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51.
Changes in carbon storage in temperate humic loamy soils after forest clearing and continuous corn cropping in France 总被引:3,自引:0,他引:3
Soil samples from forest and agricultural sites in three areas of southwest France were collected to determine the effect
of forest conversion to continuous intensive corn cropping with no organic matter management on soil organic carbon (C) content.
Soils were humic loamy soils and site characteristics that may affect soil C were as uniform as possible (slope, elevation,
texture, soil type, vegetation).
Three areas were selected, with adjacent sites of various ages of cultivation (3 to 35 yr), and paired control forest sites.
The ploughed horizon (0-Dt cm) and the Dt-50 cm layer were collected at each agricultural site. In forest sites, each 10 cm
layer was collected systematically down to 1 meter depth. Carbon concentrations were converted to total content to a given
depth as the product of concentration, depth of sample and bulk density, and expressed in units of kg m-2. For each site and each sampled layer, the mineral mass of soil was calculated, in order to base comparisons on the same
soil mass rather than the same depth.
The pattern of C accumulation in forest soils showed an exponential decrease with depth. Results suggested that soil organic
carbon declined rapidly during the first years of cultivation, and at a slower rate thereafter. This pattern of decrease can
be fitted by a bi-exponential model assuming that initial soil organic carbon can be separated into two parts, a very labile
pool reduced during the first rapid decline and more refractory fractions oxidizing at a slower rate. Sampling to shallow
depths (0-Dt cm) resulted in over-estimation of the rate of carbon release in proportion to the initial amount of C, and in
under-estimation of the total loss of C with age. The results for the 0–50 cm horizon indicated that losses of total carbon
average about 50% in these soils, ranging in initial carbon content from 19 to 32.5 kg m-2. Carbon release to the atmosphere averaged 0.8 kg m-2 yr-1 to 50 cm depth during the first 10 years of cultivation. The results demonstrate that temperate soils may also be an important
source of atmospheric carbon, when they are initially high in carbon content and then cultivated intensively with no organic
matter management. 相似文献
52.
Bienvenu Thierry Hubert Dominique Fonknechten Nuria Dusser Daniel Kaplan Jean Claude Beldjord Cherif 《Human genetics》1994,94(1):65-68
Human Genetics - Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Analysis of DNA from a pancreatic sufficient patient by means of... 相似文献
53.
Frédérique Tihy Nicolas Vogt Dominique Recan Bernard Malfoy France Leturcq Michelle Coquet Françoise Serville Daniel Fontan Jean-Michel Guillard Jean-Claude Kaplan Bernard Dutrillaux Nicole Lemieux 《Human genetics》1994,93(5):563-567
A girl with severe Becker muscular dystrophy and apparently normal chromosomes had a heterozygous deletion for exons 51, 52, and 53 of the dystrophin gene. This deletion was transmitted by her mother, who was unaffected. To differentiate the normal and the deleted X chromosomes, fluorescence in situ hybridization (FISH) was applied to metaphase chromosomes, using probes for both exons 51 and 52, which are only 388 and 113 base pairs long, respectively. FISH signals were observed in one or both chromatids of one chromosome, but never on both chromosomes, suggesting the lack of hybridization on the deleted X chromosome. Using 5-bromodeoxyuridine incorporation to differentiate the late (inactive) and the early replicating (active) X chromosomes, 77% of the signals were observed on the active X chromosomes in the mother. This percentage was only 18% in the daughter, suggesting that skewed inactivation of the X chromosomes was responsible for the phenotypic differences. 相似文献
54.
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56.
Sophie Stettler Nuchanard Chiannilkulchai Sylvie Hermann-Le Denmat Dominique Lalo François Lacroute André Sentenac Pierre Thuriaux 《Molecular genetics and genomics : MGG》1993,238(1-2):169-176
The pem locus, which is responsible for the stable maintenance of the low copy number plasmid R100, contains the pemK gene, whose product has been shown to be a growth inhibitor. Here, we attempted to isolate mutants which became tolerant to transient induction of the PemK protein. We obtained 20 mutants (here called pkt for PemK tolerance), of which 9 were temperature sensitive for growth. We analyzed the nine mutants genetically and found that they could be classified into three complementation groups, pktA, pktB and pktC, which corresponded to three genes, ileS, gltX and asnS, encoding isoleucyl-, glutamyl- and asparaginyl-tRNA synthetases, respectively. Since these aminoacyl-tRNA synthetase mutants did not produce the PemK protein upon induction at the restrictive temperature, these mutants could be isolated because they behaved as if they were tolerant to the PemK protein. The procedure is therefore useful for isolating temperature-sensitive mutants of aminoacyl-tRNA synthetases. 相似文献
57.
The autoxidation of tetralin is treated as a model reaction system to define the applicability of stereospecific autocatalysis. This concept, predicting a spontaneous amplification of enantiomeric excess generated by an autocatalytic chemical reaction, is used in several theoretical models as an explanation for the origin of natural optical activity. The reaction system investigated obeys the basic criteria of these models: a chiral intermediate (tetralin hydroperoxide) is produced from an achiral substrate (tetralin) via an autocatalytic pathway where the feedback mechanism is expected to generate a state of broken chiral symmetry. In order to test the amplification capacity of this reaction a computer analysis of the kinetic scheme is performed. This simulation is derived from the known kinetic scheme of autoxidation and is validated by fitting the experimentally observed data of hydroperoxide evolution. Calculations show that this model allows powerful amplification of enantiomeric excess and a transient amplification of the optical rotation. It is also demonstrated that the model system exhibits pronounced sensitivity toward any loss of absolute configuration of the involved chiral species. Since an amplification effect results exclusively at a high degree of stereoselectivity, it is concluded that stereospecific autocatalysis is possible in systems which show template reactions, crystallization, or colloidal effects. © 1993 Wiley-Liss, Inc. 相似文献
58.
59.
Béatrice Drouet Luis Garcia Dominique Simon-Chazottes Marie Geneviève Mattei Jean-Louis Guénet Arnold Schwartz Gyula Varadi Martine Pinçon-Raymond 《Mammalian genome》1993,4(9):499-503
Using both chromosomal in situ hybridization and molecular techniques, we report the genetic localization of the gene coding for the alpha 1 subunit of the skeletal slow Ca2+ current channel/DHP receptor gene (Cchl1a3) on human Chromosome (Chr) 1 (1q31–1q32 region) and on mouse Chr 1 region (F-G). On the basis of single-strand conformation polymorphism (SSCP-PCR) analysis in an interspecific backcross, we have determined that the Cchl1a3=mdg (muscular dysgenesis) locus is very closely linked to the myogenin (Myog) locus. 相似文献
60.
Savenkoff Claude; da Silva Nadja Lins; Lefevre Dominique; Denis Michel; Rassoulzadegan Fereidoun 《Journal of plankton research》1992,14(6):835-850
Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 104 cells ml1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 310 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect. 相似文献