Water-restricted Environments Research Articles

Determinants of anuran assemblages in Amazonian White-sand Ecosystems.

Amazonian white-sand ecosystems have predominantly sandy soils and a high amount of endemism, and several species found within them are adapted to long periods of drought. However, little is known about the variation in the structure of anuran assemblages in these ecosystems. Considering that most species are not uniformly distributed in heterogeneous landscapes, we tested the hypothesis that anuran assemblage variation in white-sand ecosystems is related to changes in vegetation structure. Specifically, we focused on a heterogeneous patch of white-sand ecosystems of the central Amazon and evaluated whether vegetation structure and soil characteristics, including root depth, influence the richness, abundance, and composition of anuran assemblages. Our results showed that low amounts of clay in the soil play an important role in structuring vegetation in these ecosystems, and these are the main factors that organize anuran assemblages. The Campinaranas close to the water bodies have a high species richness, while Campina landscapes limit the occupation of most of species. Our findings indicate that anurans undergo environmental filtering in white-sand ecosystems and are organized into hierarchical subgroups, in which only species with specialized reproduction can successfully occupy the most water-restricted environments.

Addressing the Effectiveness and Molecular Mechanism of the Catalytic CO2 Hydration in Aqueous Solutions by Nickel Nanoparticles.

Hydration of carbon dioxide in water solution is the rate limiting step for the CO2 mineralization process, a process which is at the base of many carbon capture and utilization (CCU) technologies aiming to convert carbon dioxide to added-value products and mitigate climate change. Here, we present a combined experimental and computational study to clarify the effectiveness and molecular mechanism by which nickel nanoparticles, NiNPs, may enhance CO2 hydration in aqueous solutions. Contrary to previous literature, our kinetic experiments recording changes of pHs, conductivity, and dissolved carbon dioxide in solution reveal a minimal effect of the NiNPs in catalyzing CO2 hydration. Our atomistic simulations indicate that the Ni metal surface can coordinate only a limited number of water molecules, leaving uncoordinated metal sites for the binding of carbon dioxide or other cations in solution. This deactivates the catalyst and limits the continuous re-formation of a hydroxyl-decorated surface, which was a key chemical step in the previously suggested Ni-catalyzed hydration mechanism of carbon dioxide in aqueous solutions. At our experimental conditions, which expand the investigation of NiNP applicability toward a wider range of scenarios for CCU, NiNPs show a limited catalytic effect on the rate of CO2 hydration. Our study also highlights the importance of the solvation regime: while Ni surfaces may accelerate carbon dioxide hydration in water restricted environments, it may not be the case in fully hydrated conditions.

Seleção de acessos de amendoim precoce para melhoramento genético em ambiente com restrição hídrica

ABSTRACT Peanut production is growing annually in Brazil, but with frequent droughts throughout the country, it is necessary to identify an earliness germplasm for the improved environmental adaptation of peanuts. Here, a mini-core collection of peanuts was studied to select germplasms for further use in breeding, with a focus on dry environments. Twelve agronomic traits were adopted and later used in multivariate methods based on hierarchical models (UPGMA) and graphical dispersion (canonical variables), which aimed to identify earliness accession clusters. Statistically significant differences were found for most traits, indicating that there was genetic variability among accessions. Multivariate analyses subsequently revealed coherence in the formation of three clusters, one of which (G3: PI-268-689 and AHK-85-3) combined the most promising accessions for pod production and reproductive efficiency, previously identified through analysis of variance. Therefore, both germplasms are recommended here for use in future breeding studies focused on water-restricted environments.

