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Two Gram-stain-negative, facultatively anaerobic, motile bacterial strains isolated from symptomatic bark of Populus × euramericana canker in China were investigated using a polyphasic approach, including 16S rRNA gene sequencing, multilocus sequence analysis, and biochemical and physiological assays. 16S rRNA gene sequencing indicated that these strains belonged to the genus Brenneria , family Pectobacteriaceae , and had the highest sequence similarity with Brenneria populi CFCC 11963T (98 %). DNA–DNA hybridization experiments revealed DNA–DNA relatedness values of 72.1–78.2 % between the new isolates and strains of B. populi , revealing that these strains belonged to the same species. The 16S rRNA gene sequencing and multilocus sequence analysis suggested that the two novel strains and those of B. populi are phylogenetically closely related but form two clearly separated subgroups. Based on the data, the two novel isolates represent a subspecies of B. populi for which the name B. populi subsp. brevivirga subsp. nov. is proposed with D8-10-4-5T (=CFCC 11935T=KCTC 42841T) as the type strain, with the automatic creation of B. populi subsp. populi subsp. nov. (type strain D9-5T=CFCC 11963T=KCTC 42088T).

The effects of magnetized water irrigation on the growth and ionic movements of one-year-old potted seedlings of Populus × euramericana ‘Neva’ were investigated. A magnetic treatment device was used to treat the plants. The contents of K+, Na+, Ca2+, and Mg2+in leaves and roots were analyzed by atomic absorption spectrophotometry (AAS), and the fluxes of K+, Na+, Ca2+, Mg2+, and H+in mesophyll cells and in meristematic zones were measured using a noninvasive micro-test technique (NIMT) after 30 days of treatment. After 90 days, the plants were harvested, and their growth indices and root morphology were measured. The results showed that (i) compared with nonmagnetic treatments (NMT), the magnetic treatments (MT) led to higher K+and Mg2+contents and lower Ca2+content in roots and leaves, while the Na+content was lower and the K+/Na+ratio was higher; (ii) MT enhanced Na+efflux, increased H+influx, and decreased K+and Mg2+efflux compared with NMT; (iii) MT resulted in greater height, diameter, and leaf area of the plants and increased the length, surface area, and number of root tips compared with NMT; and (iv) stomatal conductance (Gs), net photosynthetic rate (Pn), intercellular CO2concentration (Ci), and water use efficiency (WUE) were increased in MT, whereas both transpiration rate (Tr) and stomatal limiting value (Ls) were decreased compared with NMT. The results indicate that the use of magnetized water can promote plant quality and regulate the ion absorption, transpiration, and distribution. Thus, MT is conducive to the re-establishment of ionic homeostatic mechanisms via ion-selective absorption and transportation under salt stress.

In 2006, a new canker was observed on trees of Populus × euramericana ‘74/76’ and P. × euramericana ‘Zhonglin 46’ in the Henan and Shandong provinces of China. The disease, which is characterized by canker with white exudates dripping from the bark, occurred mainly in the summer. A particular gram-negative, rod-shaped bacterium was repeatedly isolated from the infected samples and proven to infect trees of P. × euramericana by Koch's postulates. Through a polyphasic taxonomic approach using sequence, DNA-DNA hybridization, chemotaxonomic, and phenotypic data, the poplar isolates were identified as Lonsdalea quercina subsp. populi, a subspecies very recently described based on isolates from oozing bark canker of poplar (P. × euramericana) trees in Hungary.

Element content and expression of genes of interest on single cell types, such as stomata, provide valuable insights into their specific physiology, improving our understanding of leaf gas exchange regulation. We investigated how far differences in stomatal conductance (g(s)) can be ascribed to changes in guard cells functioning in amphistomateous leaves. g(s) was measured during the day on both leaf sides, on well-watered and drought-stressed trees (two Populus euramericana Moench and two Populus nigra L. genotypes). In parallel, guard cells were dissected for element content and gene expressions analyses. Both were strongly arranged according to genotype, and drought had the lowest impact overall. Normalizing the data by genotype highlighted a structure on the basis of leaf sides and time of day both for element content and gene expression. Guard cells magnesium, phosphorus, and chlorine were the most abundant on the abaxial side in the morning, where g(s) was at the highest. In contrast, genes encoding H+-ATPase and aquaporins were usually more abundant in the afternoon, whereas genes encoding Ca2+-vacuolar antiporters, K+ channels, and ABA-related genes were in general more abundant on the adaxial side. Our work highlights the unique physiology of each leaf side and their analogous rhythmicity through the day.

A Gram-stain-negative, aerobic, non-motile bacterial strain, 7Y-4T, was isolated from bark tissue of Populus × euramericana. The isolate was able to grow between 10 and 37 °C, with optimal growth occurring at 28-30 °C. Strain 7Y-4T was positive for oxidase and catalase activities, but did not reduce nitrite from nitrate. Positive reactions were observed for the activities of β-galactosidase, urease and β-glucosidase, but negative reactions for the activities of gelatinase and the production of indole, acetoin and H2S. Citrate was not utilized. The major fatty acids of strain 7Y-4T are iso-C15 : 0 (28.6 %), C16 : 1ω7c/C16 : 1ω6c (31.8 %) and iso-C17 : 0 3-OH (23.3 %).The major polar lipids of the novel isolate include phosphatidylethanolamine, three unknown phospholipids (PL1-3) and six unknown lipids (L1-6), and the predominant menaquinone is MK-7. The DNA G+C content is 41.7 mol%. Analysis of 16S rRNA gene sequences revealed that the novel isolate shared the greatest sequence similarity with Sphingobacterium hotanense XH4T (93.50 %). On the basis of phenotypic and genotypic characteristics, strain 7Y-4T represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium populi is proposed. The type strain is 7Y-4T (=CFCC 11742T=KCTC 42247T).

