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1.
Isozyme diversity and genetic structure of buckwheat populations   总被引:1,自引:0,他引:1  
Genetic diversity of 35 Fagopyrum populations belonging to thirteen taxa was studied using isozyme variation at 16 loci for nine enzyme systems (ADH, α-AMY, EST, GDH, GOT, IDH, MDH, PGM, and POD). The mean number of alleles per locus (Ap) showed little variation, ranging from 1.38 to 1.71. The mean percentage of polymorphic (P) of the thirteen taxa was high, ranging from 68.75% to 93.75. The mean expected heterozygosity (He) ranged from 0.21 to 0.37. Obvious grouping of populations according to taxonomic species was found in the cluster analysis, confirmed that the thirteen taxa studied were independent, with a clear boundary. Based on the dendrogram, the phylogenic relationship of Fagopyrum species are in agreement with the achene size were found, and it was inferred that southwestern China should be the original center of cultivated buckwheat.  相似文献   

2.
The objective of this study was to investigate the impact of nucleation temperature (T n) and excipient concentration on the collapse temperature data obtained from freeze-dry microscopy (FDM) experiments. T n, the temperature of the onset of collapse (T oc), and the full collapse temperature (T fc) were determined for aqueous solutions of polyvinylpyrrolidone (PVP) 40 kDa and 2-(hydroxypropyl)-ß-cyclodextrin. Concentrations were varied from 1% to 20% (w/w) for PVP and from 1% to 30% (w/w) for the 2-(hydroxypropyl)-ß-cyclodextrin. Mutual correlation coefficients were calculated for the observed T n, T oc, and concentrations of the solutions. In addition, outliers were detected and eliminated by applying the leaving-one-out routine and calculating correlation coefficients without it. T n was found to be non-correlated with concentrations and only weakly correlated with T oc. The correlation between these two temperatures was particularly poor for the solutions of the highest and lowest concentrations. In contrast, T oc correlated much better with the corresponding concentrations, resulting in a quadratic fit for PVP and a linear fit for 2-(hydroxypropyl)-ß-cyclodextrin.  相似文献   

3.
In this work, chromosome numbers and karyotype parameters of 36 taxa of the genus Mimosa were studied, especially from the southern South America center of diversification. Results support that x = 13 is the basic chromosome number in the genus. Polyploidy is very frequent, ca. 56 % of the total of the studied species here are polyploid, confirming that polyploids are more frequent at higher latitudes. The most common ploidy levels found are 2x and 4x, but some species studied exhibit 6x and 8x. In different groups, several ploidy levels were found. Parameters of chromosome size show statistically significant differences between close species, and asymmetry index A 2 exhibited low variation between them. It is possible to infer variations of chromosome size between diploids and tetraploids and between basal and derived taxa. The present studies confirm or reveal polyploidy in several groups of South America which are highly diversified in the southernmost area of distribution of the genus, such as sect. Batocaulon ser. Stipellares and sect. Calothamnos. Our data are discussed in a taxonomic context, making inferences about the origin of some polyploid taxa. Polyploidy could be an important phenomenon that increases the morphologic diversity and specific richness in southern South America. On basis of our data, it is possible to hypothesize hybridization between same-ploidy level or different ploidy level taxa. As already shown in the literature, our results confirm the importance of the polyploidy in the speciation of the genus.  相似文献   

4.
Variability in DNA content to testis cells and sperm from F1 hybrids between the laboratory mouse (M. muscullus) and the tobacco mouse (M. poschiavinus), has been determined by flow cytometry (FMC). The F1 hybrid mouse is known to be heterozygous for seven metacentric chromosomes produced by Robertsonian fusion. Enriched populations of nuclei from late pachytene spermatocytes and round spermatids were obtained by velocity sedimentation. These nuclei, as well as epididymal sperm nuclei and spleen cells, were stained by the acriflavin-Feulgen technique for DNA and measured by FCM. Peaks in the fluorescence intensity frequency distributions resulting from these measurements were analyzed to determine their mean fluorescence intensities and their widths (coefficients of variation). Because mean intensities of corresponding cell types from M. musculus and the F1 hybrids were identical, the average DNA contents were taken to be the same. The average coefficients of variation of the peaks to fluorescence from the pachytene, spermatid, and sperm nuclei and spleen cells from M. muscullus animals were about 5%. While the peaks of fluorescence from spleen cells and pachytene nuclei from f1 hybrids also had average coefficients of variation of 5%, post-meiotic nuclei from spermatids and spermatozoa had coefficients of variationof 8%. From these results we conclude that, in these F1 hybrids, abnormal meiotic segregation causes an increased variability of 6% in the amount of DNA in the spermatozoa.  相似文献   

