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Changes in culturable aerobic bacterial communities of Sitka spruce stumps between 1 and 10 years old were investigated by isolating from the top 55 mm of the stumps. High numbers of bacteria were recovered from 15 mm below the surface of 1‐ and 2‐year‐old stumps, particularly in the sapwood, after which numbers dropped by an order of magnitude. Proportions of colony‐forming units (cfu) capable of degrading cellulose and chitin increased with stump age, whereas siderophore producers decreased. Colony‐forming units were grouped on the basis of 13 phenotypic characteristics, including colony form and colour, Gram stain, heat tolerance, siderophore production and production of various enzymes. Four groups of bacteria were identified; the proportions of the three Gram‐negative groups varied with stump age. A quadratic relationship between bacterial diversity and stump age was detected using the Shannon–Weaver diversity index. Bacterial diversity was higher 15 mm below the stump surface than in deeper sampling points. The results are discussed in terms of the possible influence of prokaryotic organisms on the development of decay communities in Sitka spruce stumps. 相似文献
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Culture medium composition affected antagonism by bacterial isolates from Sitka spruce (Picea sitchensis) stumps against Heterobasidion annosum. Fifty percent of bacterial isolates inhibited H. annosum growth on sporulation agar or yeast–dextrose–peptone agar; only 10% of isolates caused inhibition on both media. Proportions of isolates inhibiting H. annosum varied with stump age; fewer isolates from 4‐ or 6‐year‐old stumps exhibited antagonism than isolates from older or younger stumps. Fifteen isolates showing antagonism on sporulation agar were tested against H. annosum in spruce wood cubes. None of the bacterial isolates alone caused a significant weight reduction in inoculated cubes. Relative inoculation times of bacterial isolates and H. annosum had an effect on weight loss in interactions; simultaneous inoculation with isolates and H. annosum inhibited weight loss caused by H. annosum compared with bacteria‐free controls. Inoculation with bacterial isolates 10 days before H. annosum had no effect on the decay rate. In contrast, inoculation with H. annosum 10 days before bacteria increased weight loss of cubes by 200% relative to cultures lacking bacteria. The effect of a mixed bacterial inoculum on weight change in 0.2‐mm spruce wood slips co‐inoculated with H. annosum, Resinicium bicolor, Hypholoma fasciculare, Stereum sanguinolentum or Melanotus proteus differed between different fungi. 相似文献
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将思茅松毛虫7龄幼虫中肠样品倍比稀释后涂布平板分离菌株,共分离得到14株好氧细菌。以细菌基因组DNA为模板,用细菌16S rDNA通用引物(27f,1492r)对模板扩增,并用2种限制性内切酶HaeⅢ和HindⅢ对PCR扩增产物进行ARDRA多态性分析。对聚类图谱的分析结果发现,14株好氧细菌在86%的相似水平上聚成4个不同分类操作单元(OTU),表明思茅松毛虫7龄幼虫肠道内好氧细菌的遗传多样性水平偏低。室内毒力试验表明,肠道细菌杀虫死亡高峰期在4～8 d,菌株7I-5杀虫效果最佳,12 d时校正死亡率达到64.29%。 相似文献
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2006年11—12月和2007年1月,在陕西黄龙山采用样带法对褐马鸡冬季沙浴地选择进行研究。在选定的8条样带上测定54个利用样方以及96个对照样方。结果表明:褐马鸡沙浴地偏好利用下坡位、阳坡和半阴半阳坡以及山坡面和山脊,对中坡位是随机选择,避免选择中上坡位、阴坡和山沟。对林型的利用无选择性。对利用样方和任意样方进行比较,褐马鸡冬季通常选择水源距离、林边距离和人为干扰距离较小的低海拔地方作为其沙浴地,且其沙浴地以乔木数量低及其盖度、高度和直径较小、灌丛数量和高度较小但盖度大、草本盖度和高度较大以及可视度高为主要特征。褐马鸡也选择岩洞作为沙浴地,占总沙浴地的35.19%。对19个岩洞和35个非岩洞沙浴地进行比较,表明岩洞沙浴地具有人为干扰距离大、坡度大、可视度低、乔木数量和盖度较大而直径小、灌丛数量和盖度大、草本高度较高的特征。逐步判别分析表明:人为干扰距离、坡位、林边距离、海拔、可视度、灌丛盖度和乔木数量具有重要作用,由这7个变量构成的方程在对冬季沙浴地利用样方和对照样方进行区分时,正确判别率可以达到93.60%。 相似文献
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为了提高锥栗芽苗砧嫁接成活率,以野生锥栗种子作为砧木,以‘华栗3号’当年生营养枝作为接穗,采用嫩枝劈接法,研究4个嫁接时期(4月20日、5月10日、6月1日、7月10日)、5种日龄砧木(20、30、45、60、90 d)和封口材料及封口方式(铝箔、嫁接膜封顶、嫁接膜不封顶)对锥栗芽苗砧嫁接成活率的影响。结果表明:封口材料与封口方式对嫁接成活率存在较大影响,不同的封口材料与封口方式处理的嫁接苗成活率从高到低依次为:嫁接膜封顶、铝箔、嫁接膜不封顶;6月1日为最佳嫁接时期,嫁接膜封顶处理的嫁接成活率达64.00%;砧木年龄过小(20 d)或过大(90 d)均对嫁接成活不利,当砧木日龄为45 d时,嫁接成活率最高,为69.33%。 相似文献
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通过对口服蜡样芽胞杆菌（ＢＣ菌）的健康雉鸡雏及白痢雉雏鸡检验结果表明，ＢＣ菌对健康雉鸡雏肠菌群无不良影响，对白痢雉雏肠菌群具有明显的调整作用。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):71-81