Modelling allometric equations for saplings of hybrid poplar clone produce a highly accurate estimate of pure productivity and C sequestration, leading to better sales and determination of the capacity of cellulose resources and bio-energy pools. Twenty five cuttings with 25 cm length were planted within a 1×1 m2 area in the Talookola nursery, Sari, in 2011. Ten saplings were selected from the two diameter classes (0-1, 1.1-2 cm). After separating the roots and stems, they were oven-dried at 85ºC for 48 hours. According to the diameter distribution, 24 and 6 saplings, respectively, from each diameter class were uprooted. Collar diameter and height were the twe variables used to model allometric equations. Carbon factor was obtained directly by exposing the wood samples in the oven and was estimated based on organic carbon to organic material ratio. Collar diameter and height were the variables to model allometric equations. The results of allometric modelling showed that multivariate linear model including natural logarithm of diameter, logarithm of height and diameter logarithm square with mean C factor of [C] = 0.44 is the optimal equation (R2adj = 0.732 CF = 1.056) for C sequestration of superior saplings.

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Five non-spore-forming, aerobic and Gram-stain-positive bacterial strains, 10-107-8T, 1C-4, NHI3_6, 4107_1_2, and 3D-3, were isolated from Populus×euramericana bark collected in Puyang City, Henan Province, PR China. The isolates grew at 15–40 °C and pH 5–10. The optimum temperature and pH for growth were 30 °C and pH 8.0, respectively. Chemotaxonomic features included MK-10 and MK-11 as major menaquinones (type strain); predominating iso- and anteiso-branched cellular fatty acids; diphosphatidylglycerol and phosphatidylglycerol as major polar lipids (type strain); ornithine as the principal diamino acid of the cell-wall peptidoglycan (type strain); glycolyl type as cell-wall acyl type; and DNA G+C content of 66.8–67.6 mol%. These features were consistent with classification in the genus Microbacterium . Analysis of 16S rRNA gene sequence data indicated that the five isolates belonged to the genus Microbacterium and were closely related to Microbacterium halotolerans . A high 16S rRNA gene sequence similarity of 96.97 % to M. halotolerans YIM 70130T was observed. The five isolates showed less than 96.20 % 16S rRNA gene sequence similarity to the other species of the genus Microbacterium with validly published names. DNA–DNA relatedness of the five isolates with M. halotolerans JCM 13013T ranged from 35.62 % to 44.36 %. Considering the results of 16S rRNA gene sequence analysis and the physiological and biochemical characteristics, we propose that the five strains should be assigned to a novel species of the genus Microbacterium . The name proposed for the five strains is Microbacterium populi sp. nov., and the type strain is 10-107-8T ( = CFCC 11275T = KCTC 29152T).

The light-response curve of photosynthesis is an important tool used to study plant ecophysiology and can provide a scientific basis for the response of plant photosynthetic characteristics to environmental factors. At present, there are five common light-response models of photosynthesis. To gain deeper insight into the applicability of different light-response models of photosynthesis and the photosynthetic physiological characteristics of Populus euramericana cv. 'Zhonglin46', two typical light-response curves of photosynthesis in P. euramericana cv. 'Zhonglin46' leaves, one under drought stress and the other under control conditions, were measured using a CIRAS-2 portable photosynthesis system. The light-response data were divided into two groups: one set of data was used to fit light-response curves, and the other set of data was used to test them. The accuracy of the fitting and the predictions of the different models were evaluated by mean square error and mean absolute error. The results showed that the light-response curves of P. euramericana cv. 'Zhonglin46' under drought stress matched the light-saturated inhibition type and that those under the control condition matched the approaching light-saturation type. The two new models (i.e., the modified rectangular hyperbola model and modified exponential model) fit the two light-response curves and their characteristic parameters well, and the fitting results of the two models were similar. Conversely, the three traditional models (i.e., the rectangular hyperbola model, nonrectangular hyperbola model, and exponential model) did not fit the two light-response curves well; in particular, they overestimated the maximum net photosynthetic rate, underestimated the light saturation point (LSP), and did not fit the net photosynthetic rate during the light-saturated stage. The LSP calculated by the "linear method" combined with the traditional models was significantly lower than the measured values; additionally, the appropriate value of the proportional coefficient was difficult to determine, and the assumed value (empirical value) could easily lead to unreliable results by the "coefficient method". The "estimation method" based on the measured light-response data was still a relatively accurate, simple, and practical way to determine LSP. In addition, the nonrectangular hyperbolic model also had good accuracy and applicability in fitting the approaching light saturation curve on the basis of the "estimation method" to determine LSP.

