七子花苗期光合日进程及光响应

对七子花苗期光合日进程及光响应进行了研究,结果表明:(1)净光合速率的日进程曲线呈双峰型,胞间CO2浓度的日进程基本与净光合速率相反,中午胞间CO2浓度增高表明净光合速率午间降低主要受非气孔限制因素的影响。暗呼吸速率日进程呈单峰曲线,中午最高。光能利用效率以上午7∶00为最高,中午最低,以后又逐渐上升。(2)净光合速率最适温度为25～30℃,高光合有效辐射和高温下光抑制加剧。(3)29℃下饱和光强为890μmolm 2s 1,表观量子效率为0.0325,光补偿点为44μmolm 2s 1;随着光合有效辐射的增强,气孔阻力减小,但光合有效辐射过高,气孔阻力却有所上升。(4)在29℃的饱和光强下,羧化效率为0.0351,CO2补偿点为173μmolmol 1,低于或高于饱和光强,羧化效率下降,CO2补偿点升高。     

浙江天台山七子花群落主要植物种类的光合特性

对分布在浙江天台山的七子花群落主要植物种类的光合生理生态特性进行了研究。结果表明：夏季,位于群落冠层上层、林窗、林缘的七子花及主要伴生植物叶片的光合日进程均呈“双峰“曲线,有明显的光合“午休“现象。而位于冠层中、下层以及林下的七子花、草本植物,其光合日进程曲线平缓。从冠层上层到下层,七子花叶片的日均净光合速率（Pn）呈下降趋势。林窗、林缘的七子花小树叶片日均Pn比林下大,冠层上层的七子花中树叶片与林窗、林缘的小树叶片日均Pn差异不显著。七子花在不同生境中与伴生植物相比,日均Pn较低,光合能力较弱。同一植株七子花冠层上层叶片叶绿素含量最低,下层次之,中层最高。阴生草本植物在弱光下仍有很高的叶绿素含量。植物叶片的光合能力大小与叶绿素含量高低不呈正相关。相对常绿树种而言,七子花光补偿点较高、光饱和点较低,对光适应的生态幅度较窄。     

浙江天台山七子花等6种阔叶树光合生态特性

 对分布在浙江天台山的七子花(Heptacodium miconioides)等6种主要阔叶树的光合生理生态特性进行了研究,结果表明：1)夏季6种植物光合日进程均为“双峰”型,有明显的光合“午休”现象。日均净光合速率月变化呈“单峰”型,8月是一年的高峰期。日均和5～11月平均净光合速率最高的是东南石栎(Lithocarpus harlandii),最低的是天台阔叶槭(Acer amplum var. tientaiense）,七子花处于中下水平。2)相对常绿树种而言,七子花的光补偿点较高,光饱和点较低,对光     

遮荫对七子花幼苗光合特性和非结构性碳水化合物含量的影响

为探讨不同光环境下濒危植物七子花（Heptacodium miconioides）的生长及适应规律,以2年生七子花幼苗为研究对象,设置全光照、60%遮荫和90%遮荫3种光照强度,研究不同光环境对七子花幼苗的光合特性和非结构性碳水化合物（NSC）含量的影响。结果表明：（1）3种光照处理下,七子花幼苗的净光合速率（P_n）日变化均呈“单峰型”曲线,P_n日均值为全光照>60%遮荫>90%遮荫,90%遮荫下水分利用效率（W_UE）日均值显著低于全光照和60%遮荫。（2）与全光照相比,60%遮荫下七子花幼苗的光补偿点（L_CP）和暗呼吸速率（R_d）显著下降,而光饱和点（L_SP）、最大净光合速率（P_nmax）、最大羧化速率（V_cmax）、最大电子传递速率（J_max）和磷酸丙糖利用率（T_PU）无显著差异;重度遮荫（90%遮荫）导致植株的P_nmax、L_SP、L_CP、R_d、V_cmax、J_max和T_PU显著降低。（3）七子花幼苗叶片的淀粉、可溶性糖和NSC含量在60%遮荫处理中最高,90%遮荫处理下则显著下降。植株的NSC含量与P_n、V_cmax、J_max和T_PU呈显著正相关关系。综上所述,七子花在幼苗期具有一定的喜光性和耐荫能力,适度遮荫下植株可通过降低L_CP、R_d来调整叶片的光合生理,维持较高的NSC含量,从而来提高对弱光的利用率和碳同化能力,但在生产育苗过程中过度遮荫不利于七子花幼苗的生长。     

