Atmospheric Water Uptake Research Articles

Foliar water uptake improves branch water potential and photosynthetic capacity in Calligonum mongolicum

Atmospheric water is among the most important water sources for plants in arid ecosystems and plays an important role in facilitating drought stress survival in plants. However, little is known about the specific physiological benefits of foliar water uptake (FWU) for woody plants inhabiting arid desert areas. The objective of this study was to explore the physiological responses of Calligonum mongolicum to atmospheric water uptake by the assimilating branches, with a special focus on the FWU effect on shoot water status and photosynthesis. To this end, the canopies of natural C. mongolicum plants in a desert region of northwestern China were humidified in a field in-situ misting experiment and a long-term wetting experiment, during which physiological measurements of plant water relations and photosynthetic capacity were performed, alongside the observation of FWU by H218O isotopic tracing. Following the in-situ misting experiment, the water potential of the assimilating branches was significantly higher than that of the secondary branches at midnight, suggesting that FWU resulted in a reverse water potential gradient in C. mongolicum at the branch level. The 18O isotope was markedly enriched in the assimilating branches, secondary branches, and trunk xylem following the foliar uptake of 18O labeled water, indicating that the water uptake from the atmosphere by the assimilating branches could replenish the stem. The relative water content and water potential of the assimilating branches were significantly increased by FWU. The net photosynthetic rate, stomatal conductance, and maximum photochemical efficiency of C. mongolicum plants were markedly increased following the wetting treatment. Our results clearly show that C. mongolicum is capable of FWU, and that the absorbed water could be transported downward through the xylem and improve the branch water status and photosynthetic capacity. These findings provide a new perspective for deepening our understanding of the drought survival mechanism of plants in arid environments.

Harvesting water from unsaturated atmospheres: deliquescence of salt secreted onto leaf surfaces drives reverse sap flow in a dominant arid climate mangrove, Avicennia marina.

The mangrove Avicennia marina adjusts internal salt concentrations by foliar salt secretion. Deliquescence of accumulated salt causes leaf wetting that may provide a water source for salt-secreting plants in arid coastal wetlands where high nocturnal humidity can usually support deliquescence whereas rainfall events are rare. We tested the hypotheses that salt deliquescence on leaf surfaces can drive top-down rehydration, and that such absorption of moisture from unsaturated atmospheres makes a functional contribution to dry season shoot water balances. Sap flow and water relations were monitored to assess the uptake of atmospheric water by branches during shoot wetting events under natural and manipulated microclimatic conditions. Reverse sap flow rates increased with increasing relative humidity from 70% to 89%, consistent with function of salt deliquescence in harvesting moisture from unsaturated atmospheres. Top-down rehydration elevated branch water potentials above those possible from root water uptake, subsidising transpiration rates and reducing branch vulnerability to hydraulic failure in the subsequent photoperiod. Absorption of atmospheric moisture harvested through deliquescence of salt on leaf surfaces enhances water balances of Avicennia marina growing in hypersaline wetlands under arid climatic conditions. Top-down rehydration from these frequent, low intensity wetting events contributes to prevention of carbon starvation and hydraulic failure during drought.

Reconciling atmospheric water uptake by hydrate forming salts.

Magnesium and calcium chloride salts contribute to the global atmospheric aerosol burden via emission of sea spray and mineral dust. Their influence on aerosol hygroscopicity and cloud forming potential is important but uncertain with ambiguities between results reported in the literature. To address this, we have conducted measurements of the hygroscopic growth and critical supersaturation of dried, size selected nano-particles made from aqueous solution droplets of MgCl2 and CaCl2, respectively, and compare experimentally derived values with results from state-of-the-art thermodynamic modelling. It is characteristic of both MgCl2 and CaCl2 salts that they bind water in the form of hydrates under a range of ambient conditions. We discuss how hydrate formation affects the particles' water uptake and provide an expression for hydrate correction factors needed in calculations of hygroscopic growth factors, critical super-saturations, and derived κ values of particles containing hydrate forming salts. We demonstrate the importance of accounting for hydrate forming salts when predicting hygroscopic properties of sea spray aerosol.