An efficient regeneration protocol for stem disc culture of Populus euramericana, which is important species for bioenergy resource in agroforestry, was established. The number of explants that were obtained and the number of explants that regenerated varied with the genotypes. However, in all the genotypes, stem disc culture produced more regenerated shoots than did in axillary bud culture. A comparison of the effects of cytokinin type and concentration on shoot regeneration in different explants (i.e., petiole, leaf, and root segments of P. euramericana) revealed that a concentration of 0.002 mg l-1 thidiazuron (TDZ) used on petiole segments resulted in the greatest shoot regeneration (95.83%). The hormonal requirements for the greatest shoot regeneration in the three explant types varied. Different concentrations of AgNO3 and CoCl2 were added separately to the medium to stop the yellowing and subsequent necrosis of the regenerated shoots. Lower concentrations (3 and 5 mg l-1) of these compounds improved shoot regeneration and elongation, compared with the control. The in vitro-regenerated shoots were transferred to rooting medium and subsequently acclimatized. The highly efficient regeneration system of P. euramericana reported here can be used for mass propagation of this recalcitrant for regeneration, economically important tree species.

The poplar clones of Robusta and I-214 (Populus × euramericana) are characterized by fast growth and high quality biomass production. The calorific values for these poplar clones were determined, and modelling of calorific production of the entire poplar clone stands was performed. This research, dependent on age and site indexes, was conducted in four localities in Eastern Slovakia and seven in the western region of this country. Samples of bark, wood and small-wood with bark were excised from three tree stem areas and from two parts of the crown. No significant difference was observed between the two clones, with regard to either the biomass fraction or the location of the excised sample on the tree. The average calorific capacity of all biomass fractions was approximately 6.86-8.73 GJ m-3, with the lowest bark values emanating from the stem base. The mean annual calorific energy production for site indexes 40-20 after 17-26 years growth was 320-80 GJ ha-1 a-1, and this was calculable 2-3 years earlier in the I-214 clone than in Robusta. The energy use efficiency of these poplar clones was estimated at a maximum of 0.4-1.6% solar radiation utilization.

Plantations of hybrid poplars adapted to relatively poor soils and cold conditions are being established in abandoned fields and forest sites in southern Quebec. Hybrids of Populus maximowiczii are well adapted to these sites but little is known about their nutritional requirements. The objectives of this study were to develop nutritional norms (CVA, DRIS, CND) for three of these hybrids: 915508, Populus euramericana or canadensis X Populus maximowiczii; 3729, Populus nigra X Populus maximowiczii; and 915303, Populus maximowiczii X Populus balsamifera, and to apply the norms on some sites recently planted in southern Quebec. Six plantations (two per clone) were used for the determination of nutritional norms. In each plantation, individual trees were fertilized with nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) according to a factorial design with three levels of application for each nutrient (35 = 243 treatments). Tree diameter and height, unit foliar mass and foliar chemi...

Bait matrix of different treatments were evaluated against two termite species i.e. Odontotermes obesus and Coptotermes heimi both under laboratory and field conditions. Mean wood consumption in laboratory bioassays were investigated for 2, 4 and 6 weeks with maximum consumption was noted after 4 weeks. While, field experiment was conducted for 24 there was greater consumption of the loosely bound bait matrix compared to the tightly bound matrix. However, feeding was comparatively high in combinations with attractants. Overall, treated colonies experienced a 90-95% decrease in population size after 24 weeks of baiting. The queen in the royal chamber of the mound was found dead.

The relationships between above-ground stem, branch, leaf masses and stand density index (SDI) were analysed in Populus×euramericana (Dode) Guinier stands in Jiangsu Province, China. The allometric equations developed in this study accurately estimated masses of above-ground and specific above-ground tree components in stands with different SDIs. The relationship between the mean above-ground mass w and the ratio of stem to the above-ground (wS/w) was examined. With increasing w, the stem mass ratio wS/w increased. Mean masses of above-ground and tree components decreased significantly with increasing SDI at age 9 years, indicating the presence of competition-induced limitations to growth. The mean above-ground mass‐SDI and mean component mass‐SDI were strongly correlated with above-ground mass-SDI and tree component mass‐SDI, respectively. An equation describing the relationship between the mean leaf area u and SDI was developed, which fitted well for the u-SDI data. Stem mass increment exponentially increased with increasing leaf area index.

The area covered by plantations of hybrid poplar in Europe is increasing greatly because of the high profitability of these trees. However, the productivity varies widely depending on nutritional status, and it is therefore essential to identify the limiting nutrients. The aims of this study were (a) to identify the main nutrients limiting the growth and vitality of monoclonal poplar (Populus × euramericana) plantations and (b) to develop a means of early detection of nutrition-related problems in growth, based on visual crown conditions (crown transparency, VCT, and visual crown discoloration, VCD). The study was carried out in one of the most suitable areas for this species in Southern Europe. Thirty-two Populus × euramericana (clone I-214) stands displaying different levels of decline were selected for study, and tree growth, nutritional status (soil properties and foliar nutrient concentrations) and crown conditions were assessed. The stands, which were growing in soils with high contents of coarse fragments, displayed low growth rates, poor crown conditions and deficiencies in Fe, B, N, P, K, and to a lesser extent, Zn and Cu. The deficiencies increased with the age of the stand, presumably because of the higher nutrient demand in older trees. Visual crown conditions were related to growth rates and nutritional status. Predictive models were developed to relate crown conditions to the nutritional status identified by analysis of soil properties and foliar concentrations of nutrients.