桂花光合特性的光温响应

对丹桂光合特性光温响应的研究结果表明：1）净光合速率最适温度为24～28℃,在22～42℃之间,净光合速率、胞间CO2浓度、气孔导度和水分利用效率与温度的关系为二次多项式方程,暗呼吸速率和蒸腾速率与温度成线性关系;2）在控制条件下,随着温度的升高,光补偿点升高,光饱和点、表观量子效率、最大净光合速率下降.在自然条件下,丹桂光合日进程出现明显的光合“午休”,“午休”主要由非气孔限制引起,表观量子效率和光化学效率下降表明光抑制是午间非气孔限制形成和发展的深层原因.     

七子花苗期光合生理生态特性研究

对七子花苗期的光合生理生态特性进行了研究,结果表明：（1）净光合速度,蒸腾速率的日进程曲线呈“双峰”型,胞间CO2浓度的日进程基本与净光合速率相反,中午胞间CO2浓度增高表明净光合速率午间 要受非气孔限制因素的影响,暗呼吸速率日进程呈单峰曲线,中午阳高。气孔阻力的变化规律与蒸腾速率基本相反。光能利用效率以上午7：00为最高,中午最低,以后又逐渐上升。水分利用效率以7：00最高,10：00－16：00较低。（2）一天分时段光响应试验表明,饱和光强 表观量子产额上午最高,中午最低,下午有所上升。上午和下午光补 点比较接近,中午增高一倍多。不同时段遮光都使得蒸腾速率下降,以下进下降幅度最大,但使气孔阻力升高,下午增加幅度最大。（3）上午羧化效率最高,中午最低,下午稍有上升,而CO2补偿点中午最高。     

两个品种圆茄嫁接苗与自根苗的某些光合特性比较

旺盛生长期的圆茄嫁接苗功能叶片的净光合速率（Pn）显著高于自根苗;嫁接苗与自根苗功能叶片的Pn日变化均呈双峰曲线,但中午时前者的Pn下降幅度较后者小;光补偿点（LCP）、CO2补偿点（CCP）和光合冷限温度前者比后者低,光饱和点（LSP）、CO2饱和点（CSP）和光合热限温度比后者高;两者的光合最适温度没有明显差异。     

茄子嫁接苗与自根苗光合特性比较

对茄子嫁接苗与自根苗的光合生理特性进行了比较研究。结果表明,不同时期嫁接苗功能叶片的净光合速率（Pn）均显著高于自根苗;茄子嫁接苗与自根苗功能叶片的Pn日变化均呈“双峰”曲线,但嫁接苗的“午休”程度较自根苗轻;嫁接苗比自根苗有较低的光补偿点（LCP）和CO2补偿点（CCP）,较高的光饱和点（LSP）和CO2饱和点（CSP）;有较低的光合冷限温度和较高的光合热限温度,光合最适温度两者之间没有明显的差别;有较高的光饱和、CO2饱和及最适温度时的Pn;嫁接苗Pn高是因为嫁接苗胞间的光合反应的底物浓度大（Ci高）,表观量子效率（AQY）、羧化效率（CE）和光合能力（A350）高的缘故。     

温度变化对烟草光合作用光响应特征的影响

通过Li-6400光合测定系统控温,研究了大田条件下,烟草脚叶采烤期腰叶在17、20、25、30和35℃下的光合作用光响应特征。结果表明:随温度升高,净光合速率(Pn)、最大净光合速率(Pnmax)、初始斜率(α)和气孔导度(Gs)先上升后下降,在20℃下达最大值,35℃下净光合速率受强光的抑制作用明显;光补偿点(LCP)和暗呼吸速率(Rd)随温度升高而上升,但35℃下二者较30℃时有所下降;光饱和点(LSP)随温度升高而呈下降-上升-下降的变化,30℃和17℃时LSP较高;蒸腾速率(Tr)随温度上升而增强,水分利用效率(WUE)则随温度升高而下降,但20℃时水分利用效率在强光下明显较其他温度下的高。结果说明,20℃最适合烟草光合作用,此温度下气孔的水、气调节能力最强,温度高于30℃则对烟草光合作用不利。     