5.
The members of the genus Picea form a dominant component in many alpine and boreal forests which are the major sink for atmospheric CO2. However, little is known about the growth response and acclimation of CO2 exchange characteristics to high temperature stress in Picea taxa from different altitudes. Gas exchange parameters and growth characteristics were recorded from four year old seedlings of two alpine (Picea likiangensis vars. rubescens and linzhiensis) and two lowland (P. koraiensis and P. meyeri) taxa. Seedlings were grown at moderate (25°C/15°C) and high (35°C/25°C) day/night temperatures, for four months. The approximated biomass increment (ΔD2H) for all taxa decreased under high temperature stress, associated with decreased photosynthesis and increased respiration. However, the two alpine taxa exhibited lower photosynthetic acclimation and higher respiratory acclimation than either lowland taxon. Moreover, higher leaf dry mass per unit area (LMA) and leaf nitrogen content per unit area (Narea), and a smaller change in the nitrogen use efficiency of photosynthesis (PNUE) for lowland taxa indicated that these maintained higher homeostasis of photosynthesis than alpine taxa. The higher respiration rates produced more energy for repair and maintenance biomass, especially for higher photosynthetic activity for lowland taxa, which causes lower respiratory acclimation. Thus, the changes of ΔD2H for alpine spruces were larger than that for lowland spruces. These results indicate that long term heat stress negatively impact on the growth of Picea seedlings, and alpine taxa are more affected than low altitude ones by high temperature stress. Hence the altitude ranges of Picea taxa should be taken into account when predicting changes to carbon fluxes in warmer conditions.  相似文献   

6.
GAMs (Generalized Additive Models) present a growth pattern for the common filamentous algae (FA) taxa in freshwater ecosystems in Poland. Tribonema, Ulothrix taxa are an early spring species. In comparison with Rhzioclonium, Cladophora and Oedogonium taxa, the algae Zygnemataceae (e.g. Zygnema, Spirogyra) occurs in waters with lower levels of nutrients, total dissolved substances and electrical conductivity. Cladophora glomerata shows different responses to environmental gradients than C. rivularis, C. fracta. Furthermore, the algae Cladophora glomerata (Chlorophyta, Ulvophyceae) forms a thick monoalgae mat (from the surface to the bottom) in the shallow and eutrophic Lake Oporzynskie in Wielkopolska Region in Poland (Central Europe). Detailed algal mat characteristics, physical and chemical parameters of water, and pigments in thalli were measured vertically (surface, middle, bottom) and spatially (marginal and central part) in the stationary mat phase during maximal algal growth. Temperature, dissolved oxygen and PAR irradiation significantly declined as the depth of the mat increased. Water turbidity was greater in the surface layer than in deeper parts, in contrast to the concentrations of N-NO3, N-NH4 and TDS. Pigment content in the cells of C. glomerata, cell lengths and diameters of pyrenoids changed throughout the mat, from top to bottom. The obtained data were used for statistical analyses. In conclusion: dense mats of C. glomerata show a vertical stratification while the mats remain spatially homogenous. Our data suggest that mat structure be considered a biological indicator of freshwater eutrophication.  相似文献   

