Total Water Potential Research Articles

Enhancement of soil aggregation and physical properties through fungal amendments under varying moisture conditions.

Soil structure and aggregation are crucial for soil functionality, particularly under drought conditions. Saprobic soil fungi, known for their resilience in low moisture conditions, are recognized for their influence on soil aggregate dynamics. In this study, we explored the potential of fungal amendments to enhance soil aggregation and hydrological properties across different moisture regimes. We used a selection of 29 fungal isolates, recovered from soils treated under drought conditions and varying in colony density and growth rate, for single-strain inoculation into sterilized soil microcosms under either low or high moisture (≤-0.96 and -0.03 MPa, respectively). After 8 weeks, we assessed soil aggregate formation and stability, along with soil properties such as soil water content, water hydrophobicity, sorptivity, total fungal biomass and water potential. Our findings indicate that fungal inoculation altered soil hydrological properties and improved soil aggregation, with effects varying based on the fungal strains and soil moisture levels. We found a positive correlation between fungal biomass and enhanced soil aggregate formation and stabilization, achieved by connecting soil particles via hyphae and modifying soil aggregate sorptivity. The improvement in soil water potential was observed only when the initial moisture level was not critical for fungal activity. Overall, our results highlight the potential of using fungal inoculation to improve the structure of agricultural soil under drought conditions, thereby introducing new possibilities for soil management in the context of climate change.

Vortex Structure of Head Bubble in Convective Cloud Starting Plume

Abstract A developing cumulus cloud (Cu) was modeled, and dynamic, thermodynamic, and microphysical properties of an ascending head bubble reproducing the upper part of a developing Cu were investigated. The data for analysis are taken from 10-m-resolution LES of trade wind Cu under BOMEX conditions. The detection of a rising bubble is carried out using wavelet filtering of the velocity fields and microphysical fields, while a low-frequency signal of the filtering is associated with the convective-scale structure of cloud. We substantiate and discuss the representation of the bubble as a vortex ring, and estimate the parameters of this vortex ring. The simplest Hill’s vortex was chosen as a model of a vortex ring inside cloud. Analytical approximations of the radial profiles of the vertical velocity and of conservative quantities (such as total water mixing ratio and liquid water potential temperature inside and outside the bubble) are obtained. The spatial structure of these quantities is investigated using analytical expressions. Analytical models for spatial distributions of liquid water content (LWC) and adiabatic fraction (AF) are also designed and analyzed. The results demonstrate the existence of a cloud core with high values of LWC and AF up to the height of 1800 m. The horizontally averaged value of the adiabatic fraction, calculated analytically using the Hill’s vortex concept, is evaluated as 0.39, which is the typical AF value in the upper parts of such Cu. The vertical profiles of different important quantities characterizing cloud structure are presented. The analysis performed in this study allows us to conclude that a rising vortex ring plays the dominating role in formation of the thermodynamic and microphysical structure of developing Cu. Significance Statement 1) Dynamic and thermodynamic fields of a developing cumulus cloud simulated by high-resolution LES with spectral bin microphysics are separated into convective and turbulent components by means of the wavelet technique. 2) The analysis of convective component of the cloud revealed the existence of a vortex ring at the developing stage of the cloud and evaluate its parameters. 3) The analysis performed in this study allows us to conclude that a rising vortex ring plays the important role in formation of the thermodynamic and microphysical structure of developing Cu. 4) The study provides a novel insight into the cloud–environment interaction. 5) The approximating equations describing the vortex ring can be usefully applied for developing new schemes of convective parameterization.

Using Grapevine Water Status Measurements for Irrigation Scheduling of Table Grapes - A Review

Water is becoming an increasingly scarce resource, so agriculture competes with urban and industrial needs for water. The production of table grapes with high export potential is the objective of South African producers. Growth, production, ripening aspects and quality parameters of table grapes can potentially be manipulated by means of irrigation. Consequently, it is an important management practice to help ensure economically viable table grape production. The objective for optimum irrigation scheduling should be to combine soil and plant water status measurements to calibrate grapevine water potential against reliable soil water monitoring instruments. Considering previously reported literature, poorer vegetative growth was related to lower levels of leaf water potential (YL). Given that berry size is a crucial aspect for yield as well as quality, it was evident that low levels of water potential can restrict berry development, thereby reducing berry size. Bunch mass was lower where there were lower levels of YL, pre-dawn leaf water potential (YPD) and total diurnal water potential (YTot). Poorer yield was generally related to lower levels of YL experienced throughout the season. However, lower levels of YL in the post-veraison period did not affect grapevine yield. The juice TSS did not respond to levels of YL but juice total titratable acidity (TTA) was related to lower levels of YL. Grape colour was affected where wet soil conditions induced higher levels of YL as well as where dry soil conditions induced lower levels of YL.

