Variation of microfibril angle and its correlation to wood properties in poplars

The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8?to 28?between growth rings with cambial age and showed a consistent pith-to-bark trend of decline an-gles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (?0.01), and the coefficients were -0.660 for cellulose content, -0.586 for fiber length, -0.516 for fiber width and -0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largest R2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over -0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.

THE SECRETORY STIGMAS IN POPULUS: DEVELOPMENT, CYTOCHEMISTRY, ULTRASTRUCTURE AND THEIR RELATION TO INTERSECTIONAL INCOMPATIBILITY *

The stigmas of five species, Populus euphratica Oliv., P. alba L., P. simonii Carr., P. lasiocarpa Oliv. and P. nigra L. have been studied. Scanning electron microscopy re veals that exudates are present in the intercellular spaces, in the clefts between the multicel lular papillae and on the receptive surface. Release and movement of exudates can be visual ized when the fresh stigmas are stained with sudan Ⅲ and auramine O. Paraffin and semi thin resin sections of stigmas after glutaraldehyde osmium fixation evidence the lipidic nature of the exudates. Transmission electron microscopy reveals the glandular features of the stigmatic papillae cells, such as abundance of rough and smooth endoplasmic reticulum, polyribosomes, and well developed dictyosomes with secretory vesicles. Pellicle and epicuticular lamellate layers which have been considered as typical features of the dry type stigmas are also present in the species where stigmas appear extremely wet. It is concluded that stigmas in all of the five species are secretory at the receptive stage. Well developed generative and sperm cells were observed in the pollen tubes penetrating through the deep layers of the stigmatic tissue in the reciprocal crosses between P. euphratica and P. simonii, which indicated that there is no significant barrier in the stigma.

Seasonal Changes in the Ultrastructure of the Vascular Cambium in Shoots of Populus tomentosa

Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.

创网风云人物榜(五) 构造21笔的幸福

我手中握着铅笔，埋头在纸上勾勾画画。边画边想，边想边画，我要用21笔来构造我的幸福。

Microbial Community Characteristics in the Rhizosphere of Atrazine-contaminated Soil by Dendroremediation of Poplar

The change of microbial community characteristics in the different rhizo- sphere zones of hybrid poplar （Populusdeltoidsxnigra, DN34） under atrazine stress were investigated by rhizo-boxes and Biolog system in a greenhouse experiment, with sublimed sulfur and calcium hydroxide as soil pH regulators. Data from the measurement by the Biolog ECO plate demonstrated that the value of average well color development （AWCD） and the carbon source utilization of soil microorganisms in the treatments with pH regulators were promoter than CK during the initial 30 days; while the results from the 90 days indicated that the activity and the carbon source utilization of soil microbes in acid regulator treatment began to fall down, even lower than that of poplar implant treatment, then the alkaline treatment could still stimulate and promote the activity and the carbon source utilization ability of soil microbes. Overall, the activity and community structure of soil microbes in rhizo- sphere zones of atrazine-contaminated soil did not show steady regularity during the phytoremediation process by using hybrid poplars. For the reason that the Biolog E- CO plate, which only had 31 kinds of carbon sources, could not really indicate the detail information about the function diversity of community structure of soil mi- crobes. So it＇s essential for us to take more sophisticated analysis tools for further study.

Advances in Molecular Mechanism of Microbiological Degradation of Salicylate

Salicylate is a type of pollutant widely and persistently existed in environ- ment. Microbiological degradation of salicylate as one kind of biological remediation methods has the advantages of low cost, good effect and no secondary pollution, and also attracts wide attention both at home and abroad. Currently, many salicy- late-degrading bacteria are isolated and screened, while the molecular mechanism of salicylate metabolism is also worth deep research. The research about molecular mechanism of microorganism degradation was overviewed, various degrading path- ways including catechol meta-cleavage pathway and gentisate pathway were intro- duced, and the latest progress in regulating genes of salicylate degradation was summarized.

