How do water transport and water storage differ in coniferous earlywood and latewood?

The goal of this research project was to determine the water transport behaviour of earlywood versus latewood in the trunk of 21-year-old Douglas-fir [Pseudostuga menziesii (Mirb.) Franco] trees. Specific conductivity (k(s)) and the vulnerability of xylem to embolism were measured on a single growth ring and in a subset of earlywood and latewood samples within the same ring. Earlywood/latewood ratio, trunk water potential (Psi) and relative water content (RWC) were used to predict differences in conductivities and vulnerability to embolism. Earlywood has about 11 times the k(s) of latewood, and up to 90% of the total flow occurred through the earlywood. Earlywood's vulnerability to embolism followed the same trend as that of the whole wood, with 50% loss of conductivity at -2.2 MPa (P(50)). Latewood was more vulnerable to embolism than earlywood at high Psi, but as Psi decreased, the latewood showed very little further embolism, with a P(50) <-5.0 MPa. The lowest trunk Psi estimated in the field was about -1.4 MPa, indicating that latewood and earlywood in the field experienced about 42% and 16% loss of k(s), respectively. The higher vulnerability to embolism in latewood than in earlywood at field Psi was associated with higher water storage capacity (21.8% RWC MPa(-1) versus 4.1% RWC MPa(-1), latewood and earlywood, respectively). The shape of the vulnerability curve suggests that air seeding through latewood may occur directly through pores in the margo and seal off at lower pressure than earlywood pores.     

Water Footprint Symposium: where next for water footprint and water assessment methodology?

Recognizing the need for a comprehensive review of the tools and metrics for the quantification and assessment of water footprints, and allowing for the opportunity for open discussion on the challenges and future of water footprinting methodology, an international symposium on water footprint was organized. The Water Footprint Symposium was held in December 2013 at the University of Leeds, UK. In particular, four areas were highlighted for discussion: water footprint and agriculture, quantification of water footprint, industrial water footprint, and from theory to practice. Discussion was organized to focus on the “prioritization of water footprint research & applications to practical sectors”. The concept of water footprinting has helped to better communicate water management and assessment among different research and user communities. Significant research progress has been made in the relations between water footprint and agriculture, quantification of water footprint, industrial water footprint, and the transition from theory to practice. Future water footprint research needs to further enhance assessment accuracy, improve sustainability assessment methodology, develop databases, address uncertainties, and prioritize application by government and in practical sectors. More information on the symposium can be found on the water@leeds website: http://www.wateratleeds.org/conferences/2013/water-footprint-symposium.     

Does pre-dawn water potential reflect conditions of equilibrium in plant and soil water status?

Variation in base water potential (Ψ_b, a daily maximum level of plant water potential, which is presumed to correspond to the equilibrium between soil and plant water potentials) was examined in shoots of Picea abies and Vaccinium myrtillus with respect to soil (available water storage, water potential, temperature) and atmospheric (temperature, relative humidity, vapour pressure deficit) conditions. The available soil water storage (W_tr) accounted for 77% of the dynamics of Ψ_b, while the influence of atmospheric factors became evident under high evaporative demand. Ψ_b was not always observable immediately before dawn, but on 30% of observation days, the recovery continued up to an hour or two after dawn. Full equilibrium between soil and plant water potentials in P. abies in northern conditions is rather improbable by dawn in summer-time, because of the shortness of the dark period and probable night-time transpiration in the case of high atmospheric vapour pressure deficit.     

Are hot-spots occluded from water?

