陇东黄土高原若干轮作技术方案水保效能评价分析

陇东黄土高原若干轮作技术方案水保效能评价分析李锋瑞,高崇岳（兰州大学生物系７３００００）（甘肃草原生态研究所兰州７３００２０）ＳｏｉｌａｎｄＷａｔｅｒＣｏｎｓｅｒｖａｔｉｏｎＥｆｆｉｃｉｅｎｃｉｅｓｏｆｓｅｖｅｒａｌＲｏｔａｔｉｏｎＰａｔｔｅｒｎｓｏ...     

Comparisons of biomass,water use efficiency and water use strategies across five genomic groups of Populus and its hybrids

Genetic improvement and hybridization in the Populus genus have led to the development of genotypes exhibiting fast growth, high rooting ability and disease resistance. However, while large biomass production is important for bioenergy crops, efficient use of resources including water is also important in sites lacking irrigation and for maintaining ecosystem water availability. In addition, comparison of water use strategies across a range of growth rates and genetic variability can elucidate whether certain strategies are shared among the fastest growing and/or most water use efficient genotypes. We estimated tree water use throughout the second growing season via sapflow sensors of 48 genotypes from five Populus taxa; P. deltoides W. Bartram ex Marshall × P. deltoides (D × D), P. deltoides × P. maximowiczii A. Henry (D × M), P. deltoides × P. nigra L. (D × N), P. deltoides × P. trichocarpa Torr. & Gray (D × T) and P. trichocarpa × P. deltoides (T × D) and calculated average canopy stomatal conductance (G_S). We regressed G_S and atmospheric vapor pressure deficit (VPD) wherein the slope of the relationship represents stomatal sensitivity to VPD. At the end of the second growing season, trees were harvested, and their dry woody biomass was used to calculate whole tree water use efficiency (WUE_T). We found that D × D and D × M genotypes exhibited differing water use strategies with D × D genotypes exhibiting high stomatal sensitivity while retaining leaves while D × M genotypes lost leaf area throughout the growing season but exhibited low stomatal sensitivity. Across measured taxa, biomass growth was positively correlated with WUE_T, and genotypes representing each measured taxa except D × N and T × D had high 2-year dry biomass of above 6 kg/tree. Overall, these data can be used to select Populus genotypes that combine high biomass growth with stomatal sensitivity and WUE_T to limit the negative impacts of bioenergy plantations on ecosystem water resources.     

适用于获取最优化配方的一种算法

本文应用印楝种仁提取物（F3）与敌敌畏混配为例,以斜纹夜蛾（Spodopteralitura）为目标害虫,介绍一种适用于获取最优化配方的算法,在二次通用回归旋转组合设计的基础上,经参数辨识,获取二次回归方程,经失拟性、回归显著性检验,本方程基本能够反映杀虫剂用量与斜纹夜蛾幼虫死亡机率值之间的关系．在害虫防治实践中,要求在防治费用最小的基础上,目标害虫有最大的死亡率.因此,以防治目标害虫的费用作为优化算法的目标函数,以害虫死亡机率值最大作为约束条件,有如下的一组优化算式为目标函数约束条件式中a1,a2分别为参试杀虫剂1,2最低用量,b1,b2则为相应的最高用量．C1,C2分别为杀虫剂1,2的单价,N1,N2为杀虫剂l,2的用量．Y为目标害虫死亡机率值回归方程．本文所依据的试验设计中,以对数函数关系变换编码值与使用浓度之间的关系,所以应用拉格朗日求极值原理求取最优化配方．由计算所得的混配比例与其他方法所获结果一致．     

Tritium NMR studies of the human carbonic anhydrase I–benzenesulfonamide complex

Tritium NMR spectroscopy has been used to examine the complexformed by [4-³H]benzenesulfon-amide and human carbonicanhydrase I. The results show that in solution the inhibitor forms a 1:1complex with the enzyme. A 100-spin computational model of the system,constructed with reference to crystallographic results, was used tointerpret tritium relaxation behavior and ³H{¹H}NOEs. The analysis shows that the rate of dissociation of theenzyme–sulfonamide complex is 0.35 s^–1 and thatthe aromatic ring of the inhibitor undergoes rapid rotation while complexed.     

