SEARCH · PubMed Health

Results for “Populus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources

PubMed1981

An Examination of the Leaf Quaking Adaptation and Stomatal Distribution in Populus tremuloides Michx.

The leaves of quaking aspen (Populus tremuloides Michx.) have a flattened petiole that allows them to quake (oscillate and roll) under low wind velocities. It was hypothesized that this adaptation might enable the plant to respond to windy conditions that would increase transpirational losses. No effects of wind with or without leaf quaking on stomatal resistance were observed under controlled conditions in the field. If wind and leaf quaking affect stomatal resistance, such effects must be small in comparison to those caused by other factors such as leaf water potential and ambient humidity.Aspen leaves are hypostomatal with stomata evenly distributed over the abaxial surface. This observation casts serious doubt on the hypothesis that quaking is an adaptation to increase bulk air flow through amphistomatal leaves.

Journal Article↗

PubMed1982

Photosynthesis and Respiration of Developing Populus tremuloides Internodes.

The photosynthetic and respiratory performance of developing internodes of Populus tremuloides was evaluated by infrared gas analysis. Anatomical and morphological transitions were related to metabolic activity. Photosynthetic rates ranged from 6.0 to 10.0 milligrams CO(2) per decimeter squared per hour in the youngest internodes to 2.5 to 3.8 milligrams CO(2) per decimeter squared per hour in internodes with fully developed bark tissues. Respiration exceeded the rate of photosynthesis on the average by a factor of two. Stem photosynthesis increased with temperature up to 40 degrees C and declined steeply between 40 and 50 degrees C. Stem respiration increased nearly linearly to temperatures as high as 50 degrees C.

Journal Article↗

PubMed1984

Short-Term Effects of CO(2) on Gas Exchange of Leaves of Bigtooth Aspen (Populus grandidentata) in the Field.

The short term effects of increased levels of CO(2) on gas exchange of leaves of bigtooth aspen (Populus grandidentata Michx.) were studied at the University of Michigan Biological Station, Pellston, MI. Leaf gas exchange was measured in situ in the upper half of the canopy, 12 to 14 meters above ground. In 1900 microliters per liter CO(2), maximum CO(2) exchange rate (CER) in saturating light was increased by 151% relative to CER in 320 microliters per liter CO(2). The temperature optimum for CER shifted from 25 degrees C in 320 microliters per liter CO(2) to 37 degrees C in 1900 microliters per liter CO(2). In saturating light, increasing CO(2) level over the range 60 to 1900 microliters per liter increased CER, decreased stomatal conductance, and increased leaf water use efficiency. The initial slope of the CO(2) response curve of CER was not significantly different at 20 and 30 degrees C leaf temperatures, although the slope did decline significantly during leaf senescence. In 1900 microliters per liter CO(2), CER increased with increasing light. The light saturation point and maximum CER were higher in 30 degrees C than in 20 degrees C, although there was little effect of temperature in low light. The experimental results are consistent with patterns seen in laboratory studies of other C(3) species and define the parameters required by some models of aspen CER in the field.

Journal Article↗

PubMed1985

Glutamine Transfer from Xylem to Phloem and Translocation to Developing Leaves of Populus deltoides.

The distribution of (14)C from xylem-borne [(14)C]glutamine, the major nitrogen compound moving in xylem sap of cottonwood (Populus deltoides Bartr. ex Marsh), was followed in rapidly growing shoots with a combination of autoradiographic, microautoradiographic, and radioassay techniques. Autoradiography and (14)C analyses of tissues showed that xylem-borne glutamine did not move with the transpiration stream into mature leaves. Instead, most of it was transferred from xylem to phloem in the upper stem and then translocated to young developing tissues. Microautoradiography showed that metaxylem parenchyma, secondary xylem parenchyma, and rays were the major areas of uptake from xylem vessels in the stem. Accumulation in phloem (high (14)C concentrations in sieve tubes) took place in internodes subtending recently mature leaves. Little (14)C from xylem-borne glutamine was found in phloem of mature leaves, which indicates restricted retransport of glutamine that did enter the leaf. In the primary tissues of the upper stem, most (14)C was found in the phloem. Cottonwood stems have an efficient uptake and transfer system that enhances glutamine movement to developing tissues of the upper stem.

