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1.
Abstract: Lichen-forming ascomycetes and their green algal photobionts completely die off within approximately 3 years of storage at room temperature. Macroscopically this is recognizable as a colour change, the green shades of the chlorophylls being lost. In fluorescent light microscopy preparations an increase in fungal autofluorescence and a significant decrease in chlorophyll autofluorescence in the Trebouxia cells was observed. In transmission electron microscopy preparations of Xanthoria parietina and its green algal photobiont, Trebouxia arboricola, the fungal membrane systems were found to be largely broken down whereas the shrivelled algal protoplast failed to rehydrate after storage at room temperature. When stored in the desiccated state at - 20 °C, both partners of the symbiosis stayed fully viable for up to 13 years, their colouration and chlorophyll fluorescence being unchanged. Viability was measured as ascospore ejection and germination rates in Xanthoria parietina, soredium germination rates in Xanthoria fallax, Hypogymnia physodes and Parmelia sulcata, and autospore formation rate in Trebouxia cells (green algal photobiont), which had been isolated from the thalli after rehydration. Thallus fragments of Xanthoria parietina were shown to grow normally after one week of storage in LN2 without any cryoprotectant. In the desiccated state deep-frozen samples can be repeatedly brought to room temperature and back to - 20 °C without any loss of viability. Cryopreservation is therefore a suitable mode of long-term storage of viable lichen thalli for experimental studies or transplant experiments.  相似文献   
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3.
Telescopus nigriceps, was discovered in the Kermanshah region in Iran, which is the first record of this species in Iran. A comparison is made with the sympatric and parapatric Telescopus tessellatus and T. fallax iberus.  相似文献   
4.
Morphological characteristics as well as electrophoretic polymorphism have been analysed in eight samples of allis shad, Alosa alosa (L.) and twaite shad, Alosa fallax (Lacepede), collected in the Loire basin and the Gironde-Dordogne system. The morphological characteristics showed that allis and twaite shad were present in these samples. Moreover, specimens with intermediate characteristics were found in the Loire and assumed to be hybrids between the two forms. By contrast, the two species were monomorphic and electrophoretically indistingishable at the 22 loci analysed. Therefore, it cannot be excluded that these two forms correspond to a single species.  相似文献   
5.
模糊聚类法在小翅雏蝗种群动态分析中的应用   总被引:4,自引:1,他引:3  
1 引  言小翅雏蝗 (Chorthippusfallax)是我国北方草地蝗虫的优势种之一 ,主要分布在我国的内蒙古、新疆、宁夏、甘肃、青海、河北、山西、陕西等省区及国外的西伯利亚、哈萨克斯坦、蒙古等地[7,8,10 ,12 ,13 ,16] .刘长仲等[11] 对小翅雏蝗的生物学特性进行了研究 ,李鸿昌等[9] 研究了小翅雏蝗的取食行为 ,冯光翰等[1,2 ] 提出了小翅雏蝗的防治指标 ,康乐[3~ 6] 、邱星辉[5] 、颜忠诚等[17] 研究了内蒙古典型草原小翅雏蝗的时空异质性、营养生态位以及形态特征与扩散能力之间的关系 .本文依据甘肃省夏河县甘加高山草…  相似文献   
6.
豆突眼长蝽发育起点温度和有效积温的研究   总被引:4,自引:0,他引:4  
在恒温条件下 ,观察了不同温度对豆突眼长蝽ChauliopsfallaxScott生长发育的影响 ,用直接最优法和直线回归法分析数据 ,结果表明直接最优法能较好地反应实际情况。卵、1~ 5龄若虫和整个若虫期的发育起点温度分别为 7 98℃ ,7 1 6℃ ,6 5 3℃ ,8 81℃ ,6 75℃ ,8 2 7℃和 7 5 0℃ ,有效积温分别为85 8,60 8,5 2 0 ,71 4,1 0 1 5 ,66 3和 3 5 3 0日·度 ,发育速率最大时的温度分别为 3 4 84℃ ,3 4 48℃ ,3 4 1 6℃ ,3 4 1 2℃ ,3 4 75℃ ,3 5 1 1℃和 3 3 65℃。  相似文献   
7.