Equivalence of foliar water uptake and stomatal conductance?

Foliar water uptake, FWU, the uptake of atmospheric water directly into leaves, has been reported to occur in nearly 200 species spanning a wide range of ecosystems distributed globally. In order to represent FWU in land‐surface models, a conductance term is required to scale the process to the canopy level. Here we show that conductance to FWU is theoretically equivalent to stomatal conductance and that under commonly occurring conditions vapour could diffuse into leaves at rates equivalent to those reported as FWU. We therefore conclude that such ‘reverse transpiration’ could partially, or even wholly, account for FWU in some plants.

Application of fiber optic reflectance spectroscopy for the detection of historical glass deterioration

AbstractHistorical alkali silicate glass is prone to deterioration over time due to the uptake of atmospheric water and subsequent hydrolysis of the silicate matrix. Recent studies of historical glass have provided insight into the mechanism of alteration; however, few techniques can assess early onset glass alteration noninvasively. Herein, we present fiber optic reflectance spectroscopy (FORS) as an invaluable tool to analyze historical glass alteration. We study a series of artificially aged model potash glasses and assess the nature of the alkali‐depleted alteration layer by microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy, and FORS. We find that the model glass FORS spectra demonstrate peaks associated with hydroxide, liquid‐like water, and bound water. FORS was able to detect an alteration layer as thin as 0.66 µm. The model glass data were then used to generate a hydration thickness prediction curve in order to predict the alteration layer thickness of twenty‐one 19th‐century glass flutes of similar composition. In the one case that an actual flute sample was available, the predicted value was in good agreement with previous SEM measurement. The results indicate the ability of FORS to noninvasively assess glass deterioration and to understand the nature of absorbed water in historical glass objects.

Improving the Oxidative Stability of Shape Memory Polyurethanes Containing Tertiary Amines by the Presence of Isocyanurate Triols

Shape memory polymers (SMPs) have been proposed for a wide variety of biomedical applications, such as cerebrovascular aneurysm occlusion; however, risks associated with degradation byproduct formation have raised the need for more biostable formulations. In this study, the use of cyclized isocyanates, in the form of isocyanurate-containing alcohols, was examined in aliphatic SMPs as a method of improving biostability. The materials were investigated for thermomechanical behavior, shape memory response, biostability, and cytocompatibility. In vitro experiments indicated that the isocyanurate-containing porous SMPs possess similar mechanical properties, albeit with improved toughness and no impact to strain recovery shape memory behavior, although atmospheric water uptake increased. Importantly, SMP life span was greatly increased, as control materials were demonstrated to fully degrade in accelerated testing by 25 days, while the modified materials retain more than 90% of their original mass. These modifi...

Influence of atmospheric water uptake on the hydrolysis of stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate

Abstract In this paper we report on the influence of water uptake on the hydrolysis of anhydrous stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py 1,4 ]TfO) under ambient atmosphere. The effect of water uptake on the electrodeposition of tin in the employed ionic liquid containing 0.1 M SnCl 2 was also demonstrated. The hydrolysis products as well as the Sn electrodeposits were characterized by different techniques comprising; scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results show that the employed ionic liquid electrolyte strongly absorbs water under ambient conditions. Colloidal particles were formed in the electrolyte after an exposure time of about 4 weeks as a result of the hydrolysis of Sn(II) species. The electrochemical behaviour of the employed electrolyte and the morphology of tin electrodeposits were significantly influenced by the presence of water. Tin dendrites were obtained from IL-electrolyte exposed to air for one month, whereas dendrite free deposits were formed in the freshly prepared electrolyte.

