Phospholipid fatty acid composition of microbiota in the percolating water from a rice paddy microcosm

The microbiota in the percolating water from the plow layer soil in paddy fields was studied based on the composition of phospholipid fatty acids (PLFAs) in a pot experiment. The mean concentrations of PLFAs in the percolating water were 17±5 and 11±4 µg L^-1 in the planted and non-planted pots, respectively. The dominant PLFAs in the percolating water were 16: 0, 16: 1ω7c, 18: 1ω7, 18: 1ω9, il5: 0, and ail5: 0 PLFAs in both the planted and non-planted pots. The dominance percentage of 18: 3ω6c and 17: 1ω8 PLFAs increased at the late stage of rice growth in the planted pots. The percolating water from the planted pots contained in a higher percentage of straight mono-unsaturated PLFAs and a lower percentage of branched-chain PLFAs than that from the non-planted pots. Considerable differences in the PLFA composition in the percolating water were observed between the planted and non-planted treatments and with the duration of the growth period. Principal component analysis indicated that the microbiota in the percolating water was derived from the microbiota in the floodwater and in the plow layer soil. Cluster analysis showed that the similarity of the PLFA composition in the percolating water to the PLFA composition in the plow layer soil was higher than that in the floodwater. The stress factor that was estimated from the trans/cis ratio of 16: 1ω7 PLFA was 0.08±0.04 and 0.14±0.05 in the percolating water from the planted and non-planted pots, respectively, which indicated that the degree of stress on the microbiota in the percolating water from the planted pots was low in a similar way to the degree of stress on the microbiota in the floodwater, while the degree in the percolating water from the non-planted pots was similar to that in the plow layer soil, respectively.     

膜下滴灌条件下膜间不同处理对土壤水盐运移的影响

[目的]寻求合理的膜间土壤盐分累积控制方法,为指导盐碱地田间调控提供科学依据。[方法]采用覆秸秆,铺砂,喷施高分子化合物PAM,压实等方式对膜间裸地进行处理,对比分析各种处理措施的功效。[结果](1)各处理都能不同程度的减小膜间的水分蒸发量,起到保水作用。其中,在试验期间,覆秸秆的蒸发量为0.11cm,铺砂子蒸发量为0.34cm,喷施PAM为0.59cm,压实为1.55cm,而对照为2.32cm。(2)各处理都能提高膜间和覆膜窄行的土壤含水量。在覆膜窄行深度为10cm处,覆秸秆的土壤含水量相对降低率为47%,铺砂土的壤含水量为45%,施PAM的土壤含水量为56%,压实的土壤含水量为64%,对照为土壤含水量77%。(3)减小盐分在作物根层的积累。在覆膜窄行深度为10cm处,覆秸秆的相对脱盐率为3%,铺砂的相对脱盐率为2%,施用PAM的相对脱盐率为0%,压实的相对脱盐率为-16%,而对照的相对脱盐率为-28%。[结论]采用膜间处理能够减小水分散失和盐分在根层的积累,其中覆秸秆的功效最好。     

基于蛋白质反式剪接在大肠杆菌中表达鲎C因子CES多肽

鲎C因子是鲎血细胞中一种对内毒素具有高亲和力的丝氨酸蛋白酶原,可替代鲎试剂用于内毒素检测。鲎C因子N端Cys—EGF．sushil—sushi2（CES）片段中的sushil区域是与内毒素结合的关键部位。本研究在sushil结构域中的特定位点断开CES与内毒素结合的功能片段,然后分别和蛋白质内含肽SspDnaX的N端片段（IN）和C端片段0C）连接,并在大肠杆菌中表达,表达产物经亲和层析纯化、复性以及内毒素去除后,利用蛋白质反式剪接系统,在体外诱导该蛋白质内含肽发生剪接,重新得到C因子的CES蛋白,并检测其活性。实验结果表明此重组CES蛋白具有结合内毒素活性,提示在大肠杆菌系统中开发低成本内毒素检测试剂的可行性。     

