal plants to tolerate abiotic stress or improve the competitive ability of individual ramets. here i use a field experiment to determine whether clonal integration improves ramet performance for a widespread clonal tree species invading into native prairie. aspen (populus tremuloides) dominates the s ... | 2002 | 21665647 |
| simulation of 1-year-old populus tremuloides response to ozone stress at ithaca, usa, and suwon, republic of korea. | the growth of 1-year-old aspen was simulated using tregro, a computer simulation model of individual tree growth, to assess potential effects of ozone (o3). tregro was parameterized using information from a field experiment conducted at ithaca, ny, usa; the model was then applied using environmental information from suwon, korea, where o3 exposures of aspen had not been conducted. in the parameterization at ithaca, the simulated and measured total biomass differed by about 3% and the differences ... | 2001 | 11234543 |
| photosynthesis and carbon allocation of six boreal tree species grown in understory and open conditions. | one-year-old seedlings of abies balsamea (l.) mill, picea glauca (moench) voss, pinus contorta loudon, betula papyrifera marsh., populus tremuloides michx. and populus balsamifera l. were transplanted in the spring, in pots, to the understory of a mixed p. tremuloides-p. balsamifera stand or to an adjacent open site. growth and leaf characteristics were measured and photosynthetic light response curves determined in mid-august. overall, the coniferous seedlings showed less photosynthetic plastic ... | 2001 | 11276418 |
| rapid quantification of proanthocyanidins (condensed tannins) with a continuous flow analyzer. | proanthocyanidins (condensed tannins) frequently need to be quantified in large numbers of samples in food, plant, and environmental studies. an automated colorimetric method to quantify proanthocyanidins with sulfuric acid (h(2)so(4)) was therefore developed for use in a continuous flow analyzer. assay conditions were optimized using 50% methanol extracts of paper birch, sugar maple, and quaking aspen leaves. short extraction times and centrifugation of samples prevented proanthocyanidin degrad ... | 2001 | 11368578 |
| ascobotryozyma americana gen. nov. et sp. nov. and its anamorph botryozyma americana, an unusual yeast from the surface of nematodes. | a new teleomorphic genus ascohotryozyma, with a single species, a. americana, is proposed. its anamorph is a botryozyma that differs from the type species, b. nematodophila, on distributional, physiological, and molecular criteria; it is described as botryozyma americana, anam. sp. nov. ascobotryozyma is characterized by globose asci bearing four lunate ascospores. fusion of thallus cells precedes ascus formation. ascobotryozyma americana was isolated from the surface of nematodes (panagrellus d ... | 2001 | 11392486 |
| hydraulic conductance in aspen (populus tremuloides) seedlings exposed to low root temperatures. | low root temperatures significantly reduced root hydraulic conductivity and increased resistance to water flow through the roots of aspen (populus tremuloides michx.) seedlings. increased resistance to water flow could not be fully explained by the corresponding increase in water viscosity at low temperatures. the shapes of arrhenius plots of root water flow and the activation energies were dependent on the direction, sequence and extent of temperature change. the arrhenius plots suggested that ... | 2001 | 11446998 |
| food processing by animals: do beavers leach tree bark to improve palatability? | beavers store and consume tree parts in the bodies of water where they live. we examined whether such soaking renders food more palatable by leaching out undesirable compounds. in experiment 1, saplings of red maple, acer rubrum (rm), were first soaked in a pond for periods of 2, 18, and 36 days, then offered to free-ranging beavers. soaking for two days rendered rm slightly more acceptable to beavers. to further examine the time window around two days, rm sticks were soaked in distilled water i ... | 2001 | 11471937 |
| polyphenol oxidase and herbivore defense in trembling aspen (populus tremuloides): cdna cloning, expression, and potential substrates. | the biochemical anti-herbivore defense of trembling aspen (populus tremuloides michx.) was investigated in a molecular analysis of polyphenol oxidase (ppo; ec 1.10.3.2). a ppo cdna was isolated from a trembling aspen wounded leaf cdna library and its nucleotide sequence determined. southern analysis indicated the presence of two ppo genes in the trembling aspen genome. expression of ppo was found to be induced after herbivory by forest tent caterpillar, by wounding, and by methyl jasmonate treat ... | 2001 | 11473716 |
| gas chromatography-mass spectrometry method for the simultaneous determination of wood extractive compounds in quaking aspen. | we have developed a rapid gas chromatography-mass spectrometry (gc-ms) method for the detailed compositional analysis of 70 underivatized wood extractive components present in quaking aspen (populus tremuloides michx.). forty-four compounds were unequivocally identified by retention time and mass spectral comparison with standards. an additional 26 chromatographic peaks were assigned to broad chemical classes using retention time and mass spectra features. the results were compared to the respec ... | 2001 | 11486867 |
