磁环境对冬小麦幼苗叶片延伸生长的影响

在磁环境中,当充分供水和水分胁迫条件下,小麦幼苗叶片延伸生长速度（ＬＥＲ）均大于对照,且有（１）在充分供水条件下对水分敏感型品种的ＬＥＲ较不敏感型大;（２）水分胁迫条件则呈现相反规律;（３）ＲＷＣ测定值说明磁环境可以改善胁迫小麦的水分状况,因而磁环境对增强小麦旱性有作用。     

基于投入产出方法的甘肃省水足迹及虚拟水贸易研究

随着社会化进程的加快,地处西北内陆的甘肃省正面临日益严峻的水资源短缺危机,社会经济发展受到一定程度的制约,水生态环境也呈现出恶化的趋势。水足迹是近年来提出的衡量人类活动对于水生态系统影响的指标,能够帮助决策者制定水资源管理及保护的政策,从而实现地区水资源的可持续利用。运用单区域投入产出方法计算并分析了甘肃省1997、2002和2007年第一产业、第二产业和第三产业部门的虚拟水强度、水足迹以及虚拟水贸易情况。结果显示:(1)甘肃省第一产业的虚拟水强度最高,但呈现出逐年下降的趋势,水足迹也因此有所下降;(2)虚拟水贸易方面,甘肃省以虚拟水净出口为主,尤其是第一产业,每年虚拟水净出口量约全省总水资源量的10%。建议甘肃省继续巩固已有的节水成果,调整产业结构,大力发展节水型产业和高新技术产业。同时建议适当调整贸易格局,合理控制虚拟水出口,以缓解当地水资源短缺危机,保障地区水安全与生态安全。     

Metabolic processes account for the majority of the intracellular water in log-phase Escherichia coli cells as revealed by hydrogen isotopes

It is generally believed that water transport across biological membranes is essentially a near-instantaneous process, with water molecules diffusing directly across the membrane as well as through pores such as aquaporins. As a result of these processes by which water can equilibrate across a membrane, a common assumption is that intracellular water is isotopically indistinguishable from extracellular water. To test this assumption directly, we measured the hydrogen isotope ratio of intracellular water in Escherichia coli cells. Our results demonstrate that more than 50% of the intracellular water hydrogen atoms in log-phase E. coli cells are isotopically distinct from the growth medium water and that these isotopically distinct hydrogen atoms are derived from metabolic processes. As expected, the (2)H/(1)H isotope ratio of intracellular water from log-phase cells showed an appreciably larger contribution from metabolic water than did intracellular water from stationary-phase cells (53 +/- 12 and 23 +/- 5%, respectively). The (2)H/(1)H isotope ratio of intracellular water was also monitored indirectly by measuring the isotope ratio of fatty acids, metabolites that are known to incorporate hydrogen atoms from water during biosynthesis. Significantly, the difference in the isotopic composition of intracellular water from log- to stationary-phase E. coli cells was reflected in the hydrogen isotope ratio of individual fatty acids harvested at the two different times, indicating that the isotope ratio of metabolites can be used as an indirect probe of metabolic activity. Together, these results demonstrate that contrary to the common assumption that intracellular water is isotopically identical to extracellular water, these two pools of water can actually be quite distinct.     

Water structure changes induced by ceramics can be detected by increased permeability through aquaporin

Aquporins are intrinsic membrane proteins that function as water channel to transport water and/or mineral nutrients across biological membranes. In this study, we aimed to clarify whether water structure can be changed by the presence of ceramics and whether such a change can be determined by aquaporin. First, we confirmed that ceramics could transform tap water into active tap water by increasing water permeability through aquaporin. We also found that this change in water permeability by treatment with ceramics occurred in distilled water. The distilled water was determined to exhibit the same aquaporin permeability as the original tap water. Our data indicate that the aquaporin permeability of water can be changed by severe physical shocks, such as slapping and sonication, which is consistent with the implication that the aquaporin permeability is closely related to the structure of the water. In this study, using aquaporins, we first reported that the treatment of water with ceramics can affect the structure of water, and the water can retain the structure for a given period under certain condition     

封丘地区小麦耗水量与水分利用率研究

根据水量平衡方程式计算,雨养麦田5个试验麦季的耗水量分别为435.5、326.0、293.8、277.2和365.9mm,可代表该区过湿、一般和干旱年份的小麦耗水量.研究结果表明,小麦地上部分生物量与其总耗水量的相关关系不显着(r=0.67).在耗水量中,土壤储水的贡献占50%.在降雨少而土壤储水丰足的年份,其贡献高达60%,是小麦水分的重要来源.在充分施肥条件下,5个麦季的水分利用率≥11.25kg·ha^-1·mm^-1,表明适当增加肥料投入可提高农田水分利用率.     

