Periods Of Water Stress Research Articles

Identifying rice varieties for mitigating methane and nitrous oxide emissions under intermittent irrigation

Context or problemMost of the research evaluating rice varieties, a major global staple food, for greenhouse gas (GHG) mitigation has been conducted under continuous flooding. However, intermittent irrigation practices are expanding across the globe to address water shortages, which could alter emissions of methane (CH4) compared to nitrous oxide (N2O) for reducing overall global warming potential (GWP). To develop climate-smart rice production systems, it is critical to identify rice varieties that simultaneously reduce CH4 and N2O emissions while maintaining crop productivity under intermittent irrigation. ObjectiveThis study assessed CH4 and N2O emissions, grain yield, and GWP of four rice varieties cultivated under intermittent irrigation in Colombia. MethodsFour common commercial rice varieties were evaluated over two seasons―wet and dry in 2020 and 2021―in two Colombian regions (Tolima and Casanare). ResultsWet-season crop productivity was similar among varieties. However, F68 in Tolima and F-Itagua in Casanare significantly reduced yields in the dry season, likely due to periods of crop water stress. Overall, CH4 emissions and GWP were relatively low due to frequent field drainage events, with GWP ranging from 349 to 4704 kg CO2 equivalents ha−1. Accordingly, N2O emissions contributed 73% to GWP across locations, as wet-dry cycles can increase N2O emissions, creating a tradeoff for GWP when reducing CH4 through drainage. Varieties F67 in Tolima and F-Itagua in Casanare significantly reduced GWP by 32–61% across seasons, primarily by decreasing N2O rather than CH4 emissions. ConclusionsRice varietal selection achieved significant GWP mitigation with limited impacts on grain yield, mainly due to reduced N2O emissions under non-continuously flooded irrigation. Implications/significanceThis research underscores the critical role of rice varietal selection in addressing global climate-change and water-scarcity challenges, which drive the adoption of intermittent irrigation practices. By focusing on reducing N₂O emissions through appropriate variety selection, this study provides valuable insights for rice systems worldwide that are adapting to these pressing environmental challenges.

Thermographic Analysis of Green Wall and Green Roof Plant Types under Levels of Water Stress

Urban green infrastructure (UGI) plays a vital role in mitigating climate change risks, including urban development-induced warming. The effective maintenance and monitoring of UGI are essential for detecting early signs of water stress and preventing potential fire hazards. Recent research shows that plants close their stomata under limited soil moisture availability, leading to an increase in leaf temperature. Multi-spectral cameras can detect thermal differentiation during periods of water stress and well-watered conditions. This paper examines the thermography of five characteristic green wall and green roof plant types (Pachysandra terminalis, Lonicera nit. Hohenheimer, Rubus tricolor, Liriope muscari Big Blue, and Hedera algeriensis Bellecour) under different levels of water stress compared to a well-watered reference group measured by thermal cameras. The experiment consists of a (1) pre-test experiment identifying the suitable number of days to create three different levels of water stress, and (2) the main experiment tested the suitability of thermal imaging with a drone to detect water stress in plants across three different dehydration stages. The thermal images were captured analyzed from three different types of green infrastructure. The method was suitable to detect temperature differences between plant types, between levels of water stress, and between GI types. The results show that leaf temperatures were approximately 1–3 °C warmer for water-stressed plants on the green walls, and around 3–6 °C warmer on the green roof compared to reference plants with differences among plant types. These insights are particularly relevant for UGI maintenance strategies and regulations, offering valuable information for sustainable urban planning.

