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1.
Abstract. Nutrient conservation in vegetation affects rates of litter decomposition and soil nutrient availability. Although resorption has been traditionally considered one of the most important plant strategies to conserve nutrients in temperate forests, long leaf life‐span and low nutrient requirements have been postulated as better indicators. We aimed at identifying nutrient conservation strategies within characteristic functional groups of NW Patagonian forests on Andisols. We analysed C‐, N‐, P‐, K‐ and lignin‐concentrations in mature and senescent leaves of ten native woody species within the functional groups: broad‐leaved deciduous species, broad‐leaved evergreens and conifers. We also examined mycorrhizal associations in all species. Nutrient concentration in mature leaves and N‐ resorption were higher in broad‐leaved deciduous species than in the other two functional groups. Conifers had low mature leaf nutrient concentrations, low N‐resorption and high lignin/N ratios in senescent leaves. P‐ and K‐resorptions did not differ among functional groups. Broad‐leaved evergreens exhibited a species‐dependent response. Nitrogen in mature leaves was positively correlated with both N resorption and soil N‐fertility. Despite the high P‐retention capacity of Andisols, N appeared to be the more limiting nutrient, with most species being proficient in resorbing N but not P. The presence of endomycorrhizae in all conifers and the broad‐leaved evergreen Maytenus boaria, ectomycorrhizae in all Nothofagus species (four deciduous, one evergreen), and cluster roots in the broad‐leaved evergreen Lomatia hirsuta, would be possibly explaining why P is less limiting than N in these forests. 相似文献
2.
3.
J. -L. Connat E. M. Dotson P. A. Diehl 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(5):689-699
Summary [3H]-20-hydroxyecdysone ([3H]-20E) injected intoAmblyomma hebraeum females 7 days before the beginning of oviposition,viz. at the beginning of vitellogenesis, was converted to 3 polar peaks of unknown nature called 1, 2 and 3, and to apolar conjugates AP1, AP2 and AP3. AP2 have the same retention times as the esters of 20E with long chain fatty acids described inOrnithodoros moubata (Diehl et al. 1985). However, principally unmetabolized 20E was incorporated into the ovaries, and 16% of the injected labelling was recovered in the eggs, 3/4 being free 20E. When 20E was injected during oviposition, it was not converted to the polar products but only to the apolar products. At this time, 76% of the total radiolabel injected accumulated in the egg-batch, principally in the form of free unmetabolized 20E.After injection of [3H]-ecdysone (3H]-E), the three polar metabolites 1, 2 and 3, probably 20-deoxy homologues of 1, 2 and 3 described above were always produced irrespective of the time of injection. In addition, E was metabolized to 20E and to the apolar conjugates AP1, AP2, and AP3. E, 20E and peak 2 were incorporated into the ovary within the first day after injection. These 3 compounds were found in freshly laid eggs in variable proportions, the quantity of E decreasing with time while 20E and peak 2 increased. At the end of oviposition, ca. 60% of the injected radiolabel had been incorporated into the eggs. Apolar products and polar metabolites accumulating in the body were apparently not used as a source of free hormone for the eggs.Our results with tritiated ecdysteroids confirm our data concerning endogenous ecdysteroids of the eggs ofA. hebraeum (Connat et al. 1985). This species, in contrast to 2 other female ticks,Ornithodoros moubata andBoophilus microplus, incorporates free E and 20E instead of ecdysteroid conjugates into its eggs. The role of these free ecdysteroids remains to be elucidated.Abbreviations
ES
ecdysteroids
-
E
ecdysone
-
20E
20-hydroxyecdysone
-
HPLC
high-performance liquid chromatography
-
RP-18
reyerse phase with C18 aliphatic chains grafted on the silica
-
RIA
radio-immunoassay
Part of this work was realized for the PhD thesis of E.M. Dotson 相似文献
4.
We estimate the active part of cytochrome P-450, which is involved in a special substrate transformation, by measuring the initial change of the production rate as a function of the relaxation transitions between two different steady states of the reaction cycle of cytochrome P-450 using the light-reversibility of the carbon monoxide inhibition. The kinetic data of such relaxations are interpreted within a model cycle, which reduces the reaction cycle to three steps. The estimation of the rate constant of the first reduction step, derived from model simulation of the production rate, is confirmed by independent experimental study of the reduction kinetics.An application of our model to the O-deethylation of 7-ethoxycoumarin reveals that — in a time average — 10%–15% of the spectroscopically detectable cytochrome P-450 is involved in that transformation.Abbreviations Cyt. P-450
microsomal cytochrome P-450
- 7-EC
7-ethoxycoumarin 相似文献
5.
The autoactivation of factor XII (Hageman factor) induced by low-Mr heparin and dextran sulphate. The effect of the Mr of the activating polyanion. 总被引:1,自引:0,他引:1
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Human Factor XII is known to undergo autoactivation in the presence of dextran sulphate of Mr 500,000. We have now studied the dependence of this reaction on the Mr of the dextran sulphate by using fractions resolved by gel filtration. We have found that autoactivation can be induced by dextran sulphate fractions with Mr as low as 3000, and there is a marked dependence of the rate constant of autoactivation on the Mr value. Fractions with Mr below 8000 gave very low rates of autoactivation; there was a sharp increase in the rate obtained when the Mr of the dextran sulphate was greater than 10,000. Various preparations of heparin were also able to support the autoactivation of Factor XII and gave a very similar relationship between molecular size and reaction rate. The data provide support for the hypothesis that the mechanism by which the 'surface' acts in contact activation involves the presence, on the same particle, of multiple binding sites for the proteins. 相似文献
6.
