Periods Of Water Stress Research Articles

Green Roofs for domestic wastewater treatment: Experimental and numerical analysis of nitrogen turnover

The use of Green Roofs (GRs) for domestic wastewater treatment and nitrogen (N) removal is an appealing opportunity to conjugate hydrological, energetic, and water quality benefits. However, the research in this direction has been limited to few experimental studies, while the role of numerical modeling for analysis and design has been overlooked. To advance understating of reactive transport processes in GRs and investigate the use of numerical models, this study presents a comprehensive experimental and numerical investigation of the N turnover in vegetated and non-vegetated GRs exposed to domestic wastewater injection. A Bayesian framework is used to calibrate a mechanistic numerical model against multiple observations from a controlled laboratory experiment. A Global Sensitivity Analysis complements the framework to further enlighten the role of multiple physical processes. Results indicate that GRs have high nitrification capacity, which increases after wastewater application. The total leached N is 94% of the total injected N in a non-vegetated GR, compared to 67% for a vegetated GR. Nitrate leaching is negatively correlated with the root solute uptake capacity of the vegetation, which may reach up to 32% of the total injected N. Maximization of this factor is desirable and can be achieved by selecting appropriate plant species and reducing water stress periods using a proper irrigation schedule.

In vivo monitoring of drought-induced embolism in Callitris rhomboidea trees reveals wide variation in branchlet vulnerability and high resistance to tissue death.

Damage to the plant water transport system through xylem cavitation is known to be a driver of plant death in drought conditions. However, a lack of techniques to continuously monitor xylem embolism in whole plants invivo has hampered our ability to investigate both how this damage propagates and the possible mechanistic link between xylem damage and tissue death. Using optical and fluorescence sensors, we monitored drought-induced xylem embolism accumulation and photosynthetic damage invivo throughout the canopy of a drought-resistant conifer, Callitris rhomboidea, during drought treatments of c. 1 month duration. We show that drought-induced damage to the xylem can be monitored invivo in whole trees during extended periods of water stress. Under these conditions, vulnerability of the xylem to cavitation varied widely among branchlets, with photosynthetic damage only recorded once > 90% of the xylem was cavitated. The variation in branchlet vulnerability has important implications for understanding how trees like C. rhomboidea survive drought, and the high resistance of branchlets to tissue damage points to runaway cavitation as a likely driver of tissue death in C. rhomboidea branch tips.

Forage production, morphological, and chemical composition of diploid and tetraploid cultivars of Italian ryegrass in hydromorphic soils

ABSTRACT This study aimed to evaluate forage mass, morphological, and chemical composition of diploids and tetraploids Italian ryegrass cultivars in hydromorphic soil. Eight ryegrass cultivars were evaluated in a two-years completely randomised trial with four plots per cultivar. Forage production was recorded, and samples were collected to evaluate morphological and chemical composition. The contrasts methodology was used to verify differences between diploid and tetraploid cultivars. Compared to tetraploids, the diploids had the greatest number of cuts and the largest accumulation of forage in the second year, highlighting the better adaptation of cultivars in hydromorphic soils. Tetraploid ryegrass increased leaves and reduced stem and inflorescence proportion relative to diploid ryegrass. Tetraploid cultivars had lower DM, organic matter, and acid detergent fibre content than diploid cultivars. However, there was no significant difference between cultivars associated with their ploidy for the neutral detergent fibre and estimated total digestible nutrients. Additionally, only in the second year, tetraploid had lower crude protein content than diploid ones. Tetraploid ryegrass showed be less tolerant to periods of water stress due to flooding, characteristic of hydromorphic soils, resulting in less forage production than diploid ryegrass.

Growing food with less water: Chilean research team finds solutions in extreme environments

Droughts pose a growing risk to food security. Glasshouse experiments show that tomatoes inoculated with rhizobacteria from ephemeral flowering desert plants exhibit greater rates of survival and growth when subjected to periods of water stress.