水分胁迫和温度对夏蜡梅叶片气体交换和叶绿素荧光特性的影响

夏蜡梅是浙江省特有的濒危单种属物种.本文研究了不同程度土壤水分胁迫和不同温度处理对2年生盆栽夏蜡梅光合作用的影响.结果表明:轻度和中度水分胁迫下夏蜡梅净光合速率分别下降至对照的92.3%和74.3%,净光合速率的降低主要由气孔限制引起;重度水分胁迫下,净光合速率仅为对照的44.4%,主要由非气孔限制引起.夏季夏蜡梅的光合适宜温度范围在20 ℃～28 ℃,39 ℃下其净光合速率、水分利用效率和最大光化学效率显著降低,暗呼吸速率和蒸腾速率显著升高.随着水分胁迫的加重及处理温度的升高,夏蜡梅光补偿点上升,光饱和点、表观量子效率和最大净光合速率下降.重度水分胁迫及高温是制约夏蜡梅生存的重要环境因子.     

On-station comparative analysis of reproductive and survival performance between Red Maasai,Dorper, and Merino sheep breeds

The reproductive performance of ewes and the survivability of lambs to weaning have a critical economic impact on sheep farming worldwide. Further, knowledge of major mortality causes allows an opportunity for improved flock management to evade financial losses. The maximum likelihood estimates for generalised linear mixed models and chi-square test methods were used to examine 971 mating records, 839 and 763 lambs born and weaned (singles or twins) from the Naivasha Sheep and Goats station in Kenya for the years 2011 to 2020 consisting of Dorper, Red Maasai (RedM), and Merino breeds. The RedM (P < 0.05) outperformed Dorper and Merino in weaning rate, whereas reproductive performance between the three breeds was not significantly different (P > 0.05) in litter size and multiple lambings per ewe lambing. On the one hand, Dorper significantly (P < 0.05) outperformed the other two breeds only in weaning weight per lamb born. In addition, among all the major causes of death, pneumonia appeared to be the one to which Dorper breeds were most susceptible (chi-square test, P < 0.05). According to the findings of this study, neither the Dorper nor the Merino sheep breeds were reproductively superior to the RedM in an extensive semi-arid production environment. In addition, Dorper's susceptibility to the leading causes of mortality, particularly pneumonia and sheep pox, were relatively high compared to other breeds and could be a precursor to massive economic losses for Dorper sheep producers. In contrast to the indigenous RedM breed, imported sheep breeds appeared to be more susceptible to major mortality-related under an extensive production system. Therefore, regardless of weaning weight, RedM breed production appears to be a more viable investment for small-scale farmers, particularly in semi-arid regions.     

Predation rate and numerical response of Aphidoletes aphidimyza feeding on different densities of Aphis craccivora

Predation rate and numerical response are basic to any investigation of predator–prey relationships and key components in the selection of predators for biological control. The density-dependent predation rate and numerical response of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) to varying densities (5, 10, 20, 40, 60 and 80) of third-instar Aphis craccivora (Koch) (Hemiptera: Aphididae), were studied in laboratory conditions [23±1°C, 70 ± 5% relative humidity (RH), and a photoperiod of 16:8 h L:D. Predation rate data were analysed using the age-stage, two-sex consumption rate software. Net consumption rate (C₀) increased by increasing prey density. The lowest and highest net consumption rates were 20.75 and 190.8 prey nymphs at densities of 5 and 80 A. craccivora. The transformation rate from prey population to predator offspring (Q_p) increased by increasing prey density. The reproductive numerical response, in terms of eggs laid, increased curvilinearly with increasing prey density. Females laid 121.375 ± 4.301 eggs when exposed to the highest prey density (80) and 52.5 ± 1.544 eggs at lowest prey density (5). It can be concluded that different densities of A. craccivora influenced the reproductive performance of A. aphidimyza in terms of predation rate and numerical response.     