Transgenerational Effects of Water Limitation on Reproductive Mother Plants in a Common Garden of the Shrub Frangula alnus

A better understanding of responses to water limitation in woody species can help us to cope with the consequences of the progressing climate change. We focused on the putative transgenerational effects of water limitation in the maternal environment during reproduction. Water was restricted for cuttings of Frangula alnus Mill. in a common garden setting, with a Belgian (local), Italian and Swedish provenance, during the growing season of 2020 and mature berries were collected during the whole reproductive phase. Stones that were extracted from the berries were given a cold stratification. In the next spring, the germination percentage of the stones from the water restricted maternal environment was significantly higher than that of the stones from the normal maternal environment, for the three provenances, notwithstanding the fact that stone weight was not different. The timing of seedling emergence was advanced for the water-limited maternal environment, but only for the stones harvested when mature berry production was the highest (9th and 16th of July 2020). Population differentiation was observed for the timing of seedling emergence, which reflected population differentiation for bud burst of the mother plants in the common garden, including a counter-gradient effect for the Swedish provenance, and corroborating the suggestion that the timing of seedling emergence and leaf phenology may have a common genetic basis. In addition, the Swedish provenance displayed a somewhat more stable germination percentage over the whole berry collection period when the stones were harvested. A partitioning of variance analysis suggested that germination percentage is more genetically determined than timing of seedling emergence, probably reflecting the more important need to sense the environment for an adequate timing of emergence.

Drought tolerance assessment of potato (Solanum tuberosum L.) genotypes at different growth stages, based on morphological and physiological traits

The objective of this study was to determine drought tolerance of diverse potato (Solanum tuberosum L.) genotypes. The physiological and morphological responses of eight potato genotypes were assessed under well-irrigated (Wi) and deficit irrigation (Di) conditions across four different growth stages, namely, the Vegetative (VG), Tuber Initiation (TI), Tuber Bulking (TB) and maturity (MAT) stages, using an 8 × 4 × 2 factorial treatment structure with three replications. Data were collected on morphological traits such as Plant Height (PH), the Number of Leaves (NL), Tuber Yield (TY) and Total Above-Ground biomass (TAG), as well as the physiological traits such as stomatal conductance (gs), Transpiration rate (Tr), the rate of photosynthesis (A), Water Productivity (WP), Chlorophyll Content Index (CCI) and Relative Water Content (RWC). A significant (p < 0.05) genotype x water condition x growth stage effects were observed for A, Tr, WP, RWC, CCI, PH, NL, TY and TAG, which indicated the varied responses of the genotypes to the water conditions across the growth stages. This is useful when recommending the growth-stage specific and drought tolerant potato genotypes for production. Correlation analysis revealed significant and negative association between gs and WP with TY (r = −0.81; r = −0.77) at the VG stage, positive association between PH, Tr, A and WP with TY (r = 0.92; r = 0.65; r = 0.95; r = 0.88) at the TI stage.CCI positively correlated with TY (r = 0.71) at the MAT stage, and a negative association was observed between TAG with TY (r = −0.85) at the MAT stage, under Di conditions. Principal component bi-plot identified that the all-rounder genotypes that are resistant to drought in all stages include the Challenger, Sifra and Tyson. These genotypes are recommended for cultivation in water-restricted environments.

Hydrolysis of ketene catalysed by nitric acid and water in the atmosphere

Environmental contextThe detailed mechanism of hydrolysis of gas-phase ketene to form acetic acid is critical for understanding the formation of certain atmospheric contaminants. This study explores the effect of nitric acid and water on the hydrolysis of ketene in the atmosphere. The calculated results show that nitric acid is an effective catalyst in the hydrolysis of ketene to form acetic acid in atmospheric water-restricted environments. AbstractThe gas-phase hydrolysis of ketene and the unimolecular reaction of 1,1-enediol catalysed by nitric acid and water have been investigated using quantum chemical methods and conventional transition state theory with Eckart tunnelling. The theoretical calculation results show that nitric acid exerts a strong catalytic effect on the hydrolysis of ketene in the gas-phase. The calculated energy barrier for the direct reaction mechanistic pathway is reduced from 42.10kcal mol−1 in the reaction of ketene with water to 3.40kcal mol−1 in the reaction of ketene with water catalysed by HNO3. The catalytic ability of nitric acid is further proven in the hydrogen shift reaction of 1,1-enediol because the energy barrier of the unimolecular reaction of 1,1-enediol is decreased from 44.92kcal mol−1 to −4.51kcal mol−1. In addition, the calculated results indicate that there is competition between the direct and indirect mechanistic pathways with the increase of additional water molecules in the reaction of ketene with water catalysed by HNO3 and (H2O)n (n=1, 2). The calculated kinetics results show that the CH2=C=O+H2O+HNO3 reaction is significant in the gas phase of the atmosphere and the other reactions are negligible owing to the slow reaction rates. However, compared with the CH2=C=O+OH reaction, the CH2=C=O+H2O+HNO3 reaction is very slow and cannot compete with the CH2=C=O+OH reaction. CH2=C=O+OH is the main elimination pathway of ketene in the gas phase of the atmosphere. Our findings reveal that acetic acid may be formed through the hydrolysis of ketene in atmospheric water-restricted environments of the surfaces of aqueous, aerosol and cloud droplets.

