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PubMed2005

Elevated CO2 concentration, fertilization and their interaction: growth stimulation in a short-rotation poplar coppice (EUROFACE).

We investigated the individual and combined effects of elevated CO2 concentration and fertilization on aboveground growth of three poplar species (Populus alba L. Clone 2AS-11, P. nigra L. Clone Jean Pourtet and P. x euramericana Clone I-214) growing in a short-rotation coppice culture for two growing seasons after coppicing. Free-air carbon dioxide enrichment (FACE) stimulated the number of shoots per stool, leaf area index measured with a fish-eye-type plant canopy analyzer (LAIoptical), and annual leaf production, but did not affect dominant shoot height or canopy productivity index. Comparison of LAIoptical with LAI estimates from litter collections and from allometric relationships showed considerable differences. The increase in biomass in response to FACE was caused by an initial stimulation of absolute and relative growth rates, which disappeared after the first growing season following coppicing. An ontogenetic decline in growth in the FACE treatment, together with strong competition inside the dense plantation, may have caused this decrease. Fertilization did not influence aboveground growth, although some FACE responses were more pronounced in fertilized trees. A species effect was observed for most parameters.

Biomass↗
PubMed2006

Responses of condensed tannins in poplar roots to fertilization and gypsy moth defoliation.

We examined the effects of fertilization and gypsy moth defoliation on condensed tannin concentration (%CT) of hybrid poplar (Populus x canadensis cv 'Eugeneii') fine roots in the summers of 1997 and 1998. This factorial experiment included two defoliation treatments (defoliated and a foliated control) and fertilization treatments (100 kg nitrogen (N) ha(-1) and an unfertilized control). Gypsy moth (Lymantria dispar L.) populations were experimentally increased to obtain defoliation in the summers of 1996, 1997 and 1998; fertilization subplots were supplemented with NH4NO3 (100 kg N ha(-1)) in the spring of each year. Despite the severity of defoliation, the effects were small, and significant on only two sampling dates: in May 1997, when fine root %CT was 23% lower in the defoliated trees, and in November 1997, when trees in the defoliated unfertilized plots had 35% higher root %CT than trees in all other plots. Defoliation effects on root %CT did not follow the same seasonal pattern as defoliation effects on root starch content, N uptake capacity or leaf %CT. Regulation of root condensed tannin concentration appeared to be partially uncoupled from these traits. The small transient effects on root defense reflect the resilience of this early successional tree to severe early season defoliation.

Animals↗
PubMed2006

Plasticity of growth and sylleptic branchiness in two poplar families grown at three sites across Europe.

Two hybrid poplar maternal half-sib families, resulting from controlled crosses of the female parent Populus deltoides 'S9-2' with P. nigra 'Ghoy' and P. trichocarpa 'V24', were grown at three sites: northern Italy, central France and southern England. Juvenile stem growth traits (height, circumference and volume) and sylleptic branchiness (number of branches, density of branches per unit of stem height, percentage of the stem carrying branches and distance of the highest sylleptic branch to the top of the stem) were measured on 1-year-old shoots. Our general objectives were to determine the degree to which the expression of stem growth and syllepsis and the relationships between them are affected by environmental conditions and to evaluate the efficiency of indirect selection for stem growth using branching traits as secondary criteria. The performance of both families differed significantly within and between sites. Pronounced heterosis was observed and highly significant genotype x environment interactions were found for all traits across the sites. Syllepsis showed more marked genetic variation and plasticity than stem growth traits. Relationships between sylleptic branchiness and stem growth depended on environmental conditions. Heritability values at the individual level ranged between 0.09 and 0.59, but genetic gain in stem volume was not significantly improved when selection was based on sylleptic branch characteristics. However, despite strong phenotypic plasticity among sites, genotypic ranking among the sites was relatively stable.

Adaptation, Physiological↗
PubMed1990

ECOPHYS: An ecophysiological growth process model for juvenile poplar.

The ECOPHYS model is an ecophysiological growth process model of juvenile poplar clones growing under near optimal conditions. The theoretical basis for the ECOPHYS model is that (1) individual leaves drive and control growth; (2) the microenvironment at the leaf exerts primary control of photosynthetic rates; (3) leaf orientation is a major determinant of that microenvironment, (4) photosynthates produced by leaves are allocated among meristematic and respiratory sinks: and (5) the plant's genome and microenvironment regulate photosynthate allocation. The major driving variables are solar radiation, temperature, and clonal morphological and physiological factors. The user can interact or override any or all of the input variables to examine the effects of such changes on photosynthetic production and growth. Verification and sensitivity analyses of ECOPHYS are presented and discussed. The use of ECOPHYS as a research tool is illustrated with several examples. Model potential and limitations are discussed.

