Antagonistic and synergistic interactions between aluminum and manganese on growth of Vigna unguiculata at low ionic strength

Concentrations of soluble aluminum (Al) and manganese (Mn) frequently reach phytotoxic levels in acid soils. While dose response relationships for these metals are well documented, the effects of combined exposure have received less attention. We have examined the effect of combinations of Al and Mn on growth and metal accumulation in Vigna unguiculata (L.) Walp. grown in solution culture under conditions of low ionic strength (conductivities typically < 100 µS cm⁻¹). The nature of interaction between these metals varied with the specific physiological response, the part of the plant investigated, and the relative amount of stress imposed. Analysis of growth data provided evidence for amelioration of metal toxicity (antagonistic effects), although this effect was dose dependent. Analysis of metal content data provided evidence for antagonistic and synergistic (exacerbation of toxicity) effects, again depending on dose. Analysis of foliar symptoms also provided evidence for antagonisms and synergisms, with the nature of the response dependent on the specific physiological response and specific plant part investigated. In contrast with previous reports, evidence for antagonistic, synergistic, and multiplicative effects on growth, metal uptake, and expression of foliar symptoms have been obtained under physiologically and environmentally relevant conditions. These results suggest a more detailed analysis of the potential for interactions between metals in the environment is required.     

Effects of ion-pairing on calculations of ionic activities of major ions in freshwater

Ion-pairing has little effect on ionic activity calculations for weakly mineralized natural water (ionic strength < 2 mM). However, for more strongly mineralized freshwaters, corrections for ion-pairing are necessary if highly accurate ionic activities are required.     

磷对海水胁迫下芦荟幼苗离子分布的影响

研究了磷对海水胁迫下库拉索芦荟(A loe vera)幼苗干物质积累、植株含水量、在器官和组织水平上离子分布的影响。增磷显著缓解海水胁迫对芦荟生长的抑制,明显提高海水胁迫下芦荟幼苗的干物质积累和含水量。器官离子含量和X射线微区分析结果都表明,30%浓度海水胁迫下,外源磷水平的提高能显著降低芦荟幼苗根系N a 、C l-的吸收,增强K 、C a2 向地上部的运输和分配,从而维持叶片较高的K /N a 、C a2 /N a 比率,而这很可能是增磷提高芦荟对海水胁迫抗性的主要原因之一。     

Thermal Stability and Activity Regain of Horseradish Peroxidase in Aqueous Mixtures of Imidazolium-Based Ionic Liquids

Thermal deactivation kinetics of horseradish peroxidase (HRP) were studied from 45 to 90 °C in phosphate buffer and 5–25% (v,w/v) 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄] and 1-butyl-3-methylimidazolium chloride [BMIM][Cl]. HRP activity at 25 °C was not affected by the presence of ionic liquids up to 20% (v,w/v). Increasing the ionic liquids concentration up to 25% (v,w/v) changed the biphasic character of deactivation kinetics to an apparent single first-order step. The presence of 5–10% (v/v) [BMIM][BF₄] significantly improved HRP thermal stability with lower activation energies for the deactivation second phase (83–87 kJ mol⁻¹). After deactivation, enhanced activity regain of the enzyme, up to 70–80% of the initial activity, was found in 25% (v/v) [BMIM][BF₄] and 10% (w/v) [BMIM][Cl] and correlated to prevalence of the deactivation first phase.     

The Synergistic Effect of Cation and Anion of an Ionic Liquid Additive for Lithium Metal Anodes

Lithium metal anodes are steadily gaining more attention, as their superior specific capacities and low redox voltage can significantly increase the energy density of rechargeable batteries far beyond those of current Li‐ion batteries. Nonetheless, the relevant technology is still in a premature research stage mainly due to the uncontrolled growth of Li dendrites that ceaselessly cause unwanted side reactions with electrolyte. In order to circumvent this shortcoming, herein, an ionic liquid additive, namely, 1‐dodecyl‐1‐methylpyrrolidinium (Pyr1(12)⁺) bis(fluorosulfonyl)imide (FSI^?), for conventional electrolyte solutions is reported. The Pyr1(12)⁺ cation with a long aliphatic chain mitigates dendrite growth via the combined effects of electrostatic shielding and lithiophobicity, whereas the FSI^? anion can induce the formation of rigid solid–electrolyte interphase layers. The synergy between the cation and anion significantly improves cycling performance in asymmetric and symmetric control cells and a full cell paired with an LiFePO₄ cathode. The present study provides a useful insight into the molecular engineering of electrolyte components by manipulating the charge and structures of the involved molecules.     