Ethical issues and legal principles regarding joint management of shared river basins in the context of climate change and water scarcity in the Iberian Peninsula

Portugal and Spain share five large river basins. The human activities carried out in the rivers or in the river basin area generate mutual interferences and impacts on the quality and quantity of water and on the ecologic conditions of the rivers and surrounding ecosystems. Furthermore, the effects of climate change on river ecosystems in the Mediterranean region—namely drought, water scarcity, desertification, flooding, heat waves, soil salinization, invasive species—are leading to larger water stress periods and an overall reduction of ecosystem services. In this context, the main ethic challenges regarding joint management of shared river basins in the Iberian Peninsula are: territorial equity, geomorphologic equity, demographic equity, interspecies equity, development equity, intergenerational equity and cultural equity. To address these challenges, a set of principles of international environmental law are briefly analysed. These principles govern the relations between States, regulate the access to the rivers, preserve the ecologic equilibrium of the rivers, and influence risk management. The principles also limit State discretionarily towards possible river uses and shape international agreements to be adopted in the future.

To what extent can rising [CO2 ] ameliorate plant drought stress?

Plant responses to elevated atmospheric carbon dioxide (eCO2 ) have been hypothesized as a key mechanism that may ameliorate the impact of future drought. Yet, despite decades of experiments, the question of whether eCO2 reduces plant water use, yielding 'water savings' that can be used to maintain plant function during periods of water stress, remains unresolved. In this Viewpoint, we identify the experimental challenges and limitations to our understanding of plant responses to drought under eCO2 . In particular, we argue that future studies need to move beyond exploring whether eCO2 played 'a role' or 'no role' in responses to drought, but instead more carefully consider the timescales and conditions that would induce an influence. We also argue that considering emergent differences in soil water content may be an insufficient means of assessing the impact of eCO2 . We identify eCO2 impact during severe drought (e.g. to the point of mortality), interactions with future changes in vapour pressure deficit and uncertainty about changes in leaf area as key gaps in our current understanding. New insights into CO2 × drought interactions are essential to better constrain model theory that governs future climate model projections of land-atmosphere interactions during periods of water stress.

HYDRAULICS OF PINUS (SUBSECTION PONDEROSAE) POPULATIONS ACROSS AN ELEVATION GRADIENT IN THE SANTA CATALINA MOUNTAINS OF SOUTHERN ARIZONA

The ability of plants to tolerate and recover from periodic water stress affects their competitive ability, survival, and distribution, leading to shifts in plant communities as environmental conditions change. We investigated the hydraulic traits of two closely related Pinus taxa to assess population and taxonomic variability in plant hydraulic traits. We hypothesized that traits would vary with elevation but exhibit similar traits where taxa co-occurred. We measured predawn and midday leaf pressure potential (Ψp) across three seasons, xylem specific hydraulic conductivity (Ks), and vulnerability to xylem embolism (P50). These were measured on Pinus ponderosa var. brachyptera (Engelm.) Lemmon that occurred at a high elevation site (2770 m), P. arizonica Engelm. at a low elevation site (2135 m), and both species where they co-occurred at the mid-elevation site (2475 m) in the Santa Catalina Mountains of southern Arizona. Plants from the high elevation site had the least negative Ψp and the highest Ks. The two taxa differed from one another when compared between the high and low elevation sites, but they were not different where they co-occurred. The two Pinus taxa show plasticity in their hydraulic traits across sites. Conditions across the elevational gradient appear to lead to a convergent solution in hydraulic traits for these taxa where their ranges overlap but differences in traits where they do not overlap. Increasing aridity in the region could lead to shifts in suitable habitat, reduced water transport ability at range margins, and shifts in population distributions.