Template synthesis and adsorption properties of chitosan salicylal Schiff bases

To improve the adsorption properties of chemically modified chitosan, the chelating resin of salicylal chitosan Schiff bases was prepared by the template cross-linking method using Cu（Ⅱ） as template ion and ethylene glycol bisglycidyl ether as cross-linking agent in microwave, and was characterized by IR. The adsorption capacity and selectivity coefficient of the chemically modified chitosan for Cu（Ⅱ）, Fe（Ⅲ） and Zn（Ⅱ） were investigated, respectively. The results show that the adsorption capacity of the resin 2.73 mmol/g for Cu（Ⅱ） is bigger than that for other two metal ions, 0.22 mmol/g for Fe（Ⅲ）, and 0.42 mmol/g for Zn（Ⅱ）, and the selectivity coefficients are as follows: KCu（Ⅱ）/Fe（Ⅲ）=12.4, KCu（Ⅱ）/Zn（Ⅱ）=6.5.

Protection of ultrastructure in chilling-stressed banana leaves by salicylic acid

Objective： Chilling tolerance of salicylic acid （SA） in banana seedlings （Musa acuminata cv., Williams 8818） was investigated by changes in ultrastructure in this study. Methods： Light and electron microscope observation. Results： Pretreatment with 0.5 mmol/L SA under normal growth conditions （30/22 ℃） by foliar spray and root irrigation resulted in many changes in ultrastructure of banana cells, such as cells separation from palisade parenchymas, the appearance of crevices in cell walls, the swelling of grana and stromal thylakoids, and a reduction in the number of starch granules. These results implied that SA treatment at 30/22 ℃ could be a type of stress. During 3 d of exposure to 7 ℃ chilling stress under low light, however, cell ultrastructure of SA-pretreated banana seedlings showed less deterioration than those of control seedlings （distilled water-pretreated）. Conclusion： SA could provide some protection for cell structure of chilling-stressed banana seedling.

Development of two microsatellite multiplex PCR systems for high throughput genotyping in Populus euphratica

Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Tort. ＆ Gray were screened for amplification in Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were selected to set up and optimize two multiplex polymerase chain reaction （PCR） assays. Three populations containing altogether 436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate for merging genotypes to be less than 0.045.

Development, manufacture and application of Beta-Cypermethrin aqueous capsule suspension

The optimal formula of Beta-Cypermethrin aqueous capsule suspension was screened out through the experiment, preparation and manufacture of basic formulas, which has no sedimentation, suspended drops of oil, peels and agglomerating and the diameter of capsule is in range of 10-30 靘, conformed to the technical requirement. The aftereffect of the 3.3% Beta-Cypermethrin aqueous capsule suspension which was manufactured according to the optimal formula was up more than 25 days. The experiments on controlling the larvae of Dendrolinmus superans Butler and the adults of Xylotrechus rusticus L were carried out with different concentrations of this chemical. The death rate reached 80% when 250 times solution of the chemical was sprayed on stem to control the larvae of D. superans. For control of the adults of X. rusticus, 200, 400 and 600 times solution of the chemical were applied and their control effects (death rate) reached 85.23%, 74.21% and 66.59% respec-tively. Two kinds of solution (200 times and 300 times) of the chemical were used to control the larvae of D. superans in large area, and the control effect for both concentrations was over 90%.

Effects of sodium tungstate on properties of micro-arc coatings on magnesium alloys

Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate.The effects of sodium tungstate on the coating thickness, mass gain,surface morphology and corrosion resistance were studied by eddy current instrument,electronic scales,scanning electron microscope and immersion tester.With the addition of sodium tungstate,the electrolytic conductivity increases and the final voltage decreases.The sodium tungstate has a minor effect on the coating thickness,but lightens the coating color.With increasing sodium tungstate concentration,the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.

