Endophytic nitrogen-fixing Klebsiella variicola strain DX120E promotes sugarcane growth

Klebsiella variicola bacteria are found in association with plants. Little is known about their colonization patterns, roles, and mechanisms during association with the plant hosts. Here, we identified a nitrogen-fixing bacterium, DX120E, which was isolated from surface-sterilized roots of the ROC22 sugarcane cultivar, as K. variicola by phylogenetic analyses of its 16S rRNA gene, RNA polymerase β-subunit gene, and DNA gyrase subunit A gene sequences. gfp-tagged DX120E was found to colonize at the roots and aerial parts of micropropagated sugarcane plantlets by fluorescence microscopy and confocal microscopy. DX120E was able to survive in soils and colonize in root epidermal cells, intercellular spaces in root cortices, and leaf mesophyll and vascular tissues. DX120E preferentially colonized at root maturation and elongation zones and entered roots via cracks at the emergence site of lateral roots and at disrupted epidermis. DX120E may penetrate root epidermal cells with the aid of their cellulose-degrading enzymes. ¹⁵N isotope dilution assay demonstrated that DX120E was able to fix N₂ in association with ROC22 sugarcane plants under gnotobiotic condition. DX120E was also able to promote GT21 cultivar growth and plant uptake of N, P, and K under greenhouse condition. Together, this study for the first time shows that a K. variicola strain is able to colonize in its sugarcane plant hosts, to fix N₂ in association with plants, and to promote plant growth.     

Research Progress on Hair Cortisol as Evaluation Indicators of Chronic Stress

Making hair cortisol as the gold standard of reflecting chronic stress level is prospective and innovative.Hair cortisol not only can be used in detecting and estimating the chronic stress level of animals, but also can be benefit for understanding the body's physiological and pathological process and making effective health management strategy in time.Blood, saliva, urine and milk cortisol concentrations can be regarded as matrices for reflecting acute stress level as well, they have been used in detecting and establishing the diurnal profile of circulating cortisol studying.But hair which is a good supplementary matric can reflect the chronic stress level retrospectively.Hair cortisol as a reflection of the biochemical markers of chronic stress has the advantages of no invasive, relatively sensitive detection and convenient sampling stress, and hair cortisol is a heritable trait (h²=0.31).The utility of hair cortisol as a maker for HPA activity, and a useful tool for identifying genetic variation influences on long term individual differences in HPA activity.This article summarized the relationship between the cortisol and animal's healthy, the regulating mechanism and genetic adaptation change under chronic stress and the research progress of evaluation indicators during chronic stress, the research progress of hair as a matric of cortisol, the limitations and challenge of regarding hair cortisol as the biochemical marker to reflect the chronic stress level in the future.     

基于偏最小二乘的无线传感网多跳定位算法

提出了一种基于偏最小二乘的多跳定位算法(ML-PLS)。算法借助偏最小二乘对已知节点间的跳数与真实距离的建模,通过跳数、距离两者间的最大协方差共同推动节点位置的估计。ML-PLS算法对复杂部署环境具有较强的适应性,克服了传统算法只适用于各向同性网络的不足。仿真结果表明,ML-PLS算法定位精确度高且性能较稳定,并能适应不同网络环境。     

肉羊舍饲养殖技术

羊属草食反刍家畜,在草地上放牧是传统的养殖方式,在我国北方地区生态环境严重退化,不宜继续用作放牧地,为保护生态环境,我国实施了退耕还林(草)、草原承包补助奖励、林地承包等一系列保护环境的工程建设和政策。舍饲养羊成为这些地区养羊业的必然选择,羊只必须从放牧饲养转为舍饲。舍饲养羊采食方式由主动选择变成被动接受,饲料来源也不再是"百样草",而是根据自己的条件提供的几种很有限的饲料,同时羊的活动地域也受到严重限制,无法满足其基本的生理特点,其生产力、繁殖力、生活力就会出现障碍,养殖收益下降。另外,舍饲不仅要投入更多人、财、物力,而且无污染羊产品的生产难度加大,养殖成本明显增加,挫伤了农民的养殖积极性,制约了农业和农村经济的发展。为此,笔者从选种选配、饲养管理、羔羊育肥、提高舍饲养羊效益等环节分析剖解,提高舍饲养殖水平,增加肉羊养殖效益。     

浸泡和切割处理对东方百合杂交种子萌发的影响

对东方百合(Oriental hybrids)品系内杂交组合‘卡萨布兰卡’(‘Casablanca’)ב索邦’(‘Sorbone’)和‘马可波罗’(‘Marco Polo')ב索邦’的种子进行浸泡24 h、切割胚、浸泡+切割胚综合处理下萌发试验的研究.结果表明,种子切割处理能够缩短东方百合杂交种子的萌发时间,并且显著提高萌发率.切割处理的‘卡萨布兰卡’ב索邦’种子发芽势和萌发率均极显著地高于对照,发芽势达到75.56％,萌发率达到80.00％;‘马可波罗’ב索邦’种子的发芽势为100.00％,萌发率为100.00％.切割处理后的‘卡萨布兰卡’ב索邦’种子和‘马可波罗’ב索邦’种子的最适培养基均为MS+20 g/L蔗糖+9 g/L琼脂.     

磷在CaO-SiO2-FetO-P2O5与2CaO·SiO2颗粒界面间的传质行为

对2CaO·SiO2(C2S)颗粒与C2S饱和的CaO-SiO2-FetO-P2O5渣在1 500 ℃下的反应进行了实验研究,采用SEM/EDS观测了C2S颗粒与熔渣界面之间不同位置各成分的含量变化,讨论了磷在C2S颗粒与熔渣界面间的传质行为。结果表明,在C2S颗粒与其周围熔渣形成的固液两相区内生成了n·2CaO·SiO2-3CaO·P2O5(nC2S-C3P)固溶体。随着反应时间的延长,nC2S-C3P固溶体层越来越厚,在指向C2S颗粒内部方向,nC2S-C3P固溶体层中的磷含量逐渐降低。了解磷在C2S与熔渣界面间的传质行为,有助于CaO-SiO2-FetO-P2O5中nC2S-C3P固溶体形成机理的研究。     

Urban Environmental and Urban Ecological Problems in the Sustainable Development of Chongqing City and Its Countermeasures

The main urban environmental and urban ecological problems existing in the sustainable development of Chongqing city were introduced in this paper. Furthermore, the causes and features of these problems were analyzed. At last, some countermeasures, which would provide some scientific bases for accelerating the urban sustainable development of Chongqing city, were suggested.     

天水市蔬菜市场管理问题研究

通过对蔬菜批发市场、农村集贸市场、产地市场进行调查的基础上,阐述蔬菜市场建设模式、管理形式以及营销方式、外销品种和去向。针对目前天水市蔬菜市场存在的主要问题,在建设和管理方面提出几点建议。     

蓝莓贮藏适宜果实特性研究

以蓝莓为试材,探讨采摘成熟度、果实规格和品种的耐贮性,并比较不同成熟度果实贮藏前后内部品质变化,研究其贮藏适宜的果实特性。结果表明:果实全蓝色时采摘,果实内部品质、口感最佳,果实耐贮性最高,同时贮藏前后果实内部品质无显著性差异;M、L级果实耐贮性无显著性差异,但是显著高于XL级;初步得出,"蓝丰"品种的耐贮性显著优于"达柔"、"埃利奥特",贮藏60d好果率高出14%、20%。表明蓝莓贮藏适宜果实特性为果实全蓝色时采摘,果实横径低于18mm并采用"蓝丰"品种。