Effects of Groundwater Level Control on Soil Salinity Change in Farmland around Wetlands in Arid Areas: A Case Study of the Lower Reaches of the Shiyang River Basin, China

The farmland around wetlands in the lower reaches of an arid area is susceptible to salinization. To explore the effects of the groundwater level control at an irrigation cycle scale on the salt concentration of the topsoil solution, this study carried out groundwater level control and irrigation experiments using the intelligent groundwater control and in-situ field monitoring system (also referred to as the groundwater control system) in the experimental base for groundwater control of the Shiyang River basin. On this basis, this study compared and analyzed the changes in groundwater depth, soil salinity, soil moisture content, and total water potential in zones with and without groundwater control (also referred to as the control and non-control zones, respectively). Results show: (1) When the groundwater depth increased by about 50 cm under the influence of the groundwater control system, the salt accumulation layer of the soil bulk shifted downward by about 20 cm, and the topsoil bulk salt (at a depth of less than 40 cm) decreased to below 5.0 g/kg; (2) In summer, the pore water electrical conductivity (ECp) of the topsoil in the control and non-control zones exhibited alternating rapid decreases and slow increases. In the concentration stage of the soil solution, the ECp of the topsoil in the non-control zone had significantly higher increased amplitude than that in the control zone, especially 3–8 days after irrigation. At this stage, the ECp of the topsoil in the control and non-control zones increased in two (slow and rapid increase) and three (slow, rapid, and fairly rapid increase) periods, respectively; (3) At the concentration stage of the topsoil solution, both the moisture content and solution salt content of the topsoil in the control zone were in a negative equilibrium state, with the absolute values of the equilibrium values gradually increasing. In contrast, the moisture content and solution salt content of the topsoil in the non-control zone were in negative and positive equilibrium, respectively, with the absolute values of their equilibrium values gradually increasing. The groundwater control system can mitigate the concentration rate of the topsoil solution by increasing the groundwater depth and influencing the water and salt equilibrium of the topsoil solution, which can create a suitable topsoil salt environment for crop growth. This study is of great significance for determining an appropriate ecological water level interval and optimizing groundwater control strategies for farmland around wetlands.

Quantifying Coupling Effects Between Soil Matric Potential and Osmotic Potential

AbstractSoil matric potential and osmotic potential are widely accepted as two independent components of total soil water potential. However, laboratory observations repeatedly demonstrated that matric potential can vary with salt concentration, implying a potential coupling between matric potential and osmotic potential. To date, it remains elusive whether matric potential and osmotic potential are independent or not and why so, and a theoretical theory for quantifying the coupling between them is still missing. Herein, a theoretical model is developed to quantitatively explain this problem via a lens provided by a recent concept of soil sorptive potential (SSP). The proposed model substantiates that matric potential and osmotic potential are not independent. The increasing salt concentration can notably depress two variables underpinning SSP, namely relative permittivity and electrical double layer thickness, leading to non‐negligible decreasing (more negative) of matric potential in the high suction range, and increasing (less negative) of it in the low suction range. In turn, the soil‐water interactions redistribute ions in soil water, raising osmotic potential especially for clay with high cation exchange capacity. The proposed model shows excellent performance in capturing experimental data, validating its accuracy. A parametric study implies that the neglection of coupling effects can lead to a significant underestimation of soil hydraulic conductivity in the film flow regime.

