The effect of the propagation coefficient on size distribution in micellar systems

In this study the effect of the propagation coefficient on the molar distribution function in a modified shell model for micellar systems was examined. The sharpness of the micelle size distribution boundary was found to depend less on the degree of polymerization, n, than on the propagation coefficient, P. Although Kegeles (J. Phys. Chem. 83 (1979) 1728) has reported a marked sharpening of the distribution boundary when P = 2.0. we found the boundary to be fairly broad at this point. However, as values of the propagation coefficient were increased from 3 to 10, the micelle distribution boundary became increasingly sharp. The possibility of such a change in the reaction boundary arising from a structural transition, accompanied by a change in the rate of dissociation of monomer from the shell, is also discussed.     

Acclimation to temperature and temperature sensitivity of metabolism by ectomycorrhizal fungi

Ectomycorrhizal (ECM) fungi contribute significantly to ecosystem respiration, but little research has addressed the effect of temperature on ECM fungal respiration. Some plants have the ability to acclimate to temperature such that long‐term exposure to warmer conditions slows respiration at a given measurement temperature and long‐term exposure to cooler conditions increases respiration at a given measurement temperature. We examined acclimation to temperature and temperature sensitivity (Q₁₀) of respiration by ECM fungi by incubating them for a week at one of three temperatures and measuring respiration over a range of temperatures. Among the 12 ECM fungal isolates that were tested, Suillus intermedius, Cenococcum geophilum, and Lactarius cf. pubescens exhibited significant acclimation to temperature, exhibiting an average reduction in respiration of 20–45% when incubated at 23 °C compared with when incubated at 11 or 17 °C. The isolates differed significantly in their Q₁₀ values, which ranged from 1.67 to 2.56. We also found that half of the isolates significantly increased Q₁₀ with an increase in incubator temperature by an average of 15%. We conclude that substantial variation exists among ECM fungal isolates in their ability to acclimate to temperature and in their sensitivity to temperature. As soil temperatures increase, ECM fungi that acclimate may require less carbon from their host plants than fungi that do not acclimate. The ability of some ECM fungi to acclimate may partially ameliorate the anticipated positive feedback between soil respiration and temperature.     

中国黑戈壁植物多样性分布格局及其影响因素

我国西北地区内陆分布着近20万km~2的黑戈壁,由于其环境的特殊性,使其具有独特的生态系统,境内分布着多样的植被,蕴藏着大量特有的自然资源。但由于自然环境苛刻与交通条件不便,目前我国关于黑戈壁区系统的植被与物种多样性的研究还很缺乏。针对黑戈壁区植物多样性组成与分布特点,基于遥感及实地调查,采用DCCA排序和半变异函数模型等分析方法,对黑戈壁区植物群落组成,植物多样性特点及影响因素进行分析。研究结果表明:研究区植物以藜科和蒺藜科灌木或半灌木为主,群落物种生活型具有逐渐趋于简单甚至单一的特性,重要值0.1的植物主要有梭梭、红砂、白刺等13种;群落物种多样性呈现区域性的斑块化分布,结构性因子引起的物种多样性空间异质性占主导地位;作为极端干旱区,该区植物群落类型具有贫乏化及单一化的趋势,群落结构简单,植被覆盖度低,植物生长随环境的变化具有明显的可塑性,群落空间分异明显,群落空间演变具有明显的水分及土壤结构梯度;DCCA结果显示气候、土壤、地形是群落物种及类型变化的主要原因,海拔、坡位、土壤机械组成、降水、温度等环境因子对群落有着显著的影响,水土条件的空间异质性是戈壁植物多样性维持的关键因素。     

Rotifer distribution in relation to temperature and oxygen content

Lunzer Obersee, a small lake located at an altitude of 1100 m above sea level, was investigated from July 1985 to October 1987. The rotifer community consists of 7 dominant species, 7 subdominant species and 34 species which occasionally occurred in the plankton. The dominant species show rather different demands in relation to temperature and oxygen content; e.g.: Filinia hofmanni was found at a wide range of oxygen concentrations (0.6–13.3 mg O₂l^–1) and low temperatures (4–6 °O, living in the upper water layers (1–7 m) during spring and in the deeper, anoxic zone in summer. In contrast, Asplanchna priodonta was found at rather high oxygen contents (> 9 mg O₂ l^–1), ), and showed a wide range of temperature tolerance (4–15 °C).On the basis of field data the temperature and oxygen requirements of several species are described and discussed.     