Seven‐year old cuttings of pendula spruce were taller and had larger diameters than seedlings or cuttings of Norway spruce of normal crown type. Pendulous cuttings still had plagiotropic growth at age 7 years and the rate of change to orthotropic growth form was weaker than in cuttings with normal crown type. In pendulous cuttings the effect of the origin of ortet and clone on the crown symmetry was significant at age 5 years but not at age 7 years. The effect of clone on the growth form was evident at ages 5 and 7 years, but the effect of the origin of ortet was significant only in 7‐year‐old cuttings. There were no differences in plagiotrophy between clones from 4‐ and 7‐year‐old ortets. For pendulous cuttings the average height and diameter growth decreased in 5‐ and 6‐ year‐old cuttings with less pendulous crown form and with more plagiotropic growth form but this decrease had almost disappeared in 7‐year‐old cuttings. 相似文献
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大巴山木本植物区系的研究 总被引：3，自引：0，他引：3
本文通过详细的植物类群调查,对大巴山木本植物区系进行了较为系统的研究。结果表明,大巴山木本植物区系种类丰富,过渡性明显,集中了大量原始温带植物区系成分和古老孑遗植物成分,是我国第三纪植物区系的重要“避难所”。通过对该区植物区系与邻近地区植物区系之间共有种和区系成分的对比分析,表明大巴山植物区系应属华中区边缘,很可能是东亚植物区系的东西两大植物区系的交汇处。 相似文献
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云南大围山国家级自然保护区种子植物区系多样性特征 总被引：8，自引：0，他引：8
报道大围山种子植物区系的研究结果:大围山内现有野生维管植物238科1 121属3 299种,分别占全国维管植物总科、属、种数的65.38%、34.92%、12.15%.其中种子植物188科994属3 027种及变种,平均种密度高达19.69种·km-2,是全国植物物种多样性最丰富的自然保护区之一.区内种子植物的古老性、珍稀性、多样性和完整性极具代表性.其种子植物区系具有4个显著特征:1)种类组成丰富,属内种系相对贫乏,分化程度较弱;2)植物区系起源古老,古老的特有属丰富;3)大围山是多种区系成分的交汇地带,但热带分布的科占绝对优势;4)大围山植物区系与中南半岛特别是北部湾植物区系的联系紧密,同时与东亚植物区系亦有密切联系. 相似文献
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Currently, bacterial canker caused by Pseudomonas syringae is a major cause of dieback and tree death in wild cherry (Prunus avium) plantations. The evaluation of breeding collections is needed to produce less susceptible clones or cultivars. Resistance tests were performed using excised shoots (1 and 2 years old) from 79 clones in the laboratory. A subset of 10 clones was also tested in the field. The clones were inoculated with four to seven isolates of a set of 15 isolates of P. s. pv. morsprunorum, P. s. pv. syringae, P. s. pv. persicae, P. syringae pv. avii and P. fluorescens. In the laboratory tests, older and larger shoots were more susceptible. In the field test, size and age of the shoots were not related to girdling by the bacterial canker. Two‐year‐old shoots were best for clonal discrimination. Correlations between 1 and 2‐year‐old shoots were significant but not high. The isolates varied a lot between experiments, but as the clone × isolate interactions were always low, breeding could thus be facilitated. The ranking of clones was conserved quite well between two laboratory tests, but not between two others. Good agreement was found for the best clones in the laboratory tests and in the field test. However, the two worst clones in the latter were among the best in one laboratory test. At least two independent tests in the laboratory are needed to evaluate resistance/susceptibility of clones. Broad sense heritability for resistance varied from 0.27 to 0.51. Although moderate, such heritability clearly encourages a breeding approach to reduce the problem of bacterial canker. 相似文献
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系统采集了10个龄级和12个地理种源的云南红豆杉样品,用高效液相色谱(HPLC)测定树皮、3年生小枝和当年生叶的紫杉醇含量,其平均值分别为0.0048%、0.0040%和0.0151%,3年生枝和叶的紫杉醇含量相近,差异不显著。树皮的紫杉醇含量与年龄存在回归关系:Y=0.0316×e0.0067x;3年生小枝和当年生叶的紫杉醇含量与树龄不相关,但树龄小于72a时其含量随树龄增加而递增,树龄超过72a和114a后,3年生小枝和当年生叶的紫杉醇含量逐渐减少。12个云南红豆杉地理种源中,新平、宁蒗和泸水种源当年生叶的紫杉醇含量最高,在0.0077%～0.0098%间;兰坪、宁蒗和新平种源3年生小枝紫杉醇的含量最高,在0.0059%～0.0076%间;景东、木里和宁蒗种源树皮的含量最高,在0.0243%～0.0331%间。主成分分析表明,“温度因子”、“营养因子”和“光照因子”对云南红豆杉紫杉醇含量的影响最大。 相似文献