Effect of Chloroquine on antioxidant enzymes and oxidative system on (Vigna radiata) plant tissues exposed to water stress

The aim of the present study is to examine the effect of (Chloroquine CQ) on the oxidative stress under water stress effect Recently, this compound is used to treat COVID-19, Hydrogen peroxide H2O2 effect and Stimulate the enzymatic system through the exposure of the plant to water stress and interaction with Chloroquine, where the stress stimulate the production of these Oxidative Factors (Hydrogen Peroxide, Malondialdehyde(MDA), Protease increase the production of these oxidative factors increase activity through the effect of Chloroquine, This process was performed in the meristematic tissues of the cells of the permanent Mung bean (Vigna radiata) plants under experimental factors (water stress factor for 10 days with control period of 5 days) (Chloroquine factors and concentrations of 125 and 250 mg.L-1 with control treatment) were designed using a Factorial Randomized Block Design (R.B.C.D) with three replicates and 18 experimental units The experimental unit area was 2 m. The results have shown the following; The water stress period of 10 days led to the production of toxic hydrogen peroxide and increased concentration by stress. The effect of water stress was Stimulate the Production of hydrogen peroxide in Meristematic tissues. The effect of Chloroquine CQ with increased concentrations had a role in inhibiting the production of enzymatic antioxidants (Superoxide dismutase(SOD) and Catalase (CAT). The interaction between water stress and increased Chloroquine CQ concentrations has been instrumental in stimulating the production of oxidative Factors.

Scholarship on urban Africa’s water crisis narratives: the state of the art

Water crises present a global water governance challenge. To date, scholarship has tended to focus on technological and policy-based solutions, while ignoring the influence of narratives on public buy-in during such crises. Africa is expected to become hotter and drier in future, while its cities experience high levels of informal population growth and inequality. These factors combine to make African cities particularly vulnerable to times of water stress. The aim in this paper is to investigate the state of the ‘art’ on narratives framing domestic water use in African cities during periods of acute water stress and ‘crises’, using a systematic literature review of peer-reviewed academic journal articles. The findings revealed a small population of recently published papers that engage critically with state-generated narratives framing the crisis, limited to case studies on Cape Town and Windhoek. We recommend, however, a greater critical engagement with the anti-establishment narratives that can flourish during periods of acute water stress, and tend to be inflammatory and divisive in nature.

Water demand management strategies in fast-growing cities. The case of Arequipa, Perú

ABSTRACT Using a socioenvironmental perspective, this paper analyses strategies of water demand management (WDM) in Arequipa, Peru, and their perception by residents through a survey of six city districts (three in the core and three on the periphery) complemented with interviews with key stakeholders. The results show significant differences in WDM. Strategies to reduce demand through pricing are dominant. Domestic water-saving technologies are uncommon, and awareness campaigns are limited to periods of water stress. Despite differences in water access, improvements in water networks (leak repair, adequate water pressure and continuous supply) are the most demanded actions by residents.

Effects of plant growth-promoting rhizobacteria strains producing ACC deaminase on photosynthesis, isoprene emission, ethylene formation and growth of Mucuna pruriens (L.) DC. in response to water deficit

Agricultural sustainability is an increasing need considering the challenges posed by climate change and rapid human population growth. The use of plant growth-promoting rhizobacteria (PGPR) may represent an excellent, new agriculture practice to improve soil quality while promoting growth and yield of important crop species subjected to water stress conditions. In this study, two PGPR strains with 1-Aminocyclopropane-1-Carboxylate (ACC) deaminase activity were co-inoculated in velvet bean plants to verify the physiological, biochemical and molecular responses to progressive water stress. The results of our study show that the total biomass and the water use efficiency of inoculated plants were higher than uninoculated plants at the end of the water stress period. These positive effects may be derived from a lower root ACC content (−45 %) in water-stressed inoculated plants than in uninoculated ones resulting in lower root ethylene emission. Furthermore, the ability of inoculated plants to maintain higher levels of both isoprene emission, a priming compound that may help to protect leaves from oxidative damage, and carbon assimilation during water stress progression may indicate the underlining metabolic processes conferring water stress tolerance. Overall, the experimental results show that co-inoculation with ACC deaminase PGPR positively affects tolerance to water deficit, confirming the potential for biotechnological applications in water-stressed agricultural areas.