Growth and timber production of 28 poplar clones were evaluated. A set of clones was derived from 14 clones newly bred in Forestry and Game Management Research Institute in the Czech Republic, eight well-known cultivars of Populus × euroamericana planted in Europe and imported to the Czech Republic, two standard cultivars 'I-214' and 'Robusta' (Populus × euroamericana). Four clones of Populus deltoides were added to the test set. Tree spacing was 4 × 4 m. Stem diameter, tree height and stem volume production were evaluated in 6-years-old trees. Based on the results, it was concluded that the yield of four clones was higher than that of standard cultivar 'I-214'. Standing volume of two P. deltoides clones and one new Czech P. × euroamericana clone varied in the range of 77–121 m3·ha–1.

In previous experiments elevated but sub-symptomatic applications of Zn (0.1 mM and 1 mM) caused impairments in growth parameters and photosynthetic performance of Populus × euramericana (Dode) Guinier clone I-214. The aim of this work was to evaluate leaf morphological and anatomical traits in this clone in response to the same Zn concentrations. The results showed that Zn treatments induced variations in leaf dry mass, area, mesophyll thickness, intercellular spaces, stomatal density and size. Stronger modifications, especially concerning stomata characteristics induced by 1 mM Zn, were consistent with physiological impairments while those induced by 0.1 mM Zn suggested a compensatory strategy for maintaining functional integrity.

The competition–density (C–D) effect for non-self-thinning Populus deltoides and Populus × euramericana plantations from 3 to 9 years was analyzed using the reciprocal equation of the C–D effect. The C–D effect was well described by the reciprocal equation, and with the progress of time the C–D curve, on logarithmic coordinates, of the P. × euramericana plantations shifted upward faster than that of the P. deltoides plantations. With increasing physical time t, the biological time τ, i.e. the integral from zero to t of the coefficient of growth λ(t) in the general logistic curve with respect to t, increased rapidly during early growth stages and the increases in τ gradually became slow during later growth stages. This trend was more evident in the P. deltoides plantations than in the P. × euramericana plantations. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ) at a given growth stage, increased abruptly to a maximum value and then tended to decrease gradually to a constant level. On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume at a given growth stage, decreased exponentially and tended to be close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, increased gradually with increasing stand age. The differences in coefficients A, B, and λ(t) between the two species were reported.

The effect of light (blue, red, and/or green) generated by light-emitting diodes on shoot regeneration was examined in selected clones, 'I-476' and 'Dorskamp', of Populus euramericana. We found that a combination of red and blue light produced the highest percentage of shoot regeneration in comparison to monochromic or fluorescent light. Further studies of light quality and in vitro growth of ''Dorskamp'' plantlets demonstrated the suitability of combinations of red and blue light to improve most of the characteristics studied. Flow cytometry of the leaves showed that 50 % red ? 50 % blue light treatment was the most effective for inducing cell division in ''Dorskamp'', whereas monochromic red and blue were more effective in ''I-476''. Histological studies found that secondary xylem formation increased with the monochromic blue light treatment in the stem of ''I-476'', whereas in ''Dorskamp'', a combination of red and blue light (70 ? 30 %, respec- tively) was more suitable. Our study demonstrated that combinations of red and blue light increase shoot regeneration and development by stimulation of cell divi- sion, although the response may vary among genotypes of the same species. The results of this study can contribute to mass production of the selected clones for forest estab- lishment on reclaimed land and serve as an efficient pro- tocol for genetic transformation of this species.

Relatively little is known about the influences of growing-season background ozone (O3) concentrations on leaf cuticles and foliar water loss. Using fumigation chambers, leaf wettability and foliar water loss were studied in two poplar species, Populus nigra and P. euramericana, and a conifer, Pseudotsuga menziesii, under three O3 regimes; control (approx. 1 ppbv O3), urban O3 exposure (13-41 ppbv O3), and montane O3 exposure (30-45 ppbv O3). Urban O3 exposure delayed a decrease in droplet contact angles over time in Populus leaves by 2-4 wk, and decreased droplet contact angles of P. menziesii foliage. Ozone exposure increased foliar water loss and minimal conductance to water vapour for P. euramericana, but not P. nigra and P. menziesii. Both Populus species had lower photosynthetic biomass in O3 treatments, due to production of fewer new leaves, premature leaf abscission and decreased leaf size (P. euramericana only). Leaf abscission was preceded by foliar injury symptoms characteristic of O3 exposure. Results suggest that exposure to [O3] common during the growing season can increase water loss in Populus saplings, but this effect might be offset by decreased foliar biomass. Importantly, responses were highly species specific in a given O3 treatment.

