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81.
Gutiérrez C JL G González C MA Segura C I Sánchez C JA Orozco V M Fortis H 《Phyton》2015,84(2):298-305
Leonardite is an oxidized form of lignite carbon, which is obtained from fossilized organic materials. Such materials are used for the extraction of humic acids (HA). The result of the addition of HA of organic origin on soil structure is known; however, the effects of adding HA of Leonardite on soil structure have been scarcely investigated. The objectives of this research were (1) to determine the influence of humic acids derived from Leonardite in increasing the aggregate stability of an Aridisol under greenhouse conditions, and (2) evaluate the morphology of the root xylem during the phenological development of melon plants (Cucumis melo L.). Three treatments of HA solution application to the soil were used: soil without solution application (HA0), and application of HA solution to the soil with pH 6 (HA6) or (HA7). Aggregate stability (As) and bulk density (Da) were evaluated as soil variables. Development and quantification of xylem area were studied on plants. There were significant differences in aggregate stability. Also, there was an increase in the root xylem area, and the best treatment was when AH7 solution was applied. Humic acids derived from Leonardite increased the stability of soil aggregates when plants grew under greenhouse conditions, and fostered the development of xylem conduits during the fruiting stage. 相似文献
82.
83.
Estimating the rate of evolution of the rate of molecular evolution 总被引:22,自引:13,他引:22
A simple model for the evolution of the rate of molecular evolution is
presented. With a Bayesian approach, this model can serve as the basis for
estimating dates of important evolutionary events even in the absence of
the assumption of constant rates among evolutionary lineages. The method
can be used in conjunction with any of the widely used models for
nucleotide substitution or amino acid replacement. It is illustrated by
analyzing a data set of rbcL protein sequences.
相似文献
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Background
Computational prediction methods are currently used to identify genes in prokaryote genomes. However, identification of the correct translation initiation sites remains a difficult task. Accurate translation initiation sites (TISs) are important not only for the annotation of unknown proteins but also for the prediction of operons, promoters, and small non-coding RNA genes, as this typically makes use of the intergenic distance. A further problem is that most existing methods are optimized for Escherichia coli data sets; applying these methods to newly sequenced bacterial genomes may not result in an equivalent level of accuracy. 相似文献86.
87.
Rapid, sequential changes in surface morphology of PC12 pheochromocytoma cells in response to nerve growth factor 总被引:20,自引:17,他引:20 下载免费PDF全文
The effect of nerve growth factor (NGF), a substance that promotes the differentiation and maintenance of certain neurons, was studied via scanning electron microscopy utilizing the PC12 clonal NGF-responsive pheochromocytoma cell line. After 2-4 d of exposure to NGF, these cells acquire many of the properties of normal sympathic neurons. However, by phase microscopy, no changes are discernible within the first 12-18 h. Since the primary NGF receptor appears to be a membrane receptor, it seemed likely that some of the initial responses to the factor may be surface related. PC12 cells maintained without NGF are round to ovoid and have numerous microvilli and small blebs. After the addition of NGF, there is a rapidly initiated sequential change in the cell surface. Ruffles appear over the dorsal surface of the cells with 1 min, become prominent by 3 min, and almost disappear by 7 min. Microvilli, conversely, disappear as the dorsal ruffles become prominent. Ruffles are seen at the the periphery of cell at 3 min, are prominent on most of the cells by 7 min and are gone by 15 min. The surface remains smooth from 15 min until 45 min when large blebs appear. The large blebs are present on most cells at 2 h and are gone by 4 h. The surface remains relatively smooth until 6-7 h of NGF treatment, when microvilli reappear as small knobs. These microvilli increase in both number and length to cover the cell surface by 10 h. These changes were not observed with other basic proteins, with α-bungarotoxin (which binds specifically to PC12 membranes), and were not affected by an RNA synthesis inhibitor that blocks initiation of neurite outgrowth. Changes in the cell surface architecture appear to be among the earlist NGF responses yet detected and may represent or reflect primary events in the mechanism of the factor’s action. 相似文献
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SB Lanzavecchia MI Remis JL Cladera RO Zandomeni 《Entomologia Experimentalis et Applicata》2010,136(1):53-65
DNA size polymorphisms were utilized in a study of 24 natural populations of Ceratitis capitata Wiedemann (Diptera: Tephritidae) from Argentina. The first intron of alcohol dehydrogenase 1 gene (Adh1) was amplified using exon priming intron crossing‐polymerase chain reaction. Three size variants were detected among the 307 samples analyzed. To better differentiate the size variants, further digestion of PCR products with the EcoRI restriction enzyme was carried out. Complete nucleotide sequences of the three‐allele variants were obtained and single changes, insertions, deletions, and EcoRI recognition sites were located. Population allele frequencies were analyzed and a global mean heterozygosity (He) of 0.33 was obtained. In most populations, observed allelic frequencies conformed to Hardy–Weinberg expectations. Significant differences between provinces and sampling sites within these provinces, and among some populations were found. The average number of insects exchanged among populations (Nm) was estimated and high values were observed between Argentina and populations from two African countries (Morocco and Kenya), Australia, and Hawaii (Kauai). Pest introduction sources and dispersion patterns in Argentina are discussed based on these results as well as on available bibliographical data. 相似文献