Protein–protein interactions are the basis of many biological processes and are governed by focused regions with high binding affinities, the warm- and hot-spots. It was proposed that these regions are surrounded by areas with higher packing density leading to solvent exclusion around them – “the O-ring theory.” This important inference still lacks sufficient demonstration. We have used Molecular Dynamics (MD) simulations to investigate the validity of the O-ring theory in the context of the conformational flexibility of the proteins, which is critical for function, in general, and for interaction with water, in particular. The MD results were analyzed for a variety of solvent-accessible surface area (SASA) features, radial distribution functions (RDFs), protein–water distances, and water residence times. The measurement of the average solvent-accessible surface area features for the warm- and hot-spots and the null-spots, as well as data for corresponding RDFs, identify distinct properties for these two sets of residues. Warm- and hot-spots are found to be occluded from the solvent. However, it has to be borne in mind that water-mediated interactions have significant power to construct an extensive and strongly bonded interface. We observed that warm- and hot-spots tend to form hydrogen bond (H-bond) networks with water molecules that have an occupancy around 90%. This study provides strong evidence in support of the O-ring theory and the results show that hot-spots are indeed protected from the bulk solvent. Nevertheless, the warm- and hot-spots still make water-mediated contacts, which are also important for protein–protein binding.     

Exploration and determination of algal role as Bioindicator to evaluate water quality – Probing fresh water algae

ObjectivesTo explore the algal floral diversity and its role to determine water quality.MethodsThe regular monthly collection of algal and water samples was made during 2018. Unicellular algae were preserved in 2 to 3% formalin while macroalgae in 4% formalin. Microphotographs of algae were taken at the biotechnological Lab of PCSIR Lahore, Pakistan. Palmer pollution index was used to determine water quality.ResultsThe study identified 201 algal species distributed among 57 genera, 42 families, 25 orders, 10 classes and 7 divisions. The total score of Algal Genus Pollution Index of Banjosa Lake, Ali Sojal Dam, Dothan Dam, Drake Dam and Rawalakot Nullah (city) were 14, 9, 10, 18 and 25 respectively. It was revealed that Banjosa Lake has probable organic pollution, Ali Sojal Dam and Dothan Dam showed lack of organic pollution, Drake Dam indicated moderate pollution while Rawalakot Nullah (City) indicated confirm high organic pollution.ConclusionWe strongly recommend the conservation and managed status of algal species for sustainable resource of algal- derived products in future. It was revealed that the water quality of Banjosa Lake, Drak Dam and Rawalakot Nullah was affected from anthropogenic activities and needs to be managed.     

Norwegian water quality criteria — ecosystems approach

General water quality criteria for Norwegian Waters were developed by the State Pollution Control Authority in the earch 1980s. The need for further refinement of these criteria became apparent in the mid-1980s. New water quality criteria were developed in conjunction with the development of a system for assessment of water uses. Two fundamental principles are outlined for determining the classification of water quality in Norway:

1. The classification for polluted water. The basis for this system is the natural water quality without any form of influence from man. It is the influence of pollution on the water quality, or the difference between the natural water quality and the water quality today that is classified.
2. The system for assessment of water quality for various uses is based both on the existing water quality and some physical and practical properties of the environment. The water quality criteria are specific for various uses.

Comprehensive planning in Norway should include physical planning and areal planning of rivers, lakes, and coastal areas. Water use planning will become an indtegral part of comprehensive master planning. This paper describes the system for assessment of water resources uses. Explaining the principles of the system is the main feature of this paper.     

Do water molecules mediate protein-DNA recognition?

A comprehensive analysis of interfacial water molecules in the structures of 109 unique protein-DNA complexes is presented together with a new view on their role in protein-DNA recognition. Location of interfacial water molecules as reported in the crystal structures and as emerging from a series of molecular dynamics studies on protein-DNA complexes with explicit solvent and counterions, was analyzed based on their acceptor, donor hydrogen bond relationships with the atoms and residues of the macromolecules, electrostatic field calculations and packing density considerations. Water molecules for the purpose of this study have been categorized into four classes: viz. (I) those that contact both the protein and the DNA simultaneously and thus mediate recognition directly; (II) those that contact either the protein or the DNA exclusively via hydrogen bonds solvating each solute separately; (III) those that contact the hydrophobic groups in either the protein or the DNA; and, lastly (IV) those that contact another water molecule. Of the 17,963 crystallographic water molecules under examination, about 6% belong to class I and 76% belong to class II. About three-fourths of class I and class II water molecules are exclusively associated with hydrogen bond acceptor atoms of both protein and DNA. Noting that DNA is polyanionic, it is significant that a majority of the crystallographically observed water molecules as well as those from molecular dynamics simulations should be involved in facilitating binding by screening unfavorable electrostatics. Less than 2% of the reported water molecules occur between hydrogen bond donor atoms of protein and acceptor atoms of DNA. These represent cases where protein atoms cannot reach out to DNA to make favorable hydrogen bond interactions due to packing/structural restrictions and interfacial water molecules provide an extension to side-chains to accomplish hydrogen bonding.     

