南水北调中线工程陕西水源区生态环境质量综合评价

对南水北调中线陕西水源区生态环境质量进行客观评价,可为南水北调工程的顺利实施提供决策和参考.利用RS和GIS分析方法,在生态系统理论的指导下,提取了研究区影响环境质量的6个因子图层数据,叠加形成一个综合环境指数图层数据,并将其划分为4个环境分区.从空间统计分析结果来看,综合自然指数Ⅰ,Ⅱ级最好,占整个水源区面积的64.69%,Ⅲ级较好,占整个水源区面积的31.52%;Ⅳ级区综合自然指数较差,占整个水源区面积的3.79%.对整个陕南水源区进行生态环境质量综合评价研究,能够对南水北调中线水源区生态补偿和水土保持建设提供数据支持和决策依据.     

玉米新品种胜玉906的选育

胜玉906是以自交系K18为母本、C16为父本,采用杂交选育而成的杂交1代玉米新品种,该品种春播生育期126 d,株型紧凑,成株株高270～305 cm,穗位高100～115 cm,叶片数21片;果穗筒型,穗长17.2～23.0 cm,穗粗4.2～5.2 cm,穗行数16～18行,行粒数35～43粒,籽粒黄色,马齿型,出籽率87.2%～90.0%,千粒重315.0～348.0 g;田间表现抗茎腐病、穗腐病,667 m²产量在1 000 kg以上,适宜在甘肃省中晚熟春玉米类型区种植。2019年通过农业甘肃省农作物品种审定委员会审定,审定编号：甘审玉20190020。     

低温对番茄叶片POD活性及其同工酶的影响

在(13±1)℃/(7土1)℃的低温条件下研究了不同处理时间对番茄苗期和坐果期POD活性及其同工酶的影响。结果表明随处理时间延长,番茄叶片中的POD活性增高,苗期在处理6d后增加幅度较大,坐果期POD活性低于苗期。低温处理苗期耐低温品系6d时出现一条Rf=a625的新酶带,而不耐低温品系处理10d后才出现;低温处理坐果期番茄叶片无新酶带的出现,只表现为活性的增强。苗期Rr=0．625,0.6375;坐果期Rr=0.6,0．625的同工酶谱带与番茄的耐低沮性有关。番茄苗期与坐果期对低温的敏感程度近似相同,但坐果期比苗期耐低温能力弱。     

珍稀濒危植物蒜头果天然林优势种群的生态位研究

采用样方法调查广西雅长兰科植物自然保护区内3个蒜头果天然林群落,并运用Levins指数和Schoener指数对各群落主要优势种的生态位宽度和生态位重叠进行了测度。结果表明,3个蒜头果天然林群落分别为槲栎群落、蒜头果-南酸枣-朴树群落和蒜头果-槲栎群落,各群落的性质和主要优势种组成及其在群落中的地位存在较大差异;槲栎群落主要优势种生态位宽度的大小顺序与其在群落中的地位基本一致,其他2个群落则变动较大;各优势种在不同群落的生态位宽度差异较大,其中蒜头果和南蛇藤对各资源位的生态适应性较好,而其他树种则有一定或较强的选择性;各群落的上层乔木之间或生态习性相近的下层乔木之间的生态位重叠值较大,资源竞争较为激烈。针对各群落的演替趋势及蒜头果种群的生存现状,提出了蒜头果的主要保护对策。     

增施氮肥对黄土高原旱作冬小麦农田土壤干层动态的影响

依托陕西长武农田生态系统国家野外科学观测研究站十里铺长期定位观测,研究了5种不同氮肥用量(0、45、90、135、180 kg·hm^-2)对冬小麦农田土壤水分及土壤干层动态的影响。结果表明：土壤干层深度大约在50～260 cm之间;施氮量小于90 kg·hm^-2时,增施氮肥土壤耗水强度和干层深度变化较小,而施氮量超过90 kg·hm^-2时,增施氮肥平均土壤耗水强度较大,但干层深度无明显变化,干层厚度增加速度随施氮量增加而增加;丰水年的高降水量在一定程度上可以缓解土壤干燥化,减小干层厚度。     

苎麻花叶病的研究I．病原探讨

１９８５年用四环素、青霉素处理苎麻花叶病病株，症状并未减轻。用４％ＰＴＡ负染方法对病叶汁液进行电镜观察，在Ｃ２－１４、芦竹青、细叶绿品种中均见到线状病毒粒子．３次嫁接试验表明可使健康接穗产生相同症状，进一步证实此病由线状病毒引起．     

鸡抗病毒Mx基因的克隆与序列分析

用干扰素诱导剂poly（I）／（C）诱导鸡胚成纤维细胞,提取细胞总RNA,采用RT—PCR方法扩增了北京白鸡Mx基因全长编码区序列。序列分析表明：该基因编码区长2118bp,编码705个氨基酸残基,其第631位为天冬酰胺,理论上推测具有抗病毒活性。通过与GenBank中已登录的7个品系鸡Mx基因进行核苷酸系统进化树分析,结果显示,北京白鸡Mx基因与WL—N品系鸡Mx基因的亲缘关系最近。北京白鸡Mx基因序列与其他动物Mx基因序列的比较结果显示,核苷酸同源性为49．5％～76．8％,氨基酸同源性为44．1％～61．6％。据此可以推断：克隆的Mx基因具有抗病毒活性的分子特征和特征性功能结构,不同种属动物Mx基因的同源性与其亲缘关系呈正相关。     

金丝猴生态学和分子生物学研究进展

金丝猴(Rhinopithecus)是典型的经历快速辐射和近期物种形成事件的进化类群,分为川金丝猴(Rhinopithecus roxellanae)、黔金丝猴(Rhinopithecus brelichi)、滇金丝猴(Rhinopithecus bieti)、越南金丝猴(Rhinopithecus avunculus)和缅甸金丝猴(Rhinopithecus strykeri)5个种。它们共同占据着东南亚的森林和林地生态位,是非人灵长类重要物种,国内外学者在它们的宏观和微观方面都做了大量研究工作,文章就5种金丝猴各自的生态学和分子生物学研究现状进行综述,并对存在的问题提出相应的建议。     

Effects of climate change and human activity on lake shrinkage in Gonghe Basin of northeastern Tibetan Plateau during the past 60 years

Changes in the status of freshwater resources are a topic of major global,regional and local concern.This is especially so in the arid and semi-arid regions of China,where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development,as well as in sustaining natural ecosystems.Recent climate change,as well as the effects of localized human activity,such as the use of water for irrigation agriculture,may have significant effects on the status of the water resources in the region.Here,we report the results of a study of changes in the areas of lakes in Gonghe Basin,northeastern Tibetan Plateau of China,over the last 60 years.The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950 s to 1980 s.The cause is ascribed mainly to human activity including exploitation of farmland,against a background of increasing population;in addition,climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly.After the construction of several reservoirs,significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes.However,both the area of farmland and the population size remained approximately constant after 1990.We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors(precipitation and temperature).As the regional temperature reached a new high,the area of some of the lakes decreased sharply before finally maintaining a relatively steady state.We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.