Foliar water uptake: Processes,pathways, and integration into plant water budgets

Nearly all plant families, represented across most major biomes, absorb water directly through their leaves. This phenomenon is commonly referred to as foliar water uptake. Recent studies have suggested that foliar water uptake provides a significant water subsidy that can influence both plant water and carbon balance across multiple spatial and temporal scales. Despite this, our mechanistic understanding of when, where, how, and to what end water is absorbed through leaf surfaces remains limited. We first review the evidence for the biophysical conditions necessary for foliar water uptake to occur, focusing on the plant and atmospheric water potentials necessary to create a gradient for water flow. We then consider the different pathways for uptake, as well as the potential fates of the water once inside the leaf. Given that one fate of water from foliar uptake is to increase leaf water potentials and contribute to the demands of transpiration, we also provide a quantitative synthesis of observed rates of change in leaf water potential and total fluxes of water into the leaf. Finally, we identify critical research themes that should be addressed to effectively incorporate foliar water uptake into traditional frameworks of plant water movement.     

Developmental profiles in tick water balance with a focus on the new Rocky Mountain spotted fever vector, Rhipicephalus sanguineus

Recent reports indicate that the common brown dog tick, or kennel tick, Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) is a competent vector of Rocky Mountain spotted fever in the U.S.A. This tick is of concern to public health because of its high frequency of contact, as it has a unique ability to thrive within human homes. To assess the moisture requirements necessary for survival, water balance characteristics were determined for each developmental stage, from egg to adult. This is the first time that water relations in ticks have been assessed throughout the complete lifecycle. Notably, R. sanguineus is differentially adapted for life in a dry environment, as characterized by a suppressed water loss rate distinctive for each stage that distinguishes it from other ticks. Analysis of its dehydration tolerance limit and percentage body water content provides no evidence to suggest that the various stages of this tick can function more effectively containing less water, indicating that this species is modified for water conservation, not desiccation hardiness. All stages, eggs excepted, absorb water vapour from the air and can drink free water to replenish water stores. Developmentally, a shift in water balance strategies occurs in the transition from the larva, where the emphasis is on water gain (water vapour absorption from drier air), to the adult, where the emphasis is on water retention (low water loss rate). These results on the xerophilic-nature of R. sanguineus identify overhydration as the primary water stress, indicating that this tick is less dependent upon a moisture-rich habitat for survival, which matches its preference for a dry environment. We suggest that the controlled, host-confined conditions of homes and kennels have played a key role in promoting the ubiquitous distribution of R. sanguineus by creating isolated arid environments that enable this tick to establish within regions that are unfavourable for maintaining water balance.     

中国东北科尔沁沙地两种建群植物的抗旱机理

在土壤田间持水和干旱胁迫条件下,对冷蒿和差巴嘎蒿的多个抗旱性生理指标进行了测定,结果表明:1、在两种土壤水分状况下,冷蒿的水势低于差巴嘎蒿,水分相对亏缺、束缚水含量、束缚水与自由水比值、综合抗旱性指数均明显高于差巴嘎蒿,且胁迫前后冷蒿上述指标的变化幅度高于差巴嘎蒿。2、土壤田间持水量条件下冷蒿干物质累积量、硝态氮含量和硝酸还原酶活性高于差巴嘎蒿,可溶性蛋白质含量和叶绿素含量低于差巴嘎蒿。水分胁迫发生时,冷蒿蛋白质降解的幅度高于差嘎蒿;冷蒿体内脯氨酸的累积量可达胁迫前的8.2倍,差巴嘎蒿只达原来的2.2倍;冷蒿可溶性糖含量达胁迫前的1.29倍,差巴嘎蒿只达胁迫前的0.37倍;胁迫条件下冷蒿的叶绿素含量高于差巴嘎蒿。3、严酷的沙区环境条件下,冷蒿在一日内各时刻的蒸腾速率和水势均低于差巴嘎蒿,且日间波动平缓。     

