Plant Water Balance Research Articles

Temporal and spatial variations in the frequency of compound hot, dry, and windy events in the central United States

Simultaneous low humidity, high temperature, and high wind speeds disturb the water balance in plants, intensify evapotranspiration, and can ultimately lead to crop damage. In addition, these events have been linked to flash droughts and can play a critical role in the spread of human ignited wildfires. The spatial patterns and temporal changes of hot, dry, and windy events (HDWs) for two time periods, 1949 to 2018 (70-years) and 1969 to 2018 (50-years) were analyzed in the central United States. The highest frequencies of HDWs were observed at stations in western Kansas and west Texas. Annually, the highest number of events happened concurrently with the major heat waves and droughts in 1980 and 2011. Temporally, an overall decrease in the HDWs was significant in the eastern regions of North Dakota and South Dakota, and an upward trend was significant in Texas and the western part of the Great Plains. Significant trends in HDWs co-occurred more frequently with significant trends in extreme temperatures compared with low humidity or strong wind events. The results of this study provide valuable information on the location of places where HDWs are more likely to occur. The information provided could be used to improve water management strategies.

Allelopathic Interference of Plant-Water Relationships By Para-Hydroxybenzoic Acid

Soybean seedlings were used as the test species to investigate the effect of phydroxybenzoic acid (pHBA) on growth and plant-water relationships. Plants were grown in nutrient solution under greenhouse conditions and were subjected to pHBA through amendments to the growth medium. Treatments were initiated 10 days after germination and continued for either 14 or 28 days with stomatal conductance, water potential, and water use monitored periodically At harvest, effects on growth were determined and, in the 28-day study, the carbon isotope ratio (^13C:^12C) of leaf tissue was analyzed as an indicator of integrated effects on plant-water status Soybean growth was significantly reduced by 0.5mM pHBA, or higher concentrations, with the degree of inhibition being concentration dependent Plants treated with 0.75mM pHBA had significantly lower stomatal conductance, lower water potential, and less discrimination against ^13C Similar trends were apparent in 0.5mM pHBA-treated plants. Interference with plant-water balance appears to be one mechanism of action of pHBA causing a reduction in plant growth.

Plants use water in the pores of rock fragments during drought

Soils are composed of both fine and coarse materials. Coarse material (> 2 mm) is considered to be inert and is usually discarded in models of plant water balance, even though it affects soil properties. No studies have yet attempted to assess whether rock fragments may act as a water reservoir for plants. Cuttings of Populus euramericana were planted in 5-L pots containing reconstituted soil made up of fine earth (silty clay loam texture) and either limestone or inert (quartz) pebbles (rock fragments 2–5 cm) at 0, 20, and 40% volume in a cross-factorial experiment. Two drought periods were applied and the growth, evapotranspiration, water stress status by stomatal conductance, and water content of the two soil phases (fine earth and pebbles) were monitored. First, pebbles can contain water, and ignoring this water induced and underestimations of the soil available water content by respectively 11% and 30% for the treatment with 20% and 40% limestone pebbles. Second, the plants grown on limestone pebbles were up to 70% less stressed than the plants grown on inert pebbles during drought. Third, stomatal conductance, a water stress indicator, was correlated with the water content of both the fine earth and the limestone pebbles. These results demonstrate that limestone rock fragments can retain available water and act as a reservoir during drought periods.

ScPNP-A, a plant natriuretic peptide from Stellera chamaejasme, confers multiple stress tolerances in Arabidopsis