Determination of Critical Crop Water Stress Index of Tea under Drought Stress Based on the Intercellular CO2 Concentration

Climatic changes have caused seasonal drought to occur frequently in tea fields of low-mountain and hill regions over the past decades. This leads to huge losses in the quality and yields of famous tea, which restricts the economic development of the tea industry. It is crucial to implement suitable irrigation scheduling. The crop water stress index (CWSI) is the main index to assess the water status of the crop. When the crop suffers irreversible drought stress, its critical water status cannot be easily evaluated using the CWSI. The change from stomatal limitations (SLs) to non-stomatal limitations (NSLs) of photosynthesis is vital for accurately recognizing crop drought stress. Thus, the objective of this research is to determine the critical crop water stress index of tea based on intercellular CO2 concentration (Ci) dynamic responses to drought stress. During two sensitive periods of water stress (famous tea harvest season and summer drought season, which are from March to April and July to August, respectively), the dynamic changes in the CWSI in tea were calculated and analyzed based on the CWSI theoretical model. The upper and lower baselines were determined on a daily basis and during a certain period. A critical value of the CWSI represents irreversible drought damage. This was determined by the characteristic response of the Ci of tea leaves during extreme drought stress. The results showed the following: (1) during the famous tea harvest season and summer drought season, the daily variation in CWSI was similar. During a certain period, the former maintained a stable fluctuation, while the latter increased in fluctuation. (2) The Ci showed a trend of fluctuating downward to a low point and then upward during extreme drought stress. After reaching the low point, it quickly increased in the former and stabilized for a day in the latter. When the Ci reached the low point, the upper benchmark of this critical point was 13.9 μmol·mol−1, the lower benchmark was 3.4, and the CWSI was 0.27. This critical CWSI could be used as an irrigation threshold point to ensure normal production for tea fields.

Influence of successive cycles of water stress on tomato production at fruiting stage

Progressive reduction of water supply was imposed during early period (S1) and late period (S2) interceded by a recovery, with a moderate stress for first case and un intensive stress for second case, at fruiting stage of tomato (Lycopersicon esculentum Mill. cv. Rio Grand). The influence of this reduction on fruit production, shoot growth, water content (WC), relative water content (RWC), leaf area (LA), specific leaf weight (SLW), total soluble solids of fruit (T.S.S.) and maturity percentage of fruit were investigated. Repetition of water stress (S1+S2) was obviously reducing the shoot growth, fresh yield, WC, LA and maturity percentage, whereas that was not achieved in dry weight of fruits (FDW), RWC, SLW and T.S.S. Since, a significant difference was founded between the effects of S2 cycle and when that has been preceded by another one S1+S2 on accumulation of dry matter of fruit. Two successive cycles of water stress were doubled of FDW by two times of that registered in control. These results indicate that, during fruiting stage, the effect of gradually exposure of a moderate water stress period, followed by recovery, thereafter by another gradually exposure of un intensive water stress period, contributed to better accumulation of dry matter in fruit by an osmotic adjusting therefore improving water use efficiency, compared to the effect of only one high intensive of water stress applied during the second period. Repetition cycle of water stress may be useful to develop management systems for a reasonable production of tomato and thus reducing the needs of irrigation water in regions facing deficit of water supplies.

Estimation of Roof Top Rain Water Harvesting Potential: A Proposed Solution to Water Scarcity in Shrigonda Town, Maharashtra, India

The burning issue in cities will be water scarcity in the coming years. The world population in cities has increased from 29.6 percent to 56.2 percent and is predicted to reach 68.4 percent by 2050. Therefore, this study has attempted to find a solution to tackle the urban water scarcity issue. Recently, rainwater harvesting has emerged as a sustainable and effective system for water conservation in urban areas. Hence, the ward-wise rooftop area was calculated and the rooftop rainwater harvesting potential was estimated by applying the Gould & Nissen, formula for Shrigonda Town. The result reveals that the total water demand in the water stress period was 41,34,41,010 litres while the total rainwater harvesting potential was 39,07,42,128 litres, which means about 94.51 % of the total demand will be met after the rooftop rainwater harvesting system is installed. The study concludes that rooftop rainwater harvesting is considered a sustainable and best alternative tool to tackle urban water scarcity.