Water permeation through the sodium-dependent galactose cotransporter vSGLT

It is well accepted that cotransporters facilitate water movement by two independent mechanisms: osmotic flow through a water channel in the protein and flow driven by ion/substrate cotransport. However, the molecular mechanism of transport-linked water flow is controversial. Some researchers believe that it occurs via cotransport, in which water is pumped along with the transported cargo, while others believe that flow is osmotic in response to an increase in intracellular osmolarity. In this letter, we report the results of a 200-ns molecular dynamics simulation of the sodium-dependent galactose cotransporter vSGLT. Our simulation shows that a significant number of water molecules cross the protein through the sugar-binding site in the presence as well as the absence of galactose, and 70-80 water molecules accompany galactose as it moves from the binding site into the intracellular space. During this event, the majority of water molecules in the pathway are unable to diffuse around the galactose, resulting in water in the inner half of the transporter being pushed into the intracellular space and replaced by extracellular water. Thus, our simulation supports the notion that cotransporters act as both passive water channels and active water pumps with the transported substrate acting as a piston to rectify the motion of water.     

A MECHANISTIC VIEW OF THE NON-IDEAL OSMOTIC AND MOTIONAL BEHAVIOR OF INTRACELLULAR WATER

It is commonly assumed that essentially all of the water in cells has the same ideal motional and colligative properties as does water in bulk liquid state. This assumption is used in studies of volume regulation, transmembrane movement of solutes and electrical potentials, solute and solution motion, solute solubility and other phenomena. To get at the extent and the source of non-ideally behaved water (an operational term dependent on the measurement method), we studied the motional and colligative properties of water in cells, in solutions of amino acids and glycine peptides whose surface characteristics are known, and in solution of bovine serum albumin, hemoglobin and some synthetic polypeptides. Solutions of individual amino acids with progressively larger hydrophobic side chains showed one perturbed water molecule (structured-slowed in motion) per nine square angstroms of hydrophobic surface area. Water molecules adjacent to hydrophobic surfaces form pentagonal structural arrays, as shown by X-ray diffraction studies, that are reported to be disrupted by heat, electric field, hydrostatic pressure and phosphorylation state. Hydrophilic amino acids demonstrated water destructuring (increased motion) that was attributed to dielectric realignment of dipolar water molecules in the electric field between charge groups. In solutions of proteins, several methods indicate the equivalent of 2–8 layers of structured water molecules extending beyond the protein surface, and we have recently demonstrated that induced protein conformational change modifies the extent of non-ideally behaved water. Water self-diffusion rate as measured in three different cell types was about half that of bulk water, indicating that most of the water in these cells was slower in motion than bulk water. In different cell types the extent of osmotically perturbed water ranged from less than half to almost all of the intracellular water. The assumption that essentially all intracellular water has ideal osmotic and motional behavior is not supported by the experimental findings. The non-ideality of cell water is an operational term. Therefore, the amount of non-ideally behaving water is dependent on the characteristics of water targeted, i.e. the measurement method, and a large fraction of it is explainable in mechanistic terms at a molecular level based on solute—solvent interactions.     

Go with the flow: mechanisms driving water transport during vegetative growth and fruiting

Fungi need water for all stages of life. Notably, mushrooms consist of ∼90% water. Fungi degrade organic matter by secreting enzymes. These enzymes need water to be able to break down the substrate. For instance, when the substrate is too dry, fungi transport water from moist areas to arid areas by hydraulic redistribution. Once nutrients are freed from the substrate, they are taken up by transporters lining the cell membrane. Thereby an intracellular osmotic potential is created which is greater than that of the substrate, and water follows by osmosis. Aquaporins may facilitate water uptake depending on the conditions. Since fungi possess a cell wall, the cell volume will not increase much by water uptake, but the cell membrane will exert higher pressure on the cell wall, thereby building up turgor. Fungi have tightly coordinated osmotic regulatory controls via the HOG pathway. When water is getting scarce, this pathway makes sure that enough osmolytes are synthesized to allow sufficient water uptake for maintaining turgor homeostasis. The fungal network is interconnected and allows water flow when small pressure differences exist. These pressure differences can be the result of growth, differential osmolyte uptake/synthesis or external osmotic conditions. Overall, the water potential of the substrate and of fungal tissues determine whether water will flow, since water flows from an area of high- to a low water potential area, when unobstructed. In this review we aim to give a comprehensive view on how fungi obtain and translocate water needed for their development. We have taken Agaricus bisporus growing on compost and casing soil as a case study, to discuss water relations during fruiting in detail. Using the current state-of-the-art we found that there is a discrepancy between the models describing water transport to mushrooms and the story that water potentials tell us.     

