He-Ne激光预处理对镉胁迫下小麦幼苗生理特性的影响

用He-Ne激光（波长632.8 nm,辐射剂量5.43 mW/mm²）对萌动小麦种子辐照5 min,待幼苗长至一叶一心时,用150 μmol/L CdCl₂溶液进行胁迫处理,研究He-Ne激光预处理对镉（Cd²⁺）胁迫下小麦幼苗生长发育和生理特性的影响。结果显示:He-Ne激光预处理能显著降低Cd²⁺胁迫下小麦幼苗中丙二醛（MDA）、过氧化氢（H₂O₂）含量及超氧自由基（O^-·₂）产生速率,显著提高幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸氧化酶（APX）活性,并使叶片抗氧化物质谷胱甘肽(GSH)和抗坏血酸(AsA)含量以及幼苗株高、根长和干重增加。研究表明,He-Ne激光预处理可有效缓解镉胁迫对小麦幼苗生长的抑制作用,并通过促进其幼苗中酶类和非酶类抗氧化剂的产生,有效减少镉胁迫产生的脂质过氧化物含量,从而提高其耐镉性。     

基于FMEA和POSSUM评分的手术风险评估研究

??????? 目的 研究建立手术风险评估的架构,以正确决策手术时机。方法 采用用于计数死亡率和并发症发生率的生理学和手术严重性（POSSUM）评分原理进行分层计分,同时引用失效模式与效应分析方法对手术可能发生故障模式的严重度及发生可能性及风险因素的影响度3个维度进行评估。结果 建立了手术前风险预警机制及手术评估架构,利用评估架构对某综合医院2010年200例80岁高龄的手术病人进行了术前评估,结果手术后并发症的发生率较2009年同年龄的手术病人的并发症下降了10.45%。结论 在手术前对手术相关因素进行评估,可以为手术时机的选择提供参考。     

土壤干旱胁迫对九头狮子草和圆苞金足草幼苗形态和生理特性的影响

采用称重控水法控制土壤相对含水量分别为(85.0±2.5)％(对照)、(67.5±2.5)％(轻度干旱)、(50.0±2.5)％(中度干旱)和(32.5±2.5)％(重度干旱),对土壤干旱胁迫条件下九头狮子草[Peristrophe japonica (Thunb.)Bremek.]和圆苞金足草(Goldfussia pentstemonoides Nees)2年生苗的植株形态及生理特性变化进行了研究.结果表明:经土壤干旱胁迫处理30 d后供试2种植物的外部形态均有一定变化,其中九头狮子草主要变化为叶片失绿、变薄且萎蔫、枝条下垂;圆苞金足草主要变化为茎干倒伏、叶片变软且叶柄低垂.随土壤干旱胁迫程度的增加,供试2种植物叶片的自然饱和亏、临界饱和亏、需水程度、束缚水含量、束缚水与自由水的含量比值、脯氨酸含量和可溶性糖含量均呈逐渐增加的趋势且均高于对照,而自由水含量、最高水势、最低水势和可溶性蛋白质含量均逐渐降低且总体上低于对照.总体上看,在重度干旱胁迫条件下供试2种植物各生理特性均与对照有极显著或显著差异,而在轻度或中度干旱胁迫条件下部分指标与对照无显著差异.供试2种植物各生理指标的变化幅度有明显差异,在同一干旱胁迫条件下九头狮子草叶片的自然饱和亏、需水程度、自由水含量、最高水势和最低水势的降幅、脯氨酸含量和可溶性蛋白质含量的降幅均高于圆苞金足草,其临界饱和亏、束缚水含量、束缚水与自由水的含量比值和可溶性糖含量均低于圆苞金足草.综合分析结果表明:供试2种植物对土壤干旱胁迫均具有一定的耐性,但圆苞金足草具有更强的抵御干旱的生理机制.     

Speciation studies of aluminium(III)–acetate complexes under physiological conditions

Abstract

The aluminium complexes of acetic acid (ACT) have been studied using Potentiometric titrations under physiological conditions of temperature (37°C) and ionic strength (0.15 dm^?3 dm^?3 NaCI) and at different ligand to metal ratios. The variations of pH were measured with the help of a glass electrode calibrated daily in hydrogen ion concentrations. Results obtained within the pH range of 2.6–4.2 were analysed to determine stability constants using the SUPERQUAD program. Different complex combinations were considered during the calculation procedure, and evidence was found for ML₂ mononuclear species beside binuclear hydroxo-complexes M₂L(OH)₂ and M₂L(OH)₃ and metal ion hydroxides. Speciation calculations based on the corresponding constants were then used to simulate species distributions.     