Time dependency of molecular rate estimates and systematic overestimation of recent divergence times

Studies of molecular evolutionary rates have yielded a wide range of rate estimates for various genes and taxa. Recent studies based on population-level and pedigree data have produced remarkably high estimates of mutation rate, which strongly contrast with substitution rates inferred in phylogenetic (species-level) studies. Using Bayesian analysis with a relaxed-clock model, we estimated rates for three groups of mitochondrial data: avian protein-coding genes, primate protein-coding genes, and primate d-loop sequences. In all three cases, we found a measurable transition between the high, short-term (< 1-2 Myr) mutation rate and the low, long-term substitution rate. The relationship between the age of the calibration and the rate of change can be described by a vertically translated exponential decay curve, which may be used for correcting molecular date estimates. The phylogenetic substitution rates in mitochondria are approximately 0.5% per million years for avian protein-coding sequences and 1.5% per million years for primate protein-coding and d-loop sequences. Further analyses showed that purifying selection offers the most convincing explanation for the observed relationship between the estimated rate and the depth of the calibration. We rule out the possibility that it is a spurious result arising from sequence errors, and find it unlikely that the apparent decline in rates over time is caused by mutational saturation. Using a rate curve estimated from the d-loop data, several dates for last common ancestors were calculated: modern humans and Neandertals (354 ka; 222-705 ka), Neandertals (108 ka; 70-156 ka), and modern humans (76 ka; 47-110 ka). If the rate curve for a particular taxonomic group can be accurately estimated, it can be a useful tool for correcting divergence date estimates by taking the rate decay into account. Our results show that it is invalid to extrapolate molecular rates of change across different evolutionary timescales, which has important consequences for studies of populations, domestication, conservation genetics, and human evolution.     

Optimising a clearance index based on neutral red as an indicator of physiological stress for bivalves

Neutral red is a weakly cationic dye that is soluble in water, has a low toxicity for almost all classes of organisms, and has been used as a histological and vital stain since the early twentieth century. Estimating the volume of water cleared of indicator material by suspension feeding bivalves (clearance or filtration rate) was one of the earliest applications of neutral red; however, less than thirty studies have applied this methodology since it was first described in 1954. The feeding/clearance rate is used as a sensitive indicator of physiological stress and is therefore an early-warning tool that is suitable for monitoring the ecological status of water bodies. The aim of our study was to optimise a clearance index based on neutral red solution by addressing the effect of i) the acidifying pH; ii) the holding temperature before spectrophotometric reading; and the time iii) before and iv) after the acidification of solutions of neutral red used to carry out clearance assays. Furthermore, as a case study we fine-tuned the clearance assay for the edible estuarine bivalve, Cerastoderma edule. The results showed that there were no statistical differences as regards the absorbance of neutral red solutions holding at 4 or 20 °C or a solution acidified between the ranges of pH 4–5. However, the absorbance significantly decreased as the pH increased to pH 6. The time before acidification had no significant effect on absorbance. Once the neutral red solution is acidified, the absorbance decreases over time, signifying that the absorbance should be read in the first 24 h. The concentration of neutral red used in the experiences should be sufficient to allow final concentrations of over 0.5 mg/L after the clearance period, since we observed that the sensitivity of this protocol decreased at low concentrations. In the case of C. edule, the optimum clearance conditions per individual were found to be 100 ml of 4 mg/L of neutral red dye during a 30 min period in dark conditions. A bioassay using a clearance index of C. edule based on this simple colorimetric technique would appear to be a potential tool for implementation in environmental monitoring programmes for water quality assessment in accordance with European directives. We trust that the new harmonised protocol will become a widely used and cost-effective means to monitor the clearance index as an indicator of physiological stress for bivalves.     

Photorespiration Rate in Spinach Leaves Under Moderate NaCl Stress

We analyzed the effect of NaCl stress on photorespiration of spinach leaves by calculating the rate of carboxylation/oxygenation of ribulose-1,5-bisphosphate carboxylase/oxygenase, and by measuring the content of amino acids produced through photorespiration. After 20 d of NaCl stress the carboxylation rate was reduced while the oxygenation rate was not affected. The contents of serine, glycine, and alanine increased relevantly. The amount of glutamine also increased after 20 d but the amount of glutamate did not. Hence photorespiration may be stimulated under moderate NaCl stress. A relevant electron transport rate was observed under CO₂-free air, which may indicate refixation of photorespiratory CO₂. When NaCl accumulation proceeded for more than 20 d, photosynthesis was reduced and the content of photo-respiratory amino acids started to decrease, but the oxygenation rate did not change. This revised version was published online in September 2006 with corrections to the Cover Date.     