As a class of peptide hormone, plant natriuretic peptides (PNPs) play an important role in maintaining water and salt balance in plants, as well as in the physiological processes of biotic stress and pathogen resistance. However, in plants, except for some PNPs, such as the Arabidopsis thaliana PNP-A (AtPNP-A), of which the function has not yet been thoroughly revealed, few PNPs in other plants have been reported. In this study, a PNP-A (ScPNP-A) has been identified and characterized in Stellera chamaejasme for the first time. ScPNP-A is a double-psi beta-barrel (DPBB) fold containing protein and is localized in the extracellular (secreted) space. In S. chamaejasme, the expression of ScPNP-A was significantly up-regulated by salt, drought and cold stress. Changes at the physiological and biochemical levels and the expression of resistance-related genes indicated that overexpression of ScPNP-A can significantly improve salt, drought and freezing tolerance in Arabidopsis. ScPNP-A could stimulate the opening, not the closing of stomata, and its expression was not enhanced by external application of ABA. Furthermore, overexpression of ScPNP-A resulted in the elevated expression of genes in the ABA biosynthesis and reception pathway. These suggested that there may be some cross-talk between ScPNP-A and the ABA-dependent signaling pathways to regulate water related stress, however further experimentation is required to understand this relationship. In addition, overexpression of ScPNP-A can enhance the resistance to pathogens by enhancing SAR in Arabidopsis. These results indicate that ScPNP-A could function as a positive regulator in plant response to biotic stress and abiotic stress.

Comparative analysis of heavy metals accumulation in the soil - plant system by the geo-accumulation index and transpiration rate of Zea mays L

The aim of work is the assessment of the effect of water deficiency in the soil, taking into account the characteristics of the migration of heavy metals in the soil - plant system using the example of mays ( Zea mays L . ). The samples studied grew in the coastal areas of the Debet, Shnogh and Araks rivers. The selection of plant material was carried out during the growing season at the test sites in clear dry weather. The analysis of the coastal soil and annual plant on the content of Mn, Cu, Co, Zn, Mo was performed using the “Thermo Scientific Niton XRF Portable Analyzer”. According of obtained results the coefficient of the geo-accumulation index was calculated, identifying the main migration characteristics of heavy metals in the soil - plant system. Drought tolerance was identified at the seedling stage by changing the growing conditions by changing of watering of the plot. Calculation of the intensity of transpiration revealed changes in the water balance in plants depending on the soil and climatic growing conditions. According to the obtained results, it is noted that with an increase in the geo-accumulation index of heavy metals in the soil, the plant shows a significant decrease in the intensity of transpiration. Thus, in the course of the experiments, it was established that samples of corn from the arid region of Hushakert had a low level of transpiration, compared with samples from the moderately humid region of Shnogh. Combining the results on the content of heavy metals in corn kernels with the intensity of transpiration made it possible to investigate the correlation between the cumulative ability of the studied chemical elements and the regulation of water balance in the plant in response to drought. Among the main factors contributing to the increase in the migration of heavy metals is the content of potassium and calcium in the plant sample.

Expression analysis of aquaporin genes in Saussurea involucrata rosette leaves and functional analysis of upregulated SiPIP1;5A under low-temperature stress

Aquaporin proteins (AQPs), which are distributed in distinct membranes and function in the transport of water across cell membranes, are important for the water balance of plants in general, and especially for low-temperature adaptation. The expression of AQP genes in Saussurea involucrata (Kar. et Kir), which is highly tolerant to chilling and freezing stresses, should be distinctive from that of other cold-sensitive plants. Six tonoplast intrinsic protein (TIP) and eight plasma membrane intrinsic protein (PIP) genes were identified in S. involucrata. Among these, three TIPs and five PIPs were upregulated at a freezing temperature and SiPIP1;5B was upregulated only under chilling stress. Moreover, the expression profiles of AQP genes under chilling stress differed from those under freezing stress. The effects of light on AQP gene expression were maintained under both chilling and freezing stresses. Furthermore, the effect of light on the expression of different AQP genes differed under freezing stress between cases with and without cold acclimation. Specifically, the effect of light on SiPIP2;2 and SiPIP2;4B expression was abolished when no cold acclimation was performed. Functional analysis of SiPIP1;5A showed that its overexpression enhanced the low-temperature tolerance of tomato. We concluded that the upregulation of AQPs promoted the cold adaptation of S. involucrata. This research provides a preliminary foundation for understanding the tolerance to low temperature achieved through regulating the cell water balance.

Techniques to Determine the Effects of Jasmonates on Root Hydraulic Conductivity.