Yield, quality and physiological variation of strawberry in response to irrigation regimes and exogenous proline with a cost benefit analysis

Strawberry (Fragaria × ananassa Duch.) production is a major aspect of the agricultural economy in Turkey's Mediterranean region, offering high rates of employment and farm revenue. The effects of treatment of the exogenous amino acid on yield, quality, and physiological diversity for strawberry production was analyzed considering the economic aspects. To achieve this, 4 different irrigation regimes (IR (irrigation) 125, IR100, IR75, IR50) with proline treatment was tested. The total berry yield, photosynthesis and leaf water potential (LWP) significantly decreased as irrigation application rates declined. The IR125 treatment with proline (PIR125) produced the highest overall berry production. The use of proline significantly increased berry production by 23%. Exogenous proline generated 3.5 kg/1 m3 greater yields than control in terms of irrigation water use efficiency (IWUE). Under the IR50 conditions, the treatment of proline yielded a 32% higher than the control. Moreover, proline significantly increased fruit soluble solids content (SSC) by 6.4%. The production system achieves the highest cost-benefit ratio (CBR) under PIR125 whereas the lowest cost-benefit ratio under IR50. When each scenario was considered at individually, it was evident that the more water used the more efficient high tunnel strawberry production. The fact that proline generated an increase in CBR in all four irrigation regimes proves this amino acid's economic effectiveness. As a result, PIR125 is recommended for the highest efficiency and CBR in Mediterranean environment. However, it has been discovered that using proline to alleviate this problem in areas where water is limited could be quite helpful.

Analysis of Surface Water Availability to Meet Agricultural Water Demands in Kediri Regency, Indonesia

This study aims to analyze the potential of surface water to meet agricultural water needs in Kediri Regency, Indonesia. Data from government agencies (i.e., Indonesian Bureau of Meteorology, Climatology, and Geophysics and Kediri Agriculture Office) and fieldwork were analyzed to achieve the research objectives. The data obtained consisted of rainfall, temperature, infiltration capacity, soil texture, root depth, and agricultural land area. The potential of surface water resources was calculated by using the Thornthwaite–Mather water balance method. The water balance results were compared with agricultural water demands, which were calculated on the basis of the area of agricultural land and type of crop, particularly paddy fields. Critical and noncritical conditions for surface water resources were classified on the basis of the ratio between the availability of surface water resources and the demand for agricultural water. Results showed that the total surface water potential widely varied by season. The water balance calculation indicated that all subwatersheds (SWs) experienced a water surplus in the rainy season, whereas almost all SWs were deficient in surface water in the dry season, Overall, the surface water in Kediri was critical in the rainy season and more severely critical in the dry season. The results of this study indicated that the high demand for agricultural water can affect the availability of water resources in the tropics. The results are expected to be considered in determining regional planning related to the use and need of water resources and supporting infrastructures.

An Updated CLUBB PDF Closure Scheme to Improve Low Cloud Simulation in CAM6

AbstractCloud Layers Unified By Binormals (CLUBB) adopts the joint probability density function (PDF) to close higher‐order turbulence and diagnose the cloud fraction. CLUBB assumes the equal PDF width of vertical velocity () as the default closure scheme, called Analytic Double Gaussian 1 (ADG1). In this study, a new unequal width PDF closure scheme is adopted in CLUBB, in which the PDF width of is assumed to be associated with skewness and kurtosis of vertical velocity. Offline calculation shows that the updated closure scheme improves the tail in the joint PDF and produces the saturation area from the joint PDF of the total water and liquid water potential temperature closer to that derived from large‐eddy simulations than ADG1. The new PDF scheme implemented in Community Atmosphere Model Version 6 is shown to increase low cloud fraction by 20%–30% in most stratocumulus‐to‐cumulus transition regions. The updated closure scheme is found to improve the low cloud simulation by simulating more symmetric turbulence in stratocumulus and stronger turbulent transport in shallow cumulus. Furthermore, the updated closure scheme enhances the cloud fraction near the cloud base by interacting with the microphysical scheme. Our work indicates the importance of continuous improvement in the PDF closures for higher‐order turbulence schemes.

Dynamic water potential waves in unsaturated soils

Quantitative descriptions of the temporal and spatial variations of volumetric water content and total water potential in unsaturated soils have for more than nine decades focused on diffusive mechanisms as represented by the Richards equation (Richards, 1931). However, recent laboratory studies (Lo et al., 2017) have revealed short-time transient behavior of water in non-deforming unsaturated soils that is distinctly oscillatory, not diffusive. In this paper, we establish a theoretical framework to generalize the Richards equation in a systematic way to account for non-diffusive mechanisms giving rise to oscillatory behavior in the water content and total water potential. A partial differential equation is developed, with the total water potential as the dependent variable, based on the coupling of mass and linear momentum balance within the continuum theory of mixtures. This new differential equation becomes equivalent to the Richards equation when non-diffusive mechanisms can be neglected, but when this condition is not met, the governing equation describes damped propagating wave behavior of the total water potential. This dynamic wave differs from a poroelastic wave in respect to solid framework motions and wave speed, as well as time and length scales. For a rigid, homogeneous unsaturated soil, the governing equation reduces to the telegraph equation, which can be solved analytically. An inherent feature of our approach is the appearance of natural time and length scales characteristic of total water potential waves. Consideration of these natural scales for three representative soils of differing texture helps to prescribe more precisely the domain of applicability of the Richards equation.