Journal Article↗

PubMed1985

Comparative Distribution and Metabolism of Xylem-Borne Amino Compounds and Sucrose in Shoots of Populus deltoides.

The transport and metabolism of xylem-borne amino compounds and sucrose were investigated in rapidly growing shoots of cottonwood (Populus deltoides Bartr. ex Marsh.). (14)C-labeled glutamine, threonine, alanine, glutamic acid, aspartic acid, and sucrose were applied to the base of severed stems for transport in xylem. Distribution and metabolism of the compounds were followed with autoradiography, microautoradiography, and radioassay. Three utilization patterns were observed: (a) little alanine and sucrose was transported to the laminae of either mature leaves or developing leaves. These compounds were taken up from xylem free-space and utilized in adjacent tissue; (b) threonine also did not move into mature leaves but was translocated to developing leaves or utilized in the stem; (c) glutamic acid and aspartic acid were transported directly into the laminae of mature leaves via the xylem. Relatively less (14)C was retained in stems compared to the other compounds.Metabolism of the test compounds also differed considerably. (14)C from amino acids moved primarily into organic acids and protein. The (14)C from sucrose was widely distributed among the chemical fractions, with a high percentage found in structural carbohydrates. Clearly, cottonwood stems contain efficient uptake and transfer systems that differentiate among various compounds moving from root to shoot in xylem.

Journal Article↗

PubMed1985

A novel method of natural cryoprotection : intracellular glass formation in deeply frozen populus.

Correlating measurements from differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and survival of twigs after two-step cooling experiments, we provide strong evidence that winter-hardened Populus balsamifera v. virginiana (Sarg.) resists the stresses of freezing below -28 degrees C by amorphous solidification (glass formation) of most of its intracellular contents during slow cooling (</=5 degrees C per hour). It is shown that other components of the intracellular medium go through glass transitions during slow cooling at about -45 degrees C and below -70 degrees C. This ;three glass' model was then used to predict the results of differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and biological experiments. This model is the first definitive explanation for the resistance of a woody plant to liquid N(2) temperatures even if quench cooling (1200 degrees C per minute) begins at temperatures as high as -20 degrees C and warming is very slow (</=5 degrees C per hour). It is also the first time high temperature natural intracellular glass formation has been demonstrated.

Journal Article↗

PubMed1992

Immunodetection and Identification of N-(o-Hydroxybenzylamino)Purine as a Naturally Occurring Cytokinin in Populus x canadensis Moench cv Robusta Leaves.

A highly specific and sensitive enzyme-linked immunosorbent assay (ELISA) was developed for 9-beta-d-ribofuranosyl-N(6)-(o-hydroxybenzylamino)purine [(oOH)[9R]BAP] and structurally related cytokinins. As little as 3 femtomoles of the compound could be detected by this method. Cross-reactivity studies demonstrated the specificity of four polyclonal antibodies for (oOH)[9R] BAP and its free base in preference to a range of natural cytokinins and other purines. After evaluating the method by internal standardization employing [2-(3)H](oOH)[9R]BAP of high specific radioactivity as recovery marker by dilution analyses and by immunohistograms, it was possible to apply ELISA to quantify (oOH)[9R]BAP in plant extracts. In addition to (oOH)[9R]BAP, an unknown cytokinin reacting with the same antibody was detected in high performance liquid chromatography-fractionated extracts of mature Populus x canadensis Moench cv Robusta. The structure of the new compound was determined by gas chromatography-mass spectrometry and finally confirmed by synthesis as N(6)-(o-hydroxybenzylamino)purine.