不同土壤水分状况对杨树、沙棘水分关系及生长的影响

在盆栽条件下对杨树、沙棘进行了3种土壤水分处理,研究结果表明：沙棘的叶含水率在同一土壤水分下比杨树高、而水势低,说明沙棘叶的抗旱保水能力强于杨树;沙棘单叶的光合速率能够长时间维持在较高的水平,蒸腾速率却并非如此。杨树无论在生长初期,还是生长中期其单叶WUE均高于沙棘。以新生枝生物量／耗水总量计算的整体WUE在3种土壤水分条件下,杨树的WUE分别是沙棘的2．4倍、2．3倍、2倍,其差异达极显著水平,但在3种土壤水分条件下2个树种都以中度亏缺下的水分利用率最高。整个生长季节处在严重干旱下的杨树和沙棘的生长均受到显著影响,沙棘生长受干旱影响程度小于杨树,从整个生长趋势上看杨树适宜于良好水分下的生长,沙棘在适宜水分和中度亏缺下均可良好生长。     

上升流和水团对浙江中部近海浮游动物生态类群分布的影响

依据2010年4月、7月和11月对浙江中部近海上升流海域进行的海洋调查资料,运用定量、定性方法,探讨了上升流对该海域浮游动物生态类群分布的影响.结果表明:3个季节共鉴定浮游动物64种,桡足类占主要优势,包括5个生态类群,分别是暖温带近海种、暖温带外海种、亚热带近海种、亚热带外海种和热带大洋种.在种类数组成上,春季以暖温带近海种为主,夏季则是亚热带近海种和亚热带外海种居多,秋季也是亚热带种居多,其中夏季暖温带种种类数要高于春季和秋季,这一现象与同时期东黄海沿海有所不同,主要是由于上升流将一些在海洋底部度夏的暖温种带至海洋表面造成的.此外,3个季节生态类群都是以近海种为主,表明沿岸流是影响这一海域的最主要的水团.在丰度组成上,4月暖温带近海种占总丰度的98.79％,7月暖温带近海种也是组成丰度的重要部分,10月则是亚热带近海种丰度最高.丰度组成所反映的规律与种类数组成规律一致.上升流的存在导致夏季近海暖温带种大量出现,是影响这一海域浮游动物生态类群组成的重要因素;受长江径流和椒江径流的影响,近海种成为主要生态类群,是这一海域浮游动物的一个重要的生态特征.     

长白山暗针叶林苔藓枯落物层的降雨截留过程

对长白山北坡暗针叶林地面苔藓枯落物层 (苔藓植物和枯落叶交织而成的层状结构 )持水能力、截留降雨过程及动态变化进行了研究。结果表明苔藓枯落物层持水能力很强 ,最大持水量相当于 4 .8mm的降雨量 ,这个结果大于将苔藓与枯落物分开来测定的结果之和 ,说明成层结构能够提高持水能力。在一次降雨过程中对降雨截留过程的观测发现 :持水量刚开始随降雨增加而增加 ,到一定量时 ,降雨再增加 ,持水量反而缓慢下降。对持水动态变化一个月的观测 ,表明苔藓枯落物层水分蒸发较快 ,当长时间无雨时 ,持水量显著下降 ,当降雨再次发生时 ,持水量迅速回升 ,这种动态过程伴随着降雨的发生而不断往复。此外 ,在夜间苔藓枯落物层有吸收空气中水气的特点 ,吸收量受空气湿度的影响     

Evaluation of water footprint and economic water productivities of dairy products of South Africa

