Colonization and histopathology of susceptible and resistant carnation cultivars infected with Fusarium oxysporum f. sp. dianthi

Stems of the susceptible Early Sam and resistant Novada carnations were inoculated with a conidial suspension ofFusarium oxysporum f. sp.dianthi. Stem segments of either cultivar were sampled regularly and used for determination of fungal growth and for microscopical investigation.Early Sam showed typicalFusarium wilt symptoms and its stems were colonized intensively. The observed vascular browning appeared to be caused by discolouration of primary walls of infected vessels and surrounding cells. Vessels were rarely occluded with gel. Cell wall degradation led to the formation of stem cavities. Hyperplasia of xylem parenchyma was not seen.In Novada, fungal colonization remained low throughout the experiment. Macroscopic symptoms were absent except for longitudinal bursts in the stem, which appeared to be caused by hyperplasia of xylem parenchyma bordering infection. Vascular gelation occurred in the infected tissues, causing some vascular browning also. Xylem vessel regeneration was observed in the hyperplastic layer. Cavities were not formed, and wall discolouration was rare. Vascular gelation is considered part of theFusarium wilt resistance mechanism. It is followed by xylem vessel regeneration, which expresses a general plant response to vascular dysfunction rather than being part of the resistance mechanism.Although of different origin, vascular browning as such occurs in both susceptible and resistant interactions. In breeding for resistance, care should hence be taken with the current use of browning as an indication of disease.Samenvatting Anjers van de vatbare cultivar Early Sam en de resistente cultivar Novada werden geïnoculeerd met een conidiënsuspensie vanFusarium oxysporum f. sp.dianthi. Van beide cultivars werden regelmatig stengeldelen geoogst om deze microscopisch te onderzoeken en om de schimmelgroei te bepalen.Early Sam vertoonde de voor deze verwelkingsziekte kenmerkende symptomen en werd intensief gekoloniseerd. Aan het vaatweefsel waargenomen bruinkleuring bleek veroorzaakt te worden door verkleuring van de primaire wanden van geïnfecteerde vaten en de hen omringende cellen. Zelden trad er in de vaten gomvorming op. Celwandafbraak veroorzaakte de vorming van holten in de stengel. Hyperplasie van het houtparenchym werd niet waargenomen.In Novada bleef de schimmelgroei gedurende het hele experiment beperkt. Macroscopisch waren er enkel lengtescheuren in de stengel te zien, die veroorzaakt bleken te worden door hyperplasie van aan de infectie grenzend houtparenchym. In het geïnfecteerde vaatweefsel optredende gomvorming veroorzaakte ook enige bruinkleuring. In het hyperplastische weefsel werd regeneratie van houtvaten waargenomen. In de stengel werden geen holten gevormd, en verkleuring van de celwanden kwam weinig voor. De vorming van gommen in de houtvaten maakt waarschijnlijk deel uit van het resistentiemechanisme. De daarop volgende houtvatregeneratie is eerder een algemene reactie van de plant op vaatverstopping dan een deel van het resistentiemechanisme.Vaatverbruining, zij het van verschillende oorsprong, komt voor in zowel vatbare als resistente interacties. Om die reden moet men in de resistentieveredeling bij de anjer voorzichtig zijn met het gebruik van bruinkleuring als ziekteïndicatie.     

试论福建省国营林场分类管理

本文分析了福建省110个国营林场的类型、目前管理体制、管理办法及存在的问题。指出了目前国营林场管理办法中存在着种种弊端,跟深化林业改革很不适应,必须改革和完善国营林场管理机制,理顺“省办地管县监督”的管理体制,实行分类指导。本文就分类管理的依据,原则和实施办法进行了探讨,并提出了一些建议。     

水分管理方式对香根草生长发育的影响

对四种不同的水分管理条件下香根草生长研究发现：香根草最适宜在土壤水分饱和的湿润环境中生长,这时它的成活率最高,分蘖速度最快,植株高度生长也最快,定植后3个月,其对应的根体积、根干生物量、茎叶干生物量和根茎比也最高。     

类鼻疽的研究进展

本文就类鼻疽(melioidosis)的流行病学,诊断方法,免疫机理,发病机理及治疗方法 进行了综述。为重视该病的研究提出了建议。     

乌梁素海生态恢复机理与工程技术的研究

在我国干旱区典型草型湖泊—乌梁素海设立试验基地 ,进行生态恢复工程试验研究。研究表明 :乌梁素海受富营养化影响 ,正在向芦苇沼泽—碱蓬盐化草甸—白刺荒漠方向演化。生态恢复机理是 :( 1 )减少大型水生植物有机氮、磷向底质的沉降 ,削弱内源性营养物负荷的积累与储备 ;( 2 )减少大型水生植物死亡后矿化成氨态氮 ;( 3)控制底质中有机氮向水体释放生成氨态氮。采用机械化方式收割大型水生植物转移营养盐 ,抑制生物促淤效应以及对芦苇区进行园田化生态管理是乌梁素海生态恢复的关键技术 ,也是乌梁素海环境与资源持续发展的核心问题     

The urbanization of wildlife management: Social science, conflict, and decision making