Purification and Properties of α-Glucosidase and Glucoamylase from Lentinus edodes (Berk.) Sing.

An α-glucosidase and a glucoamylase have been isolated from fruit bodies of Lentinus edodes (Berk.) Sing., by a procedure including fractionation with ammonium sulfate, DEAE-cellulose column chromatography, and preparative gel electrofocusing. Both of them were homogeneous on gel electrofocusing and ultracentrifugation. The molecular weight of α-glucosidase and glucoamylase was 51,000 and 55,000, respectively. The α-glucosidase hydrolyzed maltose, maltotriose, phenyl α-maltoside, amylose, and soluble starch, but did not act on sucrose. The glucoamylase hydrolyzed maltose, maltotriose, phenyl α-maltoside, soluble starch, amylose, amylopectin, and glycogen, glucose being the sole product formed in the digests of these substrates. Both enzymes hydrolyzed phenyl a-maltoside into glucose and phenyl α-glucoside. The glucoamylase hydrolyzed soluble starch, amylose, amylopectin, and glycogen, converting them almost completely into glucose. It was found that β-glucose was liberated from amylose by the action of glucoamylase, while α-glucose was produced by the α-glucosidase.

Maltotriose was the main α-glucosyltransfer product formed from maltose by the α-glucosidase.     

Phytotoxicity induced by Phragmites australis: an assessment of phenotypic and physiological parameters involved in germination process and growth of receptor plant

This study investigated the possible phytotoxicity induced by Phargmites australis on phenotypic and physiological parameters of recipient plants with identification of major inhibitors in the donor plant. This was achieved using aqueous extracts of different organs and root exudates of P. australis in laboratory and greenhouse experiments with Lactuca sativa as the model test plant. The observed reduced liquid imbibition and altered resource mobilization in seeds of L. sativa, in particular an insufficient carbohydrate supply, demonstrated that the onset of germination might be negatively affected by phytotoxicity. Dose-response studies pointed out that oxidative stress through reactive oxygen species production could potentially cause the observed germination and seedling growth reductions. The osmotic effects by mannitol solution on germination as well as growth and physiology at a level of ?0.57 and ?0.45 bar, respectively, demonstrated that the results from aqueous plant extracts were partially induced by the osmotic potential on and above those levels. Overall, the relative strength of inhibition on measured parameters was the highest in leaf extract, followed by rhizome, root, stem, and inflorescence. Root exudates of P. australis also had negative impacts by reducing germination and growth of plant. High-performance liquid chromatography (HPLC) analysis revealed gallic acid, a potent phytotoxin, as a major compound with an order of leaf >inflorescence>rhizome>root>stem.     

Trade-offs in interspecific comparisons in plant ecology and how plants overcome proposed constraints

Comparative studies on plant species have not distinguished between two inherently different applications of the idea of a trade-off. In the first case, the theoretical trade-off between two variables leads to a trend line, about which there is a degree of scatter. Any two species in the study are expected, in theory, to show a true trade-off, i.e. feature A must decrease for feature B to increase. This I call the ‘trend line’ type of plot. In the second case, the species are expected to fill a considerable part of the space defined by two axes and the theoretical trade-off leads to a boundary line which limits the extent of the cloud of points. In this case, many interspecific comparisons are not expected to show evidence of a trade-off, but those on the boundary line are expected to do so. This I call the ‘boundary line’ type of plot. In both types of plot, species within a given clade may show a true trade-off, while large numbers of unrelated species do not.

First, I undertake to show, by means of examples, the reality of the distinction made above, and to demonstrate that statistically significant and ecologically important negative correlations between features A and B in the ‘trend line’ type of plot can be accompanied by huge variation from the trend line. Second, for plots of the ‘boundary line’ type, I undertake to show that authors have not always tested sufficiently rigorously the constraint lines concerning combinations of supposedly incompatible tolerances, and have not allowed for the absence of certain combinations of unfavourable conditions in the field and consequent lack of selection pressure for the evolution of species with a combination of extreme tolerances.

I review two examples of each kind of constrained evolution. First, I take the worldwide leaf economics spectrum and the negative correlation between growth rate in high light and survival rate in deep shade. Second, I review the supposed incompatibilities between shade tolerance and drought tolerance, and between waterlogging tolerance and drought tolerance.

I conclude that the term ‘trade-off’ is used too loosely. The common lack of true trade-offs has made possible the species richness of present-day vegetation. Also, small numbers of species have evolved combinations of tolerances that might seem improbable. Not enough research is being aimed at understanding the mechanistic basis of variation about trend lines, and the crossing of supposed boundary lines.     

When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confound a multiregional assessment

Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed‐exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco‐region or when postdeposition exposure can be minimized.