Assessment of water footprint sustainability indicators and economic water productivities is regarded as a cornerstone of the world’s sustainability goal and the reduction of the fresh water scarcity risk. These assessments are gaining much prominence because about four billion people face severe water scarcity, globally. Attaining sustainable and economically efficient water use goals requires a thorough assessment of all the existing sectors that use water. This paper examined the water footprint and economic water productivities of dairy products in South Africa for the periods 1996–2005 and 2006–2013 using the water footprint network assessment methodology. We found the total water footprints of all the selected dairy products in South Africa to be higher than the global averages are. During the period of 1996–2005, South African dairy producers utilized more green water in their dairy production. The production of butter and cheese products, whether grated or not grated, powdered or not powdered, blue-veined and cheese of all kinds had the highest total water footprints among all the dairy products in South Africa. Dairy production under a sole grazing system has high water footprints and low economic water productivities, relative to mixed production systems, for the period 2006–2013. With blue water becoming scarcer in South Africa, it is time for dairy livestock producers to shift their production to a system that is highly productive and has low water footprints. The water footprints of most of the dairy products for period 2006–2013 have reduced by varying amounts, relative to 1996–2005, which shows that water users along the dairy industry chains are managing water cautiously. Our findings have revealed dairy products that have high economic water productivities, and suggest that profit maximising and environmentally sustainable dairy producers and water users should integrate both blue water sustainability and economic water productivity indicators in their production decisions.     

Catalysis and thermostability of mitochondrial F1-ATPase in toluene-phospholipid-low-water systems

Soluble mitochondrial F1-ATPase from bovine heart can be transferred to systems composed of a nonpolar solvent (toluene), phospholipid, and water at concentrations between 0.02 and 0.05% (volume of water per volume toluene). In these systems, F1 becomes resistant to cold denaturation and acquires a remarkable thermostability; i.e., its half-life at 70 degrees C is more than 24 h. Thermostability is due to the low content of water, since increases of water concentration bring about a progressive decrease in thermostability. At 0.04% water, the enzyme fails to catalyze a single splitting of ATP per enzyme. Gradual increases in water concentration up to 2.5% result in a progressive increase of hydrolytic activity. However, even at 2.5% water, the activity is orders of magnitude lower than in totally aqueous media. At various concentrations of water (0.1-2.5% v/v) and Mg-ATP, it was found that water affects the Vmax, but not the Km. The results show that, at levels of water below 0.04% (v/v), the enzyme is in a state that does not carry out catalysis and possesses high thermostability. As the water content is increased, the enzyme acquires the progressive flexibility that is required for catalysis and for undergoing rapid thermal denaturation.     

三种苗木在不同供水条件下生理适应性及耗水特性研究

选用君迁子、臭椿、白榆三个树种苗木,在盆栽条件下,控制三种土壤含水量,研究其适应性和耗水特性。结果表明,白榆适应能力最强,其次为臭椿,而君迁子最弱,在耗水量上基本接近,但耗水系数差异明显,主要是由于三个树种在不同水分条件下物质累积量不同。     

Oxygen isotope ratios between soil water and stem water of trees in pot experiments

Since the oxygen isotopic ratio of water extracted from stems reflects that of water taken up by roots, the stem water isotope ratio can be used to analyze the source of water for plant growth. However, it is known that the fractionation of isotopes during evaporation from the surface soil increases the isotope ratio in soil water drastically. In this study, it was experimentally confirmed that the stem water of Elaeocarpus sylvestris vs. ellipticus Hara seedlings is not isotopically similar to the water source in the case where evaporation from the soil occurs actively. However, since water in these plant bodies was replaced in about 2 days in the pot experiments, the 2-day-averaged values of the soil water isotope ratio approached the stem water isotope ratio. Thus, time-course samplings of the soil and stems, and measurements of the replacement time of water in the plant body (water volume in plant/transpiration rate) are recommended for correct interpretation of the isotopic signature of soil water and stem water.     

Ames试验在水质检测方面的应用

近年来 ,水体污染日趋严重 ,各国学者从氯化后饮水中分离出多种致突变、致癌物质。为此我们采用Ames试验 ,对珠江流域主要取水点的水源水和对应自来水中的有机致突变物污染情况进行了研究。研究表明 ,部分取水点的有机致突变物污染较严重 ,并且氯化消毒后自来水的致突性大于水源水的致突性。因而 ,加强饮水中致突变物质的检测 ,改进净水消毒剂和净水流程很有必要。     

Electrical conduction in collagen. II. Some aspects of hydration

Determinations of the amount of bound water in hydrated proteins yield strongly diverging values. The cause of this is the continuity of the transition from bound to free water, and the diffeernt sensitivities to water structure of the measuring techniques. Only the methods that aim at the determination of the amount of water, whose phase remians unchanged duing freezing, yield similar values. The value for collagen as deduced from conductivity data is about 50% water of the dry weight. It is believed that this water interacts with adsorptive groups on the macromolecules, whereas the freezable water occurs in capillaries.