Development of leaf rust (Melampsora ciliata) in different species, hybrids and cultivars of poplar (Populus spp.) was studied in nursery-grown plants. Five different criteria were used to assess the disease development. The mean disease index on 10 August was 9.4% which increased to 70.0% on 10 October. The lowest disease index (5.5%) was recorded in P. yunnanensis whereas the maximum was recorded in P. × euramericana‘Rubra-Poiret’ (59.5%). The apparent infection rate per unit per day was highest in P. nigra × P. trichocarpa (9.7 × 10–2) whereas the minimum occurred in P. maximowiczii × P. berolinensis‘Oxford’ (3.3 × 10–2). The area under the disease progress curve was a maximum in P. × euramericana‘Rubra-Poiret’ (26.7) and a minimum in P. yunnanensis (1.6). Complete defoliation by the first half of October occurred in P. nigra × P. trichocarpa, which also had the maximum apparent infection rate and area under the disease progress curve. Inoculum production was highest in P. nigra × P. trichocarpa and lowest in P. maximowiczii × P. berolinensis‘Oxford’. Developpement de la rouille du peuplier a Melampsora ciliata en pepiniere, dans le nord-ouest de l’Hymalaya Le developpement de la rouille foliaire aMelampsora ciliata Barclay chez differentes especes, des hybrides et des cultivars de peuplier a eteetudie sur des plants en pepiniere. Cinq criteres ont ete utilises pour evaluer la maladie. L’indice moyen de maladie le 10 aout etait de 9,4% et de 70,0% le 10 octobre. L’indice le plus faible (5,5%) a ete observe chez Populus yunnanensis et le plus eleve chez P. × euramericana‘Rubra-Poiret’ (59,5%). Le taux d’infection apparente par unite foliaire et par jour a ete le plus eleve chez P. nigra × P. trichocarpa (9,7 × 10–2) et le plus faible chez P. maximowiczii ×P. berolinensis‘Oxford’ (3,3 × 10–2). La surface au dessous de la courbe de progression de maladie etait maximale chez P. × euramericana‘Rubra-Poiret’ (26,7%) et minimale chez P. yunnanensis (1,6%). La defoliation totale dans la premiere moitie d’octobre a eu lieu chez P. nigra × P. trichocarpa qui avait aussi le maximum de taux d’infection apparente et de surface sous la courbe de progression de maladie. La production d’inoculum etait la plus forte chez P. nigra × P. trichocarpa et la plus faible chez P. maximowiczii × P. berolinensis‘Oxford’. Entwicklung von Melampsora ciliata auf Pappelstecklingen in einer Baumschule im Nordwest-Himalaja An Stecklingen verschiedener Pappelarten, -hybriden und -sorten wurde die Entwicklung des Blattrostes Melampsora ciliata anhand von funf Parametern registriert. Der mittlere Krankheitsindex betrug am 10. August 9,4% und nahm bis zum 10. Oktober auf 70% zu. Der kleinste Indexwert wurde bei P. yunnanensis registriert, der grosste bei P. × euramericana‘Rubra-Poiret’ (59,5%). Die anhand der Symptome erkennbare Infektionsrate pro Einheit und Tag war bei P. nigra × P. trichocarpa am hochsten (9,7 × 10–2) und bei P. maximowiczii × P. berolinensis‘Oxford’ am geringsten (3,3 × 10–2). Die Flache unter der Kurve des Krankheitsverlaufs war bei P. × euramericana‘Rubra-Poiret’ am grossten (26,7) und bei P. yunnanensis am kleinsten (1,6). Eine vollstandige Entlaubung in der ersten Oktoberhalfte trat bei P. nigra × P. trichocarpa ein, die ebenfalls eine sehr hohe Infektionsrate und einen sehr progressiven Krankheitsverlauf aufwies. Die Inokulumproduktion war auf dieser Hybridpappel am hochsten, am geringsten war sie bei P. maximowiczii × P. berolinensis‘Oxford’.

Young shoots from poplar cuttings (Populus euramericana cv ʻGhoyʼ) were artificially inclined to 30° from vertical to quantify the anatomical modifications induced by this gravitational stimulus. At the end of the growing season, the tension wood tissue (from the upper face of the inclined axis) was compared to the opposite wood tissue (from the lower face), with radial position taken into account. On isolated elements after maceration, fibres and vessels were significantly longer in tension wood tissue. In the cross section, the gelatinous fibres had a smaller radial diameter than normal fibres in opposite wood. Vessel frequency and porosity were significantly lower in tension wood than in opposite wood. Solitary vessels in tension wood were less circular in cross section than in opposite wood, but their surface area did not differ. Rays were more numerous in tension wood than in opposite wood but their height did not differ between the two tissue types. Finally, there was a negative correlation between the proportion of vessel lumina (lowest in tension wood) and the proportion of fibre lumina including the G layer. The very controlled nature of this experiment (greenhouse, young clonal material, detailed anatomical observations within one growth ring) and the image analysis technology (allowing a large number of observations) enabled us to draw conclusions that may not have been seen in less-controlled experiments and /or those with smaller sample sizes.

In a greenhouse, under controlled conditions, young shoots, taken from poplar cuttings (Populus euramericana (Dole) Guinier cv. Ghoy), were artificially bent to quantify the modifications of physic...

L'influence de contraintes internes elevees dans l'arbre, et du comportement mecanique transverse du bois, sur l'importance des fentes d'abattage, a ete etudiee chez 15 peupliers I214 (clone sensible au probleme) âges de 30 ans. Pour ces arbres le protocole suivant a ete adopte: i) Estimation des deformations residuelles en 4 points a la peripherie du tronc, a une hauteur de 1,30 m. La position du pic de deformation est generalement estimee par la direction d'inclinaison de l'arbre mesuree sur 6 m. ii) Quantification des fentes sur la section d'abattage et sur une section voisine des points de mesures des deformations: longueur et profondeur maximale estimee des fissures [...]

Callus cultures of Populus×euramericana cv. ‘NL-B-132’ derived from stem and leaf tissue were compared for their content of abscisic acid and defense reactions against the basidiomycete Phaeolus schweinitzii. The callus from stems showed higher ABA-contents and a more pronounced defense reaction in comparison with leaf callus.

