重离子诱变鞘氨醇单胞菌选育毒死蜱高效降解菌株及应用

从青藏高原牦牛粪中分离出1株可降解毒死蜱的细菌,经形态和16SrDNA序列分析,鉴定其为鞘氨醇单胞菌属(Sphingomonas sp.)细菌。对其进行重离子诱变并筛选出菌株Sph-25-T1,该菌株对100mg.L-1毒死蜱的72h降解率达98.44%,比出发菌株提高27.37%。对Sph-25-T1进行传代培养,第5代时其对毒死蜱的降解率依然保持在90%以上。以喷洒毒死蜱1周后的不同土壤浸出液或蔬菜叶片做培养基时,Sph-25-T1对毒死蜱的降解率达到29.68%～78.40%。     

牛磺酸缓解脂质氧化日粮对黄河鲤生长性能和肠道健康的负面影响

为了探究牛磺酸对脂质氧化饲料饲喂下黄河鲤生长性能和肠道健康的影响,实验先用等量的氧化鱼油（记为OFO）替换基础日粮（记为FO）中的新鲜鱼油,接着将不同含量（0.4%、0.8% 和1.2%）的牛磺酸分别加入OFO组饲料中（分别记为T0.4、T0.8和T1.2）,对初始体重为（8.74±0.01）g的黄河鲤进行为期10周的养殖实验。结果显示,与FO组相比,OFO组的终末体质量、增重率、特定增长率和饲料效率均显著降低。上述所有指标在T0.4、T0.8和T1.2组中均显著高于OFO组。另外,OFO组中肝胰脏抗氧化酶的mRNA表达水平显著低于FO组,而牛磺酸添加组中肝胰脏和肠道的抗氧化酶mRNA表达均有不同程度的上调。与FO组相比,OFO组中的肠道消化酶活性,肠绒毛高度、肠绒毛宽度和肌层厚度均显著降低,而在牛磺酸添加组中均得到提高。同样的,OFO组中肠道微生物组成的丰富度和多样性显著降低,条件致病菌丰度明显升高,而有益菌的丰度却有所下降,这些不良现象在牛磺酸组中均得到明显改善。研究表明,牛磺酸可缓解脂质氧化饲料对黄河鲤造成的生长性能抑制、肠道组织结构破坏、消化功能下降及肠道菌群紊乱等不良影响。结合本研究结果,在氧化脂质饲料中牛磺酸的建议添加剂量为0.4~0.8%。本研究为进一步探索牛磺酸对鱼类肠道的生物学功能奠定理论基础。     

含ACC脱氨酶的PGPR在植物抗非生物胁迫中的作用研究进展

用含ACC脱氨酶的PGPR接种植物,可降低乙烯含量,从而减轻非生物胁迫对植物生长和发育产生的影响。归纳了水、盐碱、温度、污染物胁迫下含ACC脱氨酶的PGPR对植物的接种效应,得出PGPR可提高植物对干旱、水涝、盐碱胁迫及温度的抗性和耐受性,同时还可促进植物修复土壤污染。最后提出了展望。     

宽筋藤组织培养的初步研究

为了研究宽筋藤快繁技术,以宽筋藤健壮无病虫害的嫩茎和嫩叶作为试验材料,研究其表面消毒方法和在添加不同浓度激素的培养基上培养,对宽筋藤进行组织培养研究。结果表明：茎段表面采用75%酒精消毒30 s,用0.1%升汞浸泡5 min,无菌水漂洗2次后,再用0.1%升汞浸泡5 min,无菌水漂洗4次的效果最佳,存活率为66.7%;而叶片直接用升汞处理12 min的消毒效果较好,存活率为53.3%;适宜侧芽诱导和增殖的培养基为MS+6-BA 0.05 mg/L+GA3 0.04 mg/L+NAA 0.02 mg/L,30天的增殖系数为3;诱导愈伤组织以培养基MS+2,4-D 1.5 mg/L+BA 0.5 mg/L的效果较好,对嫩茎的诱导率可达83.3%,对嫩叶的诱导率可达76.7%,但所诱导的愈伤组织分化能力低,均不能分化不定芽;适宜生根的培养基为MS+NAA 0.1 mg/L,生根率可达到100%,且移栽成活率96%。     

甲哌鎓对棉花叶片光合生理及蜡质含量的影响

为探究甲哌鎓对棉花表皮蜡质沉积及光合生理的影响,以‘新陆早55号’棉花为试材,将甲哌鎓按有效成分0、4.5、7.5、10.5和15.0 g/hm2的剂量分别喷施于叶面,于施药后1、4、7和12 d分别测定棉花叶片的光合速率和表皮蜡质含量及12 d内叶片的叶绿素相对含量（SPAD值）。结果表明:于叶面喷施甲哌鎓后,棉花叶片光合速率、表皮蜡质含量及SPAD值与甲哌鎓浓度、处理时间之间存在一定的依赖性。4.5与7.5 g/hm2的甲哌鎓处理可提高棉花光合速率并且持续期较长;SPAD值随处理时间的延长及甲哌鎓浓度的增加而增加,表明棉花叶片叶绿素含量随之增加及叶色加深;4.5 g/hm2甲哌鎓处理更利于棉花叶片表皮蜡质的沉积。蜡质、光合速率、SPAD值相关性分析结果显示,光合速率与蜡质、SPAD值间呈极显著正相关关系,说明蜡质的沉积及叶绿素含量增加有利于棉花叶片进行有效的光合作用,增强抗逆性。     

