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41.
Le Zhang Yi-Wei Huang Jia-Lin Huang Ji-Dong Ya Meng-Qing Zhe Chun-Xia Zeng Zhi-Rong Zhang Shi-Bao Zhang De-Zhu Li Hong-Tao Li Jun-Bo Yang 《Molecular ecology resources》2023,23(2):424-439
Cymbidium is an orchid genus that has undergone rapid radiation and has high ornamental, economic, ecological and cultural importance, but its classification based on morphology is controversial. The plastid genome (plastome), as an extension of plant standard DNA barcodes, has been widely used as a potential molecular marker for identifying recently diverged species or complicated plant groups. In this study, we newly generated 237 plastomes of 50 species (at least two individuals per species) by genome skimming, covering 71.4% of members of the genus Cymbidium. Sequence-based analyses (barcoding gaps and automatic barcode gap discovery) and tree-based analyses (maximum likelihood, Bayesian inference and multirate Poisson tree processes model) were conducted for species identification of Cymbidium. Our work provides a comprehensive DNA barcode reference library for Cymbidium species identification. The results show that compared with standard DNA barcodes (rbcL + matK) as well as the plastid trnH-psbA, the species identification rate of the plastome increased moderately from 58% to 68%. At the same time, we propose an optimized identification strategy for Cymbidium species. The plastome cannot completely resolve the species identification of Cymbidium, the main reasons being incomplete lineage sorting, artificial cultivation, natural hybridization and chloroplast capture. To further explore the potential use of nuclear data in identifying species, the Skmer method was adopted and the identification rate increased to 72%. It appears that nuclear genome data have a vital role in species identification and are expected to be used as next-generation nuclear barcodes. 相似文献
42.
Influence of root density on the critical soil water potential 总被引:1,自引:1,他引:0
Estimation of root water uptake in crops is important for making many other agricultural predictions. This estimation often
involves two assumptions: (1) that a critical soil water potential exists which is constant for a given combination of soil
and crop and which does not depend on root length density, and (2) that the local root water uptake at given soil water potential
is proportional to root length density.
Recent results of both mathematical modeling and computer tomography show that these assumptions may not be valid when the
soil water potential is averaged over a volume of soil containing roots. We tested these assumptions for plants with distinctly
different root systems. Root water uptake rates and the critical soil water potential values were determined in several adjacent
soil layers for horse bean (Vicia faba) and oat (Avena sativa) grown in lysimeters, and for field-grown cotton (Gossypium L.), maize (Zea mays) and alfalfa (Medicago sativa L.) crops. Root water uptake was calculated from the water balance of each layer in lysimeters. Water uptake rate was proportional
to root length density at high soil water potentials, for both horse bean and oat plants, but root water uptake did not depend
on root density for horse bean at potentials lower than −25 kPa. We observed a linear dependency of a critical soil water
potential on the logarithm of root length density for all plants studied. Soil texture modified the critical water potential
values, but not the linearity of the relationship. B E Clothier Section editor 相似文献
43.
中国苏铁属花粉形态研究 总被引:1,自引:0,他引:1
对中国苏铁属花粉进行了光镜和扫描电镜观察。花粉中等大,极轴长26.5-35.7μm,赤道轴长20.6-26.4μm;极面观椭圆形至近圆形,赤道面观船形或肾形,具远极单沟,达两端,其开闭和形状随花粉干燥或潮湿而变化,内部具多种不规则突起,两端具皱纹;远极面外壁光滑或稀具微突起,近极面具穿孔,孔穴或蜂窝状纹饰。 相似文献
44.
Lobanok A.G. Sapunova L.I. Dikhtievski Ya.O. Kazakevich I.O. 《World journal of microbiology & biotechnology》1997,14(2):259-262
The ability to convert D-glucose into D-fructose was found in 14 out of 74 species of actinomycetes and bacteria tested. High intracellular glucose isomerase activity was displayed by Arthrobacter sp. and actinomycetes Streptomyces viridobrunneus, Streptomyces sp. 1 and Streptomyces sp. 32. The first showed maximal glucose-converting potential when cultured in both glucose and xylose media, while glucose isomerase activity of Streptomyces species could be found solely in medium supplemented with xylose. The ketose enzymatically formed from D-glucose was identified as D-fructose. 相似文献
45.
EB病毒BNLF-1基因的分子生物学研究进展 总被引:2,自引:0,他引:2
位于EB病毒基因组U5-TR区内的BNLF-1基因,其转译产物为潜伏膜蛋白(latent membrane protein1, LMP-1),由于LMP-1可以导致细胞转化并在EB病毒致癌过程中具有重要作用,因而成为近年来EB病毒分子生物学及相关肿瘤如人鼻咽癌、伯基特淋巴瘤、何杰金氏病等疾病病因发病学研究的热点,并取得了一批有重要意义的成果,文章从BNLF-1的基因结构及表达调控, LMP蛋白的结构及生化功能, LMP-1的生物学功能和LMP-1研究进行评述. 相似文献
46.
本文报道大鼠水盐负荷时,其心房特殊颗粒(ASG)的数目及钙含量发生相关变化。给大鼠禁水5d或饮2%NaCl液4d造成水盐负荷,用电镜形态计量法计数ASG,以反映心房钠尿肽(ANP)的分泌水平,电镜X射线显微分析法测定ASG中钙、硫含量及肌质同终末池(TSR)中钙含量。结果显示,禁水引起ANP分泌减少时,ASG的数密度增加(6.02±2.30增至9.97±3.21个/μm3),同时伴有钙含量增加(64±16增至92±18mmol/kg);饮盐水引起ANP分泌增加时,ASG的数密度减少(6.02±2.30减至2.96±1.62个/μm3),巨伴有钙含量减少(64±16减至38±22mmol/kg),但水盐负荷对TSR中钙浓度无任何影响。据此推论ASG作为细胞内钙库,借某种机制调控其中钙的释放而参与ANP的刺激分泌耦联过程。 相似文献
47.
中国带斑蚜属记述(同翅目:斑蚜科) 总被引:2,自引:2,他引:0
本文记述中国带斑蚜属Callipterinella Goot,19132种,其一为新亚种:河北带斑蚜Callipterinella calliptera hebeiensis subsp.nov.。新亚种的模式标本保存于中国科学院动物研究所。 相似文献
48.
A mathematical model of spike train transmission by identified molluscan neurons was obtained by Wiener analysis. Poisson-distributed sequences of near-threshold stimuli were used as input trains for model construction and testing. Assuming that the error of describing responses of the synapse-neuron system purely by mean outflow frequency is 100%, addition of a linear component to the equation of the model reduces this error to 25%, and addition of a term allowing for nonlinear properties of the system reduces it to 16%. Comparison of the standard error of predicted responses of the model to testing stimulus trains and of responses of a real neuron to these same trains showed that the prediction error with allowance for nonlinear properties does not exceed 21%. Choice of adequate criteria for comparing model and experimental results is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 49–54, January–February, 1984. 相似文献
49.
Conducting pathways of ganglia from the lumbar portion (L3–L5) of the sympathetic trunk in rabbits were studied by recording action potentials from nerves of the ganglia evoked by stimulation of other nerves of these ganglia, and by intracellular recording from single neurons. Besides the well-known system of descending preganglionic fibers, which enter the trunk through white rami communicantes and, as they pass through the ganglia, form synapses on ganglionic neurons, some preganglionic fibers were shown to enter the sympathetic chain through gray rami communicantes and to run in both ascending and descending directions, forming synaptic connections with neurons of the lumbar ganglia.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 247–254, March–April, 1984. 相似文献
50.