Journal Article↗
PubMed1991

Quantification of two-year-old hybrid poplar root systems: morphology, biomass, and (14)C distribution.

Root morphology, biomass, and (14)C distribution were studied in two 2-year-old Populus trichocarpa x P. deltoides hybrids, which originated from hardwood cuttings, to determine the pattern of root distribution in a plantation and to refine methods for root recovery. The trees were labeled with (14)CO(2) and harvested after a 72-hour chase period. Roots attached to each labeled tree were analyzed for morphological traits at the time of harvest. Detached roots from within a 1-m(3) volume of soil surrounding each tree were separated from the soil and sorted on the basis of rooting depth and root diameter. Lateral roots > 2 mm in diameter had a largely horizontal orientation at their point of origin from the cutting and extended horizontally up to 4 m from the cutting. This resulted in considerable overlap of root systems in the plantation. Results from (14)C labeling indicated that 24 +/- 4% (+/- SD) of the carbon exported from branches-labeled within two weeks after branch budset-was translocated to the root system. Dilution of the root (14)C label indicated that from 0 (> 5 mm diameter roots) to 75% (< 2 mm diameter roots) of the roots recovered from within the 1-m(3) volume of soil surrounding a harvested tree originated from other trees. Total root biomass was 6 +/- 1 Mg ha(-1) for both hybrids. Sixty percent of the root biomass was recovered directly from excavation, 16% from coarse-sieving excavated soil, and 24% from re-sorting sieved soil. The study indicated that root growth of hybrid poplars may be rapid and extensive and that detailed sorting of soil subsamples substantially improves the recovery of fine roots < 2 mm in diameter.

Journal Article↗
PubMed2026

Novel Mycoparasitic Mechanisms and Colonization Patterns on Poplar Revealed by GFP Tagging of the Biocontrol Fungus Clonostachys reniana.

Clonostachys rosea has long been the primary model for studying mycoparasitism within its genus; however, the potential of other species remains largely unexplored. In this study, we established a PEG-CaCl2-mediated protoplast transformation system for Clonostachys reniana. Our results demonstrate for the first time that this species is amenable to genetic manipulation and produces transformants with genetic stability, providing a reliable platform for functional genomic research in this fungus. Using green fluorescent protein tagging, we achieved stable transformants that retained wild-type physiological traits. Crucially, our data indicated that C. reniana utilizes a distinct mycoparasitic mechanism, which differs from the well-established sequential process of adhesion, coiling, and lysis seen in C. rosea. Confocal and scanning electron microscopy revealed that C. reniana, following initial coiling and invasive structure formation, penetrates the host hyphae of Botryosphaeria dothidea. It then grows longitudinally within the hyphal lumen, absorbing nutrients and eliminating the pathogen from the inside. Furthermore, C. reniana hyphae can colonize the intercellular spaces of the stem periderm in 84K poplar (Populus alba &#xd7; P. glandulosa) while displaying a distinct tissue-specific behavior in the roots by forming a mantle on the root surface resembling that of ectomycorrhizae. These findings establish C. reniana as a highly promising secondary model species within the Clonostachys genus. By uncovering a novel "internal-consumption" mycoparasitic mode, this study expands our understanding of the ecological diversity of biocontrol fungi and provides a powerful genetic toolset for future functional genomic research.

Clonostachys reniana↗
PubMed1992

Partial nucleotide sequence of poplar mosaic virus RNA confirms its classification as a carlavirus.

The nucleotide sequence of the 3'-proximal 1328 nucleotides of poplar mosaic virus (PMV) was determined and shown to contain two large open reading frames (ORFs). The ORF nearer to the 3' terminus of the RNA is capable of encoding a polypeptide of 14K with a 'zinc-finger' motif, and is homologous to sequences in corresponding positions in five other carlaviruses. The other ORF encodes a protein of 36K which includes two sequences of amino acids identified in tryptic digests as virion capsid protein, and has amino acid sequences in common with both carlaviruses and potexviruses.

Amino Acid Sequence↗
PubMed2004

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 distribution across the cambial region tissues in both aspen (Populus tremula, denoted poplar) and Scots pine (Pinus sylvestris) trees forming reaction wood, using tangential cryosectioning combined with sensitive gas chromatography-mass spectrometry analysis. Moreover, we have documented the kinetics of IAA during reaction wood induction in these species. Our analysis of endogenous IAA demonstrates that reaction wood is formed without any obvious alterations in IAA balance. This is in contrast to gravitropic responses in roots and shoots where a redistribution of IAA has been documented. It is also of interest that cambial growth on the tension wood side was stimulated without an increase in IAA. Taken together, our results suggest a role for signals other than IAA in the reaction wood response, or that the gravitational stimulus interacts with the IAA signal transduction pathway.

