低强度He-Ne激光对红细胞胞浆内游离钙离子浓度的影响

低强度He-Ne激光对红细胞变形性的影响已得到广泛的认可和应用,但其具体调节机制尚不明确,通过研究低强度He-Ne激光对红细胞胞浆内钙离子浓度的影响,探讨其对红细胞变形性影响的机制。采用A23187处理过的红细胞,分别用5 mW和9 mW激光照射后,观察红细胞胞浆内钙离子浓度变化。结果显示:低强度He-Ne激光照射后的红细胞与无照射组的红细胞相比,红细胞胞浆内钙离子浓度显著降低,但在本实验中钙离子浓度的降低与激光照射剂量无显著相关。由此得出结论:降低红细胞胞浆内钙离子浓度可能是低强度He-Ne激光调节红细胞变形性的重要机制。     

濒危植物长柄双花木开花物候与生殖特性

研究了长柄双花木开花过程中花部表型的变化。连续4a对其野生种群、1a对人工种群的开花物候进行了观察,并运用相对开花强度和同步性等开花物候指数分析了开花物候对其生殖的影响。结果如下：长柄双花木开花时间为9月上、中旬至11月中、下旬;单花花期一般为6～7d,单花依其形态和散粉特征可以分为4个时期：散粉前期、散粉初期、散粉盛期和凋谢期。个体开花持续时间49～55d,种群花期历时63～71d。种群内不同年度间开花物候指数没有显著差异,而种群间则存在显著差异,野生种群开花进程为渐进式单峰曲线。人工种群则为“钟”形曲线,二者均属于“集中开花模式”。长柄双花木具有2个相对开花强度的分异趋势,这种分异趋势具有进化意义。开花物候指数与生殖间的相关分析表明,始花时间与开花数量、座果率及花期长度之间均具显著负相关关系,而开花数量与花期长度之间则呈显著正相关,但均为线性相关。长柄双花木开花物候在种群间的差异和种群内年度间的相似性说明,其开花时间可能是由与其相关的复杂的微生境特征和(或)由其遗传因子决定的,同时也反映了种群间的遗传分异和种群内个体间的遗传一致性。作为一种濒危物种,长柄双花木在这种环境的选择压力之下,形成了“大量、集中开放的花”的开花模式,吸引到更多的传粉者的访问,从而达到生殖成功。     

The use of multi-parameter flow cytometry to study the impact of limiting substrate, agitation intensity, and dilution rate on cell aggregation during Bacillus licheniformis CCMI 1034 aerobic continuous culture fermentations

The main objective of this work was to establish those factors either physical (power input) or chemical (limiting substrate or dilution rate) that enhance cell aggregation (biofilm or floc formation) and cell physiological state during aerobic continuous cultures of Bacillus licheniformis. Glucose-limited steady-state continuous cultures growing at a dilution rate between 0.64 and 0.87/h and 1,000 rpm (mean specific energy dissipation rate (epsilonT) = 6.5 W/kg), led to the formation of a thin biofilm on the vessel wall characterized by the presence of a high proportion of healthy cells in the broth (after aggregate disruption by sonication) defined as having intact polarized cytoplasmic membranes. An increased epsilonT (from 6.5 W/kg to 38 W/kg) was found to hinder cell aggregation under carbon limitation. The carbon recovery calculated from glucose indicated that additional extracellular polymer was being produced at dilution rates >0.87/h. B. licheniformis growth under nitrogen limitation led to floc formation which increased in size with dilution rate. Counter-intuitively the flocs became more substantial with an increase in epsilonT from 6.5 W/kg to 38 W/kg under nitrogen limitation. Indeed the best culture conditions for enhanced metabolically active cell aggregate formation was under nitrogen limitation at epsilonT = 6.5 W/kg (leading to floc formation), and under carbon limitation at a dilution rate of between 0.64 and 0.87/h, at epsilonT = 6.5 W/kg (leading to vessel wall biofilm formation). This information could be used to optimize culture conditions for improved cell aggregation and hence biomass separation, during thermophilic aerobic bioremediation processes.     