Prehispanic Arid Zone Farming: Hybrid Flood and Irrigation Systems along the North Coast of Peru

As arid lands expand across the globe, scholars increasingly turn to the archaeological record for examples of sustainable farming in extreme environments. The arid north coast of Peru was the setting of early and intensive irrigation-based farming; it is also periodically impacted by sudden, heavy rainfall related to the El Niño Southern Oscillation (ENSO) phenomenon. While the sociopolitical effects, technologies, and engineering expertise of these irrigation systems have been thoroughly examined and theorized, little is known about how farmers managed periods of water stress. The aim of this study is to test whether arid zone farming was supported by hybrid, intermittent flood and perennial water source systems in the prehispanic past. An arroyo in the Chicama Valley was selected for preliminary data collection, and these data are presented here: (1) drone photography of the arroyo capturing the aftermath of a recent (2023) rain event; and (2) potassium (K) soil test kit results from samples collected near suspected prehispanic check dam features in the same area. The paper combines these data with comparative examples from the literature to suggest that the prehispanic features functioned as water-harvesting infrastructure. The paper concludes that sustainable, arid zone farming can be supported by hybrid, intermittent flood and perennial water source systems.

Performance of sesame varieties (<i>Sesemum indicum</i> L.) as influenced by period of stress and NPK fertilizer rates in the Sudan Savannah

Field trials were conducted at the Irrigation Research Station, Kadawa to evaluate the response of sesame varieties to stress period and NPK fertilization in Sudan savannah. The treatments were two sesame varieties (NCRIBEN 01 and NCRIBEN 03) three water stress period (at seedling, flowering and podding stages), three NPK application rates (200, 270 and 340 kg NPKha-1). The experimental design used was randomized complete block design (RCBD) laid out in a split plot arrangement where the factorial combination of fertilizer rates and water stress periods were assigned to the main plot and varieties allocated to the sub plot and replicated three times. Results showed that variety NCRIBEN 03 recorded more capsules and higher capsule weight per plant and a grain yield of 1111.4 kg ha-1 and 1168.8kgha-1, in 2012/13 and 2013/14 dry seasons respectively. Stressing sesame at podding lead to 17 and 29% decline in number of pods and pod weight per plant, respectively and31% drop in grain yield. Application of 340 kg NPK fertilizer ha1 had highest yield of 1018 and 1078 kg ha-1 in 2012/13 and 2013/14 seasons, respectively. The use of variety NCRIBEN 03 + 340 kg NPK fertilizer ha1+ stressing sesame at seedling stage will give best grain yield of sesame.

Foliar Application of Amino Acids and Nutrients as a Tool to Mitigate Water Stress and Stabilize Sugarcane Yield and Bioenergy Generation

Extended periods of water stress negatively affect sugarcane crop production. The foliar application of supplements containing specific nutrients and/or organic molecules such as amino acids can improve sugarcane metabolism, stalk and sugar yields, and the quality of the extracted juice. The present study assessed the effectiveness of the foliar application of an abiotic stress protection complement (ASPC) composed of 18 amino acids and 5 macronutrients. The experiments were carried out in the field with two treatments and twelve replicates. The two treatments were no application of ASPC (control) and foliar application of ASPC. The foliar application of ASPC increased the activity of antioxidant enzymes. The Trolox-equivalent antioxidant capacity (DPPH) was higher in ASPC-treated plants than in control plants, reflecting higher antioxidant enzyme activity and lower malondialdehyde (MDA) levels. The level of H2O2 was 11.27 nM g−1 protein in plants treated with ASPC but 23.71 nM g−1 protein in control plants. Moreover, the application of ASPC increased stalk yield and sucrose accumulation, thus increasing the quality of the raw material. By positively stabilizing the cellular redox balance in sugarcane plants, ASPC application also increased energy generation. Therefore, applying ASPC is an effective strategy for relieving water stress while improving crop productivity.