Infection by Moniliophthora perniciosa reprograms tomato Micro-Tom physiology, establishes a sink, and increases secondary cell wall synthesis.

Witches' broom disease of cacao is caused by the pathogenic fungus Moniliophthora perniciosa. By using tomato (Solanum lycopersicum) cultivar Micro-Tom (MT) as a model system, we investigated the physiological and metabolic consequences of M. perniciosa infection to determine whether symptoms result from sink establishment during infection. Infection of MT by M. perniciosa caused reductions in root biomass and fruit yield, a decrease in leaf gas exchange, and down-regulation of photosynthesis-related genes. The total leaf area and water potential decreased, while ABA levels, water conductance/conductivity, and ABA-related gene expression increased. Genes related to sugar metabolism and those involved in secondary cell wall deposition were up-regulated upon infection, and the concentrations of sugars, fumarate, and amino acids increased. 14C-glucose was mobilized towards infected MT stems, but not in inoculated stems of the MT line overexpressing CYTOKININ OXIDASE-2 (35S::AtCKX2), suggesting a role for cytokinin in establishing a sugar sink. The up-regulation of genes involved in cell wall deposition and phenylpropanoid metabolism in infected MT, but not in 35S::AtCKX2 plants, suggests establishment of a cytokinin-mediated sink that promotes tissue overgrowth with an increase in lignin. Possibly, M. perniciosa could benefit from the accumulation of secondary cell walls during its saprotrophic phase of infection.

Validating the Generality of a Closed-Form Equation for Soil Water Isotherm

Total soil water potential ψt is conventionally defined as the sum of matric potential ψm and osmotic potential ψo, i.e., ψt=ψm+ψo, when gravitational potential is ignored. Soil water isotherm (SWI) is the constitutive relationship between ψt and soil water content w, i.e., ψt(w)=ψm(w)+ψo, where ψm(w) is called soil water retention curve (SWRC) or soil water characteristic curve. SWI and SWRC are arguably the two most important soil constitutive relationships because they govern virtually all phenomena in soil such as flow, stress and deformation, and biological activities. A closed-form SWI, recast from a generalized SWRC equation for adsorption and capillarity, is experimentally validated for its generality in representing SWI. Adsorption isotherms of 49 soils, covering all spectrum of soil types with plasticity index up to 185% and specific surface area up to 600 m2/g, are used to validate the SWI equation. It is shown that the SWI equation can nearly perfectly represent the isotherms of these soils with almost all of the coefficients of determination R2≥0.99, validating the generality of the SWI equation. Comparative analysis is also conducted by using two existing SWI equations, namely, the Brunauer–Emmett–Teller (BET) equation and the augmented BET (A-BET) equation. It is demonstrated that the SWI equation is superior to the BET and A-BET equations in representing soil–water interactions by adsorption and capillarity, and in the full relative humidity range.

Water use efficiency of castor bean under semi-arid conditions of Brazil

Castor bean is one of the main and promising agricultural crops for the production of biodiesel, castor oil and castor bean cake, which have high added value, especially the castor oil. The objective of the present study was to evaluate the water use efficiency (WUE) of castor bean cultivars by assessing the soil water balance components (storage and water storage variation; internal drainage; capillary rise; irrigation depth; rainfall and actual evapotranspiration), according to the phenological stages. The experimental design was in randomized blocks, in 8 × 6 factorial scheme (eight cultivars: BRS Paraguaçu; EBDA MPA11; EBDA MPB01; IAC 2028; IAC 226; BRS Nordestina; IAC Guarani, AG IMA 110–204 and BRS Energia and six periods of evaluation), with three repetitions and 15 plants in each experimental plot. Daily monitoring of soil water content was performed with a capacitance probe (Frequency Domain Reflectometry - FDR, PR2/6 model), at depths of 0.1, 0.2, 0.3, 0.4 and 0.6 m, with 0.6 m being the lower limit of the soil control volume for castor bean. The total soil water potential gradient was determined with tensiometers installed at depths of 0.5 and 0.7 m, and the flux densities were estimated using the Darcy-Buckingham equation. Supplemental irrigation was efficient in maintaining water availability during the crop cycle. Soil water storage was lower for the most productive castor bean cultivar (EBDA MPA 11), with an inverse relationship between yield and water storage, due to its water requirement. The highest and lowest values of internal drainage and capillary rise were found for BRS Nordestina and IAC 226, respectively. EBDA MPA 11 had the best water use efficiency among the castor bean cultivars, differing only from IAC Guarani and EBDA MPB 01.