Nutrient Uptake and Yield of Wheat Varieties as Influenced by Foliar Potassium under Drought Condition

AbstractWater stress experienced by a wheat crop during growth is recognized to have accumulative effect stated as a decline in total biomass over well water potential. The yield and nutrient uptake performance of two wheat (Triticum aestivumL.) varieties (Pirsabak-2013 and Atta Habib) to foliar feeding of 2% potassium (K) at three various growth phases (Zadoks GS-22, Zadoks GS-60 and Zadoks GS-73) was explored under water restricted environment in a wire house trial at the Agriculture Research Station, Harichand, Charsadda. The target was to find out the preeminent K application stage for enhancement in the drought tolerance potential. Drought stress was generated by suppression of irrigation at the three growth phases and then K was sprayed with the carboxymethyl cellulose as a sticking agent, however Tween-20 was used as a surfactant for foliar spray. Data about several agronomic characters (plant height, spike length, number of spikelets per spike, number of grains per spike, 1000-grain weight and grain yield per plant) of crop were documented via standard techniques. Moreover, at maturity, aboveground nitrogen, phosphorus, K, sodium and calcium uptakes by the crop were determined. The results point out that drought stress at all three acute growth phases unfavorably affected plant height, spike length, number of spikelets per spike, number of grains per spike, 1000-grain weight, grain yield and nutrient uptake of the wheat plant. The exogenous K application under drought stress at all three acute growth phases boosted tolerance of wheat by decreasing noxious nutrient’s uptake and augmenting the yield and yield characters. In this concerns, both varieties exposed undeviating behavior. Extreme enhancement in all the documented yield parameters and nutrients uptake was attained when K was practiced at grain filling stage of both varieties.

Proton-Coupled Electron Transfer in a Hydrogen-Bonded Charge-Transfer Complex.

A proton-coupled electron transfer (PCET) reaction in a hydrogen-bonded charge-transfer (CT) complex of 4-([2,2'-bipyridin]-4-yl)phenol (bpy-phenol) with a F- ion has been investigated by ultrafast time-resolved transient absorption spectroscopy. The phenolic receptor molecule, bpy-phenol, binds to the F- ion through a hydrogen bond and senses the F- ion via the Stokes-shifted CT band. Upon photoexcitation, CT from the phenol residue to the bpy residue promotes proton transfer from the phenol radical cation (ArOH•+) to the fluoride ion at ultrafast time scales of <150 fs (instrument response function limited) and 3 ps, separately. The fast and slow proton-transfer times are linked to two different types of hydrogen-bonding networks between the phenol residue and fluoride ion. Crystalline water in the fluoride salt hydrates mediates the proton-transfer reaction. This work demonstrates the participation of a hydrogen-bonded water bridge within a PCET reaction in a water-restricted environment.

Hydrolysis of glyoxal in water-restricted environments: formation of organic aerosol precursors through formic acid catalysis.

The hydrolysis of glyoxal involving one to three water molecules and also in the presence of a water molecule and formic acid has been investigated. Our results show that glyoxal-diol is the major product of the hydrolysis and that formic acid, through its ability to facilitate intermolecular hydrogen atom transfer, is considerably more efficient than water as a catalyst in the hydrolysis process. Additionally, once the glyoxal-diol is formed, the barrier for further hydrolysis to form the glyoxal-tetrol is effectively reduced to zero in the presence of a single water and formic acid molecule. There are two important implications arising from these findings. First, the results suggest that under the catalytic influence of formic acid, glyoxal hydrolysis can impact the growth of atmospheric aerosols. As a result of enhanced hydrogen bonding, mediated through their polar OH functional groups, the diol and tetrol products are expected to have significantly lower vapor pressure than the parent glyoxal molecule; hence they can more readily partition into the particle phase and contribute to the growth of secondary organic aerosols. In addition, our findings provide insight into how glyoxal-diol and glyoxal-tetrol might be formed under atmospheric conditions associated with water-restricted environments and strongly suggest that the formation of these precursors for secondary organic aerosol growth is not likely restricted solely to the bulk aqueous phase as is currently assumed.