Differential effects of sodium ions on motility in the homoacetogenic bacteriaAcetobacterium woodii andSporomusa sphaeroides

The strictly anaerobic homoacetogenic bacteria Acetobacterium woodii and Sporomusa sphaeroides differ with respect to their energy metabolism. Since growth as well as acetate and ATP formation of A. woodii is strictly dependent on Na⁺, but that of S. sphaeroides is not, the question arose whether these organisms also use different coupling ions for mechanical work, i.e. flagellar rotation. During growth on fructose in the presence of Na⁺ (50 mM), cells of A. woodii were vigorously motile, as judged by light microscopy. At low Na⁺ concentrations (0.3 mM), the growth rate decreased by only 15%, but the cells were completely non-motile. Addition of Na⁺ to such cultures restored motility instantaneously. Motility, as determined in swarm agar tubes, was strictly dependent on Na⁺; Li⁺, but not K⁺ partly substituted for Na⁺. Of the amilorides tested, phenamil proved to be a specific inhibitor of the flagellar motor of A. woodii. Growth and motility of S. sphaeroides was neither dependent on Na⁺ nor inhibited by amiloride derivatives. These results indicate that flagellar rotation is driven by Δμ_Na ⁺ in A. woodii, but by Δμ_H ⁺ in S. sphaeroides. Received: 30 May 1995 / Accepted: 31 August 1995     

Plant diversity in late medieval cornfields of northern Switzerland

Weed assemblages from late medieval cornfields have been studied for the first time in northern Switzerland. Eleven samples from at least two different grain stores were investigated. The samples were collected from the carbonised remains of six wooden houses built in the late 13th century A.D. and which burnt down in the middle of the 15th century. The weed floras found in the spelt (Triticum spelta) and oats (Avena sativa) indicate a high botanical diversity in the cornfields at harvest time. Although oats are normally a summer crop and spelt a winter crop, both summer and winter crop weeds (as well as many different present-day grassland taxa) were found in each type of grain. Most of the weeds found were perennial plants, which was interpreted as an indication of both extensive tillage of the arable land and application of the three-field rotation system (Dreifelderwirtschaft). The spectra of the two palaeophytocoenoses (assemblages of ancient plant remains) studied suggest that the phytosociological method may not be reliable for classification of the late medieval remains into summer and winter crop weed communities. These findings should provide a better understanding of the development of anthropogenic plant communities, and in particular, the development of crop weed communities.     

Management of Heterodera glycines by Cropping and Cultural Practices

Heterodera glycines was identified in North Carolina in 1954, although symptoms of the disease were noted in the state at least 8 years earlier. Crop rotation experiments designed to develop management systems were initiated in 1956. Two or more years in production of a nonhost crop resulted in decreases of the nematode to low or undetectable levels with acceptable subsequent yields of soybean (Glycine max). Because of almost complete dependence on resistant cultivars and (or) nematicides for nematode control, crop rotation experiments were not conducted from 1962 to 1980. Research on control of H. glycines, beginning in 1981, emphasized biological and ecological aspects of the nematode in order to determine cropping systems that restrict the nematode to nondamaging levels. Mortality during embryogenesis was high at temperatures above 30 C. Hatching of eggs occurs readily in May and June. Postinfection development takes 2-3 weeks at weekly mean temperatures of 22-29 C and is slow above and below those temperatures. Egg production is high during the late growing season. Some cultural practices such as planting early maturing cultivars in mid-to-late June and rotation with a nonhost effectively keeps populations at low levels.     

