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151.
An evaluation of plant-borne factors promoting the solubilization of alkaline rock phosphates 总被引:4,自引:0,他引:4
T. Bekele B. J. Cino P. A. I. Ehlert A. A. Van Der Maas A. Van Diest 《Plant and Soil》1983,75(3):361-378
Summary Four experiments are described in which the uptake patterns of various crop species were shown to enhance the solubilization
of alkaline rock phosphates. In most cases, such enhancements resulted from soil acidification brought about by the alkaline
uptake patterns. In one case, the enhancement may have stemmed primarily from a high Ca-uptake rate, which might be responsible
for a shift in mass-action equilibria favoring the solubilization of rock phosphates. High uptake of Ca is expected to serve
two purposes: 1. it acts in creating alkaline uptake patterns causing a decline in soil pH, and 2. it promotes a shift in
mass-action equilibria. 相似文献
152.
James F. Leckman James W. Maas D. Eugene Redmond George R. Heninger 《Life sciences》1980,26(25):2179-2185
Repeated (N=15) administration of clonidine (0,1,5 μg/kg,p.o.) to three normotensive male subjects resulted in significant decreases in plasma free 3-methoxy-4-hydroxyphenethyleneglycol (MHPG) at three hours for both the 1 μg/kg dose (p < .05) and the 5 μg/kg dose (p < .01) when compared to concentrations following placebo. The mean decrement in plasma free MHPG following a 5 μg/kg dose was 36%. Systolic blood pressure fell a mean of 17 mmHg after 1 μg/kg and 37 mmHg after 5 μg/kg of clonidine. The application of a clonidine challenge test to assess noradrenergic receptor sensitivity is discussed. 相似文献
153.
Dr. H. J. Leenders Dr. J. Derksen Dr. P. M. J. M. Maas Prof. Dr. H. D. Berendes 《Chromosoma》1973,41(4):447-460
Vitamin B6 induces in vivo as well as in vitro the appearance of a puff at region 2–48C in Drosophila hydei. At concentrations of 10–2 M or lower, region 2–48C is the only region responding to vitamin B6 provided that oligomycin is present in the incubation medium. Pyridoxal phosphate and pyridoxamine phosphate supplied to medium containing oligomycin induce upon incubation of salivary glands a larger puff at 2–48C. — Puff 2–48C produces large quantities of a unique RNP-product; globular 140–220 Å particles which aggregate to stable complexes of 0.1–0.2 in diameter. Upon continuous in vitro incubation with vitamin B6, puff 2–48C becomes loaded with these aggregates which have never been observed in any other puff of Drosophila hydei. 相似文献
154.
Elo Urm Huey Yang Geoffrey Zubay Norman Kelker Werner Maas 《Molecular & general genetics : MGG》1973,121(1):1-7
Summary Development of a system for in vitro synthesis of N--acetyl-L-ornithinase of E. coli has made it possible to detect the argR gene product, i.e., the arginine repressor, in cell extracts. 相似文献
155.
Inducible system for the utilization of beta-glucosides in Escherichia coli. II. Description of mutant types and genetic analysis 总被引:20,自引:10,他引:10 下载免费PDF全文
Two types of mutants obtained by treating beta-gl(+) cells with nitrosoguanidine are described. One type, beta-gl(+)c, is constitutive for the biosynthesis of the aryl beta-glucoside splitting enzyme(s) and for the beta-glucoside permease; the other (beta-gl(+)sal(-)) has lost the capacity to ferment salicin, but has retained the capacity to ferment arbutin and other aryl beta-glucosides. By two successive mutational steps, beta-gl(+)sal(-)c double mutants can be obtained. Determinations of the enzymatic splitting of salicin and p-nitrophenyl beta-glucoside by beta-gl(+)sal(-) cells and extracts showed that these mutants have lost the capacity to split salicin but do split p-nitrophenyl beta-glucoside; they possess the beta-glucoside permease, and in them salicin is a gratuitous inducer for enzyme and permease biosynthesis. Studies on a beta-gl(+) strain, which splits salicin as well as p-nitrophenyl beta-glucoside, have shown that the splitting of salicin is more temperature-sensitive than that of p-nitrophenyl beta-glucoside and other beta-glucosides. Other properties of the two activities are similar. Interrupted mating experiments and cotransduction with P1kc phage showed that the genetic determinants of the beta-glucoside system map between the pyrE and ile loci. Three distinct mutational sites were found and are presumed to have the following functions: beta-glA, a structural gene for an aryl beta-glucoside splitting enzyme; beta-glB, either the structural gene for the beta-glucoside-permease or a regulatory gene; and beta-glC, a regulatory gene (or site). Escherichia coli wild-type strains are of the genotype A(+) B(-) C(+). The beta-gl(+) mutation determining the ability to ferment beta-glucosides is considered to be a permease or regulatory mutation, and the resulting genotype is A(+) B(+) C(+). The beta-gl(+)sal(-) phenotype results from a mutation in the beta-glA gene (genotype A' B(+) C(+)), and the constitutive phenotype results from a mutation in the beta-glC gene, the genotypes A(+) B(+)C(a) and A' B(+)C(a) corresponding to the phenotypes beta-gl(+)c and beta-gl(+)sal(-)c. 相似文献
156.
157.
The initiator protein RepA1 of the IncFII replicon RepFIC derived from the enterotoxin plasmid EntP307 has been cloned under the control of the lambda PL promoter. This has enabled us to overproduce this protein and study its properties. Here we show that RepA1 is a soluble basic protein with an experimentally determined molecular weight of 40,000. Deletion analysis indicates that the overproduced protein originates from the open reading frame which we previously designated as coding for RepA1. We have also shown that the replication function of the replicon RepFIC depends on the intact RepA1 coding frame. 相似文献
158.
RepFIC, a basic replicon of IncFI plasmids that has homology with a basic replicon of IncFII plasmids 总被引:5,自引:0,他引:5
It was found that a DNA segment containing genes for autonomous replication and its control (basic replicon) present in the IncFI plasmid P307 has homology with RepA, a basic replicon present in IncFII plasmids. The basic replicon in P307 is referred to as RepFIC and the homologous basic replicon in IncFII plasmids is referred to as RepFIIA. In 11 other IncFI plasmids studied a region that has homology with RepFIC and RepFIIA was demonstrated. Thus, of the several basic replicons present in IncFI plasmids, RepFIC is evolutionarily related to a basic replicon of IncFII plasmids. 相似文献
159.
160.
Production of fine roots and the seasonality of their growth in a Mexican deciduous dry forest 总被引:5,自引:0,他引:5
Very limited information regarding fine-root growth and production of tropical dry forests is available. Fine roots and small roots are defined as rootlets with diameters < 1 mm and 1.1 to 5 mm, respectively. Live and dead fine-and small-root mass fluctuations were studied over one year by means of soil core analyses in the deciduous dry forest of Chamela, Mexico, at 19° 30, 2 km inland from the Pacific Ocean. By means of systematically varying the distance of soil core extraction points from tree stems, it was shown that random core collection is justified. A difference between fine-root biomass on south and north facing slopes was documented, although this difference was significant only during the rainy season. The live/dead ratio of fine roots was highest during the rainy period. The annual fine-root production for 1989 was estimated at 4.23 Mg ha-1 by summing significant fine-root biomass changes between sampling dates. This value is higher than most of the comparable data from other ecosystems. 相似文献