Plants subjected to drought and saline stress conditions suffer from tissue dehydration. Such dehydration is caused by the imbalance between root water uptake by roots and water loss by transpiration. Therefore, determination of root hydraulic properties is crucial to understand plant water balance. Root hydraulic conductivity (L) can be used to estimate root water transport capacity. L depends on root architecture (length and diameter of the root and proliferation of secondary roots), radial water transport pathway (root xylem vessels, plasmodesmata, apoplastic space, caspary bands), and on intrinsic membrane permeability to water (aquaporins, water membrane protein channels). Different methods have been developed to measure L, such as Pressure Chamber, Free Exudation, High-Pressure Flowmeter (HPFM), and Root Pressure Probe (RPP). In this chapter, we will focus on Pressure Chamber, Free Exudation, and HPFM methods which have been used to determine the effect of jasmonates (JA) on root hydraulic conductivity.

Irrigation Requirement for Eucalyptus pellita during Initial Growth

The growth of Eucalyptus pellita in forestry plantations requires attention to water requirements, especially in the initial growth phase from seedling to field-ready plant. In this study, actual evapotranspiration (ETa), crop coefficient (Kc), and the irrigation requirement of E. pellita were assessed during the nursery growth phase (day 40–142). The experimental set-up included lysimeters with different treatments in terms of plants, drainage, and soil conditions. Plant growth and water balance were monitored during June September 2018 in an open nursery area in Riau, Indonesia. ETa was determined by the water balance lysimeter method and potential (reference) evapotranspiration (ETo) was extracted based on the Penman-Monteith method (FAO/56). The results showed that the average Kc value for E. pellita at age 40–142 days is 0.79, which exceeds that reported for E. grandis. The recommended irrigation requirement varies depending on precipitation, from 70 mL/plant/day with no rainfall to zero at precipitation of >30 mm/day. This is the first study to assess water use in E. pellita growing in pots during the nursery phase, which provides guidance on irrigation requirements during their initial growth phase.

Linking coordinated hydraulic traits to drought and recovery responses in a tropical montane cloud forest

Understanding plant hydraulic functioning and water balance during drought has become key in predicting species survival and recovery. However, there are few insightful studies that couple physiological and morphological attributes for many ecosystems, such as the vulnerable Tropical Montane Cloud Forests (TMCF). In this study, we evaluated drought resistance and recovery for saplings for five tree species spanning deciduous to evergreen habits from a Mexican TMCF. In drought simulations, water was withheld until plants reached species-specific P50 or P88 values (pressures required to induce a 50 or 88% loss in hydraulic conductivity), then they were rewatered. Drought resistance was considered within the isohydric-anisohydric framework and compared to leaf gas exchange, water status, pressure-volume curves, specific leaf area, and stomatal density. The TMCF species closed stomata well before significant losses in hydraulic conductivity (isohydric). Yet, despite the coordination of these traits, the traits were not useful for predicting the time needed for the species to reach critical hydraulic thresholds. Instead, maximum photosynthetic rates explained these times, reinforcing the linkage between hydraulic and carbon dynamics. Despite their varying hydraulic conductivities, stomatal responses, and times to hydraulic thresholds, 58 of the 60 study plants recovered after the rewatering. The recovery of photosynthesis and stomatal conductance can be explained by the P50 values and isohydry. This study raises new questions surrounding drought management strategies, recovery processes, and how lethal thresholds are defined. Further studies need to consider the role of water and carbon balance in allowing for both survival and recovery from drought.

Comparative Physiological and Biochemical Changes in Tomato (Solanum lycopersicum L.) Under Salt Stress and Recovery: Role of Antioxidant Defense and Glyoxalase Systems.