人性的爱抚

中午的街道上空空的,没有几个人。这家店铺的男人也有些困乏,忍不住趴在柜台上打起盹儿来。朦胧中,他被一阵声音惊醒。果然,靠门的地方,有一个年轻人正向里边漫无目的地张望着。他正要问些什么,年轻人突然又退了出去。

美好的心灵不介意

我们家位于约翰·霍普金斯医院的对面。我们把楼上的房间出租给来医院就诊的病人,楼下的则留给自己居住。一个夏天的傍晚。

那条弧线永远最美

“妈妈我不是想弄坏地球仪,我只想体会一下漫游地球的感觉。”

Wood Microstructure Effects on Chinese White Poplar Dyeing

In order to study the influence of wood microstructure on wood dyeing, eleven parameters of wood microstructure and 5 parameters of wood dyeing effects for 34 pieces of wood boards from 5 trees of Chinese white poplar (Populus tomentosa) were determined and the multiple regression analysis between the factors of wood microstructures and the parameters of wood dyeing effects were made. The regression results show that each variable of wood dyeing effects has higher relationship with wood microstructures, and multiple correlation coefficients between each variable of wood dyeing effects and wood microstructures are 0.483 6~0.799 8. The main factors of wood microstructures influencing wood dyeing of Chinese white poplar are proportion of wood ray, proportion of vessel and proportion of wood fiber according to comparing the standardized regression coefficients of multiple regression equation.

A simple fabricated thickness-based stiffness gradient for cell studies

In this work, we developed a simple method to fabricate a thickness-based continuous stiffness gradient for biological studies. It was made by glass slides, polydimethylsiloxane （PDMS） pre-polymer, spacer and clips only, without any sophisticated equipment. It is easy to fabricate in any general biological and pharmaceutical laboratories. The stiffness gradient was characterized in terms of apparent Young＇s modulus by atomic force microscopy （AFM） and the Young＇s modulus along the gradient was found to be 8.5- 120 kPa, which is within the physiological relevant range. HeLa-C3 ceils were cultured on the gradient to study their morphological behavior according to the substrate stiffness. Furthermore, the drug efficiency of etoposide, an anti-cancer drug, was studied along the substrate stiffness gradient. It was found that HeLa-C3 cells cultured on the soft region of the gradient （8.5-11 kPa） are more sensitive to etoposide. We believe the proposed device could promote cell investigations and drug screenings on a substrate with comparable stiffness to the native tissue.

Dense and pure high-entropy metal diboride ceramics sintered from self-synthesized powders via boro/carbothermal reduction approach

Equimolar quinary diboride powders,with nominal composition of(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2,were synthesized by boro/carbothermal reduction(BCTR)of oxide mixtures(MOx,M=Ti,Hf,Zr,Nb and Ta)using B4 C as source of B and C in vacuum.By adjusting the B4 C/MOxratios,diboride mixtures without detectable MOxwere obtained at 1600℃,while high-entropy diboride(HEB)powders with particle size of<1μm was obtained at 1800℃.The phase,morphology and solid solution evolution process of the HEB powders during the BCTR process were comprehensively investigated.Although X-ray diffraction pattern indicated the powders synthesized at 1800℃ were in a single-phase Al B2 structure,elemental mappings showed that(Ta,Ti)-rich and(Zr,Nb)-rich solid solution coexisted in the HEB powders.The distribution of niobium and zirconium atoms in HEB was unable to reach uniform until the HEB powders were spark plasma sintered at 2000°C.(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2 ceramics with a relative density of 97.9%were obtained after spark plasma sintering the HEB powders at 2050℃ under 50 MPa.Rapid grain growth was found in this composition when the sintering temperature was increased from 2000 to 2050℃,and the averaged grain size increased from 6.67 to 41.2μm.HEB ceramics sintered at 2000℃ had a Vickers hardness of 22.44±0.56 GPa(under a load of 1 kg),a Young’s modulus of^500 GPa and a fracture toughness of 2.83±0.15 MPa m1/2.This is the first report for obtaining high density HEB ceramics without residual oxide phase,benefiting from the high quality HEB powders obtained.