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排序方式: 共有106条查询结果,搜索用时 15 毫秒
1.
FRANCOISE GUERRINI CENDRINE SEGUR DIDIER GARGANI MICHEL TIBAYRENC MICHEL DOLLET 《The Journal of eukaryotic microbiology》1992,39(4):516-521
ABSTRACT We studied 31 Phytomonas stocks isolated from various hosts and a broad geographical range by isoenzyme electrophoresis (14 loci) and population genetics analysis. The total variability is considerable since many stocks share no allele. Population genetic analysis strongly suggests that Phytomonas zymodemes behave as natural clones, as already proposed by us for several other protozoan species. These clones should be considered as actual taxa in all applied studies. Latex plants and phloemic plants (coconut and palm trees) harbor distinct sets of clones; hence, latex plants studied in this article are probably not a reservoir for parasites of the coconut and palm tree. 相似文献
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AMELIA A. WOLF † BERT G. DRAKE† JOHN E. ERICKSON† J. PATRICK MEGONIGAL† 《Global Change Biology》2007,13(9):2036-2044
We examined the effects of elevated atmospheric CO2 on soil carbon decomposition in an experimental anaerobic wetland system. Pots containing either bare C4‐derived soil or the C3 sedge Scirpus olneyi planted in C4‐derived soil were incubated in greenhouse chambers at either ambient or twice‐ambient atmospheric CO2. We measured CO2 flux from each pot, quantified soil organic matter (SOM) mineralization using δ13C, and determined root and shoot biomass. SOM mineralization increased in response to elevated CO2 by 83–218% (P<0.0001). In addition, soil redox potential was significantly and positively correlated with root biomass (P= 0.003). Our results (1) show that there is a positive feedback between elevated atmospheric CO2 concentrations and wetland SOM decomposition and (2) suggest that this process is mediated by the release of oxygen from the roots of wetland plants. Because this feedback may occur in any wetland system, including peatlands, these results suggest a limitation on the size of the carbon sink presented by anaerobic wetland soils in a future elevated‐CO2 atmosphere. 相似文献
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OLIVIER PIERRE GILBERT ENGLER JULIE HOPKINS FRÉDÉRIC BRAU ERIC BONCOMPAGNI DIDIER HÉROUART 《Plant, cell & environment》2013,36(11):2059-2070
Legumes form a symbiotic interaction with Rhizobiaceae bacteria, which differentiate into nitrogen‐fixing bacteroids within nodules. Here, we investigated in vivo the pH of the peribacteroid space (PBS) surrounding the bacteroid and pH variation throughout symbiosis. In vivo confocal microscopy investigations, using acidotropic probes, demonstrated the acidic state of the PBS. In planta analysis of nodule senescence induced by distinct biological processes drastically increased PBS pH in the N2‐fixing zone (zone III). Therefore, the PBS acidification observed in mature bacteroids can be considered as a marker of bacteroid N2 fixation. Using a pH‐sensitive ratiometric probe, PBS pH was measured in vivo during the whole symbiotic process. We showed a progressive acidification of the PBS from the bacteroid release up to the onset of N2 fixation. Genetic and pharmacological approaches were conducted and led to disruption of the PBS acidification. Altogether, our findings shed light on the role of PBS pH of mature bacteroids in nodule functioning, providing new tools to monitor in vivo bacteroid physiology. 相似文献
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JOSSELIN MONTARRY DIDIER ANDRIVON ISABELLE GLAIS ROSELYNE CORBIERE GLADYS MIALDEA FRANCOIS DELMOTTE 《Molecular ecology》2010,19(9):1965-1977
Potato late blight is an example of a re‐emerging disease of plants. Phytophthora infestans was first introduced into Europe during the 19th century, where it caused the Irish potato famine. During the 20th century several additional introduction events have been suspected, especially in the mid‐70s due to the import of large quantities of potato needed after the shortage caused by drought in 1976. Here, we investigate the genetic population structure of Phytophthora infestans, at the first stages of a recent invasion process in France. A total of 220 isolates was collected from 20 commercial fields of the potato susceptible cultivar Bintje, during two consecutive years (2004 and 2005). Clustering analyses based on eight recently developed microsatellite markers reveal that French P. infestans populations are made of two differentiated genetic clusters of isolates (FST = 0.19). This result suggests multiple introductions of P. infestans into France, either through the introduction of a composite population of isolates or through the successive introduction of isolates having differentiated genetic backgrounds. Both clusters identified have a strong clonal structure and are similar regarding genetic diversity and mating type composition. The maintenance of differentiation between the two genetic clusters should result from the low or non‐existent contribution of sexual reproduction in French P. infestans populations. 相似文献
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Plant diversity in a managed temperate deciduous forest: understorey response to two silvicultural systems 总被引:6,自引:0,他引:6
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MAARTEN T.BASTIAENS RUDI G.J. WESTENDORP BERT J. VERMEER JAN N. BOUWES BAVINCK 《Pigment cell & melanoma research》1999,12(5):316-322
Ephelides and solar lentigines are benign pigmented spots, which are currently associated with an increased risk of skin cancer. These two pigmented spots are known to be discriminated by their clinical, histological, and electron microscopic characteristics, even though occasional misclassification can occur because of their similarity. It has also been questioned whether these spots are not one and the same. In this study, we have attempted to differentiate between these two pigmented spots with the use of a standardized protocol for clinical examinations on 272 healthy volunteers, paying particular consideration to their pigmentary and constitutional host factors. We found that solar lentigines 1) are more prevalent than ephelides, 2) increase in prevalence and number with higher age, and 3) are most prevalent on the trunk and occur more frequently in males than in females. A trend is also observed whereby ephelides 1) loose their prevalence with age, 2) become equally distributed on the face, arms, and trunk, and 3) occur more frequently in females. An intimate association of ephelides, but not solar lentigines, has been found with hair color and skin type. All of these findings are in agreement with most of those reported in the literature, supporting the view that ephelides and solar lentigines are different types of pigmented lesions. 相似文献
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P. DIDIER P. DE PUYTORAC N. WILBERT R. DETCHEVA 《The Journal of eukaryotic microbiology》1980,27(1):72-79
RESUME L'étude détaillée du cortex et des organelles buccaux de Cyrtolophosis mucicola montre que ce Cilié possède une organisation structural corticale comparable à celle de Woodruffia, Platyophrya, Kuklikophrya et des Colpoda . Tout en restant conforme au plan général d'organisation de ces derniers, il a des variations spécifiques décelées au niveau des organelles buccaux qui confirment la position de C. mucicola dans la famille des Cyrtolophosididae , incluse dans le sous-ordre des PLATYOPHRYINA. 相似文献