Biochemical Characterisation of a Newly Isolated Low Molecular Weight Lipase from Rhizopus oryzae NRRL 3562

Lipases are one of the industrially important biocatalyst whose demand ranks third among all the other enzymes. Because of their ability to carry out diverse range of reactions, remain active even in water restricted environment and act at interfaces, they find applications in varied fields. Purification and characterization of this enzyme is essential for its application in a wide spectrum of industrial processes. The present study deals with purification of lipase from Rhizopus oryzae NRRL 3562 in minimum steps which led to a high yield and fold increase. Lipase with specific activity of 450 IU/mg gave a single band on both native and SDS PAGE, showing purification to homogeneity. It was found to be a low molecular weight lipase of 14.45 kDa and had optimum temperature range and pH of 30-40○C and 9, respectively. The purified lipase showed specificity towards long chain (C16-18) p-Nitrophenyl esters. Stability at elevated temperatures, wide pH range and in presence of solvents makes this small lipase a potent candidate for transesterification reactions.

Hydration of pyruvic acid to its geminal-diol, 2,2-dihydroxypropanoic acid, in a water-restricted environment

In this work we present the spectroscopic characterization of 2,2-dihydroxypropanoic acid and its water complexes. Based on this information the water-mediated hydration between pyruvic acid and its geminal diol counterpart, 2,2-dihydroxypropanoic acid, was investigated at very low water concentration at ambient temperatures, using Fourier-transform mid-infrared (FTIR) and nuclear magnetic resonance spectroscopy (NMR). We experimentally observed large concentrations of 2,2-dihydroxypropanoic acid in this water-restricted environment of the carbon tetrachloride matrix. Our observation can be explained by the role of hydrogen-bonded water clusters in promoting the hydration of the carbonyl in pyruvic acid.

Seed lipases: sources, applications and properties - a review

Abstract - This paper provides an overview regarding the main aspects of seed lipases, such as the reactions catalyzed, physiological functions, specificities, sources and applications. Lipases are ubiquitous in nature and are produced by several plants, animals and microorganisms. These enzymes exhibit several very interesting features, such as low cost and easy purification, which make their commercial exploitation as industrial enzymes a potentially attractive alternative. The applications of lipases in food, detergents, oils and fats, medicines and fine chemistry, effluent treatment, biodiesel production and in the cellulose pulp industry, as well as the main sources of oilseed and cereal seed lipases, are reviewed. Keywords : Vegetable Lipases; Reactions; Sources; Application. INTRODUCTION Lipase enzymes have become more and more prominent on the enzyme biotechnology scenario due to their versatility for hydrolysis and synthesis, their catalytic reactions often being chemo-selective, region-selective or enantio-selective. Lipases are used in many sectors such as the food, pharmaceutical, fine chemical, oil chemical, biodiesel and industrial detergent industries (Freire and Castilho 2008, Alonso et al. 2005). The participation of lipases in the worldwide enzyme industry market has grown significantly and it is believed that, in the future, they will acquire importance comparable to that of the peptidases, which currently represent 25 to 40% of industrial enzyme sales (Hasan et al. 2006). Lipases act, by definition, at the organic-aqueous interface, catalyzing the hydrolysis of ester-carboxylate bonds and releasing fatty acids and organic alcohols (Pereira et al., 2003; Leal et al. 2002; Kamimura et al., 1999; Mercon et al. 1997). However, as Pottevin showed for the first time in 1906, in water-restricted environments, the reverse reaction (esterification) or even various transesterification reactions can occur (Freire and Castilho 2008, Castro et al. 2000). The term transesterification refers to the exchange of groups between an ester and an acid (acidolysis), between an ester and an alcohol (alcoholysis) or between two esters (interesterification). Their ability to catalyze these reactions with great efficiency, stability and versatility makes these enzymes highly attractive from a commercial point of view (Figure 1).