The “plastid initial,” the presumed precursor of eoplasts and proplastids, is present in the cells of the apical meristem of winter buds of poplar (Populus euramericana). The formation of the plastid initial in the cells of winter buds is initiated soon after the breaking of the innate or resting stage of dormancy, even in winter under nongrowing conditions in mid-January or early February. From this stage to March, the conglomeration of the plastid initial and the formation of prolamellar bodies is evident. In contrast to the poplar samples kept outdoors, the cells of the apical meristem of the indoor winter buds did not show any indication of the formation of the plastid initial and the buds of the latter sample did not flush even at the end of May. These results suggest that the sequence of reactions involved in the onset of regrowth may be closely related to the formation of the plastid initial.

International audience; Using cytological methods and SSR DNA marker analysis, this study revealed the formation mechanisms and the genetic constitutions of the 2n pollen in Populus × euramericana (Dode) Guinier and P. × popularis.* In P. × euramericana (Dode) Guinier, four abnormalities in microsporogenesis were observed: parallel spindle, fused spindle, tripolar spindle and premature cytokinesis. The first three can lead to first-division restitution (FDR) 2n pollen formation and the last one can form second-division restitution (SDR) 2n pollen. The SSR marker analysis results of parents and their tetraploidy filial generation confirmed that the genetic constitution of 2n pollen produced by P. × euramericana (Dode) Guinier was FDR.* In P. × popularis, three of these abnormalities were observed: parallel spindle, fused spindle and premature cytokinesis. The SSR marker analysis results showed the genetic constitution of 2n pollen produced by P. × popularis was SDR. Natural 2n female gametes in P. × euramericana (Dode) Guinier are reported for the first time. SSR analysis indicated that natural 2n female gametes of P. × euramericana (Dode) Guinier did exist and were fertile, which could be FDR genetic constitution.* The results from this study showed a great potential for using 2n gametes to produce polyploid poplar clones, which can be used effectively for polyploid breeding for poplar species in the section Aigeiros.; En utilisant des méthodes cytologiques et des analyses avec des marqueurs SSR, cette étude a révélé les mécanismes de formation et la constitution génétique du pollen 2n chez Populus × euramericana (Dode) Guinier et P. × popularis. * Chez P. × euramericana (Dode) Guinier, quatre anomalies dans la microsporogénèse ont été observées: en parallèle broche, broche fusion, tripolaire broche et une cytokinèse prématurée. Les trois premiers peuvent entraîner une première division restitution (FDR) de formation du pollen 2n et le dernier peut former une deuxième division de restitution (SDR) du pollen 2n. Les résultats de l'analyse des marqueurs SSR des parents et de leur descendanta tetraploides ont confirmé que la constitution génétique du pollen 2n produit par P. × euramericana (Dode) Guinier a été FDR. * Dans P. × popularis, trois de ces anomalies ont été observées: en parallèle broche, broche fusion et cytokinèse prématurée. Les résultats de l'analyse de marqueurs SSR ont montré que la constitution génétique du pollen 2n produit par P. × popularis a été SDR. Les gamètes naturelles femelles 2n chez P. × euramericana (Dode) Guinier ont été signalés pour la première fois. Les analyses SSR ont montré que les gamètes naturels femelles 2n de P. × euramericana (Dode) Guinier existaient et étaient fertiles, cela pourrait être la constitution génétique FDR. * Les résultats de cette étude ont montré le grand potentiel de l'utilisation des gamètes 2n pour produire des clones de peuplier polyploïdes, cela peut être utilisé efficacement pour la sélection de polyploïdes pour des espèces de peuplier de la section Aigeiros.

International audience; Genotypic variability for productivity, wateruse efficiency and leaf traits in 33 genotypes selected from an F1 progeny of Populus deltoides Bartr. ex Marsh • Populus trichocarpa L. was explored under optimal and moderate water-deficit conditions. Saplings of the 33 genotypes were grown in a two-plot open field at INRA Orle´ ans (France) and coppiced every year. A moderate water deficit was induced during two successive years on one plot by withholding irrigation, while the second one remained irrigated (control). Stem biomass and leaf structure (e.g., specific leaf area and leaf area) were measured in 2004 and 2005 and functional leaf traits (e.g., carbon isotope discrimination, D) were measured only in 2004. Tolerance to water deficit was estimated at genotype level as the ability to limit losses in biomass production in water deficit versus control trees. Stem biomass, leaf structure and D displayed a significant genotypic variability whatever the irrigation regime. For all traits, genotype ranks remained stable across years for similar irrigation conditions. Carbon isotope discrimination scaled negatively with productivity and leaf nitrogen content in controls. The most productive genotypes were the least tolerant to moderate water deficit. No relationship was evidenced between D and the level of tolerance to water deficit. The relationships between traits evidenced in this collection of P. deltoides • P. trichocarpa F1 genotypes contrast with the ones that were previously detected in a collection of P. deltoides • Populus nigra L. cultivars tested in the same field trial.

In foliage of Pinus sylvestris, Populus euramericana, and Picea abies the fatty acid composition was analyzed. Whereas clonal material of pine and poplar in controlled ozone fumigations did not show any significant differences as compared to controls, such differences were obtained in field-grown spruces showing needle loss

Populus euramericana cv. I-214 andHelianthus annuus L. cv. Russian Mammoth were exposed to various concentrations of O3 SO2 or NO2 for 2 h in a cylindrical assimilation chamber. The threshold concentrations of air pollutants for inhibition of net photosynthesis differed between the two species and also between the pollutants tested. Furthermore, the lethal concentrations where the net photosynthetic rates were completely inhibited, also differed between species and between pollutants. For SO2 and NO2,P. euramericana was more tolerant photosynthetically thanH. annuus when related to the concentration of pollutants used during the experiment. However, when related to the cumulative uptake rate of each pollutant, the photosynthetic tolerance of the two species was similar. In contrast to the effects of SO2 or NO2, the influence of O3 on net photosynthesis was quite different. The relative rates of net photosynthesis in both species showed the same linear relationship with O3 concentration. However, the relationship between the relative rate of net photosynthesis and the cumulative uptake rate of O3 differed between the two species, although it was linear in both cases.