Journal Article↗

PubMed2004

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 conductivity (L(pr)) increased more than two-fold and the relative concentration of apoplastic tracer dye trisodium 3-hydroxy-5, 8, 10-pyrenetrisulphonate (PTS(3)) in xylem exudate decreased by 73.6% in MS seedlings. Conversely, L(pr) decreased (55.3%) and PTS(3) increased (28.6%) in SS seedlings. Treatment of roots with 0.1 mM mercuric chloride decreased root volume flow density (J(v)) by about 29.0% in control and MS plants with no decrease measured in SS seedlings. Mercuric chloride also increased PTS(3) concentration in xylem exudate of control (59%) and MS (86%) seedlings with no change observed in SS plants. The results suggest that aquaporin-mediated transport is important in the regulation of root water flow under drought stress and that root water flow properties are strongly affected by the stress level. Regulation of root water flow may represent an important drought-stress resistance mechanism.

Journal Article↗

PubMed2005

Allergic contact dermatitis from salicyl alcohol and salicylaldehyde in aspen bark (Populus tremula).

Salicyl alcohol or 2-methylolphenol is a well-known allergen in phenol-formaldehyde resins and a strong sensitizer in guinea pigs. There is 1 previous report of allergic contact dermatitis from salicyl alcohol in aspen bark. We describe a second case with concomitant allergy to salicylaldehyde. An elk researcher who had handled leaves from various trees presented with eczema of the hands, face, flexures, trunk and extremities. Patch testing showed sensitivity to salicyl alcohol, salicylaldehyde, balsam of Peru (Myroxylon pereirae resin), aspen wood dust and an extract prepared from the bark of aspen (Populus tremula). Weaker reactions were observed to bark extracts of rowan (Sorbus aucuparia), tea-leaved willow (Salix phylicifolia) and goat willow (Salix caprea). We analysed salicyl alcohol and salicylaldehyde in the bark extracts and found the 2 chemicals in equal amounts, about 0.9 microg/mg in aspen bark and in lower concentrations in rowan and the willows. We did not find either of the chemicals in the test substance of balsam of Peru (Myroxylon pereirae). Besides salicyl alcohol, salicylaldehyde is also recommended to be used to screen for contact allergy to aspen. Both of these chemicals should be tested in forest workers in areas where aspen is growing.

Aldehydes↗

PubMed1984

Purification and properties of cinnamoyl-CoA reductase and cinnamyl alcohol dehydrogenase from poplar stems (Populus X euramericana).

Cinnamoyl-CoA reductase and cinnamyl alcohol dehydrogenase were purified to apparent homogeneity from poplar stems (Populus euramericana) and their main properties were studied. Only one form was identified for each enzyme. The reductase corresponded to one polypeptide of molecular weight 36 000 and the cinnamyl alcohol dehydrogenase was constituted of two identical subunits of molecular weight 40 000. These characteristics are in agreement with most of the data obtained for the same enzymes isolated from other plants. The two reductive enzymes are inhibited by thiol reagents and a metal chelator 1,10-phenanthroline. The isoelectric point of the reductase (pH 7.5) and of the dehydrogenase (pH 5.6) were determined by chromatofocusing. The cinnamoyl-CoA reductase exhibit a decreasing affinity towards feruloyl-CoA, sinapoyl-CoA and p-coumaroyl-CoA. The cinnamyl alcohol dehydrogenase, which catalyses the reduction of the three cinnamaldehydes, exhibits its highest efficiency towards coniferaldehyde. In spite of differences in the monomeric composition of lignins from xylem and sclerenchyma the reductive enzymes isolated from these two lignified tissues exhibit the same substrate specificity. Consequently, they do not play an important role in the qualitative control of lignins in poplar tissues.

Alcohol Oxidoreductases↗

PubMed1991

Involvement of an Extracellular Glucan Sheath during Degradation of Populus Wood by Phanerochaete chrysosporium.