Behaviour during elevated water temperatures: can physiology explain movement of juvenile Atlantic salmon to cool water?

1. Temperature governs most physiological processes in animals. Ectotherms behaviourally thermoregulate by selecting habitats with temperatures regulating their body temperature for optimal physiological functioning. However, ectotherms can experience temperature extremes forcing the organisms to seek temperature refuge. 2. Fish actively avoid potentially lethal temperatures by moving to cool-water sites created by inflowing tributaries and groundwater seeps. Juvenile Atlantic salmon (Salmo salar) of different age classes exhibit different behavioural responses to elevated temperatures (>23 °C). Yearling (1+) and 2-year-old (2+) Atlantic salmon often cease feeding, abandon territorial behaviour and swim continuously in aggregations in cool-water sites; whereas young-of-the-year (0+) fish continue defending territories and foraging. 3. This study determined whether the behavioural shift in older individuals (2+) occurred when basal metabolic rate, driven by increasing water temperature, reached the maximum metabolic rate such that anaerobic pathways were recruited to provide energy to support vital processes. Behaviour (feeding and stress responses), oxygen consumption, muscle lactate and glycogen, and circulating blood lactate and glucose concentrations were measured in wild 0+ and 2+ Atlantic salmon acclimated to water temperatures between 16 and 28 °C. 4. Results indicate that oxygen consumption of the 2+ fish increased with temperature and reached a plateau at 24 °C, a temperature that corresponded to cessation of feeding and a significant increase in muscle and blood lactate levels. By contrast, oxygen consumption in 0+ fish did not reach a plateau, feeding continued and muscle lactate did not increase, even at the highest temperatures tested (28 °C). 5. To conclude, the experiment demonstrated that the 0+ and 2+ fish had different physiological responses to the elevated water temperatures. The results suggest that wild 2+ Atlantic salmon employ behavioural responses (e.g. movement to cool-water sites) at elevated temperatures in an effort to mitigate physiological imbalances associated with an inability to support basal metabolism through aerobic metabolic processes.     

Does water activity rule P. mirabilis periodic swarming? II. Viscoelasticity and water balance during swarming

Following the analysis of the biochemical and functional properties of the P. mirabilis extra cellular matrix performed in the first part of this study, the viscoelasticity of an actively growing colony was investigated in relation to water activity. The results demonstrate that the P. mirabilis colony exhibits a marked viscoelastic character likely due to both cell rafts and exoproduct H-bond networks. Besides, the water loss by evaporation during migration has been measured, whereas the experimental determination of the water diffusion coefficient in agar has allowed us to estimate the net water influx at the agar/colony interface. These data drive us to propose that a periodic increase of the water activity at the colony's periphery, mainly due to the drastic surface to volume ratio increase associated with swarming, causes the periodic and synchronous cessation of migration through the dissociation of exoproduct networks, which in turn strongly alters the matrix viscoelasticity.     

How do salinity and water stress affect transport of water,assimilates and ions to tomato fruits?