Trichome-like emergences in Croton of Brazilian highland rock outcrops: Evidences for atmospheric water uptake

Background and aimsAlthough trichomes are typical features of the species-rich genus Croton, little is known about their development, anatomical structure and function. This study aims to characterize the anatomy of leaf trichomes of three Croton species restricted to Brazilian rock outcrops, and investigate their functional role in an environment with limited soil water availability. MethodsSamples of leaves at different stages of maturity were submitted to standard anatomical light and scanning electron microscopy techniques to perform a structural and developmental study. Atmospheric water uptake was investigated through the absorption of aqueous solutions of berberine hemisulfate and Indian ink. Key resultsThe so-called trichomes actually correspond to emergences because they originate from protodermal and ground meristem activity rather than from epidermal tissue. These emergences show a complex anatomy, are closely associated with the mesophyll sclereids and might be involved in leaf atmospheric water uptake. The outermost cells of the emergences are arranged radially and present non-lignified thick walls. We demonstrate that an aqueous solution can effectively penetrate through the leaf emergences, continuing through sclereids and reaching the vascular bundle or flowing across the mesophyll maximizing water distribution in the leaf tissue. ConclusionsThe complex structure and hypothesized function of Croton trichome-like emergences represent a novel finding in Euphorbiaceae. In the three species studied, these leaf emergences might play a role in atmospheric water absorption and they may be one of the clues for the occurrence of Croton in habitats with limited soil water supply where this genus is usually species-rich and abundant.

Wind induces variations in spider web geometry and sticky spiral droplet volume

Trap building by animals is rare because it comes at a substantial cost. Using materials with properties that vary across environments maintains trap functionality. The sticky spiral silks of spider orb webs are used to catch flying prey. Web geometry, accompanied by compensatory changes in silk properties, may change across environments to sustain web functionality. We exposed the spider Cyclosa mulmeinensis to wind to test whether wind-induced changes in web geometry are accompanied by changes in aggregate silk droplet morphology, axial thread width or spiral stickiness. We compared: (i) web catching area, (ii) length of total silks, (iii) mesh height, (iv) number of radii, (v) aggregate droplet morphology and (vi) spiral thread stickiness, between webs made by spiders exposed to wind and those made by spiders not exposed to wind. We interpreted co-variation in droplet morphology or spiral stickiness with web capture area, mesh height or spiral length as the silk properties functionally compensating for changes in web geometry to reduce wind drag. Wind-exposed C. mulmeinensis built webs with smaller capture areas, shorter capture spiral lengths and more widely spaced capture spirals, resulting in the expenditure of less silk. Individuals that were exposed to wind also deposited larger droplets of sticky silk but the stickiness of the spiral threads remained unchanged. The larger droplets may be a product of a greater investment in water, or low molecular weight compounds facilitating atmospheric water uptake. Either way, droplet dehydration in wind is likely to be minimized.

The influence of ageing on consolidation and sinterability of a sub-micron alumina powder

A commercial sub-micron alumina powder was used for investigation of the influence of exposure to atmospheric humidity on powder characteristics, consolidation behaviour, densification and final microstructure of alumina ceramics. A significant uptake of atmospheric water by inadequate storage confirmed by thermal analysis, XPS, and FTIR, resulted in decreased sinterability of the powder, although no significant influence on the mean size of alumina grains was observed. In addition, the effect of low temperature heat treatment (drying at 120°C and calcination at 700°C) was also studied. The sinterability of pre-dried powder increased if a wet consolidation method (pressure filtration) was used, but a negative effect of pre-drying was observed in case of dry forming (axial pressing). The calcination decreased the ability of the powder to adsorb water. The presence of aggregates formed by calcination markedly decreased the green and sintered densities in compacts consolidated by axial pressing.

Humidity affects the extensibility of an orb-weaving spider's viscous thread droplets

The prey-capture threads found in most spider orb webs rely on viscous droplets for their stickiness. Each droplet is formed of a central mass of viscoelastic glycoprotein glue surrounded by an aqueous covering, both of which incorporate hydrophilic components. We found that the extensibility of droplets on Larinioides cornutus threads increased as humidity increased. However, the deflection of the droplets' supporting axial lines did not change, indicating that atmospheric water uptake increases glycoprotein plasticity, but not glycoprotein adhesion. The extensibility of droplets, along with that of the thread's supporting axial fibers, is responsible for summing the adhesion of multiple thread droplets. Therefore, daily changes in humidity have the potential to significantly alter the performance of viscous threads and orb webs.