Effect of land use change on hydrology of forested watersheds

AbstractLand use/cover changes (LUCCs) in megacities can be rapid and extensive and lead to unintended consequences in sustainable watershed management. The aim of this study was to investigate effects of LUCC on hydrological components using Soil & Water Assessment Tool (SWAT) model in Terkos Basin, Turkey. Four LUCC scenarios (deforestation, urbanization, decrease in agricultural land and expansion in agricultural land) were set up regarding possible future land use changes in the watershed. Surface runoff was the main hydrological component that was impacted by LUCCs. Urbanization and conversion into agricultural lands scenarios resulted in considerable increases in surface runoff. Annual change of surface runoff for urbanization and conversion into agricultural lands scenarios was over 45% when compared to the baseline scenario. More remarkable changes were seen in dry months among the scenarios. Controlling the overall response of the hydrological systems to LUCC depends on better understanding of surface runoff processes. LUCC scenarios were also assessed based on freshwater availability components blue water and green water. The average annual total blue water potential, annual total green water flow and average green water storage of studied sub‐basin were 537, 584 and 108 mm/year for the baseline scenario, respectively. The trends of the blue water flow and green water storage were similar for each scenario, in that they were closely related to precipitation. This study provides valuable insight into hydrological impacts of possible land use changes on forested watersheds.

Geomatic Assessment Of Rainwater Harvesting Potential System At Cmr College Of Engineering & Technology

CMRCET campus comprises about 10 of acres land, where water is the natural resource which is being always in high demands. If the demand is not met, then it will lead to water scarcity. Therefore, RWHS can be considered as a best solution for fighting against scarcity of water. Our present study deals with the identification of the study area boundary and marking it as a Polygon in GIS, Rooftops of various block entities, paths and pavements were digitized using the Polygon vector in GIS. GIS technique is employed for locating boundaries of the study area and for calculating the areas of various types of rooftops and paths. With the application of GIS, it is possible to assess the total potential of water that can be harvested. Potential of rainwater harvesting refers to the capacity of an individual catchment that harnesses the water falling on the catchment during a particular year considering all rainy days. This present study will enable us to identify the suitable type of water harvesting structure along with the number of structures required. Our aim is to maximize water storage and minimize the runoff through drains without making use of it. Thus, Rainwater Harvesting and Conservation aim at the optimum utilization of the rain water.

Investigation of Distinctive Morpho-Physio and Biochemical Alterations in Desi Chickpea at Seedling Stage Under Irrigation, Heat, and Combined Stress.

