网络环境下高校图书馆对学生信息素养的培养

本文首先对大学生信息素养概念进行了界定,进而阐明了在图书馆网络环境背景下信息素养在大学生各项能力培养中的重要作用,并分析了当代大学生信息素养偏低的原因,文章最后给出一些提高当代大学生信息素养的途径以供高校图书馆借鉴。     

Critical period for grain number establishment of near isogenic lines of two- and six-rowed barley

In barley no studies have attempted to pinpoint the critical period for grain number determination, and it is frequently stated that the critical period is similar to that of wheat. However, there are important differences between the species and among barley genotypes (i.e. two- and six-rowed types) suggesting that this assumption requires testing. The objectives of this paper were (i) to determine the critical period for grain number determination in two- and six-rowed barleys, and (ii) to identify which yield components were more sensitive to changes in incident radiation during that period.

Two field experiments were conducted using two pairs of near isogenic lines differing only in the spike type. Shading was imposed at different periods throughout the crop cycle (from 60 days before heading to 15 days after) to reduce incident solar radiation approximately 70%.

The critical period for grain number determination tended to be slightly earlier in two- (ca. between 40 and 10 days before heading) than in six-rowed barleys (ca. between 30 days before heading until that stage). In terms of the external phenology, the beginning of the critical period for setting grains was 10 days after the beginning of stem elongation, and 10 days before flag leaf appearance in two- and six-rowed lines, respectively. Changes in the number of grains per unit area were correlated with crop growth rate during the critical period for yield determination.     

Yield and growth characteristics for cotton under various irrigation regimes on sandy soil

Over-watering cotton wastes a valuable and scarce resource; it can also lead to rank growth, nutrient leaching, and contaminated groundwater. Since under-watering can decrease yields, the question becomes one of finding the optimum application regime. An irrigation experiment was set up to apply water at six different application rates, ranging from 33% to 144% of normal, with hopes of identifying the regime that produces maximum yield. Two cultivars, Acala Maxxa and Acala PhytoGen-72 (Gossypium hirsutum L.), were planted on sandy soil and irrigated daily with a highly efficient subsurface drip irrigation system for four seasons. The results showed that on the average there was no significant difference in the yield of the two cultivars and there was no significant difference in the yield for the three wettest treatments. The driest of the three wettest treatments, treatment 4, was a critical point on the water production function curve. It represented the least amount of water applied that still produced essentially maximum yield, and it had the highest water use efficiency. This critical level of water application during mid-season was found to be, on the average, 95% of Class A pan evaporation; it corresponded to a total seasonal application of 654 mm of water. Any application less than this critical level decreased yields. Reducing the water application by 5% below the critical level caused about a 4.6% reduction in yield. The critical level produced a soil moisture level that remained nearly constant throughout the season. The final plant height was closely related to the depth of water applied, with the wettest treatment producing plant heights of 2.0 m, and the driest treatment producing plant heights of 0.6 m. At the extremes of the water application rates there were some small differences in the early-season growth rate of the plants, but the main cause of differences in final plant height was the date of cutout (cessation of main stem node production). The length of season for the driest treatment was about 4 weeks shorter than for the wettest treatment on both cultivars. Results showed that deficit irrigation of cotton on sandy soil can greatly reduce yield, and the practice should probably be avoided.     

树型金银花花蕾大小与花粉发育关系的研究

[目的]研究树型金银花花蕾大小与花粉发育的关系。[方法]采摘未开树型金银花花蕾,通过不同染液染色,获得最佳观察效果,固定、测量花蕾长度、制片、镜检。[结果]树型金银花花药用醋酸洋红染色效果比美蓝染色效果好。花药发育的时期和花蕾外观形态之间的对应关系为:花蕾长度0.48～0.71 cm处于单核早期,达到71.0%;长度在0.72～0.89 cm处于单核中期,达到65.0%;长度在0.90～1.02 cm处于单核晚期,达到67.3%;长度在1.02～1.19 cm处于有丝分裂前期,达到60.8%;长度在1.19～2.32 cm处于二核期,达到59.8%。[结论]通过观察树型金银花花蕾外观形态,可以直观确定花药发育时期,为花药单倍体培养奠定基础。     