Salinity toxicity and the post-stress restorative process were examined to identify the salt tolerance mechanism in tomato, with a focus on the antioxidant defense and glyoxalase systems. Hydroponically grown 15 day-old tomato plants (Solanum lycopersicum L. cv. Pusa Ruby) were treated with 150 and 250 mM NaCl for 4 days and subsequently grown in nutrient solution for a further 2 days to observe the post-stress responses. Under saline conditions, plants showed osmotic stress responses that included low leaf relative water content and high proline content. Salinity induced oxidative stress by the over-accumulation of reactive oxygen species (H2O2 and O2•−) and methylglyoxal. Salinity also impaired the non-enzymatic and enzymatic components of the antioxidant defense system. On the other hand, excessive Na+ uptake induced ionic stress which resulted in a lower content of other minerals (K+, Ca2+, and Mg2+), and a reduction in photosynthetic pigment synthesis and plant growth. After 2 days in the normal nutrient solution, the plants showed improvements in antioxidant and glyoxalase system activities, followed by improvements in plant growth, water balance, and chlorophyll synthesis. The antioxidant and glyoxalase systems worked in concert to scavenge toxic reactive oxygen species (ROS), thereby reducing lipid peroxidation and membrane damage. Taken together, these findings indicate that tomato plants can tolerate salinity and show rapid post-stress recovery by enhancement of their antioxidant defense and glyoxalase systems.

Elevated atmospheric CO2 concentration improves water use efficiency and growth of a widespread Cerrado tree species even under soil water deficit

Changes in atmospheric CO2 levels are accompanied by ecological interactions involving other environmental factors, such as drought, which can severely alter the water balance of plants, thereby influencing sap flow, gas exchange, and plant growth. The objective of this study was to evaluate the water use economy, leaf gas exchange, and growth of young plants of the species Lafoensia pacari subjected to high concentrations of atmospheric CO2 ([CO2]) and soil water deficit. Increased vapor pressure deficit was observed from 1200 to 1800 hours. Plants under elevated [CO2] exhibited increased leaf photosynthesis, resulting in improved growth. Specific leaf area was lower in plants under high [CO2], mainly after soil water deficit treatment. Daily irrigated plants growing under ambient [CO2] had higher stem sap flow velocity (cm h-1) and hourly sap flow (kg h-1), mainly during the hottest hours of the day, than plants under high [CO2]. Improved water use by plants growing under high [CO2] may result in increased availability of water in the soil, partially offsetting future drought events and extending the growth period.

Low-Temperature Adaptation of Winter Wheat Seedlings under Excessive Zinc Content in the Root Medium

Cold adaptation of winter wheat (Triticum aestivum L.) seedlings was investigated under excessive zinc content (1000 μM) in the root medium. The ability to adapt to chilling temperatures (4°C) in seedlings exposed over seven days to excessive Zn concentrations was lower than in seedlings exposed to optimal composition of mineral nutrients. The impaired adaptation capacity was evident from the lowered content of photosynthetic pigments in leaves, the decreased stomatal conductance, and the reduced water content in shoot tissues. The negative influence of low temperature on plant physiological parameters was enhanced with the prolongation of cold exposure under Zn excess in the root medium, unlike the alleviation of cold-induced disorders during prolonged chilling under optimal Zn concentration (2 μM). Based on this study, we propose that inhibition of photosynthesis and the disturbance of plant water balance are the main factors that impair the low-temperature adaptation of seedlings exposed to high zinc concentrations.

Leaf wetting mitigates midday depression of photosynthesis in tomato plants

We studied the effects of leaf wetting on midday depression of photosynthesis regarding plant water balance and leaf morphological traits. The plants without leaf wetting showed a significant reduction in midday photosynthesis with a concomitant decrease with leaf conductance, because of lower leaf water potential (-1.3 MPa) due to excessive transpiration water loss. However, midday depression was not observed in the plants with leaf wetting. Lower contact angle between leaf surface and water droplet showed that tomato leaves have lower water repellency. However, water on the leaf surface completely dried within 20 min indicating that effect of water coverage on stomata for CO2 uptake was small. In addition, leaf wetting significantly decreased evaporative demands, which contributed to maintaining appropriate water balance and avoided midday stomatal closure, and it contributed to mitigation of midday depression of photosynthesis.