Sphagnum plantlets, cultivated in continuous-feed bioreactors, are characterised by high levels of free endogenous phenolics and a pronounced excretion of some phenolics into the effluent culture medium. The transfer of Sphagnum fallax, precultivated in continuous-feed bioreactors, to batch cultures resulted in an increased flux through phenylpropanoid metabolism and an accumulation of p-coumaric acid to 0.1 μM and of trans-sphagnum acid up to 0.5 μM in the external medium [3H]-labelled L-phenylalanine (7.7 GBq mol?1) was rapidly taken up, resulting in an enhanced synthesis and excretion of p-coumaric and trans-sphagnum acid. Specific activities were 6.9 and 5.4 GBq mol?1, respectively, for these cinnamic acids excreted into the external medium. Endogenous pools of trans-cinnamic and p-coumaric acid did not increase and no labelling could be detected in these compounds. Cell wall-bound activity amounted to ca 14% of the applied activity after 48 h of incubation, 59% of which was recovered in dioxane/2 M HCl extracts of the cell wall. Exogenously applied trans-cinnamic acid (0.1 mM) was taken up to 46% and resulted in a transient endogenous accumulation of trans-cinnamic acid, the level of free endogenous p-coumaric and trans-sphagnum acid was found to have decreased. The concentrations of p-coumaric and trans-sphagnum acid in the culture medium rose to 17 and 2.4 μM, respectively, after 48 h of incubation in 0.1 mMtrans-cinnamic acid. Exogenously applied p-coumaric acid (0.1 mM) was taken up to 79% from the incubation solution but not stored endogenously, as metabolic products trans-sphagnum acid and an unknown p-coumaric acid-conjugate accumulated in the external medium and endogenously. These results give evidence for the biosynthetical route from phenylalanine to sphagnum acid and a channelling of pathway intermediates by the enzymes L-phenylalanine ammonia-lyase (EC 4.3.1.5) and cinnamic acid 4-hydroxylase (EC 1.14.13.11).  相似文献   
8.
Cytosolic and plastidic l -glutamine synthetase (EC 6.3.1.2) isoenzymes from Sphagnum fallax Klinggr. (Klinggr. clone 1) were separated by size-exclusion and ion exchange chromatography. The cytosolic enzyme (GS1) was purified to apparent electrophoretic homogeneity. The native enzyme had a molecular mass of 390 ± 20 kDa as estimated by gel filtration and was apparently composed of 8 subunits with molecular masses of 48 kDa. GS1 activity could be measured from pH 6.8 to 8.6 in 50 m M imidazole buffer, with a broad optimum between pH 7.2 and 8.0. The Km values were 2.5 m M , 0.5 m M and 0.5 m M for l -glutamate, ammonium and ATP, respectively. The enzyme was inhibited by more than 10 m M ammonium or glutamate. The incorporation of 15NH4+ into amino acids was observed in vivo using 15 NMR. Label from ammonium was first detected in the amide N of glutamine, and only subsequently in the amino N of glutamate. Moreover, no assimilation was detected in the presence of the specific GS inhibitor methionine sulfoximine. These observations are consistent with a dominant role for GS in the assimilation of ammonium in Sphagnum .  相似文献   
9.
Nitrogen represents a critical nutrient in raised bogs. In Sphagna , dominating this habitat, the prevalent storage amino acid asparagine is catabolized predominantly by the enzyme L-asparaginase (EC 3.5.1.1). L-asparaginase activity has been detected in each of 10 Sphagnum species investigated. In Sphagnum fallax Klinggr. (Klinggr. clone 1) cultivated under axenie conditions in continuous feed bioreactors, the enzyme displayed a light dependent increase in activity. We separated two isoforms, designated L-asparaginase 1 and 2, characterized by their different elution patterns from an anion-exchange column. In stem segments only L-asparaginase 2 could be detected, whereas in capitulae L-asparaginase 1 represented the dominating isoform. Purified chloroplasts displayed no L-asparaginase activity. Almost the entire activity was located in the cytosohc fraction. L-asparaginase 1 and 2 have been purified 82-fold and 188-fold, respectively, by ion-exchange, size-exclusion and hydrophobic interaction chrornatography. Identical pH optima (8.2) and molecular weights (126 000) were determined. The Km values for asparagine (7.4 m M for L-asparaginase 1 and 6.2 m M for L-asparaginase 2) were in the range of those described for higher plants. On the other hand Sphagnum L-asparaginase is comprised of four subunits as are the L-asparaginases of microorganisms. So, the characteristics of the bryophyte enzyme appear to be intermediate between those from higher plants and those from microorganisms.  相似文献   
10.
SYNOPSIS. Oxytricha fallax and Stylonychia pustulata possess 6 rows of dorsal bristle units. Each dorsal bristle unit consists of a pair of kinetosomes; the anterior kinetosome has a cilium and the posterior kinetosome a ciliary stub. The kinetosome pair, located at the bottom of a cortical pit surrounding the cilium and ciliary stub, is surrounded by an asymmetrical fibrillar mass. Future rows 1-4 are formed from 2 sets of primordia originating within mature dorsal rows 1-3. Rows 5 and 6 originate from the anterior regions of both right marginal cirral primordia. Old dorsal bristle units utilized in formation of primordia are presumably maintained in the new rows of the proter and opisthe; those outside the primordia are resorbed. The morphogenetic pattern of the Oxytrichidae is similar to those of the Urostylidae and Holostichidae, but quite different from that of the Euplotidae.  相似文献   
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