氮和水分添加对内蒙古荒漠草原放牧生态系统土壤呼吸的影响

土壤呼吸是生态系统碳循环的重要组成部分, 同时也是评价生态系统健康状况的重要指标, 对于评估退化草地恢复过程中生态系统功能具有重要意义。该研究在内蒙古四子王旗短花针茅(Stipa breviflora)荒漠草原长期放牧实验平台上进行, 该平台设置对照(CK)、轻度(LG)、中度(MG)和重度(HG) 4个放牧强度。通过在4个放牧处理区设置氮、水添加实验处理, 探讨不同放牧强度背景下, 氮、水补充对荒漠草原土壤呼吸过程的影响。结果表明: (1)历史放牧强度除2015年对土壤呼吸无显著影响, 2016和2017年都有显著影响, 放牧区3年平均土壤呼吸速率基本都高于对照区。此外, 氮和水分添加显著增加了MG区土壤呼吸速率, HG区氮、水同时添加对土壤呼吸速率有显著增加作用; (2)无论是历史放牧强度, 还是氮、水添加处理, 都没有改变荒漠草原生长季土壤呼吸速率的季节动态变化趋势, 土壤呼吸速率基本表现为单峰曲线模式, 峰值出现在水热同期的7月份; (3)不同年份生长季土壤呼吸速率对氮、水处理的响应并不相同, 氮添加至第3年产生显著影响。水分添加在平水年份(2015和2017年)对土壤呼吸产生显著影响, 但在丰水年份(2016年)无显著影响。氮、水共同添加分别在CK、LG和HG区3年平均土壤呼吸速率显著高于单独加水处理, 说明氮添加的有效性依赖于水分条件, 两者表现为协同作用; (4)不同处理下荒漠草原土壤呼吸的温度敏感性(Q₁₀)值介于1.13-2.41之间, 平均值为1.71。在无氮、水添加时, 放牧区的Q₁₀值都小于CK区, 总体表现为CK 大于 MG 大于 LG 大于 HG; 加水和氮水共同添加处理后, Q₁₀值都有明显增加, 其中NW处理下Q₁₀值都增加到2.0以上。上述结果说明在过去受不同放牧强度影响的荒漠草原在停止放牧后的恢复过程中, 土壤水分仍是影响土壤呼吸的主导环境因子, 外源氮添加只有在满足一定水分供给的基础上才起作用, 尤其是过去的重度放牧区土壤呼吸速率对氮、水补充的响应最为强烈。该研究结果可以为评估荒漠草原恢复过程中土壤呼吸速率受养分和水分影响提供基础资料和依据。     

Use of Two Industrial Wastes as Soil Amendments: Effect on Dissolved Reactive Phosphorus in Runoff

To control the dissolved reactive phosphorus (DRP) concentration in a soil solution, a number of soil amendments were tested. In the current study, Blast Furnace Slag (BFS) and Water Treatment Residues (WTR) were tested on bare soil under two rainfall intensities and two soil roughness levels. The soil was fertilized with P (KH₂PO₄) at a rate of 400 kg ha^?1 while BFS and WTR were applied at a rate of 5 g per 100 g of soil. Two soil roughness levels were exposed to artificial rainfall intensities of 30 and 65 mm h^?1. Three rainfall events were performed on each treatment. The runoff water generated over an area of 0.5 m² with a slope of 8% was collected at different time intervals and analyzed for DRP, Al, Fe, and K concentrations. The results showed that, regardless of rainfall intensity and soil roughness, the concentration of DRP in the runoff water increased with increasing runoff time from the unamended plots. However, in the BFS- and WTR-amended soils, the DRP concentration decreased with runoff time. Dissolved reactive P and DRP loads were the lowest from the WTR-amended plots, followed by the control and the BFS treatment plots. Water treatment residues reduced the mean DRP concentration by 27.3% and the DRP load by 32% compared to unamended plots. The two rainfall intensities significantly affected the DRP concentration and load. Under the low rainfall intensity, the DRP concentration and load were higher compared to the high rainfall intensity. The overall DRP concentration was not affected by changes in soil roughness. However, the DRP loads were higher from the plots with low soil roughness levels, especially during the first and second runs. Both the BFS and WTR were also effective in reducing the DRP concentrations in the drain water collected during the runoff events. The concentrations of Al, Fe, and K in the runoff water were not affected by the soil amendments. However, the electrical conductivity and pH readings were higher from the BFS-amended plots.     

The effect of the osmotic potential and specific ion concentration of the nutrient solution on the uptake and reduction of nitrate by barley seedlings

Summary Short-term absorption experiments were conducted with intact barley (Hordeum vulgare L.) seedlings to observe the effects of the osmotic potential (Ψ^π) and salt species on nitrate uptake andin vivo nitrate reduction. The experiments consisted of growing barley seedlings for 5 days in complete nutrient solutions salinized to (Ψ^π) levels of −0.6, −1.8, −3.0, −4.2, and −5.4 bars with NaCl, CaCl₂ or Na₂SO₄. After the absorption period, the seedlings were separated into shoots and roots, weighed, then analyzed for NO₃. The nutrient solutions were sampled for NO₃ analysis each day immediately before renewing the solutions. The accumulative loss of NO₃ from the solutions was considered to be uptake whereas NO₃ reduction was the difference between uptake and seedling content. Lowering the (Ψ^π) of the nutrient solutions resulted in decreased concentrations of NO₃ in the plant, little or no effect (except at the lowest (Ψ^π) level) on uptake, and increased nitrate reductase activity. Increased rates of NO₃ reduction were in particular associated with the Cl concentration of the nutrient solution.     