| a kunitz trypsin inhibitor gene family from trembling aspen (populus tremuloides michx.): cloning, functional expression, and induction by wounding and herbivory. | three kunitz trypsin inhibitor genes were isolated from trembling aspen (populus tremuloides) by pcr and cdna screening. based on sequence similarity, they were grouped into two classes. southern blots showed complex banding patterns and a high level of restriction fragment polymorphism between different aspen genotypes, suggesting that these trypsin inhibitors are members of a large, rapidly evolving gene family. one of the trypsin inhibitor genes, ptti2. was over-expressed in escherichia coli ... | 2001 | 11488481 |
| photosynthesis and light-use efficiency by plants in a canadian boreal forest ecosystem. | measurements of the photosynthetic response to midsummer irradiance were made for 11 species representing the dominant trees, understory shrubs, herbaceous plants and moss species in an old black spruce (picea mariana (mill.) b.s.p.) boreal forest ecosystem. maximum rates of photosynthesis per unit foliage area at saturating irradiance, a(max), were highest for aspen (populus tremuloides michx.), reaching 16 micromol m(-2) s(-1). for tamarack (larix laricina (du roi) k. kock) and p. mariana, ama ... | 2001 | 11498339 |
| effects of genotype, nutrient availability, and defoliation on aspen phytochemistry and insect performance. | genetic and environmental variability, and their interactions, influence phytochemical composition and, in turn, herbivore performance. we evaluated the independent and interactive effects of plant genotype, nutrient availability, and defoliation on the foliar chemistry of quaking aspen (populus tremuloides) and consequences for performance of gypsy moths (lymantria dispar). saplings of four genotypes were grown under two conditions of nutrient availability and subjected to three levels of artif ... | 2001 | 11504029 |
| genotypic variation in growth and physiological responses of finnish hybrid aspen (populus tremuloides x p. tremula) to elevated tropospheric ozone concentration. | saplings of six finnish hybrid aspen (populus tremuloides michx. x p. tremula l.) clones were exposed to 0, 50, 100 and 150 ppb ozone (o3) for 32 days in a chamber experiment to determine differences in o3 sensitivity among genotypes. based on the chamber experiment, three clones with intermediate sensitivity to o3 were selected for a free-air o3 enrichment experiment in which plants were exposed for 2 months to either ambient air (control) or air containing 1.3 x the ambient o3 concentration. w ... | 2001 | 11600339 |
| root water flow and leaf stomatal conductance in aspen (populus tremuloides) seedlings treated with abscisic acid. | exogenous abscisic acid (aba) applied to the roots and excised shoots of aspen (populus tremuloides michx.) inhibited stomatal conductance. however, the effect of aba on stomatal conductance was more pronounced in the excised shoots compared with the intact seedlings. approximately 10% of the aba concentration applied to the roots was found in the xylem exudates of root systems exposed to a hydrostatic pressure of 0.3 mpa. a similar concentration of aba applied to the excised shoots produced a f ... | 2001 | 11678278 |
| variation in the susceptibility of the forest tent caterpillar (lepidoptera: lasiocampidae) to bacillus thuringiensis variety kurstaki hd-1: effect of the host plant. | host-mediated effect on the efficacy of bacillus thuringiensis berliner against larvae of the forest tent caterpillar. malacosoma disstria hübner, was investigated under controlled conditions. host plants used in this study were quaking aspen, populus tremuloides michx., a preferred host, and sugar maple, acer saccharum marsh., a secondary host. larvae were reared in the laboratory on leaves of these hosts, and upon reaching the third, fourth, and fifth instar, they were fed leaves treated with ... | 2001 | 11681676 |
| perception of aspen and sun/shade sugar maple leaf soluble extracts by larvae of malacosoma disstria. | we investigated the behavioral feeding preference and the chemoreception of leaf polar extracts from trembling aspen, populus tremuloides, and from sun and shade sugar maple, acer saccharum, by larvae of the polyphagous forest tent caterpillar, malacosoma disstria, a defoliator of deciduous forests in the northern hemisphere. three polar extracts were obtained from each tree species: a total extract, a water fraction, and a methanol fraction. m. disstria larvae were allowed ad libitum access to ... | 2001 | 11710605 |
| growth responses of populus tremuloides clones to interacting elevated carbon dioxide and tropospheric ozone. | the intergovernmental panel of climate change (ipcc) has concluded that the greenhouse gases carbon dioxide (co2) and tropospheric ozone (o3) are increasing concomitantly globally. little is known about the effect of these interacting gases on growth, survival, and productivity of forest ecosystems. in this study we assess the effects of three successive years of exposure to combinations of elevated co2 and o3 on growth responses in a five trembling aspen (populus tremuloides) clonal mixture in ... | 2001 | 11789918 |
| consequences of elevated carbon dioxide and ozone for foliar chemical composition and dynamics in trembling aspen (populus tremuloides) and paper birch (betula papyrifera). | atmospheric chemical composition affects foliar chemical composition, which in turn influences the dynamics of both herbivory and decomposition in ecosystems. we assessed the independent and interactive effects of co2 and o3 fumigation on foliar chemistry of quaking aspen (populus tremuloides) and paper birch (betula papyrifera) at a free-air co2 enrichment (face) facility in northern wisconsin. leaf samples were collected at five time periods during a single growing season, and analyzed for nit ... | 2001 | 11789920 |