7.
Thermodynamic models predict that H2 is energetically favorable for seafloor microbial life, but how H2 affects anabolic processes in seafloor-associated communities is poorly understood. Here, we used quantitative 13C DNA stable isotope probing (qSIP) to quantify the effect of H2 on carbon assimilation by microbial taxa synthesizing 13C-labeled DNA that are associated with partially serpentinized peridotite rocks from the equatorial Mid-Atlantic Ridge. The rock-hosted seafloor community was an order of magnitude more diverse compared to the seawater community directly above the rocks. With added H2, peridotite-associated taxa increased assimilation of 13C-bicarbonate and 13C-acetate into 16S rRNA genes of operational taxonomic units by 146% (±29%) and 55% (±34%), respectively, which correlated with enrichment of H2-oxidizing NiFe-hydrogenases encoded in peridotite-associated metagenomes. The effect of H2 on anabolism was phylogenetically organized, with taxa affiliated with Atribacteria, Nitrospira, and Thaumarchaeota exhibiting the most significant increases in 13C-substrate assimilation in the presence of H2. In SIP incubations with added H2, an order of magnitude higher number of peridotite rock-associated taxa assimilated 13C-bicarbonate, 13C-acetate, and 13C-formate compared to taxa that were not associated with peridotites. Collectively, these findings indicate that the unique geochemical nature of the peridotite-hosted ecosystem has selected for H2-metabolizing, rock-associated taxa that can increase anabolism under high H2 concentrations. Because ultramafic rocks are widespread in slow-, and ultraslow-spreading oceanic lithosphere, continental margins, and subduction zones where H2 is formed in copious amounts, the link between H2 and carbon assimilation demonstrated here may be widespread within these geological settings.Subject terms: Microbial ecology, Water microbiology, Microbial biooceanography, Microbiome, Biogeochemistry  相似文献   

8.
桂江流域附生硅藻群落特征及影响因素   总被引:5,自引:0,他引:5  
研究了桂江流域水质、土地利用、地理因素对河流附生硅藻群落的影响。结果显示,桂江流域电导率(Conductivity,Cond.)由下游至源头呈降低趋势,其它水质参数变化趋势不明显。主成分分析(Principle Component Analysis,PCA)显示前两个主成分共解释了56.2%的水质特征,第一轴反映了氨氮(NH4-N)、硝氮(NO3-N)、总氮(Total Nitrogen,TN)的变化梯度,第二轴反映了水温(WT)、pH、Cond.、溶解氧(Dissolve Oxygen,DO)的变化梯度。桂江流域硅藻特定污染敏感指数(Specific PolluoSensitivity Index,IPS)和硅藻生物指数(Biological Diatom Index,IBD)下游低于源头,差异不显著,与多项水质、土地利用以及地理因子呈线性显著相关。24个样地共发现112种硅藻,丰富度大于5%的37种,丰富度最大的几个种类依次为Achnanthidium minutissimum,A.pusilla,A.tropica,Cymbella laevis。对应分析(Corresponding Analysis,CA)显示桂江流域存在3个差异较大的硅藻群落,流域下游以Nitzschia recta为优势种,A.lanceolata、Amphora montan、Planothidium frequentissimum在中下游丰度较高,上游区域种类较多。典型相关分析(Canonical Correspondence Analysis,CCA)排序前两轴解释了硅藻群落变异程度的28.60%,CCA排序轴1与水质(Cond.、WT、NH4-N、NO3-N、TN)和土地利用(城市面积、农田面积、植被覆盖)显著负相关,与地理因素(流域面积、海拔、坡度)显著正相关,第二轴与浊度(NTU)显著正相关(P<0.05)。偏典型相关分析(Partial CCAAnalyses)显示,土地利用、地理因子、水质分别解释了桂江流域硅藻群落变异的7.20%,17.50%,48.50%。结果表明,桂江流域附生硅藻群落结构是水质、地理因子和土地利用共同作用的结果,水质起决定性作用,电导和不同形态的氮是影响附生硅藻群落结构的主要水质因素。  相似文献   

9.
Leaves of Photinia glabra, P. serrulata, P. glabra × serrulata, P. × fraseri, Heteromeles arbutifolia, Cotoneaster pannosa, and Eriobotrya japonica were investigated for oil and n-alkane content and for hydrogen cyanide production. Benzaldehyde proved to be the major volatile oil component in all taxa except Eriobotrya which yielded no oil upon steam distillation. A conjugated aldehyde was present in all taxa of Asian origin but essentially absent from the New World form Heteromeles. The presence of cyanogenic compounds was indicated in all species again excepting Eriobotrya. C 24H 50 to C 33H 68n-alkanes were presentin all taxa. The patterns of composition showed distinct differences along generally recognizable generic limits and again supported the separate placement of Heteromeles.  相似文献   