An investigation of silver electrodeposition from ionic liquids: Influence of atmospheric water uptake on the silver electrodeposition mechanism and film morphology

The electrodeposition of silver from two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) and N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ([C4mPyr][TFSI]), and an aqueous KNO3 solution on a glassy carbon electrode was undertaken. It was found by cyclic voltammetry that the electrodeposition of silver proceeds through nucleation–growth kinetics. Analysis of chronoamperometric data indicated that the nucleation–growth mechanism is instantaneous at all potentials in the case of [BMIm][BF4] and [C4mPyr][TFSI], and instantaneous at low overpotentials tending to progressive at high overpotentials for KNO3. Significantly, under ambient conditions, the silver electrodeposition mechanism changes to progressive nucleation and growth in [C4mPyr][TFSI], which is attributed to the uptake of atmospheric water in the IL. It was found that these differences in the growth mechanism impact significantly on the morphology of the resultant electrodeposit which is characterised ex situ by scanning electron microscopy and X-ray diffraction.

Ultrastructural organization of the anal organs in the anal capsule of Craterostigmus tasmanianus Pocock, 1902 (Chilopoda, Craterostigmomorpha)

We describe the ultrastructural organization of the anal organs of Craterostigmus tasmanianus, which are located on the ventral side of the bivalvular anal capsule. Each part of the capsule bears four pore fields with several anal pores. The pores lead into a pore canal, which is surrounded by the single-layered epithelium of the anal organs. Each anal organ is composed of four different cell types: transporting cells of the main epithelium, junctional cells, isolated epidermal glands, and the cells forming the pore canal. The transporting cells exhibit infoldings of the outer cell membranes, forming a basal labyrinth and a poorly developed apical complex. The cells are covered by a specialized cuticle with a widened subcuticular layer. Only the cuticle of the main epithelium is covered by a mucous layer, secreted by the epidermal glands. The ultrastructural organization of the anal organ is comparable to the coxal and anal organs of other pleurostigmophoran Chilopoda. It is likely that the coxal and anal organs of the Pleurostigmophora are homologous, due to their identical ultrastructural organization. Differences concerning the location on the trunk of Pleurostigmophora are not sufficient to reject a hypothesis of homology. Anal organs are found not only in Craterostigmomorpha, but also in most adult Geophilomorpha, and in larvae and most adults of Lithobiomorpha. The anal organs of C. tasmanianus are thought to play an important role in the uptake of atmospheric water. J. Morphol.

Monitoring the Effect of Environmental Changes on Coating Properties with EIS

It is well known that most coatings show a measurable water uptake when immersed in neutral aqueous solutions. This can for instance be measured with Electrochemical Impedance Spectroscopy (EIS). In that case the capacitive behaviour of the intact coating is studied. Since the dielectric constant, and therefore the capacitance, of the coatings changes considerably when water is absorbed, the study of capacitance as a function of immersion time gives information on the permeation of water in the coating polymer. In some cases also the deviation from capacitive behaviour is studied using a Constant Phase Element (CPE). In practical service conditions most coatings are not continuously immersed in neutral aqueous solutions, but they are exposed to humid air or to chemical solutions. In some cases the chemical solutions are even produced by corrosion processes underneath the coating. For instance in the case of cathodic delamination the pH underneath the coating in a blister may be as low as pH 3 (anode) and as high as pH 12-14 (cathode). In numerous new accelerated tests this information is used and temperature and humidity are cycled, chemicals are introduced etc. Most electrochemical tests evaluate coatings only in immersion, simply because this is the most suitable way to apply these techniques. With some small changes EIS can however also be used to study water uptake from the atmosphere. This paper presents measurements on atmospheric water uptake as a function of relative humidity. It appears that the maximum concentration of water inside the coatings (S) can be described using Henry's law. The diffusion coefficient (D) appears to be dependent on the amount of water that is present in the coating when the experiments are started. In addition some measurements on the effect of temperature changes and the influence of a high pH test solution on the results of EIS measurements are presented. From the experiments with temperature changes it becomes clear that both S and D follow an Arrhenius behaviour. Especially for the S this gives the remarkable result that the change in the amount of water in the coating when the temperature is raised is opposite for water absorption from air or from liquid as is also predicted by the Arrhenius equation for S. However, due to curing effects this behaviour is not always measurable. The experiments with an electrolyte containing NaOH show that an increase in pH gives a large increase in coating capacitance, possibly caused by the ad- or absorption of OH - by the coating polymer.