Fuzzy modeling of vegetable straw cover crop productivity at different nitrogen doses

The Direct Planting System (DPS), also referred to as direct seeding or no-tillage farming, is distinguished by the permanent occupation of the agricultural land with plant crops besides the maintenance of the straw under the soil surface. However, for its effectiveness, it is necessary to adopt suitable cover crops for each region. Sorghum has a high tolerance to the dry season and a high volume of dry matter production, which are important characteristics for adoption as a cover crop. Millet, besides having a high resistance to periods of water stress, has also a high concentration of biomass production. In this context, the present work aimed to analyze, through the use of mathematical models, the effects of nitrogen in sorghum and millet crops, adopted as vegetation cover crops, under different levels of nitrogen in relation to the dry matter production variables. The comparison of the fuzzy (Gaussian and triangular) and polynomial regression models was performed using statistical tests and verification of the determination coefficient. Analytically, the best statistical parameters for triangular fuzzy modeling were verified in comparison to the Gaussian fuzzy model and polynomial regression of degree two. However, in relation to the behavior of the mathematical modeling curve, the Gaussian model proved to be best in keeping with the reality of the agronomic phenomena, mainly due to the smoothing of the curve over the data set.

Leaf turgor loss point shapes local and regional distributions of evergreen but not deciduous tropical trees.

Summary The effects of climate change on tropical forests will depend on how diverse tropical tree species respond to drought. Current distributions of evergreen and deciduous tree species across local and regional moisture gradients reflect their ability to tolerate drought stress, and might be explained by functional traits.We measured leaf water potential at turgor loss (i.e. ‘wilting point’; πtlp), wood density (WD) and leaf mass per area (LMA) on 50 of the most abundant tree species in central Panama. We then tested their ability to explain distributions of evergreen and deciduous species within a 50 ha plot on Barro Colorado Island and across a 70 km rainfall gradient spanning the Isthmus of Panama.Among evergreen trees, species with lower πtlp were associated with drier habitats, with πtlp explaining 28% and 32% of habitat association on local and regional scales, respectively, greatly exceeding the predictive power of WD and LMA. In contrast, πtlp did not predict habitat associations among deciduous species.Across spatial scales, πtlp is a useful indicator of habitat preference for tropical tree species that retain their leaves during periods of water stress, and holds the potential to predict vegetation responses to climate change.

Reassessing the Role of Potassium in Tomato Grown with Water Shortages

Potassium (K) is closely related to plant water uptake and use and affects key processes in assimilation and growth. The aim of this work was to find out to what extent K supply and enhanced compartmentation might improve water use and productivity when tomato plants suffered from periods of water stress. Yield, water traits, gas exchange, photosynthetic rate and biomass partition were determined. When plants suffered dehydration, increasing K supply was associated with reduction in stomatal conductance and increased water contents, but failed to protect photosynthetic rate. Potassium supplements increased shoot growth, fruit setting and yield under water stress. However, increasing the K supply could not counteract the great yield reduction under drought. A transgenic tomato line with enhanced K uptake into vacuoles and able to reach higher plant K contents, still showed poor yield performance under water stress and had lower K use efficiency than the control plants. With unlimited water supply (hydroponics), plants grown in low-K showed greater root hydraulic conductivity than at higher K availability and stomatal conductance was not associated with leaf K concentration. In conclusion, increasing K supply and tissue content improved some physiological features related to drought tolerance but did not overcome yield restrictions imposed by water stress.