10.
Understanding the evolutionary history of the species in a particular region provides insights into how that fauna was formed. Of particular interest to biogeographers is examining the impact a geographical barrier had in generating temporal genetic diversity among codistributed species. We examined the impact a major New World barrier, the Isthmus of Tehuantepec (IT) in southern Mexico, had on a regional bird fauna. Specifically, genetic data from 10 montane-forest bird taxa were analysed using approximate Bayesian computation (ABC) to test the hypothesis of simultaneous intraspecific diversification at the IT. Because effective population size (Ne) has the greatest impact on coalescent times, thereby affecting tests of divergence among codistributed taxa, we chose priors for both current and ancestral Ne using empirical estimates of theta. The ABC method detected two discrete diversification events. Subsequent analysis with the number of diversification events constrained to two suggests that four taxa diverged in an older event, with the remaining six diverging more recently. Application of a range of mutation rates from 2.0 to 5.0% Myr−1 places both events within the Pleistocene or Late Pliocene, suggesting that fluctuations in montane habitat induced by climate cycles and a late Pliocene seaway may have fractured this montane bird fauna. The results presented here suggest this avian fauna responded in a relatively concerted fashion over the last several million years.  相似文献   

11.
We present phylogenetic analyses of 32 taxa of Amaryllidaceae tribe Galantheae, 6 taxa of other Eurasian genera of Amaryllidaceae and Phaedranassa dubia as outgroup in order to provide a phylogenetic framework for selection of candidate plants for lead discovery in relation to Alzheimer’s disease. We used DNA sequences from the nuclear ribosomal internal transcribed spacer (ITS) and the plastid matK and trnL-F regions. Phylogenetic analyses using maximum parsimony and Bayesian inference strongly support a monophyletic tribe Galantheae in a narrow sense, including only Acis, Galanthus and Leucojum. Infrageneric relationships of Galanthus only partly support previous classifications. Alkaloid profiles and inhibition of acetylcholinesterase (AChE) were investigated for 18 taxa using gas chromatography–mass spectrometry (GC–MS) and an assay measuring inhibition of AChE activity. AChE inhibitory activity was found in all investigated clades and was correlated with alkaloid profiles of the plants. Lowest IC50 values were expressed by extracts containing either galanthamine or lycorine type compounds. Evaluation of available chemistry and activity data in a phylogenetic framework could be used to select target species for further investigation.  相似文献   

12.
Morphological variation within and between the taxa of the Altissimae (Vernonia altissima, V. ovalifolia, andV. flaccidifolia) and Giganteae (V. gigantea) was investigated. The data for these studies were obtained from population samples, herbarium specimens, and greenhouse-grown transplants. The taxa were hybridized in all possible combinations, and F2 progeny were produced fromV. altissima XV. ovalifolia F2’s. Fertility in the hybrids was estimated by examination of chromosome pairing at meiosis and by pollen stainability. It is concluded thatVernonia altissima should be regarded as a synonym ofV. gigantea and thatV. ovalifolia should be reduced to subspecific rank asV. gigantea ssp.ovalifolia. The evolution of the two subspecies ofV. gigantea is discussed.Vernonia flaccidifolia is maintained at the species level.  相似文献   

13.
The influence of 15 hydroxy-benzoic acids upon active inorganic phosphate absorption by barley roots was examined. For each compound an inhibition constant (ki) was determined, i.e. the concentration of compound required to bring about a 50% inhibition of absorption. The ki values of the benzoic acids were strongly correlated with their octanol—water partition coefficients and their pKa values. This suggests that the inhibition of normal membrane functions, brought about by benzoic acids, results from a generalized increase in cell membrane permeability. Salicylate derivatives were generally more inhibitory than would be predicted from their partition coefficients; their pronounced toxicity probably arises from structural impediments to their detoxication.  相似文献   