Observations by transmission electron microscopy of wood samples of Populus tremula inoculated with the white rot fungus Phanerochaete chrysosporium showed that, at certain stages of their growth cycle, hyphae were encapsulated by a sheath which seems to play an active role in the wood cell wall degradation. Chemical and immunochemical techniques and C nuclear magnetic resonance spectroscopy were applied to demonstrate the beta-1,3-1,6-d-glucan nature of the sheath. Double-staining methods revealed the interaction between the extracellular peroxidases involved in lignin degradation and the glucan mucilage. The glucan was also shown to establish a material junction between the fungus and the wood cell wall. It was concluded that, by means of these interactions, the sheath provides a transient junction between the hyphae and the wood, thus establishing a point of attachment to the site of the degradation. The association of peroxidases to the glucan matrix is in favor of the role of the sheath as a supporting structure. Furthermore, that the sheath was hydrolyzed during the attack demonstrated its active role both in providing the H(2)O(2) necessary to the action of peroxidases and in providing a mode of transport of the fungal enzymes to their substrates at the surface of the wood cell wall.

Journal Article↗

PubMed1984

Pollen-pistil interactions in interspecific crosses of Populus (sections Aigeiros and Leuce): pollen adhesion, hydration and callose responses.

Intersectional crosses between species of sections Aigeiros (Populus deltoides, P. X euramericana or P. nigra) and Leuce (P. alba or P. tremuloides) are known to be reciprocally incompatible. The site of pollen tube arrest is on the stigma surface in pollinations between pistils of section Leuce and pollen of section Aigeiros; tubes failed to penetrate the stigma surface. In reciprocal matings, pollen of section Leuce germinated and tubes penetrated the stigma and style, where arrest occurred. Rejection may be accompanied by swelling of the tube tips, and callose plug formation. In the cross between P. deltoides and P. alba a callose response was detected in the cell walls of the transmitting tissue, adjacent to the rejected pollen tubes.

Microscopy, Electron, Scanning↗

PubMed1989

Isolation of flavonoids from Populus nigra as delta 4-3-ketosteroid (5 alpha) reductase inhibitors.

Inhibitors of delta 4-3-ketosteroid (5 alpha) reductase, which had been prepared from rat prostate and converted testosterone to 5 alpha-dihydrotestosterone and 4-androstene-3,17-dione, were isolated from 50% ethanol extract of Populus nigra. They were identified as pinobanksin (I, 3,5,7-trihydroxyflavanone), 3,7-dimethylquercetin (II, 3',4',5-trihydroxy-3,7-dimethoxyflavone) and pinocembrin (III, 5,7-dihydroxyflavanone). Compound III showed the most potent inhibitory activity among them.

5-alpha Reductase Inhibitors↗

PubMed1992

Platelet aggregation inhibitors from Populus sieboldii Miquel.

The water extract of Populus sieboldii Miquel (Salicaceae) inhibited arachidonic acid-induced platelet aggregation. Pyrocatechol and salicyl alcohol were isolated as active constituents. Pyrocatechol showed an inhibitory effect on platelet aggregation induced by arachidonic acid with IC100 value of 4 microM, which was 25 times more potent than aspirin.

Drugs, Chinese Herbal↗

PubMed1996

Isolation and analysis of cinnamic acid 4-hydroxylase homologous genes from a hybrid aspen, Populus kitakamiensis.

Cinnamic acid 4-hydroxylase (CA4H) is the second enzyme involved in phenylpropanoid biosynthesis and is a member of the cytochrome P-450 superfamily. Three CA4H homologous genes, cyp73A, cyp73b, and cyp73c, and a cDNA clone of cyp73a were isolated from a genomic library and a cDNA library of a hybrid aspen; Populus kitakamiensis, and were characterized. They might be interrupted by two introns each. cyp73a and cyp73b were very similar to each other not only in coding regions but also in non-coding regions. Southern blot analysis showed that four homologous genes for CA4H constructed a small gene family in the diploid genome of P. kitakamiensis. In the promoter regions, there were many common cis-element-like sequences in phenylpropanoid biosynthesis genes.