Biological Transport↗
PubMed2004

Transient release of oxygenated volatile organic compounds during light-dark transitions in Grey poplar leaves.

In this study, we investigated the prompt release of acetaldehyde and other oxygenated volatile organic compounds (VOCs) from leaves of Grey poplar [Populus x canescens (Aiton) Smith] following light-dark transitions. Mass scans utilizing the extremely fast and sensitive proton transfer reaction-mass spectrometry technique revealed the following temporal pattern after light-dark transitions: hexenal was emitted first, followed by acetaldehyde and other C(6)-VOCs. Under anoxic conditions, acetaldehyde was the only compound released after switching off the light. This clearly indicated that hexenal and other C(6)-VOCs were released from the lipoxygenase reaction taking place during light-dark transitions under aerobic conditions. Experiments with enzyme inhibitors that artificially increased cytosolic pyruvate demonstrated that the acetaldehyde burst after light-dark transition could not be explained by the recently suggested pyruvate overflow mechanism. The simulation of light fleck situations in the canopy by exposing leaves to alternating light-dark and dark-light transitions or fast changes from high to low photosynthetic photon flux density showed that this process is of minor importance for acetaldehyde emission into the Earth's atmosphere.

Acetaldehyde↗
PubMed2005

Characteristics of electrical signals in poplar and responses in photosynthesis.

To gain an understanding of the role of electrical signaling in trees, poplar (Populus trichocarpa, Populus tremula x P. tremuloides) shoots were stimulated by chilling as well as flaming. Two kinds of signal propagation were detected by microelectrode measurements (aphid technique) in the phloem of leaf veins: (1) basipetal, short-distance signaling that led to rapid membrane hyperpolarization caused by K+-efflux within the leaf lamina; and (2) acropetal, long-distance signaling that triggered depolarization of the membrane potential in the leaf phloem. In the latter, the depolarizing signals travel across the stem from the manipulated leaves to adjacent leaves where the net CO2 uptake rate is temporarily depressed toward compensation. With regard to photosystem II, both heat-induced long-distance and short-distance signaling were investigated using two-dimensional "imaging" analysis of chlorophyll fluorescence. Both types of signaling significantly reduced the quantum yield of electron transport through photosystem II. Imaging analysis revealed that the signal that causes yield reduction spreads through the leaf lamina. Coldblocking of the stem proved that the electrical signal transmission via the phloem becomes disrupted, causing the leaf gas exchange to remain unaffected. Calcium-deficient trees showed a marked contrast inasmuch as the amplitude of the electrical signal was distinctly reduced, concomitant with the absence of a significant response in leaf gas exchange upon flame wounding. In summary, the above results led us to conclude that calcium as well as potassium is involved in the propagation of phloem-transmitted electrical signals that evoke specific responses in the photosynthesis of leaves.

Chlorophyll↗
PubMed1995

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 was expressed in the cytosol, GS activities were up to 100 times greater than in other lines. Overexpression of GR or GS in the cytosol had no effect on glutathione levels, but chloroplastic-GR expression caused a doubling of leaf glutathione and an increase in reduction state. The high-chloroplastic-GR expressors showed increased resistance to photoinhibition. The herbicide methyl viologen inhibited CO2 assimilation in all lines, but the increased leaf levels of glutathione and ascorbate in the high-chloroplastic-GR expressors persisted despite this treatment. These results suggest that overexpression of GR in the chloroplast increases the antioxidant capacity of the leaves and that this improves the capacity to withstand oxidative stress.

Antioxidants↗
PubMed1997

Cinnamyl Alcohol Dehydrogenase: Identification of New Sites of Promoter Activity in Transgenic Poplar.

Stem sections from poplar that were stably transformed with a eucalypt cinnamyl alcohol dehydrogenase promoter-[beta]-glucuronidase construct were prepared by using either a technique routinely used in herbaceous species or a technique designed to take into account the particular anatomy of woody plants. Although both preparation techniques confirmed the pattern of expression previously observed (C. Feuillet, V. Lauvergeat, C. Deswarte, G. Pilate, A. Boudet and J. Grima-Pettenati [1995] Plant Mol Biol 27: 651-657), the latter technique also allowed the detection of other sites of promoter activity not revealed by the first technique. In situ hybridization confirmed the expression pattern obtained with the second sample preparation technique.