Effect of tissue and atmosphere's parameters on human eye temperature distribution

A three dimensional finite element method analysis was employed to investigate the effect of tissue and atmosphere parameters namely, ambient temperature, ambient convection coefficient, local blood temperature, and blood convection coefficient upon temperature distribution of human eyes. As a matter of simplification, only eye ball and skull bone are considered as the system of eye modeling. Decreasing the local blood temperature and keeping it cool is one of the most important ways to control bleeding during surgeries. By lower temperature of body organs such as the eye, the need for oxygenated blood is reduced, allowing for an extension in time for surgery. With this in mind, this study is done to see which one of parameters, such as ambient temperature, ambient convection coefficient, local blood temperature, and blood convection coefficient, has an effective role in decreasing the temperature of the eye. To this end, 3 different paths were employed to find out about the temperature distribution through the eye. The analysis of the three paths demonstrates the interaction of ambient and blood temperature in modeling temperature changes in specific locations of the eye. These data will be important in applications such as eye surgery, relaxation, and sleep therapy.     

Muscle temperature and muscle metabolism during short-term exercise in the goat

1. 1.|External heat exchangers acting on lower aortal blood temperature were used to dissociate hindleg muscle temperature (T_hlm) from general internal temperature (T_int) during short-term exercise of moderate intensity.

2. 2.|In series 1 39°C T_hlm was combined with 40.6°C T_int, and in series II 42°C T_hlm was combined with 39.8°C T_int.

3. 3.|At constant work rates, the 3°C difference in muscle temperature did not result in significantly different concentrations of muscle metabolites.

4. 4.|It is concluded that high local muscle temperature without general hyperthermia does not influence muscle metabolism during short-term moderate excercise.

稻麦作物呼吸作用与植株氮含量、生物量和温度的定量关系

陆地生态系统碳循环是全球变化研究的重要议题之一,准确估算植被的呼吸作用对于客观评价植被在陆地生态系统碳循环中的作用具有重要意义。为探讨作物生长、植株氮含量和环境温度对呼吸作用的综合影响,研究以盆栽为主并与大田试验相结合,基于逐步收割法和静态暗箱-气相色谱技术,于2 0 0 2年和2 0 0 3年冬小麦和水稻生长季原位测定了作物地上部分CO2 排放速率,并同时测定了作物生物量、氮含量和环境温度。试验处理分为常规管理、不同氮肥水平、不同播种期和不同种植密度。研究结果表明:稻麦作物暗呼吸系数(Rd)不是常数,而是正比于植株氮(N )含量,两者的关系可用方程Rd=4 .74 N - 1.4 5 (R2 =0 .85 ,n=12 2 ,p<0 .0 0 1)来定量表述。用方程RD=(4.74 N - 1.4 5 )×Q( T- 2 5) /1 01 0 ×W模拟的作物暗呼吸量(RD)与大田测定结果一致。用国际上著名的作物模拟模型估算的稻麦作物维持性呼吸与用此方程模拟的结果具有可比性,而采用陆地生态系统模型(TEN)估算的结果则远高于本项研究,TEM用于估算农业植被的呼吸作用可能是不适合的。     

A model of canopy photosynthesis incorporating protein distribution through the canopy and its acclimation to light, temperature and CO2

Background and Aims

The distribution of photosynthetic enzymes, or nitrogen, through the canopy affects canopy photosynthesis, as well as plant quality and nitrogen demand. Most canopy photosynthesis models assume an exponential distribution of nitrogen, or protein, through the canopy, although this is rarely consistent with experimental observation. Previous optimization schemes to derive the nitrogen distribution through the canopy generally focus on the distribution of a fixed amount of total nitrogen, which fails to account for the variation in both the actual quantity of nitrogen in response to environmental conditions and the interaction of photosynthesis and respiration at similar levels of complexity.

Model

A model of canopy photosynthesis is presented for C₃ and C₄ canopies that considers a balanced approach between photosynthesis and respiration as well as plant carbon partitioning. Protein distribution is related to irradiance in the canopy by a flexible equation for which the exponential distribution is a special case. The model is designed to be simple to parameterize for crop, pasture and ecosystem studies. The amount and distribution of protein that maximizes canopy net photosynthesis is calculated.

Key Results

The optimum protein distribution is not exponential, but is quite linear near the top of the canopy, which is consistent with experimental observations. The overall concentration within the canopy is dependent on environmental conditions, including the distribution of direct and diffuse components of irradiance.

Conclusions

The widely used exponential distribution of nitrogen or protein through the canopy is generally inappropriate. The model derives the optimum distribution with characteristics that are consistent with observation, so overcoming limitations of using the exponential distribution. Although canopies may not always operate at an optimum, optimization analysis provides valuable insight into plant acclimation to environmental conditions. Protein distribution has implications for the prediction of carbon assimilation, plant quality and nitrogen demand.     