Studies have been carried out on the causes of wood deterioration in poplars following decline due to water stress in Italy. The incidence of 21 wood decay fungi, among which Trametes trogii Berk, is the most widely spread, is reported. Some suggestions for reducing the damage are offered.

International audience; Stem diameter, total plant height and number of sylleptic branches of three poplar (Populus) genotypes were followed during the first growing season of a high density intensively cultured plantation (in Central Italy) both under ambient CO$_2$ (Control) and under elevated atmospheric CO$_2$ (550 ppm) using the FACE technique. The three poplar genotypes belonged to different species of Populus alba L., Populus nigra L. and Populus x euramericana Dode (Guinier). All three genotypes responded by an enhanced growth performance but the extent of their response to the FACE treatment was different. A stem volume index was calculated considering the stem composed by a truncated cone in the lower part and by a cone in the upper part. At the end of the first growing season, stem volume index was increased in the FACE treatment by 54% to 79% as compared to Control treatment, depending on the genotype. This increased stem volume index was caused by an increase of basal stem diameter rather than by an enhancement of plant height. Number of sylleptic branches was stimulated by more than 35% in the P. nigra genotype. The results confirm the optimal performance of this new POPFACE experiment and show the positive response of this fast-growing tree species to elevated CO$_2$ conditions at an ecosystem scale even if considering the genotypic differences.; Performance de croissance de plants de Populus exposés à une atmosphère enrichie en dioxide de carbone durant la première saison de croissance dans l'expérimentation POPFACE. Le diamètre du tronc, la hauteur totale et le nombre des branches sylleptiques de trois génotypes de peuplier (Populus) ont été suivis durant la première saison de croissance d'une plantation de haute densité en culture intensive (en Italie Centrale), à la fois sous air ambiant (350 ppm, plantes témoins), et sous atmosphère enrichie en CO$_2$ (550 ppm) en utilisant la technique FACE. Les trois génotypes de peuplier utilisés font partie d'espèces différentes : Populus alba L., Populus nigra L. et Populus x euramericana Dode (Guinier). Les trois génotypes ont tous répondu au traitement FACE par une augmentation de la croissance, mais avec des intensité différentes. Un index de volume du tronc a été calculé en considérant le tronc comme étant composé d'un cône tronqué pour sa partie inférieure, et d'un cône pour la partie supérieure. À la fin de la saison de croissance, l'index de volume du tronc était supérieur de 54 % à 79 % , en fonction du génotype, pour le traitement FACE par rapport aux plants témoins. Cette augmentation de l'index de volume du tronc est principalement due à l'augmentation du diamètre basal des troncs, plus qu'à l'augmentation de la hauteur des plants. Le nombre des branches sylleptiques a été augmenté de plus de 35 % par le traitement FACE, pour le génotype Populus nigra. Ces résultats, tout en illustrant le bon fonctionnement du nouveau dispositif expérimental POPFACE, confirment, à l'échelle de l'écosystème, qu'une atmosphère enrichie en CO$_2$ a pour effet une augmentation de la croissance de ces espèces ligneuses à croissance rapide.

26 different compounds have been investigated experimentally for their sensitizing capacity in guinea pigs. 19 of these occur in propolis as well as in poplar bud exudates, and 14 of them are also found in balsam of Peru. 4 caffeates and benzyl isoferulate were found to be strong sensitizers. 7 compounds were moderate, and 13 compounds showed only weak sensitizing potency. Methyl cinnamate was negative. Patch tests in 11 propolis-sensitive patients once more revealed 3-methyl-2-butenyl caffeate and phenylethyl caffeate as the major sensitizers. In addition to the 8 compounds already known to occur in propolis as well as in balsam of Peru, we detected 5 further substances that both materials have in common. Among these, benzyl isoferulate is considered a noteworthy sensitizer. Coniferyl benzoate, which was shown to be a moderate sensitizer, is present in fresh samples of balsam of Peru, while in propolis it has been detected only once so far. The flavonoid aglycones occurring in poplar bud exudates, and hence also in propolis, are weak sensitizers which play only a minor role in propolis hypersensitivity.

Summary Overwintering bark of poplar ( Populus x euramericana cv. ›Robusta‹) contains three major storage polypeptides with 32, 36 and 38 kDa. They exhibit very similar physicochemical and immunological properties, and could be related to a storage polypeptide with 32 kDa isolated from the wood of dormant poplars. The present study describes the structural and immunological homologies between vegetative storage proteins in bark and wood of poplar.

