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31.
Isolation,purification and chemical composition of maize root cap slime 总被引:10,自引:0,他引:10
Annie Chaboud 《Plant and Soil》1983,73(3):395-402
Summary The total root exudate isolated axenically from roots is shown to constitute an extremely heterogenous population of particulate and soluble material. Differences in protein and total sugars contents, and neutral sugar composition throughout stages of total root exudate purification are reported. The importance of controlled collection and purification conditions to ensure valid analysis and composition of purified maize root cap slime are discussed. 相似文献
32.
Summary The effect of competition pressure on the sequential pattern of adult emergence was studied by using the experimental population
of the azuki bean weevil. The density and pattern of emergence curves of the parental adult induced the changes in the shape
of emergence curve of the progeny as well as the number of progeny individuals. In order to explain these changes, a simple
mathematical model which has two independent variables, the population density and the capacity of environment, was introduced.
The model generated basically similar patterns of emergene curves as observed in the present experiments. This means that
the model displayed well the competition pressure which differentially acted upon early-born and late-born individuals in
the populations being at different densities and which were differentially received by individual progeny according to the
sequential distributions of parents. This different severity of competition pressure resulted in the difference of time when
the pressure compelled influences on the sequential distribution of adult emergence. Therefore, early developed individuals
may have good chance to survive, but the competition pressure works as a factor modifying their fundamental superiority, especially
in the scramble type of competition.
Intense crowding of the azuki bean weevil gave rise to the scramble type of competition in the relation between the numbers
of adults emerged in two successive generations. When parental emergence concentrated in a short term and at high density,
the competition becomes intense, resulting in the inferiority of early developed individuals, in the decrease in number at
the next generation and in the increase of duration for emergence. 相似文献
33.
Summary Two multivariate statistical procedures were used to determine the basic trends of morphologic and geographic variations between
males of a common stored-grain mite,Glycyphagus destructor (Schrank) collected from Canada and Japan. All analyses were carried out on physical measurements of 25 morphological features. Three
principal component analyses bases on the Canadian (50 specimens), Japanese (50 specimens) and the combined populations from
the 2 countries (100 specimens) revealed that the first component, accounting for 40% of the variability in all 3 solutions
represented a measure of the morphologic dimension of the body. The second component, which explained over 18% of the variability,
is a measure of the leg dimension.
Smaller clusters of variates characteristic of the population from each county were also evident. Discriminant analysis, performed
with the Canadian and Japanese populations, identified the variates that differed between the 2 populations and provided an
approximate appraisal of interrelations. The general conclusion based on these analyses is that the Canadian and the Japanese
populations are morphologically distinct. The difference is most evident in the diameters of genu 2, lengths of the sensory
seta WI, lengths of the body, and the distances between the vertical external setae.
Contribution No. 446, from Research Station, Canada Department of Agriculture, Winnipeg, Manitoba, Canada. 相似文献
34.
我们用改进了的寡聚核苷酸诱导突变法,将两个单一限制性内切酶位点引入人胰岛素前体B链与C链连接处附近,及C链与A铁连接处附近。用含U模板法将B链第30个残基密码子ACC改成ACG,从而引入MluⅠ位点。用修改了的缺口双链DNA突变法,将A链第4个残基密码于GAG改成CTG,引入了一个PstⅠ位点。突变效率的为17%-36%。这个突变体在人胰岛素前体结构及蛋白质折叠的研究中,将有利于更换不同的C-肽。 相似文献
35.
F. Heinmets 《Cell biochemistry and biophysics》1989,14(3):283-323
A model-system is established to analyze purine and pyrimidine metabolism leading to DNA synthesis. The principal aim is to
explore the flow and regulation of terminal deoxynucleoside triophosphates (dNTPs) in various input and parametric conditions.
A series of flow equations are established, which are subsequently converted to differential equations. These are programmed
(Fortran) and analyzed on a Cray X-MP/48 supercomputer. The pool concentrations are presented as a function of time in conditions
in which various pertinent parameters of the system are modified. The system is formulated by 100 differential equations. 相似文献
36.