激活标签法及其在植物基因工程上的应用

激活标签法是新近发展起来的一种用于基因分离和鉴定的方法。它通过诱变使特定内源基因发生过量表达,而产生显性功能获得型突变,从而对基因进行鉴定和分析。因为具有独特的性质已使其成为发现新基因和进行基因功能分析的有效工具。本文综述了激活标签法的原理、研究现状和在植物基因工程上的应用。 Abstract:Activation tagging is a new method for isolation and functional identification.It can generate dominant gain-of-function mutants by overexpression of a particular endogenous gene.Due to this special characteristics of activation tagging,this method has been a powerful tool for new gene discovery and gene functional analysis.This paper reviewed the principle and study conditions of activation tagging,as well as its use in plant genetic engineering.     

Divergent apparent temperature sensitivity of terrestrial ecosystem respiration

Aims Recent studies revealed convergent temperature sensitivity of ecosystem respiration (R e) within aquatic ecosystems and between terrestrial and aquatic ecosystems. We do not know yet whether various terrestrial ecosystems have consistent or divergent temperature sensitivity. Here, we synthesized 163 eddy covariance flux sites across the world and examined the global variation of the apparent activation energy (Ea), which characterizes the apparent temperature sensitivity of and its interannual variability (IAV) as well as their controlling factors.Methods We used carbon fluxes and meteorological data across FLUXNET sites to calculate mean annual temperature, temperature range, precipitation, global radiation, potential radiation, gross primary productivity and R e by averaging the daily values over the years in each site. Furthermore, we analyzed the sites with>8 years data to examine the IAV of Ea and calculated the standard deviation of Ea across years at each site to characterize IAV.Important findings The results showed a widely global variation of Ea, with significantly lower values in the tropical and subtropical areas than in temperate and boreal areas, and significantly higher values in grasslands and wetlands than that in deciduous broadleaf forests and evergreen forests. Globally, spatial variations of Ea were explained by changes in temperature and an index of water availability with differing contribution of each explaining variable among climate zones and biomes. IAV and the corresponding coefficient of variation of Ea decreased with increasing latitude, but increased with radiation and corresponding mean annual temperature. The revealed patterns in the spatial and temporal variations of Ea and its controlling factors indicate divergent temperature sensitivity of R e, which could help to improve our predictive understanding of R e in response to climate change.     

The relationship between respiration and temperature in leaves of the arctic plant Saxifraga cernua

Abstract Saxifraga cernua, a perennial herb distributed throughout the arctic and subarctic regions, shows high levels of dark respiration. The amount of respiration exhibited by leaves and whole plants at any temperature is influenced by the pretreatment temperature. Plants grown at 10°C typically show higher dark respiration rates than plants grown at 20°C. The levels of alternative-pathway respiration (or cyanide-insensitive respiration) in leaves of S. cernua grown at high and low temperatures were assessed by treating leaf discs with 0.25 mol m^?3 salicylhydroxamic acid during measurements of oxygen consumption. Alternative pathway respiration accounted for up to 75% of the total respiration. Tissues from 20°C-grown plants yielded a Q₁₀ of 3.37 for normal respiration, and of 0.97 for alternative-pathway respiration. Tissues from 10°C-grown plants yielded a Q₁₀ of 2.55 for normal respiration, and of 0.79 for alternative-pathway respiration. The alternative pathway does not appear to be as temperature sensitive as the normal cytochrome pathway. A simple energy model was used to predict the temperature gain expected from these high rates of alternative-pathway respiration. The model shows that less than 0.02°C can be gained by leaves experiencing these high respiration rates.     

西伯利亚蝗气门结构及呼吸代谢对高温胁迫的响应

【目的】掌握西伯利亚蝗Gomphocerus sibiricus的气门结构和呼吸代谢应对高温胁迫的响应策略。【方法】运用扫描电镜观察西伯利亚蝗气门超显微结构,多通道昆虫呼吸仪测定18~42℃处理下西伯利亚蝗的O_2吸收率、CO_2释放率、代谢率和呼吸商。【结果】西伯利亚蝗共有10对气门,胸部2对,腹部8对,呈圆形或椭圆形,内侧着生有筛板,呈刺凸状,分布密集。18~42℃范围内,随温度升高,西伯利亚蝗呼吸代谢呈先上升后下降的趋势。18℃时西伯利亚蝗雌雄成虫的O_2吸收率、CO_2释放率和代谢率值显著小于其他温度下的相应值(P<0.05),雌虫分别为0.0022 m L/min、0.0019 m L/min和0.0210 m L/(g·min),雄虫分别为0.0016 m L/min、0.0016 m L/min和0.0236 m L/(g·min);21~27℃范围内,西伯利亚蝗雌雄成虫的呼吸代谢变化平稳,超过30℃呼吸代谢各指标值迅速上升,至36℃时雌雄成虫的O_2吸收率和代谢率值均显著大于其他温度下的相应值(P<0.05);雌虫分别为0.0071 m L/min和0.0592 m L/(g·min),雄虫分别为0.0089 m L/min和0.1108 m L/(g·min),39℃时CO_2释放率显著大于其他温度下的相应值(P<0.05),雌雄成虫分别为0.0074 m L/min和0.0067 m L/min。【结论】依据西伯利亚蝗呼吸代谢随温度变化特征可以判断,随气候持续变暖,西伯利亚蝗仍将是新疆高山、亚高山草原的重要致灾类群。     