南阳烤烟矿质元素及化学成分次适宜因子与土壤生态因子的典型相关分析

为了解南阳烤烟矿质元素及主要化学成分次适宜因子及其与土壤生态因子的关系,选取代表南阳不同生态类型的13个样点的土壤样品和烟叶样品,以及2个津巴布韦、14个巴西的优质烟样,测定烟样矿质元素及化学成分与土壤生态因子.对优质烟与南阳烤烟间矿质元素及主要化学成分指标的比较表明,南阳烤烟矿质元素及主要化学成分次适宜因子为磷、钾、钙、钠、烟碱、总糖、还原糖、淀粉.对次适宜因子与土壤生态因子进行典型相关分析的结果表明,在一定范围内,随着土壤锌含量提高,烟叶还原糖呈显著增加趋势而烟碱呈显著减少趋势:土壤氨化菌数减少、硝化菌数增加,烟叶烟碱显著增加而总糖、淀粉、磷含量显著减少;随土壤放线菌数减少、解钾菌数增加,烟叶还原糖含量增加;随土壤铜含量提高,烟叶钙、钠含量减少;随土壤硝化菌数减少、真菌数增加,烟叶钙含量呈增加趋势而钠含量呈减少趋势.改良土壤特别是改良土壤微生物性状可望改善烟叶质量.     

澜沧江中下游流域土壤侵蚀时空演变特征

为了探究土壤侵蚀演变机制,以澜沧江中下游流域为研究区域,利用改进的土壤流失方程(RUSLE)模型,开展流域内土壤侵蚀时空演变特征研究,引入随机森林算法探讨了流域内土壤侵蚀因子的相对重要程度。结果表明:澜沧江中下游流域2005—2015年土壤侵蚀量为0～1.89万t/(km²·a),平均土壤侵蚀模数为0.252万t/(km²·a),中下游子流域平均土壤侵蚀模数处于较低风险以上和中风险侵蚀以下级别。自2005年以后,澜沧江中下游流域土壤侵蚀空间分布特征呈现中度侵蚀风险区域扩张,高度和低度侵蚀风险收缩的趋势。随机森林算法结果发现植被覆盖管理因子和地形因子是影响澜沧江中下游流域土壤侵蚀的主要因素,土壤可蚀性因子、降雨侵蚀因子和水土保持措施因子的相对重要程度偏低,均未超过20%。可见,土壤侵蚀的时空异质性主要是由于植被覆盖和地形影响改变了局部气候而导致的。     

苦荞芽期黄酮合成关键酶和MYB转录因子基因的表达分析

苦荞(Fagopyrum tataricum)作为一种药食两用植物,富含以芦丁为主的黄酮类化合物.苦荞芽期芦丁含量较高,其分子机制尚不清楚.本研究选用西荞2号,采用AlCl3法测定了苦荞芽期6～10 d胚轴和子叶中的总黄酮,采用半定量RT-PCR分析其黄酮合成途径中主要关键酶基因苯丙氨酸氨裂解酶基因(Pal)、查尔酮异构酶基因(Chi)和黄酮醇合酶基因(Fls),以及MYB转录因子基因FtMyb1、FtMyb2和FtMyb3的相对表达水平,并对三者之间的相关性进行了统计学分析.结果表明,以相关系数绝对值大于0.75为阈值,子叶中,总黄酮的积累与FtMyb3表达显著正相关(0.9625),与FtMyb2表达显著负相关(-0.8572); Chi与FtMyb2表达显著正相关(0.8468),与FtMyb3表达显著负相关(-0.8010):Pal、Chi和Fls表达彼此显著正相关,相关系数分别为0.9119、0.8920和0.7584.子叶中总黄酮含量在4.58％～5.54％之间,且随芽期递增.Pal、Chi和Fls整体表达趋势相似,均呈现先升高后降低的趋势,且Fls的表达水平明显高于前二者.FtMyb2和FtMyb3整体表达趋势相反,FtMyb2呈下降趋势,FtMyb3呈上升趋势.胚轴中,总黄酮含量与Chi显著负相关(-0.8989); Fls与Chi显著负相关(-0.7498).结果提示,苦荞芽期黄酮合成的分子机制较为复杂,但部分基因表达仍存在显著相关性联系,为进一步选择苦荞分子操作靶位点提供参考.     