Ultrastructure of the rectal sac, the site of water vapour uptake from the atmosphere in larvae of the oriental rat flea Xenopsylla cheopis

A portion of the hindgut of Xenopsylla cheopis larvae, the rectal sac, is extraordinarily enlarged and differentiated into a specialized organ displaying well-elaborated transporting epithelia. This organ is unique among insect recta because of gutter-like arrangement of two ultrastructurally distinct cell types with an asymmetrical position of the membranemitochondria complexes. The cells of the dorsal gutter have highly folded apical plasma membranes on the lumen side. The cells of the ventral gutter show deep infoldings of the basal plasma membrane on the haemolymph side. Less elaborate folds originate from the opposite sides of the cells. The nuclei of the dorsal epithelial cells are located in the basal part; those of the ventral cells in the apical portion of the cell. The ultrastructural features of the rectal sac, its ventilation synchronized with rhythmic opening of the anus during phases of active water vapour uptake, as well as the reversible arrest of uptake by experimental occlusion of the anus, reveal that condensation and uptake of atmospheric water take place in this organ.

Heterostyly inPrimula. 3. Pollen water economy: a factor in the intramorph-incompatibility response

The pollens from pin (long-styled) and thrum (short-styled) flowers ofPrimula differ markedly in water economy. While pin pollen is little affected by atmospheric humidity, the germinability of thrum pollen in liquid medium is sensitive to the conditions experienced during the immediately preceding period, being depressed when the grains are partly desiccated, although capable of being restored with subsequent controlled rehydration. The tubes produced by incompletely rehydrated thrum pollen show abnormal growth forms, suggesting that the effect is on the membranes of the vegetative cell, a conclusion supported by observations on membrane state using the fluorochromatic reaction. Thrum pollen stripped of part of the material carried in the cavities of the exine by rinsing with a lipid solvent loses much of its capacity for the uptake of atmospheric water, indicating that, in this morph, some factor facilitating hydration is transferred from the sporophytic parent during pollen maturation. Implications of these differences in the physiology of the pin and thrum pollens for the functioning of the intramorph-incompatibility system are discussed.

Atmospheric Water Uptake by an Atacama Desert Shrub

Nolana mollis, a succulent-leaved shrub of the extreme coastal desert of Chile, has the capacity to condense water on its leaves out of unsaturated atmospheres, Metabolic energy would have to be expended to move this water either from the leaf surface directly to the mesophyll or, when dripped to the soil, from there into the roots. Because of the unusual aridity of its habitat and of the utilization of water-use-efficient metabolism by Nolana, at least during certain periods, such an energy expenditure could be effective.

The site of active uptake of atmospheric water in larvae of Tenebrio molitor

Larvae starved and desiccated for 8 days will then take up water from 93% r.h., the gain ceasing by 7 days. The rate and amount of uptake were the same in those starved at 0% r.h. as in those starved at 53% r.h. Tying off the last abdominal segment prevents uptake while tying off the first abdominal segment allowed one-third as much gain as controls. This supports the theory that active uptake of atmospheric water is by way of the rectum and not the body cuticle. Because of the time taken to reach equilibrium, of the same uptake after exposure at 53% as after 0% r.h., and of a large overshoot in uptake, it is suggested that the phenomenon in this species is a by-product of drying the faeces and not a vital aspect of the physiology of water balance.