Micorrizas arbusculares em pomares de mangueira no semiárido brasileiro: influência da fenologia, do manejo e da variedade

ABSTRACT: Arbuscular mycorrhizal fungi (AMF) increase the absorption surface of roots, providing greater absorption of water and nutrients from the soil by plants. Thus, it is important to know how arbuscular mycorrhizae are affected by factors such as phenology, management and varieties in mango (Mangifera indica) orchards in the irrigated semi-arid region. With this objective, soil and root samples were collected during the vegetative, flowering and fruiting stages, and in the water stress period before flowering, always on the same trees. The study was carried out in mango orchards of the Keitt and Palmer varieties, in agricultural farms located in Juazeiro - BA and Petrolina - PE, both under conventional management (with fertilizers and paclobutazol). The soil was used to quantify the number of AMF spores and phosphorus content. Mycorrhizal colonization in roots was evaluated in qualitative terms (presence of hyphae, vesicles and arbuscles) and quantitative terms (% of colonization). Total mycorrhizal colonization was high, with averages above 65%, and higher values in the fruiting period. Colonization by vesicles and arbuscles was on average above 45% and 17%, respectively, with higher means also during fruiting. The number of AMF spores in the soil averaged over 130 spores in 50 g of soil, with higher values in the period of water stress. The phosphorus content in the soil did not influence mycorrhizal colonization and the number of spores in the soil. The association of AMF with mango trees was generally affected by management and phenology, regardless of the cultivated varieties.

Role of Hydrophilic Biopolymers Concoction Seed Coating on Seed Germination and Field Performance of Blackgram (Vigna mungo L.)

Background: Blackgrm is one of the most important pulse crops majorly cultivated in rainfed conditions of India. Soil moisture deficit,low and erratic rainfall, use of poor quality seeds,poor crop stand and improper crop managementresulting in lower productivity in rainfed ecosuystem . Reduced crop stand alone leads to 30% deficit in production combined.Availability of technology to overcome drought stress is one of the way to expand blackgram cultivation in dry tracks. Hydrophilic polymers may have great potential in restoration and reclamation, when used the polymers correctly and an ideal situations will have atleast 95 % of their stores water available for plant absorption. There are N number of inorganic polymers available in the market, that can be applied in the farm of soil application. Studies on Hydrophilic bio polymer seed coating to mitigate water stress is very megar or nil. Hence, the present study was formulated in blackgram as hydrophilic bio polymer seed coating on seed germination and field emergence. Method: Seed coating experiment consists of seven hydrophilic biopolymers (Ethyl cellulose, Methyl cellulose, Carboxyl methyl cellulose, Agar, Gum Arabic, Xanthangum and Carrageenan); two coating methods (dry and dry powder concoction). The germination test conducted in sand media with 60 % Water Holding Capacity of sand and PEG induced water stress and evaluated for seed quality parameters against uncoated seeds. Field experiments conducted with water stress periods of 10 days, 20 days and 25 days after life irrigation and observed for biometric and yield parameters. Results: Results revealed that blackgram seeds coated with bio polymer concoction of xanthan gum : carrageenan : agar agar (4:1:1) @ 20 g / kg performed better in terms of all seed quality parameters and withstand water stress upto 20 days after life irrigation with the yield increase of 53% over stressed control (skipping irrigation for 20 days after life irrigation) and can be recommended as a pre sowing treatment for drought mitigation in blackgram.

Transpiration rates from mature Eucalyptus grandis × E. nitens clonal hybrid and Pinus elliottii plantations near the Two Streams Research Catchment, South Africa

