羔.羊.缺.硒.症.的.防.治

发病原因 长期单一饲喂含硒量低的饲料是引发该病的主要原因.薛庄农场地处沂河岸边,饲料主要以河床内的青草、树叶以及自己种植的山芋干为主,饲料中低硒或缺硒,因而导致该病发生.     

mzhy@mail.hebau.edu.cn

 以陆地棉冀无2031无菌苗下胚轴为外植体，在MS中附加激素0.1mg/L IAA+0.1mg/L 2,4-D+0.1mg/L KT的培养基上诱导出愈伤组织。选择疏松愈伤组织继代到附加0.1mg/L ZT的培养基中，经2~3个月的继代培养诱导出颗粒状疏松胚性愈伤组织。胚性愈伤组织在无激素、每升加2g谷氨酰胺和0.5g天门冬酰胺的胚性愈伤增殖萌发培养基上培养2个月左右，可陆续形成不同时期的体胚苗。对冀无2031不同时期的体细胞萌发后的体胚苗进行观察，发现了真叶畸形苗、子叶节生根胚、胚轴侧生根胚、腋芽丛生苗和以腋     

fanyang@mails.gscas.ac.cn或fanyang@mails.gscas.ac.cn

 太行山低山区干旱缺水严重，大大制约了山区经济发展。雨水集蓄利用技术是发展山区旱作林果业和旱作农业的重要技术手段。笔者在分析雨水集蓄利用理论和技术的基础上，对雨水汇集、蓄存和高效利用技术进行系统总结。并对其存在问题进行分析，提出相应的对策。     

wwgao@public3.bta.net.cn

 概述了目前植物源杀菌剂植物资源、有效成分、构效关系、作用机理的研究现状。总体来讲，在具有抗菌活性植物资源筛选方面已经做了大量工作，但大多停留在植物初提物；有效成分的分离纯化、构效关系及作用机理的研究较少有待进一步深入。     

weihong@mail.caas.net.cn

 通过对五大牧区草原区草原资源现状及其分布、草原生产力及载畜能力以及水资源现状及开发利用潜力分析，按照国民经济发展和增加农牧民收入要求，预测2010年五大牧区草原区草业发展对水资源的需求。研究结果表明，2010年五大牧区草原区农牧民人均纯收入为3400元，其中人均畜牧业纯收入2584元，需要养殖牲畜总数16413万羊单位，饲草料需求量1198.2亿kg。牧区产草总量可达1003亿kg，载畜能力13705万羊单位。尚有2708万羊单位，年需要饲料约195亿kg，需要发展灌溉饲草料地来解决，对水资源的需求量将达到     

山.林.区.羊.舍.的.改.造.与.设.计.

山羊是群居性动物,合群性强,喜欢群居群牧.山羊一生中有一半以上的时间是在羊舍内度过的,群居密度越大,群居时间越长,对环境及其相互之间的影响越大.山林区植被覆盖率高,雨水多,湿度大,温差大.这些因素给山羊生产造成一定影响.例如山羊生长发育适宜湿度为50%～70%,适宜温度为8～18℃,而山林区相对湿度高达80%以上,气温在8～18℃范围内的时间短.     

ynwildflower@yahoo.com.cn

 介绍了将瑞香狼毒黄花变型（Stellera chamaejasme f. chrysantha）作为切花进行引种驯化、栽培和繁殖所取得的进展，讨论了其商业开发利用前景、存在的限制性因子、可能的解决方法及今后研究的重点。     

chengxu@cau.edu.cn

 从荷兰和北京的农业经济特征的对比出发，分析了荷兰农业成功的因素，如农民合作意识强，研究、推广、教育三位一体，和基础设施完善等；并对其外向型农业形成的主客观因素及存在问题进行了分析；最后对北京市如何确立农业主导优势产业及发展外向型、高附加值农业进行了论述。     

jgjws@yahoo.com.cn

 通过对四川省温江、双流两地不同设施种植年限土壤中微生物数量及其生物量碳的研究，结果表明，不同设施种植年限大棚土壤中的微生物数量是露地的1.63~3.50倍，且大棚土壤中好气性微生物总数随种植年限的增加有逐渐降低的趋势，三大微生物数量占微生物总数的比例中，细菌表现为随设施种植年限的增加而增加；放线菌和真菌表现为下降；露地土壤微生物多样性指数分别是设施年限为1a、2a和4a的大棚土壤的1.29倍、2.28倍和3.45倍，前者明显高于后者。随设施年限的增加，土壤微生物生物量碳、有机碳及微生物对有机碳的利用率都表现     

chinachudong@sina.com.cn

 概述了分子标记的种类，分析了杂种优势研究中常用的几种分子标记的原理、特点。综述了分子标记在作物杂种优势群划分和杂种优势利用模式构建、杂种优势预测以及杂种优势遗传基础研究中的利用现状。并对分子标记在杂种优势研究中的进一步利用进行了展望。     

Cytology of Phleum sp. affin. P. montanum C. Koch

Diploid, tetraploid, and hexaploid plants occurred in foreign plant introductions of P. sp. affin. P. montanum from Turkey and Iran. Within-progeny variations in polyploid levels indicate that divergent races occurred as interspersed but natural populations. One to six B-chromosomes of varying sizes in addition to the normal chromosome complement were present in some plants. Their behaviours appeared essentially similar to those recorded for other species. Certain of the plants examined exhibited cytological features similar to those observed in known hybrids. These included prophase pycnosis, stickiness, split metaphase I plates, unoriented chromosomes at M-1, and low levels of pollen stainability. These features were absent in microsporocytes of other plants. Low open-pollination seed set characterized all plants examined. This may be due to hybridity or possibly to response to ecological conditions of the new environment.Results of co-operative work of the Crops Research Division, A.R.S., U.S. Department of Agriculture, and the Wisconsin Agricultural Experiment Station, Madison, Wisconsin.Former Graduate Student, Department of Agronomy, Wisconsin Agricultural Experiment Station, and Geneticist, Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture.     

U.S. Economic Growth vs. Environmental Conditions

A widely-held belief is that stricter environmental regulations stifle economic growth. To determine empirically the effect of environmental conditions and policies on state-level per capita income growth, a Barro-type economic growth model was estimated for the years 1982 to 1991, which correspond to two consecutive troughs in the business cycle. States with better environmental conditions had significantly higher income growth rates during this period. At the same time, stricter environmental policies did not significantly depress income growth. Data used include recently developed, consistent measures of environmental policy and quality for individual states, as well as data from the 1980 U.S. Census and Bureau of Economic Analysis.