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Mitochondrial cytochrome b gene sequences and morphological data (body length, hind foot length, etc.) for twelve populations with pairwise distances 27–600 km in Qinghai-Tibetan Plateau (distributed in Qinghai, Gansu and Sichuan Province, and at the altitude 3020–4550 m) in Western China were used to investigate the phylogeographical pattern of Plateau zokor (Myospalax baileyi Thomas). There was a little disparity between mtDNA genetic distance and morphological Euclidean distance on population relationships. However, there is a significant correlation (P <0.001) calculated by Mantel’s tests was validated between mtDNA and morphology distances. Analysis of Molecular Variance showed that most of the observed genetic variations occurred between populations, indicating little maternal gene flow between them, as a result of geographical restrictions. Phylogenetic analysis coupled with cluster analysis together showed that the substantial population structuring and phylogenetic discontinuities existed within this species. The evident allopatric population structuring of this subterranean rodent may mostly result from its specialized subterranean excavating behavior with high energy costs, predation from grassland raptors and also the influences of perennial tundra and environmental desiccation in the Qinghai-Tibetan Plateau.
A three-dimensional (3D) time-domain method is developed to predict ship motions in waves. To evaluate the FroudeKrylov (F-K) forces and hydrostatic forces under the instantaneous incident wave profile, an adaptive mesh technique based on a quad-tree subdivision is adopted to generate instantaneous wet meshes for ship. For quadrilateral panels under both mean free surface and instantaneous incident wave profiles, Froude-Krylov forces and hydrostatic forces are computed by analytical exact pressure integration expressions, allowing for considerably coarse meshes without loss of accuracy. And for quadrilateral panels interacting with the wave profile, F-K and hydrostatic forces are evaluated following a quad-tree subdivision. The transient free surface Green function (TFSGF) is essential to evaluate radiation and diffraction forces based on linear theory. To reduce the numerical error due to unclear partition, a precise integration method is applied to solve the TFSGF in the partition computation time domain. Computations are carried out for a Wigley hull form and S175 container ship, and the results show good agreement with both experimental results and published results
Reaumuria soongorica (Pall.) Maxim., a perennial semishrub, is able to survive almost complete tissue dehydration when water is withheld from it, and then the stem can rehydrate on rewatering. In this work, a series of experiments were conducted to characterize the drought-induced changes in two-year-old Reaumuria soongorica. The plants were subjected to dehydration by withholding water for 15 days. Net photosynthetic rate (Pn), maximal photochemical efficiency of photosystem (Fv/Fm) and the activity of ribulose-l,5-bisphosphate carboxylase (RuBPCO) were significantly decreased under drought stress, but phosphoenolpyruvate carboxylase (PEPCase) activity increased in the leaf extracts. Content of chlorophylls and carotenoids had no marked variation. Zeaxanthin, the xanthophyll cycle pigment, increased during drying. Plants exposed to drought showed accumulation of sucrose, with lower soluble protein content than in the control plants. The SDS-PAGE protein profile showed a 52 kD polypeptide disappearing under progressive drought stress, but no drought-induced protein occurred. All these findings indicate that the metabolic network systems of Reaumuria soongorica have a robust regulation capability for management of severe drought stress.
Three genes of the lipoxygenase (LOX) family in peach (Prunus persica var. compressa cv. Ruipan 4) were cloned, and their expression patterns during fruit ripening were analyzed using real-time quantitative PCR. All of the three peach LOX genes had been expressed during fruit ripening; however, their expression patterns were significantly different. During the normal ripening of peach fruits, the expression levels of PpLox1, PpLox2 and PpLox3 increased in varying degrees accompanying upsurge of ethylene evolution. After treated by methyl jasmonic acid (MeJA), the peak of ethylene releasing occurred in advance, and the declining rate of fruit hardness was accelerated, the expression level of the three peach LOX genes in fruits markedly enhanced at the early stage of storage, but significantly decreased at the late storage stage. So, it could be suggested that all three LOXs relate to fruit ripening; however, their functions might be different. PpLox1 expression increase along with the upsurge of ethylene evolution in both control and MeJAtreated peach fruits suggested that PpLox1 probably played a major role in the peach fruit ripening. Expression peak of PpLox2 appeared at the 1 DAH (days after harvest) in both control and MeJA-treated peach fruits, while obvious changes in ethylene evolution and fruit hardness was not observed, which suggested that the rise of PpLox2 expression can be induced by certain stimulation related to ripening, such as harvesting stress and MeJA treatment. The expression of PpLox3 kept a lower level in the natural ripening fruits, whereas raced up at the early stage of storage in the fruits treated with MeJA, which indicated that PpLox3 was expressed inductively and had minor roles during the normal ripening of peach fruits, but when encountered with external stimulation, its expression level would rapidly enhance and accelerate the ripening of peach fruit.
Based on Landsat 8-OLI (operational land imager) images and field surveys, we mapped soil salinization across seven ecosystems in the Manas River basin (MRB), and two models of soil salinization (namely an index model and a sensitivity model) were constructed on a regional scale and on the scale of a unit. ArcGIS ordinary Kriging interpolation was used to determine the spatial distribution of the sensitivity of each ecosystem to soil salinity. The ecosystems differed markedly in their sensitivity: the grassland ecosystem was the most sensitive and the farmland ecosystem was the least sensitive; the other five ecosystems, in descending order of their sensitivity, were desert, urban, forest, wetland, and shrubland. In terms of area, the ecosystems less sensitive to salinity accounted for 40% of the total area; those slightly sensitive accounted for approximately 24%; moderately sensitive, 12%; highly sensitive, 14.5%; and extremely sensitive, 9.5%. The extremely sensitive areas were mostly distributed around Lake Manas while the highly sensitive areas were mainly downwind of the lake. The moderately sensitive areas were occupied mainly by the wetlands and grasslands, the slightly sensitive areas by the deserts, and the least sensitive areas by the farmlands.