Global climatic instabilities have become the main reason for drastic yield losses in chickpea. This shift in climate could be a great threat in the future for food security in developing countries. Chickpea production is badly hampered by heat stress coupled with drought stress, and these factors can reduce yields by 40–45%. To mitigate yield losses due these abiotic factors, irrigation supplementation could be the best strategy. The present study aimed to (i) investigate the tolerance response of 9 desi chickpea genotypes against heat stress (H), irrigation (I), and a combination of both (I+H) through morphophysiological and biochemical indices at early growth stage, and (ii) assess yield performance across multiple locations of the country. Results revealed that under irrigation treatment, all genotypes perform well, but the genotypes D-09027 and D-09013 showed best performance because, as compared to control, they retained root length, seedling fresh weight, root fresh weight, root dry weight, esterase activity, Malondialdehyde (MDA) content, total chlorophyll, and total carotenoids. Shoot length and total phenolic contents (TPC) increased in both genotypes. Superoxide dismutase (SOD) and peroxidase (POD) increased in D-09027 and retained in D-09013. Catalase activity increased in D-09013 and retained in D-09027. Protease activity, total water potential and osmotic potential decreased in both genotypes and depicted high yield potential with 27 and 30% increase in yield over Bhakhar-2011 (check), respectively. In case of heat stress, maximum tolerance was found in genotypes CH104/06 and D-09013 with no change in shoot and root length, seedling dry weight, shoot fresh and dry weight, root dry weight, relative water content, turgor water potential, catalase (CAT) activity, esterase activity, increased root fresh weight, peroxidase activity (POD), ascorbate peroxidase activity (APX), and lycopene with low accumulation of protease and Malondialdehyde content (MDA). Both genotypes depicted high yield potential with 30 and 43% increase in yield over check across multiple locations of the country. Under the combined treatment, most genotypes showed good performance, while CH104/06 was selected as best performer genotype because significant of its increased root fresh weight, lycopene content, chlorophyll b, total carotenoids, total chlorophyll, retained shoot length, root length, seedling fresh and dry weight, total water potential, osmotic potential, relative water content, peroxidase activity (POD), catalase, esterase, and its ascorbate peroxidase (APX) activity and total soluble proteins (TSP) showed highest yield potential with 43% increase over check. Identified best performing and tolerant genotypes can further be employed for breeding climate-smart chickpea genotypes for sustainable production under changing climate.

Linear Relationship of a Soil Total Water Potential Function and Relative Yield—A Technique to Control Salinity and Water Stress on Golf Courses and Other Irrigated Fields

A simple empirical approach is proposed for the determination of crop relative yield (%) through the soil total water potential (kPa). Recurring to decimal logarithms, from analytical exponential expressions, a linear simple relationship of soil total water potential Ψt (matric Ψm + potential Ψo) function and crop relative yield was studied and developed. The combination of the salinity model, the soil water retention model and the matric potential approach were used to reach this objective. The representation of turfgrass crop relative yield (%) versus a function of soil total water potential f(Ψt) values was shown through a log-normal graph (y = a + mx); the log scale axis “y” (ordinates) defines relative yield Yr, being two the origin ordinate “a” and “m” the slope; the normal decimal scale axis “x” (abscissa) is the function of soil total water potential f(Ψt). Hence, it is possible, using only two experimental points, to define a simple linear relation between a function of soil total water potential and crop relative yield, for a soil matric potential value lower than −20 kPa. This approach was first tested on golf courses (perennial turfgrass fields), but it was further decided to extend it to other annual crop fields, focused on the model generalization. The experimental plots were established, respectively, in Algarve, Alentejo and Oeiras (Portugal) and in the North Negev (Israel). Sprinkler and trickle irrigation systems, under randomized blocks and/or water and salt gradient techniques, were used for water application with a precise irrigation water and salt distribution. Results indicated that there is a high agreement between the experimental and the prediction values (R2 = 0.92). Moreover, the precision of this very simple and easy tool applied to turfgrass fields and other irrigated soils, including their crop yields, under several different sites and climatic conditions, can contribute to its generalization.

Experimental Study on the Lateral Seepage Characteristics in the Tension Saturated Zone.

To study the lateral seepage field in the tension saturated zone (TSZ), an experiment with no evaporation and precipitation infiltration was carried out in a self-made seepage tank filled up with fine sand. Based on the data and plots obtained, the lateral seepage field distribution features in the TSZ can be divided into three area for discussion: ascending area, descending area, and the nearly horizontal flow area. In the ascending and descending area, the total water potential gradient diminished from the recharge area to the discharge area and the seepage velocity was faster. In the nearly horizontal flow area, the total water potential gradient was lower and the seepage velocity was slower. The pressure potential gradually decreased horizontally from the recharge area to the discharge area, while in the vertical profile, it gradually decreased from the bottom to the top in the whole seepage area. In the absence of evaporation, the vertical water exchange among the saturated zone, TSZ, and unsaturated zone in nearly horizontal flow area is weak. Contrarily, in the ascending area and descending area, vertical water flows through both the phreatic surface and the upper interface of the TSZ. When there is lateral seepage in the TSZ, the thickness of the TSZ generally increases from the ascending area to the nearly horizontal area and then to the descending area. It should be pointed out that in the nearly horizontal area, the TSZ thickness is approximately equal to the height of the water column. Overall, the lateral seepage in the TSZ can be regarded as a stable siphon process, hence the siphon tube model can be further used to depict this lateral seepage.