Timing of short period water stress determines potato plant growth, yield and tuber quality

Potato growth in humid climate regions is facing increasing challenges due to short period stresses in water deficit and excess. However, there is a lack of quantitative information on the effects of short period of water stress on potato plant growth and its implications on potato yield and tuber quality. In this study, we conducted a pot experiment to test the effects of short period (2weeks) of water deficit and water excess, respectively, applied at four different potato growth stages (sprouting, vegetative, tuberization and bulking stage) on potato vegetative development and tuber yield and quality. The results show that short period of water deficit overall had negative impacts while short period of water excess had slightly positive impacts on potato vegetative development and tuber yield and quality. For water deficit, the most sensitive periods were the vegetative and tuberization stage whereas for water excess, there were mostly no-significant differences between different potato growth stages. Although the impact of water deficit at the sprouting stage was minor, it was broad and long-lasting. These results confirm the benefits of supplemental irrigation and suggest the low risk of over-irrigation in well drained fields. They further suggest that when the availability of water for irrigation is limited, using water strategically during the period when potato needs water the most can maximize the benefits of supplemental irrigation.

Substrate composition affects the development of water stress and subsequent recovery by inducing physiological changes in Cistus albidus plants

Organic residues (compost) can be used as growth medium but may contain phytotoxic ions that, combined with a water deficit may alter the behavior of plants. The experiment was carried out in a growth chamber with Cistus albidus in a commercial substrate, C (sphagnum peat, coconut fiber and perlite, 8:7:1) and a mixture of compost substrates, Cp (slurry compost, coconut fiber and perlite, 3:6:1). Plants were grown in pots under well-watered, maintaining values of Ψl around −0.9 MPa (WW) and water-stressed (WS) conditions, where the irrigation was removed until reached values of Ψl around −3.0 MPa (water stress period), after then, water was re-established in all plants (recovery period). Although, the well-watered plants had a leaf water potential (Ψl) around −0.9 MPa, stomatal conductance (gs) was 125 mmol m−2s−1 in the commercial substrate and 30 mmol m−2s-1 in compost. The time taken to reach the threshold value at which water stress occurs was 13 days in the commercial substrate and 53 days in compost. Water-stressed plants in the commercial substrate had significantly lower values of Ψl and gs than well-watered. Plants in compost maintained values of gs similar in both irrigation treatments (WW and WS) and accumulated less biomass than those that grown in commercial. The water stress in compost led an increase in the adaxial epidermis, parenchyma and mesophyll, whereas water stress in commercial the proportions of the different tissues decreased. Higher lipid peroxidation values were found in plants grown in both substrates under water stress. The recovery time of the plants, until manage Ψl values around −0.9 MPa, depended on the type of substrate. The restoration of irrigation in commercial substrate act as a new stress, as reflected in the photochemical mechanisms.

Rootstock Effects on Water Relations of Young Almond Trees (cv. Soleta) When Subjected to Water Stress and Rehydration

Rootstocks with size controlling potential are being used in newly planted intensive almond orchards. Due to increased water scarcity, characterizing the response of these rootstocks to water deficit is required. The current work aims to assess whether the rootstock can improve their drought tolerance. We investigated the morphological and physiological response of P. dulcis “Soleta” either self-rooted or grafted on Rootpac-20 rootstock. Plant responses were evaluated during a water stress period (withholding irrigation for 20 days) and subsequent recovery in potted plants under greenhouse conditions. Self-rooted plants had a higher capacity to control vigour than plants grafted onto Rootpac-20, both under full irrigation and no irrigation conditions. Stressed plants exhibited severe dehydration, as indicated by lower leaf water potential and relative water content. Removing irrigation reduced stomatal conductance in grafted and self-rooted plants by a similar extent, suggesting an efficient stomatal control, while the reduction in the net photosynthesis rate was more marked in grafted plants compared to non-grafted plants. Self-rooted plants under water stress increased their root to shoot ratio and water use efficiency, which are positive aspects for growth and survival of these plants.