Leaf economics and plant hydraulics drive leaf : wood area ratios.

Biomass and area ratios between leaves, stems and roots regulate many physiological and ecological processes. The Huber value Hv (sapwood area/leaf area ratio) is central to plant water balance and drought responses. However, its coordination with key plant functional traits is poorly understood, and prevents developing trait-based prediction models. Based on theoretical arguments, we hypothesise that global patterns in Hv of terminal woody branches can be predicted from variables related to plant trait spectra, that is plant hydraulics and size and leaf economics. Using a global compilation of 1135 species-averaged Hv , we show that Hv varies over three orders of magnitude. Higher Hv are seen in short small-leaved low-specific leaf area (SLA) shrubs with low Ks in arid relative to tall large-leaved high-SLA trees with high Ks in moist environments. All traits depend on climate but climatic correlations are stronger for explanatory traits than Hv . Negative isometry is found between Hv and Ks , suggesting a compensation to maintain hydraulic supply to leaves across species. This work identifies the major global drivers of branch sapwood/leaf area ratios. Our approach based on widely available traits facilitates the development of accurate models of above-ground biomass allocation and helps predict vegetation responses to drought.

Of Storage and Stems: Examining the Role of Stem Water Storage in Plant Water Balance.

Stems of land plants provide mechanical support and long-distance transport of water and carbohydrates. Although it has long been recognized that plant stems can also store water, it remains uncertain what role stem water plays in mitigating drought stress and maintaining whole plant function ([

Ozone effects on plants in natural ecosystems.

Tropospheric ozone (O3 ) is an important stressor in natural ecosystems, with well-documented impacts on soils, biota and ecological processes. The effects of O3 on individual plants and processes scale up through the ecosystem through effects on carbon, nutrient and hydrologic dynamics. Ozone effects on individual species and their associated microflora and fauna cascade through the ecosystem to the landscape level. Systematic injury surveys demonstrate that foliar injury occurs on sensitive species throughout the globe. However, deleterious impacts on plant carbon, water and nutrient balance can also occur without visible injury. Because sensitivity to O3 may follow coarse physiognomic plant classes (in general, herbaceous crops are more sensitive than deciduous woody plants, grasses and conifers), the task still remains to use stomatal O3 uptake to assess class and species' sensitivity. Investigations of the radial growth of mature trees, in combination with data from many controlled studies with seedlings, suggest that ambient O3 reduces growth of mature trees in some locations. Models based on tree physiology and forest stand dynamics suggest that modest effects of O3 on growth may accumulate over time, other stresses (prolonged drought, excess nitrogen deposition) may exacerbate the direct effects of O3 on tree growth, and competitive interactions among species may be altered. Ozone exposure over decades may be altering the species composition of forests currently, and as fossil fuel combustion products generate more O3 than deteriorates in the atmosphere, into the future as well.

Regulation of the water balance of the cotton varieties under salting conditions

The article provides information on water balance management in saline conditions of medium-fiber cotton varieties. All physiological parameters studied with increasing soil salinity vary in both species depending on biological and individual characteristics of the varieties, and the salinity of the Bukhara-8 variety against the S-6524 variety is scientifically based. During the transpiration, the water potential of the leaf and the pressure in the kselema are reduced due to water loss. The transpiration of water inside the leaves is largely controlled by the oral cavity. On the basis of both indicators, soil moisture content was maintained at 70% of total moisture content (T.N.S.). In the bottles, different levels of soil salinity were formed by chlorine ion depending on the air dried mass of the soil. Prior to field experiments, saline areas of varying salinity were identified. In both varieties, the intensity of transpiration was lower in the control and experimental variants in the morning hours, higher in the afternoon, and again in the evening. The negative effects of salts have changed the water balance of the cotton and limit the water availability of plants. In saline soils a deep and sufficient analysis of the water balance of plants and their management and water supply is required. According to the obtained data, the cost of day and residual water shortages was higher for S-6524 grade and lower for Bukhara-8 grade. In defining salinity resistance of agricultural plants, it is also recommended to study water deficiency in leaves.