Amino Acid Sequence↗

PubMed1997

Transient expression of goat growth hormone gene in poplar (Populus alba L.) protoplasts: a quick method for detection of foreign gene expression in mRNA level.

We developed a sensitive, accurate, and fast method to detect foreign gene expression using reverse transcriptase-mediated polymerase chain reaction (RT-PCR) in poplar tree (Populus alba L.) protoplasts. Template total RNA was purified by removing the transfected foreign gene vector completely with DNase I treatment before the RT reaction. Expression of cDNA that encodes goat growth hormone was confirmed at the mRNA level 24 h after electroporation mediated DNA transfer.

Animals↗

PubMedDate not supplied

RT-PCR analysis and stress response capacity of transgenic gshI-poplar clones (Populus x canescens) in response to paraquat exposure.

Stress response capacity (Fv/Fm at 690 nm and F690/F735 at Fmax) of untransformed hybrid poplar, Populus x canescens (P tremula x P alba), and two transgenic lines overexpressing gamma-ECS (gamma-glutamylcysteine synthetase) either in the cytosol (cyt-ECS) or in the chloroplast (chl-ECS) was studied in response to the herbicide paraquat (4.0 x 10(-9) to 4.0 x 10(-6) M) for 21 days. Significant differences at sublethal (4.0 x 10(-7) M) and bleaching (4.0 x 10(-6) M) concentrations of paraquat were observed with about a two-fold and eight-fold decrease in the photosynthetic activity (Fv/Fm at 690 nm and F690/F735 at Fmax), respectively. None of the gshI transgenic lines (cyt-ECS, chl-ECS) with elevated GSH content exhibited significant tolerance to paraquat. Semiquantitative RT-PCR of the cyt-ECS clone was used for gene expression analysis of the nuclear encoded rbcS gene and the stress responsive gst gene. Expression of the constitutively expressed 26SrRNA ribosomal gene was probed as a control for all RT-PCR reactions. The relative intensities of gene expressions normalized to the level of 26SrRNA intensity showed a 50% decrease in the nuclear encoded rbcS expression and a 120% increase in the stress responsive gst gene expression of the paraquat treated (4.0 x 10(-7) M) samples of the transgenic poplar line (cyt-ECS).

Animals↗

PubMed1999

Genotypic variation for condensed tannin production in trembling aspen (POPULUS TREMULOIDES, salicaceae) under elevated CO2 and in high- and low-fertility soil.

The carbon/nutrient balance hypothesis suggests that leaf carbon to nitrogen ratios influence the synthesis of secondary compounds such as condensed tannins. We studied the effects of rising atmospheric carbon dioxide on carbon to nitrogen ratios and tannin production. Six genotypes of Populus tremuloides were grown under elevated and ambient CO(2) partial pressure and high- and low-fertility soil in field open-top chambers in northern lower Michigan, USA. During the second year of exposure, leaves were harvested three times (June, August, and September) and analyzed for condensed tannin concentration. The carbon/nutrient balance hypothesis was supported overall, with significantly greater leaf tannin concentration at high CO(2) and low soil fertility compared to ambient CO(2) and high soil fertility. However, some genotypes increased tannin concentration at elevated compared to ambient CO(2), while others showed no CO(2) response. Performance of lepidopteran leaf miner (Phyllonorycter tremuloidiella) larvae feeding on these plants varied across genotypes, CO(2), and fertility treatments. These results suggest that with rising atmospheric CO(2), plant secondary compound production may vary within species. This could have consequences for plant-herbivore and plant-microbe interactions and for the evolutionary response of this species to global climate change.

Journal Article↗