Ingestion Rates of Some Daphnia Species in a Shallow Lake (Lake Balaton,Hungary)

Filtering rates of three species of Daphnia were studied in situ by the ¹⁴C technique during the summer in a lake with a water temperature of 20-25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3-5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates of D. cucullata, D. hyalina and D. galeata averaged 7.8, 10.3 and 9.2 ml ind.⁻¹ day⁻¹, respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter-feeding crustaceans is suggested to be approximately 7 % per day.     

广西地区脑血管病城乡抽样对比分析

本文着重分析了广西城市和农村脑血管病发病情况的差异。我们发现城市CVD发病率、患病率明显高于农村,但是农村CVD的死亡率高于城市,其中我们对其原因作了初步的探讨。     

Comparative vital statistics along the pastoral nomadism-sedentarism continuum

Vital statistics on pastoral nomadic and sedentarizing nomadic societies are by-and-large non-existent. Such information is highly important for both academic and policy-making reasons as pastoral nomadism as a mode of life is disappearing. This paper attempts to gather and present as much information as possible on crude birth and death rates and natural increase rates for various pastoral nomadic societies in different African and Middle Eastern countries. The information is arranged by a subdivision into nomads, seminomads, and sedentarized nomads. A summarization of this information suggests a possible pattern by which birth rates rise, death rates fall (but may rise in certain circumstances), and natural increase rates rise along the nomadism-sedentarism continuum. Such a possible pattern has several policy implications for governments assessing the needs of a nomadic society undergoing a process of change in its socio-ecological relationships.This article was written while the author was a visiting scholar at the Department of Geography at the University of California. The author wishes to thank Nga and Allen Scott and Melanine M. Patton, as well as two anonymous referees, for their assistance and suggestions for this paper.     

On the interpretation of some planktonology equations

Summary The concept of the mean value of a function is used to interpret some population-dynamics equations. The well-known formula for the per capita growth rate r gives a precise mean value for any (not only exponentially growing) populations. This result is used to derive the birth and death rate equations of Paloheimo (1974) with minimal initial limitations.Abbreviations t time - N number of animals - E number of eggs - r specific (i.e. per capita) population growth rate - b specific birth rate - d specific death rate - D duration of embryonic development     

光周期和温度对虎斑蝶卵、幼虫及蛹存活的影响

通过在人工气候箱内设定不同光周期和温度梯度单虫饲养观察个体发育史,研究了光周期和温度对虎斑蝶Danaus genutia幼期存活的影响,研究结果可为该高观赏价值蝶种的规模化养殖提供依据。结果表明,在长光照(L∶D=15∶9)条件下,17.5、20.0、22.5、25.0、27.5、30.0℃时虎斑蝶卵的孵化率分别为63.72%、71.67%、65.75%、75.00%、67.12%、59.56%,幼虫的存活率分别为85.67%、85.96%、91.19%、89.20%、80.86%、68.78%,蛹的存活率分别为82.76%、100.00%、96.00%、97.06%、100.00%、100.00%;在短光照(L∶D=9∶15)条件下,17.5、20.0、25.0、30.0℃时虎斑蝶卵的孵化率分别为86.36%、67.06%、75.00%、77.50%,幼虫的存活率分别为85.05%、84.59%、85.74%、80.78%,蛹的存活率分别为93.30%、94.12%、100.00%、100.00%。结果表明,17.5℃和30.0℃均不利于虎斑蝶幼期的存活,20.0～27.5℃是其幼期生长发育适宜的温度范围。长光照利于幼虫的存活,短光照利于卵的孵化和蛹的羽化;在17.5～30.0℃内,较高的温度利于蛹的羽化,而较低的温度利于卵的孵化和幼虫的存活;温度对虎斑蝶卵的孵化、幼虫的存活及蛹的羽化影响大于光周期;在养殖生产上,建议将幼期养殖温度控制在20.0～27.5℃,幼虫期饲养在长光照下为宜,卵和蛹期置于短光照下为宜。