Forage crops alter soil bacterial and fungal communities in an apple orchard

In this study, we investigated the effects of planting three types of forage crops in an apple orchard on the soil microbial community structure. The apple orchard was intercropped with native grasses (NG), red clover (RC; Trifolium pratense L.), ryegrass (RE; Trifolium repens L.), and no vegetation (CT control; clean tillage). We obtained soil samples from depths of 0–20, 20–40, and 40–60?cm from the different treatment plots in the orchard and analysed them using a high-throughput DNA sequencing technique. The three forage crops had affected the soil bacterial and fungal community structures. Compared with CT control, intercropping with NG increased the proportion of Acidobacteria and reduced those of Nitrospirae and Verrucomicrobia, whereas intercropping with RC increased the proportions of Nitrospirae and Verrucomicrobia and reduced that of Planctomycetes. Intercropping with RE increased the proportions of Nitrospirae and Chloroflexi, whereas reduced that of Acidobacteria. Furthermore, unlike in the other treatments, intercropping with NG increased the proportion of Zygomycota in the 0–20-cm soil layer. Intercropping with RC increased the proportion of Chytridiomycota in all the three soil layers, whereas intercropping with RE increased the proportion of Basidiomycota in the 20–40-cm soil layer. Collectively, these findings suggest that intercropping with forage crops, especially RC, in an apple orchard, could alter soil microbial community structure. In our previous study, we showed that microbial sole-carbon-source utilisation is changed by intercropping with forage crops; thus, it can be considered as an effective approach to improve the efficiency of soil C cycling in the apple orchard by altering the microbial community structure.     

杉木动态黏弹行为的时温等效性

运用时温等效原理研究含水率为0.6%的木材试样的动态黏弹性质。在25～150℃温度范围内,通过频率扫描(0.1～20Hz)试验获得不同恒定温度水平下木材的贮存模量和损耗因子值。将其他温度下的黏弹性曲线通过水平移动因子平移并叠合连接至参考温度(本研究中为135℃)曲线,分别生成一定频率范围内的贮存模量和损耗因子主曲线。通过最小二乘拟合法,采用Arrhenius方程对水平移动因子与温度的关系曲线进行拟合分析。结果表明:贮存模量主曲线的水平移动因子与温度的关系曲线在25～150℃内满足Arrhenius方程,因此利用时温等效原理描述木材的动态刚度性质是适用的;但时温等效原理无法预测木材的松弛转变行为。     

时域核磁共振技术在木材科学研究领域的应用

时域核磁共振技术（TD-NMR）作为一种先进的表征手段,能快速、精准测量木材中自由水和吸着水的动态变化,也可以基于水分信息表征木材孔隙分布,因此已被广泛应用于木材科学研究领域。文中归纳了时域核磁共振技术用于测量木材含水率、水分性质、水分分布及木材孔隙分布的方法,并对主要研究结果进行综述,以期为相关领域的研究和应用提供理论参考。     

Application of time–temperature superposition principle to Chinese fir orthotropic creep

The application of time–temperature superposition principle (TTSP) to orthotropic creep in dry Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) was investigated through a sequence of short-term tensile creep for longitudinal (L), radial (R), and tangential (T) specimens in the temperature range of 30–150 °C. A visual assessment for the validity of TTSP was carried out by applying the approximated complex plane (ACP). The results showed that TTSP was well matched for R and T specimens using horizontal shift factor to construct master curves. As for L specimen, an additional vertical shift factor was applied to construct a smooth master curve, owing to the temperature-dependent compliance. Based on the application of ACP, the creep model governed by a power law was proposed to successfully depict the master curve for each main anatomy direction. The present study partially provided the firsthand data in verifying the applicability of TTSP of the orthotropic viscoelasticity of Chinese fir wood, and successfully constructed the rheological model to predict the orthotropic creep response. More importantly, the result can function as the base to the structural safety designs for the engineering structures of Chinese fir in practice.     

喷播机液压转向集成块典型孔道结构流场分析及优化

针对喷播机原有液压系统管路结构复杂,容易泄漏,振动和噪声大的问题,将液压转向集成块应用在喷播机转向机构中,并且利用FLUENT软件对其特征孔道的流场进行数值仿真研究。结果表明:1)集成块可以有效减少原有液压系统管路结构,使液压系统结构紧凑,实现元件之间无管道连接,同时减少了系统泄漏、振动和噪声;2)通过分析孔道结构对其内部流场的影响,验证了集成块孔道内部压力损失与孔道结构以及流体的速度有关,在工作条件允许的情况下,应降低流体的速度,以减少压力损失;3)通过优化孔道结构可以降低压力损失,如T型孔道中增加工艺孔,可使压力损失降低8%左右,当进油口孔道和出油口孔道直径不一致时,建议出油口直径取0.8~1.2倍进油口直径。