排序方式： 共有17条查询结果，搜索用时 15 毫秒
11.
Extensive sampling of endophytically growing bacteria from shoots of diseased Salix viminalis clones were performed in trials at two experimental sites in central Sweden. Field, greenhouse and laboratory studies were conducted to identify and characterize the plant‐associated bacteria and determine their possible role in the severe dieback appearing in short rotation forestry (SRF) plantations in Sweden during the last few years. The most frequently isolated types were found to be non‐fluorescent Pseudomonas fluorescens (biotype A, C, G) and Sphingomonas spp. (23%). Erwinia spp., P. fluorescens, P. syringae and Xanthomonas spp. each constituted 11–14% of the bacterial isolates respectively. After biochemical characterization and screening for ice‐nucleation activity (INA) 78 of the originally 279 isolated bacterial strains were selected for pathogenicity tests and further analyses. Of the 78 selected isolates, 95% were found to be pathogenic, giving different degrees of necrotic reactions after inoculation to Salix plants. Half of these pathogens (46%) also showed strong INA (at temperatures between ?2.5 and ?5°C). With respect to both isolation frequency, clonal distribution in the field, ice‐nucleation ability and necrotic reactions of willow in laboratory tests, we consider the following types to be the most important pathogens in the field: Erwinia spp., P. syringae, Sphingomonas/P. fluorescens spp. (biotype A, C, G) and Xanthomonas spp. Reported damage and dieback in many SRF‐plantations are, according to our results, very likely to be a consequence of bacterial infections, particularly of pathogenic INA‐strains, which both initiate freezing stress and aggravate the frost damage of plants by subsequent invasion of plant tissues leading to complete death of plants under field conditions. 相似文献
12.
A field experiment was conducted to study the effects of peat amendment and crop production system on earthworms. The experiment was established on a field previously cultivated with oats and with silt as the main soil type. Perennial crops strawberry, timothy and caraway, and annual crops rye, turnip rape, buckwheat, onion and fiddleneck were cultivated with conventional methods. All the crops were grown with and without soil amendment with peat. Earthworms were sampled twice: 4 and 28 months after establishment of the experiment. In the former case part of the experimental plots were soil sampled and hand sorted for estimation of earthworms. In the latter case all experimental plots were sampled and both soil sampling and mustard extraction was carried out. Soil organic carbon and microbial biomass was measured at 14 and 28 months. Peat increased the abundance of juvenile Aporrectodea caliginosa by 74% in three growing seasons, but had no effect on adult numbers. Lumbricus terrestris numbers were not increased by peat treatment. Three season cultivation of caraway favoured both A. caliginosa and L. terrestris. An equal abundance of A. caliginosa was also found in plots cultivated with turnip rape and fiddleneck. Total earthworm and especially A. caliginosa numbers were very small in plastic-mulched strawberry beds. This was mainly attributed to repeated use of the insecticide endosulfan. With the strawberry plots omitted there was a significant correlation between soil microbial N measured at 14 months and juvenile Aporrectodea spp. and Lumbricus spp. numbers measured at 28 months. Adult earthworm numbers were not associated with either soil organic C or microbial biomass. 相似文献
13.
用湿筛倾析-蔗糖离心法分离土样中丛枝菌根真菌的孢子,并用形态学方法对其进行种类鉴定。研究结果显示,攀西地区的豆科蔬菜中共分离出2属9种丛枝菌根真菌,球囊霉属(Glomus)8种,G.luteum、G.mosseae、G.aggregatum、G.lamellosum、G.claroideum、G.etunicatum、G.intraradices、G.occultum;无梗囊霉属(Acaulospora)1种,A.delicata。丛枝菌根真菌与攀西豆科蔬菜的共生性良好,其种类较多,种群结构丰富。 相似文献
14.
Field surveys and inoculation experiments were carried out in order to determine the most important stem-canker fungi on willows planted for energy production. The pathogenicity of different fungal isolates and factors influencing infection were studied in the field and in greenhouse experiments, where canker extension was measured after inoculation either on dormant plants or on plants undergoing active growth. 相似文献
15.
Journal of Plant Diseases and Protection - Detection and identification of ice-nucleation active (INA) bacteria, was carried out in several independent investigations from diseased willow plants in... 相似文献
16.
Ramstedt KL Center SA Randolph JF Yeager AE Erb HN Warner KL 《American journal of veterinary research》2008,69(5):647-651
OBJECTIVE: To assess the influence of meal ingestion and orally administered erythromycin on gallbladder volume in dogs. ANIMALS: 22 healthy dogs. PROCEDURES: Ultrasonographically determined gallbladder dimensions in unsedated dogs were used to calculate volume. Measurements were recorded after food was withheld for 12 hours (time 0) and 15, 30, 45, 60, 90, and 120 minutes after a 100-g meal without (n = 22) or with erythromycin (1.0 mg/kg [7], 2.5 mg/kg [7], and both dosages [8]). Gallbladder ejection fraction represented the percentage of volume change from time 0. Intraday and interday coefficients of variation determined operator repeatability and physiologic variation. RESULTS: We did not detect significant differences in gallbladder volume per unit of body weight between treatments at time 0 or in ejection fraction percentage within or between treatments. Median time 0 gallbladder volume was 0.6 mL/kg (range, 0.4 to 1.9) but was > 1.0 mL/kg in 3 of 22 (14%) dogs and or= 25% with at least 1 treatment, but 2 dogs with a gallbladder volume or= 25% were typical. No treatment consistently induced greater gallbladder contraction. Dogs with a gallbladder volume > 1.0 mL/kg and ejection fraction < 25% may require a combined meal and erythromycin protocol. 相似文献
17.
Defoliation-induced changes in grass growth and C allocation are known to affect soil organisms, but how much these effects in turn mediate grass responses to defoliation is not fully understood. Here, we present results from a microcosm study that assessed the role of arbuscular mycorrhizal (AM) fungi and soil decomposers in the response of a common forage grass, Phleum pratense L., to defoliation at two nutrient availabilities (added inorganic nutrients or no added nutrients). We measured the growth and C and N allocations of P. pratense plants as well as the abundance of soil organisms in the plant rhizosphere 5 and 19 d after defoliation. To examine whether defoliation affected the availability of organic N to plants, we added 15N-labelled root litter to the soil and tracked the movement of mineralized 15N from the litter to the plant shoots.When inorganic nutrients were not added, defoliation reduced P. pratense growth and root C allocation, but increased the shoot N concentration, shoot N yield (amount of N in clipped plus harvested shoot mass) and relative shoot N allocation. Defoliation also reduced N uptake from the litter but did not affect total plant N uptake. Among soil organisms, defoliation reduced the root colonization rates of AM fungi but did not affect soil microbial respiration or the abundance of microbe-grazing nematodes. These results indicate that interactions with soil organisms were not responsible for the increased shoot N concentration and shoot N yield of defoliated P. pratense plants. Instead, these effects apparently reflect a higher efficiency in N uptake per unit plant mass and increased relative allocation of N to shoots in defoliated plants. The role of soil organisms did not change when additional nutrients were available at the moment of defoliation, but the effects of defoliation on shoot N concentration and yield became negative, apparently due to the reduced ability of defoliated plants to compete for the pulse of inorganic nutrients added at the moment of defoliation.Our results show that the typical grass responses to defoliation—increased shoot N concentration and shoot N yield—are not necessarily mediated by soil organisms. We also found that these responses followed defoliation even when the ability of plants to utilize N from organic sources, such as plant litter, was diminished, because defoliated plants showed higher N-uptake efficiency per unit plant mass and allocated relatively more N to shoots than non-defoliated plants. 相似文献