金丝垂柳组织培养体系建立研究

对金丝垂柳组织培养技术进行了研究,结果表明:取外植体带有侧芽的茎条切段进行组织培养,以MS为基本培养基,附加不同浓度的6-BA和NAA进行分化诱导,可获得无根丛生苗,以附加不同浓度的NAA可获得生根植株。     

Photosynthetic and transpirational responses of red spruce understory trees to light and temperature

Understory red spruce (Picea rubens Sarg.) trees, between 20 and 50 cm in height and 12 years or more in age, were collected from mid- and high-elevation stands in north-central Vermont and placed in a closed-cuvette system to measure photosynthetic and transpirational responses to photosynthetic photon flux density (PPFD) and temperature. Photosynthesis, dark respiration, transpiration and water-use efficiency of trees from both stands responded to changes in PPFD and temperature in similar ways. Trees from both stands exhibited maximum rates of net photosynthesis at temperatures between 15 and 20 degrees C, and exposure to higher temperatures resulted in reduced rates of photosynthesis and increased rates of respiration. Net photosynthetic rates generally increased with increasing light intensity but began to level off at 250 micro mol m(-2) s(-1). Water-use efficiency was maximal when temperature and PPFD were at 15 degrees C and above 400 micro mol m(-2) s(-1), respectively.     

Foliage browning and shoot death in Sitka spruce and other conifers in northern Britain during winter 1983–84

A hitherto undescribed form of injury to Sitka spruce and other conifers occurred in plantations throughout northern Britain during the dormant season 1983–84. Damage consisted primarily of shoot death which was typically concentrated in a zone of variable extent below the upper few whorls of the tree. It occurred predominantly in forests in the west and was most severe in older crops at high elevation. Possible causes are discussed and it is concluded that the damage was probably climatic in origin.     

In vitro interactions in artificial and wood‐based media between fungi colonizing stumps of Sitka spruce

Interspecific interactions between fungi that colonize stumps of Picea sitchensis in Scotland were tested in dual cultures on Norkrans agar, spruce sawdust and in autoclaved blocks cut from roots. Isolates were ranked according to competitive ability on the different media, based on their ability to overgrow competitors or to form deadlock interactions. On the defined medium, Phaeolus schweinitzii was the species most able to overgrow competitors, followed by Stereum sanguinolentum and Heterobasidion annosum; Resinicium bicolor was the least able to overgrow competitors on this medium. By contrast, R. bicolor was the most competitive on spruce sawdust medium. Deadlocking interactions were formed most often in dual cultures on Norkrans agar. Observation of hyphal interactions on Norkrans agar under the microscope identified several different response types including growth of thin hyphae compared to control cultures, hyphal coiling, vacuolation of hyphae, hyphal lysis of one competitor and deposition of crystals in the agar. Hymenomycetes caused varying amounts of decay in autoclaved root blocks. Resinicium bicolor was able to replace other species in most co‐inoculations. Stereum sanguinolentum appeared to be the least competitive species in root block inoculations, being replaced by Melanotus proteus and R. bicolor, although interactions with H. annosum varied widely. These results indicate that substrate has a marked effect on interspecific fungal interactions, with wood‐based, particularly intact woody tissues closely matching competitive behaviour displayed in the field.     

Fishing effort redistribution in response to area closures

Spatial fishery closures will induce fishing effort to either move to open areas or to cease to fish. When designing a short- or long-term closed area management regime, the expected impact of that closure will depend upon how that effort is redistributed. We present a redistribution model based upon Ideal Free Distributions (IFDs) which is intermediate in complexity between analyses in which effort is distributed uniformly over open areas and models of full fleet dynamics. The IFD models incorporate the fundamentals of the decision process invoked by fishers facing relocation and the ensuing catch rates that result from the addition or removal of effort. Two classes of models were tested: an Availability model where catch rate declines were proportional to abundance; and an Abundance model where abundance declines at an exponential rate with the entry of displaced effort into an area. Results of these models were compared with uniform and proportional redistribution methods. The IFD-based methods included relative cost of relocation, thereby illustrating the importance of both catch rates and movement costs in designing closed area regulations. To demonstrate the methods, hypothetical area closures to United States pelagic longliners in the western Atlantic were examined and the impact of those closures on bycatch rates was evaluated. Guidance for selecting an appropriate model structure for a particular closed area problem is given.     

集思广益拓展禽病防控策略——第58届西方禽病会议内容精选

2009年5月22～25日,第58届西方禽病会议在美国加利福尼亚州萨卡拉门托市举行.该会议每年在美国定期举行,参会代表是来自全球的禽类健康专家.     

Management strategies for attenuating herbicide resistance: untoward consequences of their promotion

Herbicide resistance is of major concern to global agriculture and its management is therefore crucial to ensure agricultural productivity. Seven typically recommended management strategies are: (1) rotate herbicides, (2) use herbicide mixtures, (3) follow label directions, (4) include non-selective herbicides as rotational compounds, employ (5) economic thresholds and (6) cultural weed control practices, and (7) monitor changes in weed populations. The primary objective of these strategies is to reduce the selection pressure for resistance. There are many situations, however, where the above strategies are impractical/impossible to implement, ineffective, and/or counter-effective. Therefore, in this review we have outlined these conflicts and concluded that adopting the currently promoted herbicide resistance management strategies may not always be effective in delaying the onset of herbicide resistance.     

Preliminary findings of Salmonella spp. in captive green iguanas (Iguana iguana) and their environment

Captive reptiles are routinely identified as reservoirs of Salmonella spp. and reports of reptile-associated salmonellosis are increasing. Unfortunately, little is known about the epidemiology of Salmonella spp. and green iguanas. We did a limited survey of a green-iguana farm in El Salvador to identify sources of Salmonella spp. in green iguanas and their environment. A limited number of samples for microbiological culture were collected from iguanas (adult, hatchling, and embryos) and their environment (food, water, soil, shelter, insects, and wild-caught lizards). Salmonella spp. was isolated from the intestine of both adult (3/20) and hatchling iguanas (8/20). There was no evidence of Salmonella spp. in the reproductive tracts of female iguanas (0/10). Salmonella spp. was isolated from the surface of 40% (7/16) of the egg surfaces tested. Salmonella spp. was not identified from the externalized yolk-sac of the iguana embryos tested. Soil samples from a breeding pen and a nest were both positive for Salmonella spp. Eight different Salmonella spp. serotypes were identified in this survey. These results suggest that horizontal transmission of Salmonella spp. is a potential source of exposure to hatchling iguanas at this facility.     

霉菌毒素造成经济损失：霉菌毒素结合剂的成本与效益评定

家禽饲料配方师在决定使用某种添加剂时,包括霉菌毒素吸附剂,必须要做出评断,使用该种添加剂后,是否能得到比其成本高得多的经济效益,即我们通常说的效益与成本比。 我们在饲料中使用霉菌毒素结合剂,如酯化葡配甘露聚糖有许多原因。通常是因为日常的试验室检测工作发现了饲料或原料中有霉菌毒素存在。但有时不一定能检测出。这可能是由于抽样误差或某些霉菌毒素测定方法的灵敏度,或由于影响家禽的霉菌毒素-黄曲霉毒素,镰刀菌毒