锡林河流域一个羊草群落中土壤呼吸与生物量之间的相关性分析(英)

采用根系生物量梯度上土壤呼吸变化趋势线外推法对锡林河流域一个羊草 (Leymuschinensis (Trin .)Tzvel.)群落中根系呼吸占土壤总呼吸的比例进行了估计 ,对生物量各组分 (地上、地下部分 )之间以及它们与土壤呼吸间的相关性进行了分析。结果表明 :在测定年度 (1998年 )整个生长季的不同月份 ,该群落中根系呼吸量占土壤呼吸总量的比例在 14 %～ 39%之间 ,平均为 2 7% ;地上总生物量及根系生物量与土壤呼吸间的相关性较差 ,但地上活生物量与土壤呼吸间存在着显著的乘幂关系。上述结果与国外同类研究结果相比 ,具有很好的一致性。     

锡林河流域一个羊草群落中土壤呼吸与生物量之间的相关性分析

采用根系生物量梯度上土壤呼吸变化趋势线外推法对锡林河流域一个羊草(Leymus chinensis (Trin.) Tzvel.)群落中根系呼吸占土壤总呼吸的比例进行了估计,对生物量各组分(地上、地下部分)之间以及它们与土壤呼吸间的相关性进行了分析.结果表明:在测定年度(1998年)整个生长季的不同月份,该群落中根系呼吸量占土壤呼吸总量的比例在14%～39%之间,平均为27%;地上总生物量及根系生物量与土壤呼吸间的相关性较差,但地上活生物量与土壤呼吸间存在着显著的乘幂关系.上述结果与国外同类研究结果相比,具有很好的一致性.     

A response-surface analysis of the relative importance of the temperature,salinity and body weight on the respiratory metabolism of the white shrimp Litopenaeus vannamei (Boone, 1931)

We used a response-surface analysis to determine the importance of different factors affecting the resting routine metabolic rate (QO₂) of the white shrimp Litopenaeus vannamei. The oxygen consumption rates were estimated using a multi-factorial design with 28 combinations of different salinities (15, 20, 25, 30, 35, 40 and 45 psu) and temperature (20, 25, 30 and 35 °C) values. The response-surface analysis produced a quadratic function showing that temperature more profoundly affects the oxygen consumption rate. Response-surface curves were generated to predict the optimal conditions resulting in oxygen consumption to better understand the successful growth of this species.     

A computer model of temperature distribution inside a lossy sphere after microwave radiation

The temperature distribution inside a lossy sphere resulting from the absorption of microwave energy was approximated by successive numerical iterations, of the thermal energy equation. Heat transfer within the sphere by conduction was considered. In the model energy was not dissipated by convection but was contained in the sphere for over 200 seconds. Exposure of a 5-cm sphere to 3,000 MHz at 30 mW/cm² for 200 seconds was calculated to produce a temperature rise of 0.56°C near the front surface.     

Seed quality and carbon primary metabolism

Improving seed quality is amongst the most important challenges of contemporary agriculture. In fact, using plant varieties with better germination rates that are more tolerant to stress during seedling establishment may improve crop yield considerably. Therefore, intense efforts are currently being devoted to improve seed quality in many species, mostly using genomics tools. However, despite its considerable importance during seed imbibition and germination processes, primary carbon metabolism in seeds is less studied. Our knowledge of the physiology of seed respiration and energy generation and the impact of these processes on seed performance have made limited progress over the past three decades. In particular, (isotope‐assisted) metabolomics of seeds has only been assessed occasionally, and there is limited information on possible quantitative relationships between metabolic fluxes and seed quality. Here, we review the recent literature and provide an overview of potential links between metabolic efficiency, metabolic biomarkers, and seed quality and discuss implications for future research, including a climate change context.