沙柳营养繁殖苗培育技术研究

采用不同方法研究了沙柳营养繁殖苗培育技术,结果表明:沙柳的着生环境越接近原生的基质条件,沙柳扦插生长也越具有优势。通透性好的沙基质有利于沙柳扦插成活。沙柳扦插苗头2年生长最快,3年后生长逐渐减退。     

Genetic Diversity of European and Chinese Oilseed Brassica rapa Cultivars from Different Breeding Periods

The Brassica oilseed crops went through two major breeding bottlenecks during the introgression of genes for zero erucic acid and low glucosinolate content, respectively, which may lead to reduced genetic biodiversity of the crop. This study investigates the impact of these bottlenecks on the genetic diversity within and across European and Chinese winter B. rapa cultivars. We compared eight cultivars from Europe and China, representing three different seed qualities from three different breeding periods： （1） high erucic acid, high glucosinolates （＋＋）; （2） zero erucic acid, high glucosinolates（0＋）; （3） zero erucic acid, low glucosonolates （00, canola quality）. Diversity was estimated on 32 plants per cultivar, with 16 simple sequence repeat （SSR） markers covering each of the B. rapa linkage groups. The analysis of molecular variance （AMOVA） showed that genetic variations within cultivars, across cultivars and across regions （Europe and China） were significant, with about 60% of the total variation within cultivars. There was a slight, but non-significant loss in genetic diversity within cultivars when comparing the three breeding periods as indicated by effective number of alleles （2.39, 2.23, and 1.99 for breeding periods 1, 2, and 3, respectively）, Shannon information index （0.93, 0.90, 0.75）, and expected heterozygosity （0.51, 0.49, 0.42）. By cluster analysis （UPGMA dendrogram） and principal coordinate analysis, Chinese and European cultivars were clearly divided into two distinct groups. In conclusion, quality improvement did not significantly reduce the genetic diversity of European and Chinese B. rapa cultivars.     

大型泄洪洞衬砌混凝土施工期温度场和温度应力的仿真计算

【目的】探明地下衬砌混凝土出现裂缝的原因,研究进一步采取综合温控措施防裂的有效性和合理性。【方法】结合工程实际情况,在考虑混凝土热力学参数随混凝土龄期的变化,以及坝体分层浇筑过程对温度应力影响的基础上,利用大型有限元软件对泄洪洞衬砌施工过程中的温度场和温度应力进行了三维仿真计算。【结果】仿真结果给出了衬砌混凝土温度场、温度应力分布及其随时间变化的规律,即于开浇后的第2天达到最大温度值,第3天即开始出现较大拉应力值,而极值出现在中后期。【结论】在混凝土浇筑过程中,应采取降低浇筑温度等措施;在浇筑后的10~28 d温降期间,要对混凝土表面施行流水养护等温控措施,严格各项施工规范。     

水稻亲本、杂交后代的成熟期倒伏指数及关系研究

以籼型三系不育系宜香1A、II-32A、冈46A和恢复系宜恢7633、宜恢7008、宜恢1525等为材料,通过对亲本和杂交后代倒伏指数的分析,发现母本、父本各节间倒伏指数存在较明显的差异,倒3节间的倒伏指数差异达极显著水平.这种差异直接影响着后代倒伏指数的变化,特别是母本对后代的影响效果更为明显.父母本抗倒能力强,则后代较易表现强的抗倒力,同时也受父母本间互作效应和它们与环境互作效应的综合影响.     

贮藏期对花生种质籽粒成分影响研究

常温干燥贮藏是植物种质资源保存的重要方式之一。研究表明,在常温干燥条件下,经过11年的保存,花生不同类型籽粒成分发生程度不同的变化,其中总糖含量随贮藏时间而增加,蛋白质和粗脂肪含量整体呈降低趋势,脂肪酸中除油酸含量随贮藏时间延长而升高外,棕榈酸与亚油酸含量均降低。VE除多粒型与中间型外,其余类型花生种质均随贮藏时间延长而降低。同时,花生种质的外观品质性状不随贮藏时间延长而发生显著变化。     

奶牛干奶期饲养管理要点

无论对奶牛还是奶牛饲养管理者干奶期的饲养管理都很重要,本文从干奶期长短,干奶方法,干奶期奶牛的饲养和管理,干奶期乳房炎和其它代谢疾病的预防和控制等方面介绍了实践中奶牛干奶期应注意的几个要点。