Drought-tolerant naturalized populations of Lotus tenuis for constrained environments

A perennial forage legume species tolerant to water stress would be useful to improve pasture and animal productivity in the central zone of Chile. The growth, dry-matter (DM) production, and drought tolerance of twelve accessions of Lotus tenuis Waldst & Kit, Syn. L. glaber, naturalized in Chile were evaluated with the objective to select contrasting genotypes, tolerant and sensitive to drought, for future breeding programmes. The accessions were sown in pots of 1.3 L containing a volcanic soil (Andisol). A completely randomized design with all combinations of Lotus accessions and four water treatments [100, 70, 40, and 10% of soil water availability (SWA)] was used. The relative rate of stem elongation (RRSE), the shoots and roots DM production, the relative water content (RWC), and the specific leaf area (SLA) were measured. A drought-sensitivity index (DSI) and the interaction genotype×environment were calculated. The RRSE, the DM production, RWC, and SLA all showed a significant reduction (P<0.05) in the treatment with the higher water restriction (10% SWA). There were significant differences (P<0.05) within RRSE and DM production genotype means, but the RWC and SLA did not differ among populations. The DSI varied broadly among genotypes, from 0.49 to 1.34, and was correlated negatively with DM production under water stress (10% SWA). It was concluded that the Lotus tenuis populations showed water-stress tolerance genetic variability, with accessions Lt14 and Lt4 the most contrasting. These findings will permit us to identify chromosomal regions associated with drought-tolerant genotypes which will allow us to accelerate the development of cultivars adapted to water-restricted environments.

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process not previously considered to occur in water-restricted environments. In this study, we spectroscopically identified methylglyoxal diol (MGD) and obtained the gas-phase partial pressures of MG and MGD. These results, in conjunction with the relative humidity, were used to obtain the equilibrium constant, K(P), for the water-mediated hydration of MG in the gas phase. The Gibbs free energy for this process, DeltaG(o), obtained as a result, suggests a larger than expected gas-phase diol concentration. This may have significant implications for understanding the role of organics in atmospheric chemistry.

A comparative study of the synthesis of n-butyl-oleate using a crude lipolytic extract of Penicillum coryophilum in water-restricted environments

We evaluated the potential of a lipolytic extract from Penicillium corylophilum for use in biocatalysis. Lipolytic activity was stable when the extract was incubated in the presence of hydrophobic solvents. In fact, when the extract was incubated in n-heptane with an initial water activity of 0.95, the activity increased by 30%. Synthesis of n-butyl-oleate in different systems was compared. In AOT/ n-heptane reverse micelles, a 100% yield of ester was obtained within 12 h, with a water content (W 0, [H 2O]/[AOT]) of 10. Several macro-heterogeneous systems involving n-heptane as the solvent were also compared. Direct addition of lyophilised enzymatic preparation to this system gave a 100% yield in 48 h, with an initial water activity of 0.11. Performance was poorer with direct addition of enzymatic preparation co-lyophilised with β-cyclodextrin and with addition of enzymatic preparation immobilized on a hydrophobic gel, with yields significantly less than 100%. We conclude that the lipolytic extract of P. corylophilum can be used in synthesis reactions in low-water systems, which justifies further efforts to purify lipolytic enzymes from the extract and to undertake an in-depth evaluation of their potential for use in biocatalysis, for the production of fine chemicals.

Catalytical properties of N-glycosylated Gluconacetobacter diazotrophicus levansucrase produced in yeast

The influence of N-glycosylation on the kinetic and catalytical properties of a bacterial fructosyltransferase (LsdA) produced in Pichia pastoris was studied. The glycosylated enzyme behaved similarly to non-glycosylated LsdA when substrate specificity, fructo-oligosaccharide (FOS) production, sucrose hydrolysis or levan formation reactions were carried out under different experimental conditions. The kinetic parameters for native or yeast-expressed LsdA determined at 60oC, condition for the highest hydrolytic activity, followed a conventional Michaelis-Menten kinetics. Synthase activity of this levansucrase increased in water-restricted environments by addition of salt or organic solvent to the reaction mixtures.