Journal Article↗
PubMed1998

Ozone sensitivity in hybrid poplar is correlated with a lack of defense-gene activation

Ozone is a major gaseous pollutant thought to contribute to forest decline. Although the physiological and morphological responses of forest trees to ozone have been well characterized, little is known about the molecular basis for these responses. Our studies compared the response to ozone of ozone-sensitive and ozone-tolerant clones of hybrid poplar (Populus maximowizii x Populus trichocarpa) at the physiological and molecular levels. Gas-exchange analyses demonstrated clear differences between the ozone-sensitive clone 388 and the ozone-tolerant clone 245. Although ozone induced a decrease in photosynthetic rate and stomatal conductance in both clones, the magnitude of the decrease in stomatal conductance was significantly greater in the ozone-tolerant clone. RNA-blot analysis established that ozone-induced mRNA levels for phenylalanine ammonia-lyase, O-methyltransferase, a pathogenesis-related protein, and a wound-inducible gene were significantly higher in the ozone-tolerant than in the ozone-sensitive plants. Wound- and pathogen-induced levels of these mRNAs were also higher in the ozone-tolerant compared with the ozone-sensitive plants. The different physiological and molecular responses to ozone exposure exhibited by clones 245 and 388 suggest that ozone tolerance involves the activation of salicylic-acid- and jasmonic-acid-mediated signaling pathways, which may be important in triggering defense responses against oxidative stress.

Journal Article↗
PubMed2000

Ozone sensitivity in hybrid poplar correlates with insensitivity to both salicylic acid and jasmonic acid. The role of programmed cell death in lesion formation.

Our earlier studies demonstrated that the ozone-sensitive hybrid poplar clone NE-388 displays an attenuated level of ozone-, wound-, and phytopathogen-induced defense gene expression. To determine if this reduced gene activation involves signal transduction pathways dependent on salicylic acid (SA) and/or jasmonic acid (JA), we compared the responses of NE-388 and an ozone-tolerant clone, NE-245, to these signal molecules. JA levels increased in both clones in response to ozone, but only minimal increases in SA levels were measured for either clone. Treatment with SA and methyl jasmonate induced defense gene expression only in NE-245, indicating that NE-388 is insensitive to these signal molecules. DNA fragmentation, an indicator of programmed cell death (PCD), was detected in NE-245 treated with either ozone or an avirulent phytopathogen, but was not detected in NE-388. We conclude that these clones undergo two distinct mechanisms of ozone-induced lesion formation. In NE-388, lesions appear to be due to toxic cell death resulting from a limited ability to perceive and subsequently activate SA- and/or JA-mediated antioxidant defense responses. In NE-245, SA-dependent PCD precedes lesion formation via a process related to the PCD pathway activated by phytopathogenic bacteria. These results support the hypothesis that ozone triggers a hypersensitive response.

Apoptosis↗
PubMed2001

Transgenic manipulation of the metabolism of polyamines in poplar cells.

The metabolism of polyamines (putrescine, spermidine, and spermine) has become the target of genetic manipulation because of their significance in plant development and possibly stress tolerance. We studied the polyamine metabolism in non-transgenic (NT) and transgenic cells of poplar (Populus nigra x maximowiczii) expressing a mouse Orn decarboxylase (odc) cDNA. The transgenic cells showed elevated levels of mouse ODC enzyme activity, severalfold higher amounts of putrescine, a small increase in spermidine, and a small reduction in spermine as compared with NT cells. The conversion of labeled ornithine (Orn) into putrescine was significantly higher in the transgenic than the NT cells. Whereas exogenously supplied Orn caused an increase in cellular putrescine in both cell lines, arginine at high concentrations was inhibitory to putrescine accumulation. The addition of urea and glutamine had no effect on polyamines in either of the cell lines. Inhibition of glutamine synthetase by methionine sulfoximine led to a substantial reduction in putrescine and spermidine in both cell lines. The results show that: (a) Transgenic expression of a heterologous odc gene can be used to modulate putrescine metabolism in plant cells, (b) accumulation of putrescine in high amounts does not affect the native arginine decarboxylase activity, (c) Orn biosynthesis occurs primarily from glutamine/glutamate and not from catabolic breakdown of arginine, (d) Orn biosynthesis may become a limiting factor for putrescine production in the odc transgenic cells, and (e) assimilation of nitrogen into glutamine keeps pace with an increased demand for its use for putrescine production.

Animals↗
PubMed1983

Effects of low concentrations of o(3) on net photosynthesis, dark respiration, and chlorophyll contents in aging hybrid poplar leaves.