盐胁迫下植物细胞离子稳态重建机制

土壤盐渍化是困扰世界粮食产量的一大难题。在盐胁迫环境中,植物获得耐盐能力的一个重要策略是建立新的离子稳态(ionic homeostasis)。盐胁迫下植物细胞离子稳态依赖于膜转运蛋白(泵、载体和离子通道)。利用蛋白质的生化功能分析和突变体功能互补等方法,目前已克隆和鉴定了许多参与离子稳态重建的膜转运蛋白。综述了盐胁迫下植物细胞离子稳态重建的最新研究进展。     

长沙市不同污染程度区域桂花和香樟叶表面PM2.5吸附量及其影响因素

为阐释不同污染程度下城市绿化植物吸滞PM_2.5机理、解析污染物来源,应用气溶胶再发生器定量测定长沙市常见的2种园林绿化树种(桂花和香樟)植物叶片PM_2.5吸附量,同时应用原子力显微镜(AFM)观察了不同污染区(交通区、文教区、清洁区)植被的叶表面微形态特征,使用离子色谱仪测定样品中水溶性离子含量.结果表明: 污染程度与植物叶表面PM_2.5吸附量呈正相关,不同植物单位叶面积PM_2.5吸附量全年均值表现为交通区(0.56±0.04 μg·cm^-2)＞文教区(0.48±0.06 μg·cm^-2)＞清洁区(0.33±0.02 μg·cm^-2),植物单位叶面积PM_2.5吸附量季节变化为冬季(0.70±0.10 μg·cm^-2)＞春季(0.43±0.14 μg·cm^-2)＞秋季(0.39±0.12 μg·cm^-2)＞夏季(0.31±0.09 μg·cm^-2),桂花的单位叶面积PM_2.5吸附量大于香樟;污染程度轻的区域的植物叶片比较光滑,污染程度重的区域的叶片较粗糙,植物粗糙度排序为交通区(195.45±16.09 nm)＞文教区(176.99±8.45 nm)＞清洁区(131.88±12.98 nm);不同污染程度地区PM_2.5离子含量均表现为冬季最大,其次是春季和秋季,夏季最低;3个污染区PM_2.5离子成分均以Na⁺、NH₄⁺、Cl^-和Br^-这4种离子为主,不同程度污染区PM_2.5污染均以移动源污染为主.     

Stability and kinetic behavior of immobilized laccase from Myceliophthora thermophila in the presence of the ionic liquid 1‐ethyl‐3‐methylimidazolium ethylsulfate

The use of ionic liquids (ILs) as reaction media for enzymatic reactions has increased their potential because they can improve enzyme activity and stability. Kinetic and stability properties of immobilized commercial laccase from Myceliophthora thermophila in the water‐soluble IL 1‐ethyl‐3‐methylimidazolium ethylsulfate ([emim][EtSO₄]) have been studied and compared with free laccase. Laccase immobilization was carried out by covalent binding on glyoxyl–agarose beads. The immobilization yield was 100%, and the activity was totally recovered. The Michaelis‐Menten model fitted well to the kinetic data of enzymatic oxidation of a model substrate in the presence of the IL [emim][EtSO₄]. When concentration of the IL was augmented, the values of V_max for free and immobilized laccases showed an increase and slight decrease, respectively. The laccase–glyoxyl–agarose derivative improved the laccase stability in comparison with the free laccase regarding the enzymatic inactivation in [emim][EtSO₄]. The stability of both free and immobilized laccase was slightly affected by small amounts of IL (<50%). A high concentration of the IL (75%) produced a large inactivation of free laccase. However, immobilization prevented deactivation beyond 50%. Free and immobilized laccase showed a first‐order thermal inactivation profile between 55 and 70°C in the presence of the IL [emim][EtSO₄]. Finally, thermal stability was scarcely affected by the presence of the IL. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:790–796, 2014