Influence of Reverse Micellar Environments on the Fluorescence Emission Properties of Tryptophan Octyl Ester

A number of recent studies have presented perspectives on the hydrophobic fluorescence probe tryptophan octyl ester (TOE). This molecule has attracted notable attention as a suitable model for the natural fluorophore tryptophan, in case of membrane proteins. We report here, for the first time, the fluorescence emission behaviour of TOE in reverse micelles of aerosol-OT (AOT) in n-heptane, containing different amounts of water. Relevant studies in representative homogeneous solvent media are also included for comparison. The fluorescence emission parameters (especially emission maximum, relative intensity, and anisotropy) of TOE are found to exhibit significant variation upon changes in the water/surfactant molar ratio (w0) of the reverse micelles. Fluorescence decay studies on TOE which we have also performed, indicate biexponential decay kinetics in reverse micelles as well as in homogeneous solvent media. The implications of these findings are examined in relation to the potentialities of TOE as a novel fluorescence probe for membrane proteins present in water restricted environments prevailing at the interfaces of biomembranes (for which reverse micelles serve as ideal model systems).

Flow injection determination of free and total cholesterol in animal greases using enzymes in non-aqueous media.

A non-covalently coimmobilized bienzymic reactor of horseradish peroxidase (HRP) and cholesterol oxidase (COD), operating in a continuous organic flowing stream of 1X10-3 M p-anisidine in buffer-saturated (pH 7.0) toluene, has been employed for cholesterol determination in animal greases, such as pig, beef, and chicken fat, and codfish liver oil. The method provides a good linear relationship up to 1.8 X 10-3 M cholesterol and average recoveries of 99.5%, a high sensitivity, with a detection limit of 1 X 10-6 M of cholesterol and a good precision (an interday RSD of 1.8% for the determination of total cholesterol in a codfish oil sample). The method permits the direct spectrophotometric determination of free cholesterol present in animal grease samples without any pre-treatment, and the total cholesterol determination after a microwave-assisted saponification. The bienzymic reactor exhibits a good stability in the water-restricted environment, being possible to perform more than 180 analyses during a period of 10d with 1mg of HRP, and 1 mg of COD, equivalent to 220 purpurogallin units and 23 U, respectively.

Characterization of the Fluorescence Emission Properties of 7-Azatryptophan in Reverse Micellar Environments

The amino acid analogue 7-azatryptophan has attracted significant recent attention as a novel optical probe for protein structure, function and dynamics. We report here, for the first time, its fluorescence emission behavior in a membrane mimetic model system, namely reverse micelles of aerosol-OT in n-heptane, containing varying amounts of added H2O or D2O. Upon increase in the water/surfactant molar ratio from 0.5 to 50 the emission maximum undergoes a pronounced red shift (by 20 nm), which is accompanied by dramatic quenching of the fluorescence emission and sharp decrease in its average lifetime. These data are used to infer the microenvironments of the fluorophore in the reverse micelles. Furthermore, the highly sensitive dependence of the fluorescence emission parameters of 7-azatrytophan on the water content of the reverse micelles highlights its suitability as a probe for water restricted environments, with possible applications to interfacial regions of biomembranes.

Biocatalysis and biorecognition in nonaqueous media. Some perspectives in analytical biochemistry

Biocatalysis and, to a lesser extent, biorecognition in non-aqueous media (including organic solvents as well as supercritical fluids and gases) constitute at present an exciting research area which has already demonstrated its biotechnological potential in numerous, varied applications. Less attention, however, has been paid to its analytical possibilities, even though many advantages have been postulated and a wide range of poorly water-soluble analytes are present in samples (or waste materials) from food and drink, petrochemical, pharmaceutical, military and other industries. The main approaches, developed in recent years to exploit the use of enzymes, antibodies or antibody mimics in water-restricted environments for analytical purposes, as well as possible future directions are briefly discussed.