The study was conducted in order to determine whether water stress affects the accumulation of dry matter in tomato fruits similarly to salinity, and whether the increase in fruit dry matter content is solely a result of the decrease in water content. Although the rate of water transport to tomato fruits decreased throughout the entire season in saline water irrigated plants, accumulation rates of dry matter increased significantly. Phloem water transport contributed 80–85% of the total water transport in the control and water-stressed plants, and over 90% under salinity. The concentration of organic compounds in the phloem sap was increased by 40% by salinity. The rate of ions transported via the xylem was also significantly increased by salinity, but their contribution to fruit osmotic adjustment was less. The rate of fruit transpiration was also markedly reduced by salinity. Water stress also decreased the rate of water transport to the tomato fruit and increased the rate of dry matter accumulation, but much less than salinity. The similar changes, 10–15%, indicate that the rise in dry matter accumulation was a result of the decrease in water transport. Other parameters such as fruit transpiration rates, phloem and xylem sap concentration, relative transport via phloem and xylem, solutes contributing to osmotic adjustment of fruits and leaves, were only slightly affected by water stress. The smaller response of these parameters to water stress as compared to salinity could not be attributed to milder stress intensity, as leaf water potential was found to be more negative. Measuring fruit growth of girdled trusses, in which phloem flow was inactive, and comparing it with ungirdled trusses validated the mechanistic model. The relative transport of girdled as compared to ungirdled fruits resembled the calculated values of xylem transport.     

Cubic phases of ternary amphiphile–water systems

The reversed cubic phases (Q_II) are a class of self-assembled amphiphile–water structures that are rich in diversity and structural complexity. These nanostructured liquid crystalline materials are generating much interest owing to their unique surface morphology, biological relevance and potential technological and medical applications. The structure of Q_II phases in binary amphiphile–water systems is affected by the molecular structure of surfactant, water content, temperature and pressure. The presence of additives also plays an important role. The structure and phase behaviour of ternary Q_II phases, which are comprised of two miscible amphiphiles and water, significantly differ from the binary system alone. The modulation of the phase behaviour through the addition of a second amphiphile offers an opportunity to control the size and shape of the nanostructures using a ‘bottom-up’ approach. In this mini-review, we discuss the structure of reversed cubic phases of amphiphile–water systems and highlight the modulation of cubic-phase structure in ternary-phase systems. We also extend this review to bulk cubic phases and the corresponding nanoscale dispersions, cubic-phase nanoparticles.     

The energy–water nexus: are there tradeoffs between residential energy and water consumption in arid cities?

Water scarcity, energy consumption, and air temperature regulation are three critical resource and environmental challenges linked to urban population growth. While appliance efficiency continues to increase, today’s homes are larger and residents are using more energy-consuming devices. Recent research has often described the energy–water nexus as a “tradeoff” between energy and water due to reduced temperatures resulting from irrigated vegetation. Accordingly, some arid cities have implemented landscape-conversion programs that encourage homeowners to convert their yards from grass (mesic) to drought-tolerant (xeric) landscapes to help conserve water resources. We investigated these relationships in Phoenix, Arizona by examining energy and water data for the summer months of June–September 2005 while temperature variability was analyzed from a local heat wave. Results show parallel consumption patterns with energy and water use strongly correlated and newer homes using more of both. The counterintuitive findings show that “drought-resistant” models may not be beneficial for community health, environment, or economics and that this issue is further complicated by socio-economic variables.     

Could biofuel development stress China's water resources?

Concerns over energy shortages and global climate change have stimulated developments toward renewable energy. Biofuels have been developed to replace fossil fuels to reduce the emissions of greenhouse gases and other environmental impacts. However, food security and water scarcity are other growing concerns, and the increased production of biofuels may increase these problems. This study focuses on whether biofuel development would stress China's water resources. Cassava‐based fuel ethanol and sweet sorghum‐based fuel ethanol are the focus of this study because they are the most typical nongrain biofuels in China. The spatial distribution of the total water requirement of fuel ethanol over its life cycle process was simulated using a biophysical biogeochemical model and marginal land as one of the types of input data for the model to avoid impacts on food security. The total water requirement of fuel ethanol was then compared with the spatial distribution of water resources, and the influence of the development of fuel ethanol on water resources at the pixel and river basin region scales was analyzed. The result showed that the total water requirement of fuel ethanol ranges from 37.81 to 862.29 mm. However, considering water resource restrictions, not all of the marginal land is suitable for the development of fuel ethanol. Approximately 0.664 million km² of marginal land is suitable for the development of fuel ethanol, most of which is located in the south of China, where water resources are plentiful. For these areas, the value of fuel ethanol's water footprint ranges from 0.05 to 11.90 m³ MJ^?1. From the water point of view, Liaoning province, Guizhou province, Anhui province and Hunan province can be given priority for the development of fuel ethanol.     