Shoots of poplar (Populus euramericana L. cv. Flevo) were exposed to filtered air, SO2, NH3 or a mixture of SO2 and NH3 for 7 weeks in fumigation chambers. After this exposure gas exchange measurements were carried out using a leaf chamber. As compared to leaves exposed to filtered air, leaves pretreated with 112-mu-g m-3 SO2 showed a small reduction in maximum CO2 assimilation rate (P(max)) and stomatal conductance (g(s)). They also showed a slightly higher quantum yield and dark respiration. In addition, the fluorescence measurements indicated that the Calvin cycle of the leaves pretreated with 112-mu-g m-3 SO2 was more rapidly activated after transition from dark to light. An exposure to 64-mu-g m-3 NH3 had a positive effect on P(max), stomatal conductance and NH3 uptake of the leaves. This positive effect was counteracted by an SO2 concentration of 45-mu-g m-3. The exposure treatments appeared to have no effect on the relationship between net CO2-assimilation and g(s). Also, no injury of the leaf cuticle or of epidermal cells was observed. Resistance analysis showed that NH3 transfer into the leaf can be estimated from data on the boundary layer and stomatal resistance for H2O transfer and NH3 concentration at the leaf surface, irrespective of whether the leaves are exposed for a short or long time to NH3 or to a mixture of NH3 and SO2. In contrast SO2 uptake into the leaves was only partly correlated to the stomatal resistance. The results suggest a large additional uptake of this gas by the leaves. The possibility of a difference in path length between SO2 and H2O molecules is proposed.

Growth curves of successive leaves of Populus euramericana (Dode) Guinier ‘Robusta’ have been determined. With ample supply of water and nutrients the growth of a poplar shoot follows a fixed pattern: an initial logarithmic acceleration phase followed by a stationary phase in which leaves of equal size are produced at a constant rate. Analysis of growth curves of leaves enabled the growth curves of leaf primordia to be predicted. These primordial growth curves are compared to the indirectly determined growth curves of primordia by measuring the lengths of successive leaf primordia in the apex during the stationary phase of growth. The increase in length of successive leaves in the acceleration phase of growth continues for a longer period at high than at low irradiace. The relative growth rates of leaf primordia, leaves and internodes are discussed in terms of shoot growth and phyllotaxis.

Two Euramerican poplar clones, ‘I-214’and ‘I-45/51′, were badly damaged by frost cracks in 1981 and 1985. Thermocouples attached to 12 trees showed that clone ‘I-45/51’was more resistant to winter and late frosts, possibly due to its significantly thicker and rougher bark in comparison to ‘I-214′.

Gross heat of combustion using an oxygen bomb calorimeter at ovendry condition was determined and analyzed for 2-year-old sprouts of 10 hybrid Populus L. clones of diverse genetic background. Values showed a clonal range of 14% from a low of 4357 cal g−1 (1 cal = 4.1868 J) to a high of 4955 cal g−1. Clones of section Aigeiros Duby (cottonwood) showed significantly greater energy potential than representatives of section Leuce Duby (aspens). There was a significant interaction of clones × sprouts indicating environmental conditions or manner of growth may influence the magnitude of clonal differences. No relationship was found between potential energy and stem specific gravity.Sample discs from a 5-year-old P. tremuloides stem and an 8-year-old P. × euramericana cl. DN-30 were also analyzed by individual growth rings. No relationship was found with density. Outer bark (rhytidome) showed higher calorific values than inner bark (secondary phloem). The possible implication in breeding poplars for energy production is discussed.

Three collections of Melampsora larici-populina Kleb. originating from Belgium, France and the Netherlands were compared for their pathogenicity on eleven poplar clones. Qualitative type reactions suggest the existence of two pathogenic races designated E1 and E2. E2 is able to infect some clones previously considered to be resistant.

Beaufils’ Diagnosis and Recommendation Integrated System (DRIS) was used to diagnose nutrient balance through foliar analysis on hybrid poplar clone 1–45/51. The norms for N, P, K, Ca and Mg were evaluated and tested for increased diameter growth through fertilizer treatments in the field.

Observation de la distribution des inclusions de tanin dans les cellules cambiales prelevees en automne et automne/hiver sur deux types d'arbres temperes, le peuplier et le marronnier

Chrysomela scripta Fabricius adults showed a feeding preference for the youngest, most succulent leaves of tissue-cultured Populus × euramericana. Larvae fed equally on all leaves with water contents greater than 73%. Larvae chose shoot bark for feeding after all leaves with water contents greater that 70% had been consumed. Larvae reared on immature foliage had shorter developmental times and higher prepupal weights than those reared on mature foliage.

Potted poplar ramets showed increased concentrations and rates of synthesis of phenolic compounds within 52 hours of having 7 percent of their leaf area removed by tearing, as did undamaged plants sharing the same enclosure. Damaged sugar maple seedlings responded in a manner similar to that of the damaged poplars. Nearby undamaged maples had increased levels of phenolics and hydrolyzable and condensed tannin within 36 hours, but exhibited no change in rates of synthesis. An airborne cue originating in damaged tissues may stimulate biochemical changes in neighboring plants that could influence the feeding and growth of phytophagous insects.

Populus euramericana (Dode) Guinier cv. Robusta plants were cultivated at irradiances of 7.5, 15 and 30 W m−2 (32.5, 65 and 130 μmol m2 s−1), 400–700 nm at 22°C and a relative humidity between 40 and 60% on a gravel culture subirrigated with Hoagland's nutrient solution. The basal diameter of the growing shoot, a measure of the number of apical cells participating in growth, increased proportionally to irradiance and was correlated with mature leaf length. The development of the length of the growing shoot (Lgs) depended also on the nutritional status of the (young) shoot. Lgs was strongly correlated with the rate of height growth.