Spatio-Temporal Variation of Ozone Concentrations and Ozone Uptake Conditions in Forests in Western Germany

The study analyzes the long-term trends (1998–2019) of concentrations of the air pollutants ozone (O3) and nitrogen oxides (NOx) as well as meteorological conditions at forest sites in German midrange mountains to evaluate changes in O3 uptake conditions for trees over time at a plot scale. O3 concentrations did not show significant trends over the course of 22 years, unlike NO2 and NO, whose concentrations decreased significantly since the end of the 1990s. Temporal analyses of meteorological parameters found increasing global radiation at all sites and decreasing precipitation, vapor pressure deficit (VPD), and wind speed at most sites (temperature did not show any trend). A principal component analysis revealed strong correlations between O3 concentrations and global radiation, VPD, and temperature. Examination of the atmospheric water balance, a key parameter for O3 uptake, identified some unusually hot and dry years (2003, 2011, 2018, and 2019). With the help of a soil water model, periods of plant water stress were detected. These periods were often in synchrony with periods of elevated daytime O3 concentrations and usually occurred in mid and late summer, but occasionally also in spring and early summer. This suggests that drought protects forests against O3 uptake and that, in humid years with moderate O3 concentrations, the O3 flux was higher than in dry years with higher O3 concentrations.

Seawater neutralization and gypsum amelioration of bauxite refining residue to produce a plant growth medium

Alumina production waste (bauxite refining residue) is highly alkaline, saline, and sodic, and hence cannot support plant growth for revegetation. Gypsum (CaSO4.2H2O) amendment of bauxite residue can lower alkalinity and improve the residue Ca status, but given the large gypsum requirement, efficient gypsum use is imperative. We investigated gypsum amelioration of residue sand (RS), examining changes in RS chemistry, and growth of Rhodes grass (Chloris gayana). Furthermore, we examined whether gypsum amelioration of RS should occur before or after seawater neutralization. We found that Ca from gypsum (20 t ha−1) was retained within the surface 0.2 m of RS, regardless of whether the gypsum was applied before or after seawater neutralization. This Ca was retained both as exchangeable Ca and as a precipitate (either calcite or hydrotalcite), with ca. 50% retained as exchangeable Ca in both approaches. Gypsum at 20 t ha−1, or even lower, provided sufficient Ca for maximum growth of Rhodes grass, in the surface, but higher rates would be required to allow Ca movement down the Na-dominated profile to ameliorate a larger rooting depth – this being important in environments where there are prolonged periods of water stress. The information presented will guide the efficient use of gypsum to ameliorate bauxite refining wastes.

Confidence intervals for the common coefficient of variation of rainfall in Thailand.

The log-normal distribution is often used to analyze environmental data like daily rainfall amounts. The rainfall is of interest in Thailand because high variable climates can lead to periodic water stress and scarcity. The mean, standard deviation or coefficient of variation of the rainfall in the area is usually estimated. The climate moisture index is the ratio of plant water demand to precipitation. The climate moisture index should use the coefficient of variation instead of the standard deviation for comparison between areas with widely different means. The larger coefficient of variation indicates greater dispersion, whereas the lower coefficient of variation indicates the lower risk. The common coefficient of variation, is the weighted coefficients of variation based on k areas, presents the average daily rainfall. Therefore, the common coefficient of variation is used to describe overall water problems of k areas. In this paper, we propose four novel approaches for the confidence interval estimation of the common coefficient of variation of log-normal distributions based on the fiducial generalized confidence interval (FGCI), method of variance estimates recovery (MOVER), computational, and Bayesian approaches. A Monte Carlo simulation was used to evaluate the coverage probabilities and average lengths of the confidence intervals. In terms of coverage probability, the results show that the FGCI approach provided the best confidence interval estimates for most cases except for when the sample case was equal to six populations (k = 6) and the sample sizes were small (nI < 50), for which the MOVER confidence interval estimates were the best. The efficacies of the proposed approaches are illustrated with example using real-life daily rainfall datasets from regions of Thailand.