Anastassia Kanavarioti Sherwood Chang Diann J. Alberas 《Journal of molecular evolution》1990,31(6):462-469
Summary Selected imidazolide-activated nucleotides have been subjected to hydrolysis under conditions similar to those that favor their template-directed oligomerization. Rate constants of hydrolysis of the P–N bond in guanosine 5-monophosphate 2-methylimidazolide (2-MeImpG) and in guanosine 5-monophosphate imidazolide (ImpG), kh, have been determined in the presence/absence of magnesium ion as a function of temperature and polycytidylate [poly(C)] concentration. Using the rate constant of hydrolysis of 2-MeImpG and the rate constant of elongation, i.e., the reaction of an oligoguanylate with 2-MeImpG in the presence of poly(C) acting as template, the limiting concentration of 2-MeImpG necessary for oligonucleotide elongation to compete with hydrolysis can be calculated. The limiting concentration is defined as the initial concentration of monomer that results in its equal consumption by hydrolysis and by elongation. These limiting concentrations of 2-MeImpG are found to be 1.7 mM at 37°C and 0.36 mM at 1°C. Boundary conditions in the form of limiting concentration of activated nucleotide may be used to evaluate a prebiotic model for chemical synthesis of biopolymers. For instance, the limiting concentration of monomer can be used as a basis of comparison among catalytic, but nonenzymatic, RNA-type systems.We also determined the rate constant of dimerization of 2-MeImpG, k2=0.45±0.06 M–1 h–1 in the absence of poly(C), and 0.45±0.06k20.97±0.13 M–1 h–1 in its presence at 37°C and pH 7.95. This dimerization, as well as the trimerization of 2-MeImpG, which represent the first steps in the oligomerization reaction, are markedly slower than the elongation of longer oligoguanylates, (pG)
n
n>6. This means that in the presence of low concentrations of 2-MeImpG (1.7 mM) the system directs the elongation of longer oligomers more efficiently than the formation of short oligomers such as dimers and trimers. These results will be discussed as a possible example of chemical selection in template-directed reactions of nucleotides. 相似文献
37.
We analyzed bilateral finger prints of 3158 individuals from 13 Iranian populations of diverse origins, for digital patterns,
using the topological method. Some male/female differences, and a great deal of heterogeneity in interpopulational variation
was observed. Distance analysis, and the resultant dendrograms separated the populations studied, but the separation was not
in agreement with the known ethnohistory of this region. Comparison of the obtained results with those based on the traditional
methodology showed that the traditional methodology gives better results in measuring population distances. 相似文献
38.
Linkage mapping of genes for resistance to leaf,stem and stripe rusts and ω-secalins on the short arm of rye chromosome 1R 总被引:1,自引:0,他引:1
N. K. Singh K. W. Shepherd R. A. McIntosh 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(5):609-616
Summary The genes controlling resistance to three wheat rusts, viz., leaf rust (Lr26), stem rust (Sr31) and stripe or yellow rust (Yr9), and -secalins (Sec1), located on the short arm of rye chromosome 1R, were mapped with respect to each other and the centromere. Analysis of 214 seeds (or families derived from them) from testcrosses between a 1BL.1RS/1R heterozygote and Chinese Spring ditelocentric 1BL showed no recombination between the genes for resistance to the three rusts, suggesting very tight linkage or perhaps a single complex locus conferring resistance to the three rusts. The rust resistance genes were located 5.4 ± 1.7 cM from the Sec1 locus, which in turn was located 26.1 ± 4.3 cM from the centromere; the gene order being centromere — Sec1 — Lr26/Sr31/Yr9 — telomere. In a second test-cross, using a different 1BL.1RS translocation which had only stem rust resistance (SrR), the above gene order was confirmed despite a very large proportion of aneuploids (45.8%) among the progeny. Furthermore, a map distance of 16.0 ± 4.8 cM was estimated for SrR and the telomeric heterochromatin (C-band) on 1RS. These results suggest that a very small segment of 1RS chromatin is required to maintain resistance to all three wheat rusts. It should be possible but difficult to separate the rust resistance genes from the secalin gene(s), which are thought to contribute to dough stickiness of wheat-rye translocation lines carrying 1RS. 相似文献
39.
The major developments in the field of nuclear activation analysis, from 1936 to 1989, are discussed. The developments are
grouped into five consecutive time periods. The impact of various scientists on the development of the field in the first
35 years is also discussed. 相似文献
40.
Rainer Haase 《植被学杂志》1990,1(3):345-352
Abstract. Direct gradient analysis (Canonical Correspondence Analysis) of northern Bolivian savanna vegetation revealed correlations between the composition of plant communities and physical and chemical soil properties. Cover/abundance values for 193 species from 27 sites were related to data on eight soil factors. A water-regime variable and the percentage of sand and silt were correlated with the first axis of the species-environment biplot and explained most of the variation in community composition. Along this axis, species and sites of flood-plain vegetation were separated from sites not affected by flooding rivers. The second axis of the biplot was correlated with soil-chemical variables, namely extract-able phosphate, base saturation, organic carbon, pH, and effective cation exchange capacity. Part of the variation in community composition can be explained by these soil nutrient variables. Grassland communities were separated from woody vegetation along the soil nutrient gradient, and floodplain communities of white-water rivers from those of clear-water rivers. The results of the gradient analysis indicate that the soil texture-moisture gradient is the prime factor determining the variation in the floristic composition of the savanna communities examined, and that, in addition, the soil nutrient gradient accounts for some of the variation. 相似文献