14.
Milk fatty acid (MFA) have already been used to model methane (CH4) emissions from dairy cows. However, the data sets used to develop these models covered limited variation in dietary conditions, reducing the robustness of the predictions. In this study, a data set containing 140 observations from nine experiments (41 Holstein cows) was used to develop models predicting CH4 expressed as g/day, g/kg dry matter intake (DMI) and g/kg milk. The data set was divided into a training (n=112) and a test data set (n=28) for model development and validation, respectively. A generalized linear mixed model was fitted to the data using the marginal R2(m) and the Akaike information criterion to evaluate the models. The coefficient of determination of validation (R2(v)) for different models developed ranged between 0.18 and 0.41. Form the intake-related parameters, only inclusion of total DMI improved the prediction (R2(v)=0.58). In addition, in an attempt to further explore the relationships between MFA and CH4 emissions, the data set was split into three categories according to CH4 emissions: LOW (lowest 25% CH4 emissions); HIGH (highest 25% CH4 emissions); and MEDIUM (50% remaining observations). An ANOVA revealed that concentrations of several MFA differed for observations in HIGH compared with observations in LOW. Furthermore, the Gini coefficient was used to describe the MFA distribution for groups of MFA in each CH4 emission category. The relative distribution of the MFA, particularly of the odd- and branched-chain fatty acids and mono-unsaturated fatty acids of observations in category HIGH differed from those in the other categories. Finally, in an attempt to validate the potential of MFA to identify cases of high or low emissions, the observations were re-classified into HIGH, MEDIUM and LOW according to the proportion of each individual MFA. The proportion of observations correctly classified were recorded. This was done for each individual MFA and for the calculated Gini coefficients, finding that a maximum of 67% of observations were correctly classified as HIGH CH4 (trans-12 C18:1) and a maximum of 58% of observations correctly classified as LOW CH4 (cis-9 C17:1). Gini coefficients did not improve this classification. These results suggest that MFA are not yet reliable predictors of specific amounts of CH4 emitted by a cow, while holding a modest potential to differentiate cases of high or low emissions.  相似文献   

15.
Individual specimen trees (or replicated clonal material) of 33 species and hybrids in theCupressaceae andTaxodiaceae were injected with gibberellic acid (GA3) solutions, to test the general applicability of cone induction techniques developed forThuja plicata. Reproductive material for taxonomic study was subsequently available in 82% of treated taxa, compared with 39% of untreated. The latter generally produced small numbers of male or female cones, but both were formed in abundance in half the hormone-treated taxa. Eleven species and hybrids are reported for the first time as responding to GA3.  相似文献   

16.
A statistical analysis was made of the structures of 95 proteins of known sequence belonging to 13 families of erystallographically known conformations, with the object of predicting helices, loops and β-structures. The short-range interactions of the polypeptide chains were assumed to be due to amino acid residue pairs separated by m residues (m = 0, 1, 2, … 6). Four prediction functions (helix, loop, random coil and β-structure) were estimated by a linear combination of statistical quantities of different m values, modified from those which have been used for the x2-test, as a measure of the statistical constraint. The coefficients used in the combination were determined to make the number of correct assignments as large as possible. The coefficients (cm1 values) for helix prediction showed that the contribution of residue pairs separated by one residue is the most important. This seems contradictory to the accepted idea that residue pairs separated by two or three residues are most important. The coefficients (cm2 values) for loop prediction suggest that the long-range interactions (m ≥ 7) are as important as the short-range interactions (m ≤ 6), because the coefficients do not decrease as m increases.The proportion of residues correctly predicted as helical was 85.3% (58.8% for an alternative definition as an index of error, %cor. ass. 2), while the proportion of correct assignments of loops was 64.4% (%cor. ass. 2). Predictions of β-structures were made with 90.1% of the residues correct (52.3% for %corr. ass. 2), on the basis of a different set of statistical data. Initiation sites for β-structures can be inferred to be regions rich in Ile, Val, Leu and Phe. Predictions were also made for both the light and heavy chains of human EU myeloma immunoglobulin G1.  相似文献   