ULTRASTRUCTURE,DEVELOPMENT AND CYTOPLASMIC ROTATION OF SETA-BEARING CELLS OF COLEOCHAETE SCUTATA (CHLOROPHYCEAE)1

Part of the cytoplasm, which always contains the plastid, of seta-bearing cells of Coleochaete scutata Bréb. rotates clockwise about the base of the seta. Many golgi bodies, vesicles and much endoplasmic reticulum occupy the bridges between the rotating central core of cytoplasm and the stationary peripheral layer of these cells. The setae, which grow from their base, are devoid of organelles other than vesicles and elongate mitochondria. At irregular intervals along the thin seta wall are annular thickenings containing callose. Microtubules which encircle the base of the seta disappear on treatment with colchicine. This drug had no effect on the speed of rotational streaming or the growth rate of existing hairs but did inhibit the development of new setae. Cytochalasin B slowed, but did not stop, streaming after 3 h exposure. However caffeine, but not EDTA, EGTA or the Ca ionophore A23187, reversibly inhibited cyclosis. The mechanism of cytoplasmic rotation is discussed in the light of these drug treatments and the presence of actin in the alga.     

How much heat can we grow in our cities? Modelling UK urban biofuel production potential

Biofuel provides a globally significant opportunity to reduce fossil fuel dependence; however, its sustainability can only be meaningfully explored for individual cases. It depends on multiple considerations including: life cycle greenhouse gas emissions, air quality impacts, food versus fuel trade‐offs, biodiversity impacts of land use change and socio‐economic impacts of energy transitions. One solution that may address many of these issues is local production of biofuel on non‐agricultural land. Urban areas drive global change, for example, they are responsible for 70% of global energy use, but are largely ignored in their resource production potential; however, underused urban greenspaces could be utilized for biofuel production near the point of consumption. This could avoid food versus fuel land conflicts in agricultural land and long‐distance transport costs, provide ecosystem service benefits to urban dwellers and increase the sustainability and resilience of cities and towns. Here, we use a Geographic Information System to identify urban greenspaces suitable for biofuel production, using exclusion criteria, in 10 UK cities. We then model production potential of three different biofuels: Miscanthus grass, short rotation coppice (SRC) willow and SRC poplar, within the greenspaces identified and extrapolate up to a UK‐scale. We demonstrate that approximately 10% of urban greenspace (3% of built‐up land) is potentially suitable for biofuel production. We estimate the potential of this to meet energy demand through heat generation, electricity and combined heat and power (CHP) operations. Our findings show that, if fully utilized, urban biofuel production could meet nearly a fifth of demand for biomass in CHP systems in the United Kingdom's climate compatible energy scenarios by 2030, with potentially similar implications for other comparable countries and regions.     

Superimposing hip extension on knee flexion evokes higher activation in biceps femoris than knee flexion alone

Hamstring muscle function during knee flexion has been linked to hamstring injury and performance. However, it is unclear whether knee flexion alone (KF) requires similar hamstring electromyography (EMG) activity pattern to simultaneous hip extension and knee flexion (HE-KF), a combination that occurs in the late swing phase of sprinting. This study examined whether HE-KF maximal voluntary isometric contraction (MVIC) evokes higher (EMG) activity in biceps femoris long head (BFlh) and semitendinosus (ST) than KF alone. Effects of shank rotation angles were also tested. Twenty-one males performed the above-mentioned MVICs while EMG activity was measured along ST and BFlh. Conditions were compared using a one-way mixed functional ANOVA model under a fully Bayesian framework. Higher EMG activity was found in HE-KF in all shank rotation positions than in KF in the middle region of BFlh (highest in the 9th channel, by 0.022 mV [95%CrI 0.014 to 0.030] in neutral shank position). For ST, this was only observed in the neutral shank position and in the most proximal channel (by 0.013 mV [95%CrI 0.001 to 0.025]). We observed muscle- and region-specific responses to HE-KF. Future studies should examine whether hamstring activation in this task is related to injury risk and sprint performance.