Demonstration of the root surface electrogenic ion pump activity revealed from the seasonal inversion in the phase relation between electro-radicogram and the diurnal oscillation of air temperature in a field tree (Diospyros kaki)

Re-examination of the electro-radicogram (ERG) obtained during past 10 years research (Masaki and Okamoto in Trees (Berl) 21:433–442, 2007) enabled us to discriminate the excess activity of the electrogenic ion pump in the root surface cell membrane over that of the xylem pump during most of the foliate phase. The trans-root electric potential (TRP) is defined as the difference between V _ps (electric potential difference between symplast and bulk water phase surrounding the root) and V _px (electric potential difference between symplast and xylem apoplast). The diurnal oscillation of TRP followed that of the air temperature and/or light intensity with a delay of several hours during defoliate phase. This means the superiority of the electrogenic activity of the xylem pump over that of the root surface pump. However, after leaf expansion, TRP began to oscillate inversely with the temperature change with a short delay, indicating the superiority of the electrogenic activity of the surface ion pump over that of the xylem pump. An experimental lumbering of the surroundings of the kaki tree in foliate phase prominently increased the ERG amplitude, keeping the inverted phase relation, with the increase in transpiration caused by the increased illumination. An incidental sudden fall of the temperature and illumination caused an inverse reaction.     

Pastoralist Responses to Floodplain Rehabilitation in North Cameroon

This paper examines the responses of mobile pastoralists to a floodplain rehabilitation program in north Cameroon. From 1993 to 1999, we measured changes in number of camps and herds, and the time they spent in the 600 km² of the Logone floodplain that was reflooded in 1994. The first year, few pastoralists anticipated the reflooding or its impact, and the increase in grazing intensity was caused by a prolonged stay of pastoralists who already used the area for transit. The following three years showed a sharp increase in the number of camps and herds, which stabilized from 1997 onwards. Overall, grazing intensity increased threefold, following the gradually recovering perennial grasslands, with no signs of overexploitation of the area. These developments closely match the ideal preemptive distribution model. We also examined how reflooding affected pastoral incursions in the Waza National Park located in the floodplain.

Formation of toxic fibrils of Alzheimer's amyloid beta-protein-(1-40) by monosialoganglioside GM1, a neuronal membrane component

A pathological hallmark of Alzheimer's disease (AD) is the deposition of amyloid beta-protein (Abeta) in fibrillar form on neuronal cells. However, the role of Abeta fibrils in neuronal dysfunction is highly controversial. This study demonstrates that monosialoganglioside GM1 (GM1) released from damaged neurons catalyzes the formation of Abeta fibrils, the toxicity and the cell affinity of which are much stronger than those of Abeta fibrils formed in phosphate-buffered saline. Abeta-(1-40) was incubated with equimolar GM1 at 37 degrees C. After a lag period of 6-12 h, amyloid fibrils were formed, as confirmed by circular dichroism, thioflavin-T fluorescence, size-exclusion chromatography, and transmission electron microscopy. The fibrils showed significant cytotoxicity against PC12 cells differentiated with nerve growth factor. Trisialoganglioside GT1b also facilitated the fibrillization, although the effect was weaker than that of GM1. Our study suggests an exacerbation mechanism of AD and an importance of polymorphisms in Abeta fibrils during the pathogenesis of the disease.     

金矮生苹果叶片气体交换参数对土壤水分的响应

 在黄土高原半干旱地区,通过测定10年生金矮生苹果（Malus pumila cv. Goldspur）叶片气体交换参数与土壤水分的定量关系,探讨了土壤水分胁迫对光合作用的影响规律,以确定苹果园节水灌溉适宜的土壤水分调控标准。结果表明：叶片的净光合速率（Pn）、蒸腾速率（Tr）、水分利用效率（WUE）、气孔导度（Gs）、细胞间隙CO2浓度（Ci）和气孔限制值（Ls）对土壤水分的变化具有明显不同的阈值反应。土壤含水量（SWC）大约在田间持水量的60%～86%范围内,Pn和Tr均保持较高的水平,小于田间持水量的60%～86%后,两者均随土壤湿度的减少而明显下降。维持较高叶片水分利用效率（WUE）的SWC约在田间持水量的50%～71%左右。当SWC小于田间持水量的48%以后,Gs和Ls明显降低,而Ci急剧增加,水分胁迫条件开始直接作用于叶肉细胞,导致光合速率下降,由气孔限制因素转变为非气孔因素。据此我们认为：在半干旱黄土高原地区,金矮生苹果园节水灌溉适宜的SWC范围大约在田间持水量的50%～71%左右,所允许的土壤水分亏缺程度为田间持水量的48%左右。