太阳能加热的地上式户用沼气生产系统热性能分析

为对太阳能加热的地上式户用沼气生产系统的推广应用和优化设计提供指导,试验研究了该型系统的热性能,对系统中真空管太阳能热水器日平均集热效率、沼气池散热量和热水-料液传热系数与相关因素的关系进行了分析。试验表明,当日平均环境温度在-2.1~-8.6℃变化时,沼气池内料液温度可维持在(27±2)℃的范围内。得到了太阳能热水器日平均集热效率、沼气池散热量和热水-料液传热系数的计算公式;研究发现沼气池内料液温度对热水-料液传热系数的影响很大,随着料液温度的提高,传热系数显著增加。     

循环经济作用机理探讨

从循环经济的内在本质、经济本质及其社会特征、核心作用和关键环节等角度,初步探讨了循环经济的作用机理。     

Prediction of hydraulic conductivity and sorptivity in soils at steady-state infiltration

The purpose of this study was (1) to find a matching factor (u) between infiltration rate and hydraulic conductivity during steady-state infiltration, and (2) to propose equations based on infiltration and soil moisture-retention functions for prediction of the hydraulic conductivity K(θ) within the rapidly (non-capillary) drainable pores (RDP) and capillary-matrix pores of soils. The K(θ) of capillary pores was divided into K(θ)_SDP, K(θ)_WHP and K(θ)_FCP within slowly drainable pores (SDP), water-holding pores (WHP) and fine capillary pores (FCP), respectively. Five soil profiles of calcareous sandy loam, alluvial saline and non-saline clay, located at the Nile Delta, were used to apply the proposed equations. The highest and the lowest values of K(θ)_RDP were observed in calcareous and saline clay soil profiles, respectively. Values of K(θ)_RDP remained higher than those for capillary pores in the studied soils. The predicted values of K(θ) in capillary and non-capillary pores classes were in the expected range for unsaturated hydraulic conductivity. Water sorptivity (S) was determined at initial unsaturated soil water conditions and calculated at steady-state infiltration (S _w) using a derived equation. There was a decrease in S with an increase in soil water content; i.e. at steady-state infiltration, S decreased by 35–40% in calcareous soils and by 45–60% in alluvial clay soils. The parameter values of u and S _w tended to be uniform in calcareous soils, but nonuniform in saline and non-saline clay soils.     

Energy balance and partition in Inner Mongolia steppe ecosystems with different land use types

Land use change and grassland degradation are two of the most critical problems ubiquitously found in arid and semi-arid areas in Northern China. Energy fluxes, including net radiation (R_n), latent heat flux (LE), sensible heat flux (H) and soil heat flux (G), were examined over an entire year (December 2005 to November 2006) in different steppe ecosystems – the steppe and cropland in Duolun and the fenced and grazed steppe in Xilinhot – in Inner Mongolia based on direct measurements from four eddy-covariance flux towers. The seasonal changes in R_n, LE, H and G of the four sites were similar, with very low values during the period of snow cover from December to February, followed by a gradual increase in the growing season. The opposite seasonal patterns of the LE and H fraction resulted in significant seasonal changes in Bowen ratio (β). Human activity in cropland ecosystems not only resulted in a rapidly shift between LE and H, but also triggered a decrease in latent heat fraction because of a shortened growing season of crop plants. The significantly positive relationships between canopy surface conductance (g_c) and LE/LE_eq of all of the study sites suggested that a lack of precipitation coupled with high VPD conduced remarkable decreases of stomatal conductance. This could impede the latent heat partitioning of available energy (R_n − G) in semi-arid ecosystems, Inner Mongolia. The obvious decrease in the values of g_c and the decoupling factor (Ω) in both the cropland and the degraded steppe suggested that land use change could depress latent flux fraction and increase its sensitivity to air and soil drought.