Menadione sodium bisulphite regulates physiological and biochemical responses to lessen salinity effects on wheat (Triticum aestivum L.).

Salinity is a significant constraint for plant survival and productivity. Therefore, an immediate solution to this problem is sought to meet the human population's food demands. Recently, Menadione sodium bisulphite (MSB) has emerged as a significant regulator of plant defense response under abiotic stress. Studies on MSB are scarce, and a few reports on salinity (Arabidopsis and okra) and cadmium stress (okra) are present in the literature. However, these studies did not include the impact of MSB on physiological and plant water relation attributes, critical mediators of plant survival, and yield production under stress. Our results studied the impact of MSB on wheat administered to NaCl salinity in hydroponics medium. We used two wheat cultivars (salt-sensitive MH-97 and salt-tolerant Millat-2011, based on our pre-experimental studies). Seeds were primed in different MSB doses [control (unprimed), hydroprimed, 5, 10, 20, and 30mM]. Salinity significantly diminished growth, chlorophyll molecules, photosynthesis, total free amino acids, water and turgor potentials, K, Ca, and P contents of wheat when administered NaCl salinity in the nutrient solution. Besides, a noteworthy accretion was present in oxidative stress markers [hydrogen peroxide & malondialdehyde], proline, ascorbic acid, antioxidant enzyme activities, and Na+ accumulation under salinity. Moreover, MSB noticeably enhanced chlorophyll molecules, proline, and oxidative defense to improve photosynthesis, plant water relations, and diminish specific ions toxicity. Our results manifested better defense regulation in salt-administered plants primed with 5 and 10mM MSB. Our findings strongly advocated the use of MSB in improving plant salinity tolerance, particularly in wheat.

Seedlings from two Agave species differing in microhabitat evolve different tolerance mechanisms to drought and shade under nurse plants

ABSTRACT We studied two Agave species differing in microhabitat; when adult, A. striata is light-tolerant and A. salmiana is drought-tolerant. However, both species establish under nurse plants. The aim of this work was to investigate the ecophysiological mechanisms of these two species to tolerate different shade and water conditions at the seedling stage. Seedlings were grown for six months under two water treatments (well-irrigated and drought) and three shade treatments, denominated high shade (HS), medium shade (MS) and low shade (LS) (241, 563 and 804 µmol m−2 s−1 of photosynthetic photon flux density, respectively). Concentrations of chlorophylls a and b, total chlorophylls, carotenoids and water potential (Ψ) were analyzed. The decreasing shade levels in combination with the regime “well-irrigated” did promote increased concentration of carotenoids in A. salmiana but not in A. striata. Besides, the well-irrigated plants produced high concentration levels of chlorophyll b and total chlorophyll in both species, showing no changes due to shade treatments. Conversely, drought generated significantly low concentrations of the pigments in A. striata with no variations due to shade treatments. Furthermore, concentrations of the pigments of A. salmiana under drought at HS and MS were similar to those for well-irrigated plants, but diminished at LS. Likewise, drought reduced Ψ in A. striata but not in A. salmiana, regardless of the shade effect. These results indicate that the tolerance of seedlings to drought stress and decrease in shade in A. salmiana relates to its mechanisms for maintaining hydration, whereas in A. striata this depends on mechanisms that keep the concentration of pigments stable. Thus, Agave species evolve different mechanisms for tolerating drought and low solar radiation stress.

Evaluation of Ionic Osmotica in Succulent and Non-succulent Xero-halophytes Inhabiting Hot Oases

This research was carried out at Kharga and Dakhla, in the western Egyptian desert. The species investigated include basically those of different ecological affiliations as well as different life forms, in order to have comparative indications in the ionic means of adjustment. During winter and summer, the water soluble ions in both soil and plants were analyzed. Also, the total osmotic water potential and the share of ionic radicals of plants were calculated. The data revealed that, halophytic species maintain osmotic adjustment due to accumulation of ions depending on seasonal and species variation and ionic osmotic potential which were related to chlorides, sodium and potassium. The seasonality or location has the dominant effect on Na+, K+, Cl- and SO4-2 concentrations in halophytes Suaeda and Cressa and affected by the interaction (S x L) in case of Z.coccenium. The ionic osmotic potential of Na+/K+ and Cl- / SO4-2 ratios for salt tolerance in studied species were discussed.