Two trials were completed to investigate the effects of luprostiol in swine. The first trial was to evaluate parturition induced by various dosages of luprostiol compared with those of lutalyse or vehicle. Sows were assigned by random allotment to one of the following treatments on Day 112 of gestation: Group A, control (0 mg luprostiol); Group B (1.88 mg luprostiol); Group C (3.75 mg luprostiol); Group D (7.5 mg luprostiol); Group E (15 mg luprostiol); Group F (10 mg lutalyse). All prostaglandin-treated groups farrowed earlier than the controls (P<0.05), with Groups D (26.3 h), E (31.0 h) and F (25.8 h) having the shortest treatment-to-first-pig intervals, and Groups A (76.0 h), B (54.4 h) and C (40.0 h) having the longest intervals. Luprostiol-treated sows had the shortest farrowing time (P<0.05; range = 3.2 to 3.9 h). Significant differences were found for the time (min) between births: Group A (32.1), Group B (28.4), Group F (35.5) took longer than Group C (20.2), Group D (21.0) and Group E (21.6). In a second trial, 20 crossbred pregnant sows received either vehicle or luprostiol (7.5 mg) on Day 112 of gestation. Progesterone concentrations declined rapidly (P<0.05) in luprotiol treated females but were unchanged in control females during the 24-h collection period. The results of these trials show 7.5 mg luprostiol to be the most effective dose for inducing farrowing. 相似文献
7.
Pedro J. N. Silva Richard K. Koehn Walter J. Diehl III Robin P. Ertl Elaine B. Winshell Mauro Santos 《Biochemical genetics》1989,27(7-8):451-467
Four samples of the musselMytilus edulis were taken between 1984 and 1987 from Stony Brook, New York, and used to study the glucose-6-phosphate isomerase (GPI) polymorphism
in this species.In vitro specific activity andin vivo flux measured in the same animals were found to be significantly correlated. A significant effect of GPI genotype on flux
was observed in one of the samples; overall, significant evidence of effect of genotype on enzyme activity was also obtained.
GPI activities of common genotypes tend to deviate less from the population mean than those of rare (frequency less than 5%)
genotypes. This suggests the possibility that rare GPI genotypes are rare as a consequence of having biochemical properties
that deviate from an optimum level and, therefore, having a lower fitness. In support of this hypothesis, we found in one
of our samples that shell length is a concave function of GPI activity with an intermediate optimum activity level.
The financial support provided to P.J.N.S. by the Luso-American Educational Commission (Fulbright Program), the Instituto
Nacional de Investigacao Científica (Portugal), and the Faculdade de Ciências da Universidade de Lisboa during several stages
of this research is gratefully acknowledged. Financial support from the Ministerio de Educatión y Ciencia (Spain) in the form
of a postdoctoral Fulbright/MEC fellowship to M.S. is also gratefully acknowledged. Research was supported by National Science
Foundation Grant BSR-8415060 to R.K.K. This is contribution No. 736 from the Program in Ecology and Evolution, State University
of New York at Stony Brook.
On leave from Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande C2, Lisboa, Portugal. 相似文献
8.
Distributions of polymorphisms among pathways of carbohydrate metabolism in the earthworm Eisenia fetida (Oligochaeta). 总被引:1,自引:0,他引:1
W J Diehl D L Williams 《Comparative biochemistry and physiology. B, Comparative biochemistry》1992,101(1-2):83-90
1. Activities and genetic banding patterns of 36 isozymes in carbohydrate metabolism were detected by spectrophotometry and starch-gel electrophoresis, respectively, in the earthworm Eisenia fetida. 2. Polymorphisms were not distributed randomly among metabolic pathways, activity levels, or gene copy numbers. 3. In glycolysis and the Krebs cycle, 16% of the loci were polymorphic and polymorphisms occurred only when multiple copies of the loci existed. 4. In other pathways, 45% of the loci were polymorphic and the distribution of polymorphisms was independent of gene copy number. 5. Polymorphisms may affect metabolic phenotypes and natural selection may have led to conserved biochemical activity in glycolysis and the Krebs cycle. 相似文献
9.
Application of automated DNA sizing technology for genotyping microsatellite loci. 总被引:21,自引:0,他引:21
J S Ziegle Y Su K P Corcoran L Nie P E Mayrand L B Hoff L J McBride M N Kronick S R Diehl 《Genomics》1992,14(4):1026-1031
Highly polymorphic microsatellite loci offer great promise for gene mapping studies, but fulfillment of this potential will require substantial improvements in methods for accurate and efficient genotyping. Here, we report a genotyping method based on fluorescently labeled PCR primers and size characterization of PCR products using an automated DNA fragment analyzer. We capitalize on the availability of three distinct fluorescent dyes to label uniquely loci that overlap in size, and this innovation increases by threefold the number of loci that can be analyzed simultaneously. We label size standards with a fourth dye and combine these with the microsatellite PCR products in each gel lane. Computer programs provide very rapid and accurate sizing of microsatellite alleles and efficient data management. In addition, fluorescence signals are linear over a much greater range of intensity than conventional autoradiography. This facilitates multiplexing of loci (since signal intensities often vary greatly) and helps distinguish major peaks from artifacts, thereby improving genotyping accuracy. 相似文献
10.