17.
18.
The effect of rising salinity levels on freshwater ecosystems is of concern in many parts of the world, including Australia and southern Africa. Most studies on the salinity tolerance of freshwater macroinvertebrates only consider older life-stages, which are suspected of being more tolerant than early life-stages, such as eggs and hatchlings. The salinity tolerances of ten taxa from south-east Australia and two taxa from South Africa, to the artificial seawater, Ocean Nature, were investigated. From the Barwon River in south-west Victoria, the following taxa were tested Amarinus lacustris (Hymenosomatidae), Paratya australiensis (Atyidae) Physa acuta (Physidae), Lymnaeidae, Plectrocnemia sp. (Polycentropodidae), Anisocentropus sp. (Calamoceratidae), Hydrobiosidae, unidentified Polycentropodidae and Dinotoperla thwaitesi (Gripopterygidae). Chironomus tepperi (Chironomidae) from a laboratory colony stocked from central New South Wales was also investigated. The South African limpets Burnupia stenochorias (Ancylidae) were collected in the Eastern Cape and shrimps Caridina nilotica (Atyidae) from a colony stocked from Kwazulu-Natal were studied. The salinity tolerances of the eggs and hatchlings ranged from 0.8 to >47 mS cm?1 with a mean of 17 mS cm?1. Where reliable estimates are available, the eggs or hatchlings had a salinity tolerance between 5% and 100% of the 72-hour LC50 of older stages, although for insects this was <50%. This study has thus confirmed that salinity tolerances of young stages can be less than the acute tolerances of older stages.  相似文献   

19.
This study examined the log-transformed mechanomyographic (MMGRMS) and electromyographic (EMGRMS) amplitude vs. force relationships for aerobically-trained (AT), resistance-trained (RT), and sedentary (SED) individuals. Subjects performed isometric ramp contractions from 5% to 90% maximal voluntary contraction. Muscle biopsies were collected and thigh skinfolds, MMG and EMG were recorded from the vastus lateralis muscle. Linear regression models were fit to the log-transformed EMGRMS and MMGRMS vs. force relationships. The slope (b coefficient) and the antilog of the y-intercept (a coefficient) were calculated. The AT group had the highest percentage of type I fiber area, the RT group had the highest percentage of type IIa fiber area, and the SED group had the highest percentage of type IIx fiber area. The a coefficients were higher for the AT group than the RT and SED groups in both the MMGRMS and EMGRMS vs. force relationships, whereas the b coefficients were lower for the AT group than the RT and SED groups only in the MMGRMS vs. force relationship. The group differences among the a coefficients may have reflected subcutaneous fat acting as a filter thereby reducing EMGRMS and MMGRMS. The lower b coefficients for the AT group in the MMGRMS patterns may have reflected fiber area-related differences in motor unit activation strategies.  相似文献   

20.
A rod shaped, non-motile, endospore forming, Gram-stain positive and moderately halotolerant strain, designated as NCCP-168T, was isolated from salt mines sampled in the Karak district of Khyber Pakhtunkhwa Province in Pakistan. To delineate its taxonomic position, the strain was subjected to polyphasic characterization. Cells of strain NCCP-168T can grow at 10–40 C (optimum at 30–35 C), in a pH range of 5.0–9.0 (optimum at pH 8.0) and in 0–17 % (w/v) NaCl on agar medium. The phylogenetic analysis based on the 16S rRNA gene sequence showed that strain NCCP-168T belongs to the genus Bacillus with the highest similarity to Bacillus seohaeanensis BH724T (97.1 %), and less than 97 % similarity with other closely related taxa (95.6 % with B. subtilis subsp. subtilis NCIB3610T). DNA–DNA relatedness between strain NCCP-168T and the type strains of closely related species was lower than 30 %. Chemotaxonomic data (major menaquinone, MK-7; cell wall peptidoglycan type, A1γ [meso-diaminopimelic acid]; major fatty acids, iso-C15:0 29.9 %, anteiso-C15:0 29.3 %, iso-C16:0 11.4 %, iso-C14:0 8.9 % and anteiso-C17:0 7.0 %; major polar lipids, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine) support the affiliation of strain NCCP-168T with genus Bacillus. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain NCCP-168T can be distinguished from the closely related taxa and thus represents a novel species in the genus Bacillus, for which the name Bacillus pakistanensis sp. nov. is proposed, with the type strain NCCP-168T (= KCTC 13786T = DSM 24834T = JCM 18975T).  相似文献   

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