A number of imprinted genes have been observed in plants, animals and humans. They not only control growth and developmental traits, but may also be responsible for survival traits. Based on the Cox proportional hazards (PH) model, we constructed a general parametric model for dissecting genomic imprinting, in which a baseline hazard function is selectable for fitting the effects of imprinted quantitative trait loci (iQTL) genotypes on the survival curve. The expectation–maximisation (EM) algorithm is derived for solving the maximum likelihood estimates of iQTL parameters. The imprinting patterns of the detected iQTL are statistically tested under a series of null hypotheses. The Bayesian information criterion (BIC) model selection criterion is employed to choose an optimal baseline hazard function with maximum likelihood and parsimonious parameterisation. We applied the proposed approach to analyse the published data in an F2 population of mice and concluded that, among five commonly used survival distributions, the log-logistic distribution is the optimal baseline hazard function for the survival time of hyperoxic acute lung injury (HALI). Under this optimal model, five QTL were detected, among which four are imprinted in different imprinting patterns.
Kozlov’s pika is a rare and endangered lagomorph species with a limited distribution in the southern Kunlun Mountains in western China. Because of its endangered status, Kozlov’s pika is considered a priority species for research and conservation action. Genetic variation and molecular evolution of the Kozlov’s pika were studied based on a total of 14 individuals from four locations along the eastern boundary between Xinjiang and Tibet province (35.20–36.48°N, 86.08–83.04°E) on extremely high elevation (usually over 4800 m a.s.l.). The density of local populations was about 3–4 per ha, living in a typical alpine desert grassland habitat. The complete mitochondrial cytochrome b (cytb) gene was amplified and sequenced. Based on the cytb gene sequences the genetic variation and molecular evolution were analyzed. Unexpected high haplotype diversity (0.956 ± 0.045) but low nucleotide diversity (0.00537 ± 0.00126) was found, indicating past demographic expansion. Significant partitioning of variance (P <0.01) among populations (46.7%), and within populations (53.3%), indicating low level of genetic differentiations among local populations. Our results gave an optimistic survival status of Kozlov’s pika at the genetic level. Bayes Empirical Bayes analysis with model M2a and M8 detected three positively selected amino acid sites at the significance level of 0.05. The mutant types with either or both of the mutations aspartic acid to asparagine and glutamic acid to lysine had higher isoelectric point values. We suggested these mutant types might have biological significance to help individuals to adapt to the extremely high elevation habitats.
Phytohormone auxin plays an important role in fruit development and is perceived by the TIR1/AFB family of F-box proteins as auxin receptors involved in auxin signal pathway. Cucumber (Cucumis sativus L.) fruit development is either parthenocarpic or non-parthenocarpic. However, little is known on TIR1 and AFB participation in the early stage of cucumber fruit development. In present study, TIR1 and AFB2 were isolated from cucumber. CsTIR1 and CsAFB2 were highly expressed in leaves and ovaries. Their transcript levels decreased in parthenocarpic and pollinated fruits, but continuously up-regulated in aborted fruits, indicating that down-regulation of CsTIR1 and CsAFB2 may be in favor of cucumber fruit set and development. The transcript levels of CsTIR1 and CsAFB2 were significantly induced in leaves by NAA, 6-BA, GA₃, ABA, and ethephon. The expression levels were up-regulated by ABA and ethephon treatments. This expression patterns was accordant with the aborted fruits. Thus, CsTIR1 and CsAFB2 may be important regulators during cucumber fruit development.
Effective discrimination of non-complementary nucleotides is an important factor to ensure the accuracy of hybridization-based nucleic acid analyses. The current study investigates the effects of the chemical nature, the positions, the numbers, and the cooperative behavior of mismatches as well as insertions on 20-mer and 30-mer duplexes. We observed the hybridization stability trend affected by mismatches: G:T ≈ G:G > G:A > A:A ≈ T:T > A:C ≈ T:C > C:C. The experimental data show that mismatches at the center of the oligonucleotide probes have a more profound destabilizing effect on the hybridization stability than those at either ends. Insertions also demonstrate a similar destabilizing effect as mismatches. These results provide useful information for designing DNA microarray nucleotide probes and for improving the discrimination accuracy of hybridization-based detections.
Understanding composition, structure and spatial heterogeneity in soil seed banks is important for the management of grassland ecosystem. Although the effect of fencing and grazing on vegetation composition is widely known, information on species composition, seed density and spatial heterogeneity of soil seed banks in sandy grasslands under fencing and grazing is still lacking. We measured the species composition and seed density of soil seed banks in fenced grassland, grazed grassland and grazed shrubby grassland in Horqin Sand Land, Northern China. By applying the geostatistical methods, we assessed how fencing and grazing affected spatial heterogeneity of soil seed banks in sandy grasslands. Total seed density and species richness in soil seed banks were lower in fenced grassland than in either grazed grassland or grazed shrubby grassland. Seed density and species richness of annual species in soil seed banks were also lower in fenced grassland than in either grazed grassland or grazed shrubby grassland, while those of perennial species showed a reverse trend. The analysis of spatial autocorrelation ranges, fractal dimensions and distribution pattern maps from geostatistical methods showed that spatial heterogeneity of seed density and species richness in soil seed banks were also lower in fenced grassland than in either grazed grassland or grazed shrubby grassland. Continuous fencing increases the seed density and species richness of perennial species in soil seed banks, as well as results in a decrease in spatial heterogeneity of seed density and species richness in soil seed banks. So, continuous fencing should be considered to restore the degraded sandy grasslands in management of semiarid grassland ecosystems.
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