Physiological properties and biological implications of the water vapour sorption mechanism in larvae of the oriental rat flea, Xenopsylla cheopis (Roths.)

Partially dehydrated third-stage larvae of Xenopsylla cheopis take up water vapour from the air after transference to higher humidities. A net uptake of vapour occurs at relative humidities from close to saturation down to 65 per cent r.h., the critical equilibrium humidity. The amount of vapour taken up from the air, until the larvae achieve equilibrium, is greater the higher the relative humidity (Fig. 1); the larvae maintain this equilibrium at a high environmental humidity with a high water content and at a lower humidity with a lower water content. At 93 per cent r.h. and 25°C water vapour is transported from the air into partially dehydrated larvae at an approximately constant rate of 11 μg/hr per larva or 2·0 μg/hr per mm2 surface area and continuously for an average period of 6 hr until the equilibrium water content is achieved. The uptake curve, then, rather abruptly takes a horizontal course (Fig. 2); water loss and water uptake become balanced and the starving larvae remain unchanged in weight for 24 to 48 hr. Water is transferred faster into partially dehydrated larvae the higher the humidity to which the larvae are exposed. The rate of transpiration at 0 per cent r.h. and 25°C is 4·7 μg/hr per larva or 0·9 μg/hr per mm2 surface area. Net sorption of vapour from almost saturated air is approximately twice as fast as transpiration into dry air.Vapour uptake is related to the r.h. (relative vapour pressure) of the air and not to its absolute vapour pressure or to its saturation deficit; we have to infer that the equilibrium vapour pressure at the absorbing site on the surface of the larvae increases with temperature by the same amount as the vapour pressure in the air. This relationship shifts at temperatures not far from the upper lethal limit of the larvae.Equilibrium water contents are established not only by partially dehydrated larvae which are transferred to humidities above the critical equilibrium humidity but also by hydrated larvae which are transferred to lower humidities, as long as these are above the critical equilibrium humidity. These hydrated larvae lose water until their water content is depleted to a level which corresponds to the humidity to which the larvae are exposed. As soon as this level is reached, equilibrium is established (Figs. 3, 4).Uptake of water vapour by dehydrated larvae and retention of water by hydrated ones are temperature-dependent. Equilibrium water contents cannot be established below 13°C, whereas 35°C is close to the upper limit (Figs. 5, 6, 7). Within the favourable range the rate of uptake increases markedly with temperature.The equilibrium water content is delicately balanced. Regaining water occurs whenever the water content of the larvae is lowered below the equilibrium level characteristic for the humidity to which the larvae are exposed (Fig. 8).Larvae, after their final defaecation (prepupae), absorb four to five times more water vapour from the air than larvae in the feeding stage (Fig. 9). While the feeding larvae reach an equilibrium water content within approximately 6 hr, water uptake continues in the prepupae for an additional 42 hr. The increased vapour uptake by the prepupae is initiated invariably shortly after the final defaecation, while there is neither an increase in the ambient humidity nor a preceding adequate decrease of the water content of the organism; in fact it takes place even when the prepupae are transferred to a lower humidity. Vapour uptake ceases 2 days before the larval-pupal ecdysis takes place.Larvae do not develop into pupae at humidities substantially below the critical equilibrium humidity. The lower limit for development at different temperatures is related to the r.h. of the air just as the equilibria follow the r.h. and not the saturation deficit. Equilibria can be achieved only at temperatures at which the larvae develop into pupae.The vapour pressure of the haemolymph of insects can be taken as in equilibrium with an r.h. of not less than approximately 99 per cent r.h. Net uptake of atmospheric water into the haemolymph of flea larvae, however, takes place at 65 per cent r.h. This requires that osmotic forces of some 584 atm must be overcome by the animal. Uptake and retention of water depend upon metabolically driven processes. The mechanism is not known.