How do membrane proteins sense water stress?

Maintenance of cell turgor is a prerequisite for almost any form of life as it provides a mechanical force for the expansion of the cell envelope. As changes in extracellular osmolality will have similar physicochemical effects on cells from all biological kingdoms, the responses to osmotic stress may be alike in all organisms. The primary response of bacteria to osmotic upshifts involves the activation of transporters, to effect the rapid accumulation of osmoprotectants, and sensor kinases, to increase the transport and/or biosynthetic capacity for these solutes. Upon osmotic downshift, the excess of cytoplasmic solutes is released via mechanosensitive channel proteins. A number of breakthroughs in the last one or two years have led to tremendous advances in our understanding of the molecular mechanisms of osmosensing in bacteria. The possible mechanisms of osmosensing, and the actual evidence for a particular mechanism, are presented for well studied, osmoregulated transport systems, sensor kinases and mechanosensitive channel proteins. The emerging picture is that intracellular ionic solutes (or ionic strength) serve as a signal for the activation of the upshift-activated transporters and sensor kinases. For at least one system, there is strong evidence that the signal is transduced to the protein complex via alterations in the protein-lipid interactions rather than direct sensing of ion concentration or ionic strength by the proteins. The osmotic downshift-activated mechanosensitive channels, on the other hand, sense tension in the membrane but other factors such as hydration state of the protein may affect the equilibrium between open and closed states of the proteins.     

Ribozyme catalysis revisited: is water involved?

Enzymatic catalysis by RNA was discovered 25 years ago, yet mechanistic insights are emerging only slowly. Thought to be metalloenzymes at first, some ribozymes proved more versatile than anticipated when shown to utilize their own functional groups for catalysis. Recent evidence suggests that some may also judiciously place structural water molecules to shuttle protons in acid-base catalyzed reactions.     

Pharmaceuticals: a threat to drinking water?

Recently, considerable interest has developed regarding the presence of pharmaceuticals in the environment, but there has been comparatively little study on the potential of these substances to enter potable supplies. This is surprising because drinking water would provide a direct route into the body for any drugs that might be present. Although many countries employ advanced treatments, such as granular activated carbon, membrane technologies, ozonation and ultraviolet radiation, for treating water intended for human consumption, some compounds have been shown to be unaffected by such processes. Here, we examine the levels of drug substances reported in drinking water around the world. The possible implications of the presence of these compounds are highlighted and assessed, and recommendations are made for further research.     

Halogen–water–hydrogen bridges in biomolecules

The importance of water in biological systems has long been recognized in chemistry and biology communities. In this article we describe a new manner by which water affects biomolecular behaviors, called halogen–water–hydrogen bridge (XWH bridge), that is, one hydrogen bonding (H-bonding) in water-mediated H-bond bridge is replaced by halogen bonding (X-bonding). Although behaving similarly to water-mediated H-bond motif, the XWH bridge usually stands in multifurcated forms and possesses stronger directionality. Quantum mechanical analysis on several model and real systems reveals that the XWH bridges are more thermodynamically stable than other water-involved interactions, and this stability is further enhanced by the cooperation of X-bonding and H-bonding. Crystal structure survey clearly demonstrates the significance of XWH bridges in stabilization of biomolecular conformations and in mediation of protein–protein, protein–nucleic acid, and receptor–ligand recognition and binding. These findings shed light into the potential value of XWH bridges in drug design and biological engineering.