Chronic exposure of hybrid poplar (Populus deltoides x trichocarpa) plants to low concentrations of ozone had negative impact upon net photosynthetic capacity, dark respiration, and leaf chlorophyll contents. Exposure to as much as 0.20 microliters per liter O(3) had no immediate effect on net photosynthesis (P(n)), but chronic exposure to 0.125 or 0.085 microliters per liter had a number of gradual effects on CO(2) exchange. These included increased dark respiration and consequently increased light compensation points in very young leaves (4-6 days old); and decreased P(n), leaf chlorophyll a and b contents, light saturation points, and apparent quantum yields in leaves 10 to 70 days old. Decreased P(n) was partially due to accelerated aging in leaves exposed to O(3), and lightsaturated P(n) was linearly related to chlorophyll a + b contents. Differences in light-saturated P(n) between control and O(3)-treated leaves of the same age were mostly due to photosaturation in O(3)-treated leaves and to a much lesser extent to lowered apparent quantum yields. Also, since P(n) and dark respiration were most affected by O(3) at different leaf ages, distinct modes of action are suggested. The effects of leaf aging on CO(2) exchange were considerable, but typical of other species. However, careful monitoring of the interacting effects of leaf age and pollutant exposure was needed in order to characterize the impact of chronic O(3) exposure upon CO(2) exchange.

Journal Article↗
PubMed1992

Expression of foreign genes in transgenic yellow-poplar plants.

Cells of yellow-poplar (Liriodendron tulipifera L.) were transformed by direct gene transfer and regenerated into plants by somatic embryogenesis. Plasmid DNA bearing marker genes encoding beta-glucuronidase (GUS) and neomycin phosphotransferase (NPT II) were introduced by microprojectile bombardment into single cells and small cell clusters isolated from embryogenic suspension cultures. The number of full-length copies of the GUS gene in independently transformed callus lines ranged from approximately 3 to 30. An enzyme-linked immunosorbent assay for NPT II and a fluorometric assay for GUS showed that the expression of both enzymes varied by less than fourfold among callus lines. A histochemical assay for GUS activity revealed a heterogeneous pattern of staining with the substrate 5-bromo-4-chloro-3-indoyl-beta-d-glucuronic acid in some transformed cell cultures. However, cell clusters reacting positively (blue) or negatively (white) with 5-bromo-4-chloro-3-indoyl-beta-d-glucuronic acid demonstrated both GUS activity and NPT II expression in quantitative assays. Somatic embryos induced from transformed cell cultures were found to be uniformly GUS positive by histochemical analysis. All transgenic plants sampled expressed the two marker genes in both root and shoot tissues. GUS activity was found to be higher in leaves than roots by fluorometric and histochemical assays. Conversely, roots expressed higher levels of NPT II than leaves.

Journal Article↗
PubMed1992

Rapid Activation of Phenylpropanoid Metabolism in Elicitor-Treated Hybrid Poplar (Populus trichocarpa Torr. & Gray x Populus deltoides Marsh) Suspension-Cultured Cells.

Elicitor induction of phenylpropanoid metabolism was investigated in suspension-cultured cells of the fast-growing poplar hybrid (Populus trichocarpa Torr. & Gray x Populus deltoides Marsh) H11-11. Treatment of cells with polygalacturonic acid lyase or two fungal elicitors resulted in rapid and transient increases in extractable l-phenylalanine ammonia lyase and 4-coumarate:coenzyme A ligase enzyme activities. The substrate specificity of the inducible 4-coumarate:coenzyme A ligase enzyme activity appeared to differ from substrate specificity of 4-coumarate:coenzyme A ligase enzyme activity in untreated control cells. Large and transient increases in the accumulation of l-phenylalanine ammonia-lyase and 4-coumarate:coenzyme A ligase mRNAs preceded the increases in enzyme activities and were detectable by 30 minutes after the start of elicitor treatment. Chalcone synthase, cinnamyl alcohol dehydrogenase, and coniferin beta-glucosidase enzyme activities were unaffected by the elicitors, but a large and transient increase in beta-glucosidase activity capable of hydrolyzing 4-nitrophenyl-beta-glucoside was observed. Subsequent to increases in l-phenylalanine ammonialyase and 4-coumarate:coenzyme A ligase enzyme activities, cell wall-bound thioglycolic acid-extractable compounds accumulated in elicitor-treated cultures, and these cells exhibited strong staining with phloroglucinol, suggesting the accumulation of wall-bound phenolic compounds.

Journal Article↗