Robust stochastic optimal short-term generation scheduling of hydrothermal systems in deregulated environment

Hydrothermal systems play a significant role in electric energy systems as important power generation units, which have been studied in previous researches considering remarkable efforts. The optimal short-term hydrothermal scheduling (STHS) aims to attain optimal production scheduling of thermal and hydro plants for determining minimum operation cost of providing demand in the determined time interval. Different constraints should be studied in the solution of such issue containing limitations associated with water discharge, water storage, power production of plants, power balance of the system and water balance of hydro plants. In addition, valve impacts of thermal plants and complex hydraulic coupling of hydro plants are the other operational and technical constraints. In this study, the robust stochastic STHS is studied considering market price and demand uncertainties. Accordingly, robust optimization method is employed in this study to model price uncertainties. In addition, the uncertainties of load demand are handled using scenario-based modeling procedure. The scheduling problem of hydrothermal system is studied in a deregulated environment, where the hydrothermal system belongs to the private company and is capable to sell the surplus generated power to the market. Accordingly, the company aims to obtain maximum profit by selling power to market in addition to supplying power demand of the company. The introduced scheme for stochastic robust STHS is simulated and the provided solutions are investigated to verify the effectiveness of the scheme.

Effects of lead and cadmium ions on water balance parameters and content of photosynthetic pigments of prairie cordgrass (Spartina pectinata Bosk ex Link.)

The aim of the work was to assess the impact of a varied level of soil contamination with lead and cadmium ions on selected physiological parameters of prairie cordgrass. The content of photosynthetic pigments in leaves (chlorophyll a, b, total chlorophyll and carotenoids) and water balance of plants on the basis of two indicators (RWC – relative water content in tissues and WSD – water saturation deficit) were determined. Pot-vegetative experiments were performed using a complete randomization method in a one-factor system. The factor in the first experiment was the level of soil contamination with lead (28.15, 56.30, 112.60 mg Pb · kg soil–1), in the second experiment – the level of soil contamination with cadmium (4.60, 10.00, 18.39 mg Cd · kg soil–1). The levels of soil contamination with lead did not influence the content of chlorophyll a, b and total chlorophyll in prairie cordgrass leaves. In the case of carotenoids, an increase in their content was demonstrated after introducing lead into the soil at the dose of 28.15 mg Pb · kg soil–1 compared to the control. Soil contamination with cadmium did not affect the content of chlorophyll a, total chlorophyll and carotenoids in the leaves of prairie cordgrass. The highest level of soil contamination with lead contributed to the reduction of chlorophyll b. Lead at doses of 56.30 and 112.60 mg · kg soil-1 caused deterioration in the water balance parameters of the prairie cordgrass. In the case of soil contamination with cadmium, this relationship was demonstrated only for the dose of 10.00 mg Cd · kg soil–1.

Modeling of rainfall and fertilization factor of sugarcane productivity in Asembagus sugar factory Situbondo

Sugarcane is one of the important plantation crops commodities in plantation sub-sector development in East Java. However, domestic sugar needs are increasing every year, even making the government decide on the policy to import sugar. This situation shows that sugar is a basic requirement in Indonesia. The profitability of sugar agro-industry is influenced by climate and price. Low price and production risks affect the company's sustainable resilience. Rainfall is an important climate element and determines the plant water balance. While the incidence of climate anomalies in Indonesia has been shown to predominantly affect agricultural production and food security, besides that the fertilization process is also a major factor influencing the production of sugar cane produced. Fertilizer can provide nutrients in the soil, so that sugar cane can grow well. Sugar production in Asembagus factory every year has fluctuations, some of the dominant factors are the influence of rainfall and fertilization. The results showed that rainfall(X1) and fertilization(X2) significantly affected sugarcane productivity(Y). The regression model is Y = 33633 + 9,43X1 − 2,10X2. The modeling results are expected to be used as a company recommendation to determine policies in increasing Asembagus sugar factory production and more productive sugarcane cultivation techniques.