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排序方式: 共有269条查询结果,搜索用时 15 毫秒
51.
M.J.J. Hoogsteen E.A. Lantinga E.J. Bakker P.A. Tittonell 《Communications in Soil Science and Plant Analysis》2018,49(13):1541-1552
The Loss-on-Ignition (LOI) method is widely employed for measuring the organic matter (OM) content of soil samples. There is a risk of carbonate losses when calcareous soil samples are analyzed through LOI, but this has never been investigated in detail. Moreover, a worldwide standard protocol for determining the carbonate content of soils is not available. The aims of this study were (i) to evaluate two commonly employed carbonate analysis procedures using calcareous and non-calcareous soil samples: the gravimetric method with (GMF) and without (GM) the addition of the antioxidant iron(II) chloride (FeCl2) and the acetic acid dissolution procedure (AAD); (ii) to evaluate the effect of ignition temperature on losses of pure calcite, calcite-quartz and calcareous soil samples. We found that the average apparent carbonate content of the non-calcareous soils was greatest for the GMF method followed by the AAD procedure. The GM method showed the smallest apparent carbonate contents. For the calcite-quartz sand mixture, ignition losses started at 600°C and increased with temperature in a sigmoidal way. LOI values stabilized at 750°C when 80% of the carbon dioxide was released. We recommend the GM procedure for carbonate analysis because the apparent carbonate contents of the non-calcareous soil samples were smallest. Furthermore, we recommend an LOI temperature of 550°C because at this ignition temperature 99.8% of the total calcite fraction remains in the soil samples. 相似文献
52.
53.
The influence of the siderophore produced by plant growth‐promoting Pseudomonas putida strain WCS358, pseudobactin 358 (PSB358), on chlorophyll synthesis and iron(III) reduction in carnation cultivars Lena and Pallas grown in hydroponics was studied. Ferric pseudobactin 358 (4 μM) stimulated chlorophyll synthesis in cv. Lena, but not in cv. Pallas. FeEDDHA stimulated chlorophyll synthesis in both cultivars. Differences between the two carnation cultivars in the utilization of FePSB358 as an iron source are correlated with differences in iron efficiency reactions of the two cultivars: Fe‐deficient plants of cv. Lena produced more and longer root hairs than Fe‐deficient plants of cv. Pallas, and the ferric reducing activity of cv. Lena was higher than that of cv. Pallas. 相似文献
54.
An Outlook on the Localisation and Structure-Function Relationships of R Proteins in <Emphasis Type="Italic">Solanum</Emphasis> 总被引:2,自引:2,他引:0
Erik Slootweg Wladimir Tameling Jan Roosien Ewa Lukasik Matthieu Joosten Frank Takken Jaap Bakker Aska Goverse 《Potato Research》2009,52(3):229-235
The co-evolution of plants and plant-pathogens shaped a multi-layered defence system in plants, in which Resistance proteins
(R proteins) play a significant role. A fundamental understanding of the functioning of these R proteins and their position
in the broader defence system of the plant is essential. Sub-project 3 of the BIOEXPLOIT programme studies how R proteins
are activated upon effector recognition and how recognition is conveyed in resistance signalling pathways, using the solanaceous
R proteins Rx1 (from S. tuberosum spp. andigena; conferring extreme resistance against Potato Virus X), I-2 (from S. lycopersicon; mediating resistance to Fusarium oxysporum) and Mi-1.2 (from S. lycopersicon; conferring resistance to Meloidogyne incognita) as model systems. The results obtained in this project will serve as a model for other R proteins and will be translated
to potential applications or alternative strategies for disease resistance. These include the modification of the recognition
specificity of R proteins with the aim to obtain broad spectrum resistance to major pathogens in potato. 相似文献
55.
Aska Goverse Geert Smant Liesbeth Bouwman Erin Bakker Jaap Bakker 《Potato Research》2009,52(3):209-213
The EU Framework 6 Integrated Project BIOEXPLOIT concerns the exploitation of natural plant biodiversity for the pesticide-free
production of food. It focuses on the pathogens Phytophthora infestans, Septoria tritici, Blumeria graminis, Puccinia spp. and Fusarium spp. and on the crops wheat, barley, tomato and potato. The project commenced in October 2005, comprises 45 laboratories
in 12 countries, and is carried out by partners from research institutes, universities, private companies and small-medium
enterprises. The project has four strategic objectives covered in eight sub-projects. These objectives relate to (i) understanding
the molecular components involved in durable disease resistance, (ii) exploring and exploiting the natural biodiversity in
disease resistance, (iii) accelerating the introduction of marker-assisted breeding and genetic engineering in the EU plant
breeding industry, and (iv) coordinating and integrating resistance breeding research, providing training in new technologies,
disseminating the results, and transferring knowledge and technologies to the industry. 相似文献
56.
About 19 cultivars, which had originated from backcrosses between F1 LA (Longiflorum × Asiatic) hybrids (2n = 2x = 24) as
female parents and Asiatic cultivars as male parents (2n = 2x = 24), were analyzed with genomic in situ hybridization. 17
of them were triploid (2n = 3x = 36), and two aneuploid (2n = 3x + 1 = 37). The triploid cultivars had resulted from the functional
2n eggs produced by the female parents (F1 hybrids) because first division restitution (FDR) occurred in their meiosis during
megasporogenesis. Similarly, the aneuploid cultivars had originated from viable 2n + 1 eggs. The extra chromosome in cultivar
041555 or 041572 resulted from one univalent or one half-bivalent which might have lagged behind when the sister chromatids
of the other univalents and half-bivalents were segregating during the FDR process in their LA hybrid parents, respectively.