Increasing urbanization of rural landscapes has created new challenges for wildlife management. In addition to changes in the physical landscape, urbanization has also produced changes in the socio-cultural landscape. The greater distancing from direct interaction with wildlife in urbanized societies has led to the emergence of a culture whose meanings for wildlife are less grounded in the utilitarian/instrumental orientation of rural agrarian systems. Urban perspectives on wildlife are comprised of more highly individualized emotional/symbolic values. This shift creates two problems with respect to managing wildlife in an urbanizing landscape. First the increased diversity in values and meanings increases the likelihood for social conflicts regarding wildlife management while at the same time making socially acceptable resolutions more intractable. This in turn requires fundamental changes in decision-making paradigms and the research approaches used to inform decision making. Second, as remaining rural communities feel the pressures of urbanization, wildlife conflicts become conflicts not just over wildlife but conflict over larger socio-political concepts such as equity, tradition, private property rights, government control, power, and acceptable forms of knowledge. This paper examines the wildlife management implications of changes associated with increasing urbanization and employs two case studies to illustrate these issues. First a study of a controversy over urban deer management provides insights into how to map conflicting values and search for common ground in an urban culture with increasingly individualistic values for wildlife. Specifically, the analysis illustrates that common ground may, at times, be found even among people with conflicting value systems. The second case study examined a ranching community faced with predator reintroduction. This case study illustrates tensions that occur when the community of interest (i.e. a national public) is broader than the community of place in which the problem occurs. In this latter situation, the debate centers around more than just different views about the rights of animals. It also entailed the rights of individuals and communities to decide their future. The conclusion discusses the need for wildlife institutions to adapt their underlying decision making philosophy including the way science is integrated into decision making processes in light of the changes in social context caused by urbanization.     

Effects of winter wheat cultivars and seed rate on the biological characteristics of naturally occurring weed flora

Summary Differential competitive ability of six winter wheat cultivars and traits that confer such attributes were investigated for a range of seed rates in the presence or absence of weeds for a naturally occurring weed flora in two successive years in split-plot field experiments. Crop height and tillering capacity were considered suitable attributes for weed suppression, although competitiveness is a relative rather than an absolute characteristic. Maris Huntsman and Maris Widgeon were the most competitive cultivars whereas Fresco was the least competitive. Manipulation of seed rate was a more reliable factor than cultivar selection for enhancement of weed suppression, although competitiveness of cultivars Buster, Riband and Maris Widgeon was not enhanced by increased seed rate. Crop densities ranging between 125 and 270 plants m⁻² were found to offer adequate weed suppression. Linear relationships were observed between individual and total weed species dry weight and reproductive structures per unit area.     

水稻不同品种或组合对甲磺隆耐药性差异的机制研究

以水稻乙酰乳酸合成酶(ALS)比活力为研究对象,通过在离体和活体条件下比较其对甲磺隆的敏感性水平,探讨了水稻不同品种或组合的耐药性差异机制。结果表明,离体条件下不同水稻品种或组合ALS对甲磺隆均较敏感,当甲磺隆浓度为100 μg/L时,对ALS比活力抑制率达60%以上,且活力百分比与甲磺隆浓度对数成直线负相关关系,相关程度显著或极显著;活体条件下ALS活力均受到甲磺隆不同程度的抑制,但同一品种ALS活力不随甲磺隆浓度的变化而呈现规律性变化。在甲磺隆浓度相同时,活体条件下所有供试水稻品种ALS活力均显著高于离体条件下的ALS活力,影响程度与植株耐药性差异基本一致,说明甲磺隆在水稻体内存在较强代谢失活作用,代谢失活差异是水稻不同品种或组合对甲磺隆的耐药性差异机制。     

二点叶螨对氧乐果、甲氰菊酯、四螨嗪及螨嗪菊酯混剂的抗药性

以兰州吐鲁沟公园金花忍冬植物上采集的二点叶螨为敏感种群,在室内盆栽菜豆苗上饲养繁殖后分别用氧乐果、甲氰菊酯、四螨嗪及螨嗪菊酯(甲氰菊酯 四螨嗪)混剂喷雾处理20代,获得二点叶螨抗氧乐果种群(抗性指数RF=35.84倍)、抗甲氰菊酯种群(RF=479.79倍)、抗四螨嗪种群(RF=67.26倍)以及抗混剂螨嗪菊酯种群(RF=26.75倍)。用生化法测定离体酶活性的结果表明,上述四个抗性种群的形成与体内羧酸酯酶、磷酸酯酶、谷胱甘肽转移酶的活力增加及乙酰胆碱酯酶的活性降低有关。4个抗性种群对常用15种供试药剂交互抗性测定结果表明,氧乐果、甲氰菊酯与联苯菊酯、三氟氯氰菊酯、水胺硫磷、久效磷、氰久合剂有交互抗性,甲氰菊酯还与螨蚧克有交互抗性;四螨嗪与三氯杀螨醇(RF=14.15倍)、齐螨素(RF=10.26倍)有交互抗性;螨嗪菊酯与双甲脒、氧乐菊酯有负交互抗性,RF值分别为0.85、0.71倍。     

Integrated Pest Management in Cocoa Agroforests in Southern Cameroon: Constraints and Overview

Imports of pesticides have long been subsidised for use in the cocoa agroforests of the humid forest zone of southern Cameroon. With the liberalisation of the cocoa and pesticides sectors and the devaluation of the local currency (CFA franc), farmers are facing fluctuations in the price paid for cocoa and the high cost of farm inputs. Without the support of the extension services, they themselves have developed traditional integrated control methods based on the use of plant extracts mixed with conventional pesticides. From a survey of 300 cocoa farmers, the study assesses the farmers' command of these methods, the pests controlled, the problems encountered and the institutional constraints in the definition and dissemination of integrated control methods. The study concludes with recommendations for research and development towards the better definition and dissemination of integrated control methods. This revised version was published online in July 2006 with corrections to the Cover Date.