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Radix scutellariae was used alone or in combination with other medicinal herbs in the treatment of type 2 diabetes mellitus in China. At present, the pharmacokinetics of baicalin in type 2 diabetic rats following oral administration of Radix scutellariae extract was investigated. The results showed that the pharmacokinetics (especially AUC) of baicalin in type 2 diabetic rats after oral administration of Radix scutellariae extract was remarkably different from that in normal rats. Then the mechanism which resulted in the increased AUC of baicalin in diabetic rats was investigated from system clearance and presystemic metabolism. And it was found that the increased AUC of baicalin in diabetic rats at least partly resulted from higher production of baicalein in the intestinal tract of type 2 diabetic rats. Moreover, the activity of β-glucuronidase in intestinal mucosa of type 2 diabetic rats was demonstrated to be higher than that in normal rats, which confirmed the results above. In conclusion, the pharmacokinetic behavior of baicalin was significantly altered in type 2 diabetic rats after orally administrated Radix scutellariae extract, which may partly result from the increased activity of intestinal β-glucuronidase under the pathological state of type 2 diabetes mellitus. 相似文献
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T. A. Coutinho J. Roux K‐H. Riedel J. Terblanche M. J. Wingfield 《Forest Pathology》2000,30(4):205-210
Ralstonia solanacearum, the causal agent of bacterial wilt, has one of the widest host ranges of all phytopathogenic bacteria. This pathogen was first reported on Eucalyptus spp. in the late 1980s in Brazil. Since then, there have been reports of its occurrence on this host in Australia, China and Venezuela. Early in 1997, an 18‐month‐old clonally propagated Eucalyptus grandis × Eucalyptus camaldulensis (GC) hybrid in Zululand, KwaZulu/Natal, showed signs of wilting. The vascular tissue of infected trees was dicoloured and bacterial exudation was produced from cut surfaces. The bacterium was consistently isolated from diseased tissue, purified and identified as R. solanacearum biovar 3 race 1, using the BioLog bacterial identification system. Inoculation trials were conducted on three E. grandis × E. camaldulensis clones (GC515, GC550 and GC505). Clone GC550 displayed wilting after 3 days and all cuttings subsequently died. Clones GC515 and GC505 appeared to be less susceptible with cuttings not showing signs of disease until 7 days after inoculation. After 14 days, 90 and 80%, respectively, of cuttings of these two clones had died. This is the first report of bacterial wilt on Eucalyptus in South Africa. 相似文献
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《Forest Ecology and Management》1997,93(3):205-214
Tree age distribution determines stand size structure and is related to disturbance history and stand dynamics. Data are presented from 40 pure larch stands from six locations on the Taimyr peninsula and Evenk region in the northern open forests of Russian Siberia. A Weibull density function was used to describe actual age distribution and to simulate age distribution. Larch age distributions have similar patterns in different locations over the study area. All stands were found to have a multi-aged structure. The average coefficient of variation for age is about 48%. The range of tree ages exceed 400 years in the oldest forests. The patterns of age distribution change for different age groups. For the youngest stands (40–80 years old) the age distribution was leptokurtic and positively skewed, whereas for middle-aged forests (80–180 years old) it tended to be more mesokurtic and symmetric. In the oldest stands (more than 180 years old) the distribution had a platykurtic form. A high correlation was found between the Weibull function coefficients and the coefficient of age variation and for the mean age. The oldest forests were found in river valleys. Middle-aged forests occur more commonly on middle slopes and the youngest forests occupy top slopes and uplands. A more normal tree age distribution assumes a study area less damaged by forest fires than in the more southern parts of the boreal forest. 相似文献