That the majority of cultivars possessed recombinant chromosomes showed that intergenomic recombination might play an important
role during the selection of the cultivars directly from BC1 progenies. That five cultivars of the 15 recombinant cultivars
only had reciprocal recombinant chromosomes and 10 cultivars had non-reciprocal recombinant chromosomes indicates that the
latter are more important. Because 9 of the 10 non-reciprocal recombinant cultivars possessed substitutions for recombinant
segments, it also indicated that such substitutions could be an important source for the genetic variation in the sexual triploid
BC1 progenies. In such cases there was a potential for the expression of the recessive genes of the backcross parent in a
nulliplex (aaa) condition in the substituted segments. Genetic variation resulting from such nulliplex loci might have played
a role in the selection of some of the cultivars. 相似文献
57.
Variability of fine root (diameter < 2 mm) distribution was investigated in four 55 to 56-year-old Maritime pine (Pinus pinaster) stands using a combination of trench wall observations and destructive sampling. Our objectives were to assess patterns
of fine root distribution, to estimate tree fine root biomass and to explore interactions with understorey vegetation in a
gradient of relevant site conditions. Results showed that root density decreased with soil depth in all stands, and variability
appeared to be highest in litter and subsoil layers especially where compacted soil layers occurred. Roots were clustered
in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size
and number of root channels were comparable in all four stands. Overall fine root biomass at depths of 0–120 cm ranged from
2.7 to 7.2 Mg ha−1 and was highest for the two driest stands. The use of trench wall records made it possible to reduce the variability of these
estimates. Understorey species represented as much as 90% of the total number of fine roots in the upper layers, and the understorey
formed a considerable proportion of the total ecosystem biomass, suggesting that understorey species are likely competitors
for nutrients in this ecosystem. Further studies should focus on the interaction of the understorey and pine roots and the
ecological significance of clustered roots and nutrient distributions. 相似文献
58.
Agnieszka Marasek-Ciolakowska Songlin Xie Paul Arens Jaap M. van Tuyl 《Euphytica》2014,198(3):389-400
Meiotic polyploidisation via crossing with 2n gamete producing genotypes and interploidy crosses are two of the main methods currently used to obtain polyploid tulips. In our study diploid 2n gamete producing F1 hybrids of Darwin hybrids (Tulipa gesneriana × Tulipa fosteriana) and triploid hybrid resulting from ‘Rhodos’ × ‘Princeps’ cross were used as pollen donor and crossed with cultivars of T. gesneriana in the following combination: 2x × 2x, 3x × 2x, 2x × 3x, and 3x × 3x. The progenies resulting from crosses at diploid level were mostly diploid, whereas a few seedlings were triploid. In 3x × 2x crosses aneuploids with chromosome constitution in between triploid and tetraploid (43–45 chromosomes) were predominant, but also one tetraploid (2n = 4x = 48) and four pentaploids (2n = 5x = 60) were obtained. In 2x × 3x crosses most progenies were triploid with the exception of a few aneuploids (3x + 1 and 3x ? 1), whereas in 3x × 3x cross diploid and aneuploid genotypes were recorded with chromosome number varied from 27 to 34. These results indicate that triploid parents produced aneuploid as well as euploid (x, 2x, 3x) gametes and that success in ploidy manipulation in tulip depends to a large degree on the ploidy level of the parental genotypes used for hybridization. Genome constitution of selected population of F1 and BC1 hybrids was analyzed through genomic in situ hybridization (GISH). GISH analysis of the BC1 showed a considerable amount of intergenomic recombination which is desirable for introgression breeding. 相似文献
59.
Ruhl M Bonis NR Reichart GJ Sinninghe Damsté JS Kürschner WM 《Science (New York, N.Y.)》2011,333(6041):430-434
The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 10(3) gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change. 相似文献
60.
J. Muskens M. H. Mars A. R. W. Elbers K. Van Maanen D. Bakker O.‐R. Kaaden 《Zoonoses and public health》2003,50(5):231-234
A total of 15 822 cattle aged 3 years and older, belonging to 378 randomly selected herds, were tested for paratuberculosis using an absorbed enzyme‐linked immunosorbent assay (ELISA); 3.3% tested positive. This percentage was lowest for the group of cattle aged 3–4 years (2.3%) and highest for cattle with the age of 5–6 years (4.5%). The mean Sample to Positive (S/P) ratio of seropositive cattle vaccinated against paratuberculosis was higher (0.75 ± 0.33) than that of seropositive, non‐vaccinated cattle (0.58 ± 0.26). Faecal samples of 422 ELISA‐positive cattle were cultured for the presence of Mycobacterium avium subsp. paratuberculosis, 12% of these were contaminated. The percentage of non‐contaminated samples with positive culture results was 17.3%, with a substantial difference between vaccinated (1.7%) and non‐vaccinated cattle (20.2%). Of the positive cultures, the number of colonies varied from 1–10 (22% of cultures), 11–100 (22%), to more than 100 (55%). The percentage of ELISA‐positive, non‐vaccinated cattle tested culture‐positive was positively correlated with the magnitude of the S/P ratio. This percentage varied from 12% (S/P ratio 0.3–0.5) to 58% (S/P ratio > 1.1), a result that might have implications for interpretation of the test. In this study, the percentage of ELISA‐positive cattle with positive faecal culture results was limited and these individuals were mostly moderate to heavy shedders. 相似文献