Abstract. Pine plantations are the dominant species currently planted within the South African commercial forestry industry. Improvements in bio-economy markets for dissolving wood pulp products have seen an expansion in fast-growing Eucalyptus plantations due to their higher productivity rates and better pulping properties than pine. This has raised concerns regarding the expansion of Eucalyptus plantations and how they will affect water resources as they have been reported to have higher water use (quantified using transpiration rates) than pine. We measured transpiration rates (mm yr−1), diameter at breast height (quantified as quadratic mean diameter, Dq, m) and leaf area index of an 8-year-old Eucalyptus grandis × Eucalyptus nitens clonal hybrid (GN) and a 20-year-old Pinus elliottii. Transpiration rates were measured for two consecutive hydrological years (2019/20 and 2020/21) using a heat ratio sap-flow method, calibrated against a lysimeter. In the 2019/20 year, annual transpiration for P. elliottii exceeded GN by 28 %, while for the 2020/21 hydrological year, there was no significant difference between the transpiration of the two species, despite a 17 % and 21 % greater leaf area index for P. elliottii than GN in 2019/20 and 2020/21 measurement years respectively. Quadratic mean diameter increments were statistically similar (p > 0.05) in 2019/20, whereas the 2020/21 year produced significant differences (p<0.05). Tree transpiration is known to be influenced by climatic variables; therefore, a random forest regression model was used to test the level of influence between tree transpiration and climatic parameters. The soil water content, solar radiation and vapour pressure deficit were found to highly influence transpiration, suggesting these variables can be used in future water-use modelling studies. The profile water content recharge was influenced by rainfall events. After rainfall and soil profile water recharge, there was a rapid depletion of soil water by the GN trees, while the soil profile was depleted more gradually at the P. elliottii site. As a result, trees at the GN site appeared to be water stressed (reduced stem diameters and transpiration), suggesting that there was limited access to alternative water source (such as groundwater). The study concluded that previous long-term paired catchment studies indicate that eucalypts use more water than pine; however, periods of soil water stress and reduced transpiration observed in this study must be accommodated in hydrological models. Long-term total soil water balance studies are recommended in the same region to understand the long-term impact of commercial plantations on water resources.

The effects of wildfire frequency on post-fire soil surface water dynamics

Increasing wildfire frequency in the Mediterranean Basin could affect future plant-soil–water-dynamics. The capacity of soils to retain water is a key parameter affecting plant post-fire regeneration. Yet, few research has looked at how different soil properties related to water retention is affected by increasing wildfire frequency. This study aimed at understanding the relationship between wildfire frequency, soil–water-related properties and the dynamics of surface water in soils. To this, after a 2012-summer wildfire in Portugal, three sets of three replicate maritime pine stands with contrasted wildfire frequency were selected (0 vs. 1 vs. 4 fires since 1975). At each of the nine study sites, three re-sprouter shrubs and neighbouring bare soil were chosen (54 microsites). There, soil cover, soil–water retention curves and surface (0–5 cm) soil–water-related properties (texture, bulk density, organic matter content, soil moisture, soil surface water repellency) were monitored for one year. Furthermore, records of post-fire soil moisture dynamics were analysed continuously using 72 probes installed at 2.5 and 7.5 cm depth. The hillslopes affected by 1 fire showed higher plant recovery than the 4 fires hillslopes. During the dry season, the threshold for water stress was reached 17 days sooner in the 4 fires hillslopes, and also 10 days sooner on bare microsites. Periods of plant water stress were longer and bare soil patches size bigger. The increase in wildfire frequency promoted high soil organic matter contents but less available water content, stressing the importance of soil organic matter quality characterization in water-related properties.

MONITORIZAREA DINAMICII UNOR AGENŢI DE DĂUNARE DIN POMICULTURĂ ÎN CONTEXTUL SCHIMBARILOR CLIMATICE DIN ULTIMUL DECENIU

Nowadays, the average values of the main parameters of the local climate and microclimate have changed significantly compared to the pre-industrial period. The immediate consequences are quite obvious, namely: the earlier initiation of vegetation of the most fruit tree species (with about 2 weeks), the increase in the frequency of damages caused by late spring frosts, the prolongation of periods of water stress into the soil and in the atmosphere, accompanied by the blocking photosynthetic activity and increased cell respiration, increased frequency and severity of burns on fruits through the combined effect of insolation and extremely high temperatures, earlier ripening and decreased fruit firmness and acidity. Changes have become obvious in the biological cycle of pests, harmful for fruit growing, especially by the appearance of additional generations with high aggressiveness, the increase of the risk, frequency, intensity and duration of the attack of pathogens. In fruit growing, the depletion of the level and quality of the harvest is caused by bacterial and fungal pathogens (over 155; 41%), pests (over 132; 35%), viruses, viroids and mycoplasmas (over 67; 17%) and dominant mono- and dicots (over 26; 7%). In the last 20 years, technical means have appeared, which allow the monitoring the physico-chemical and humidity parameters of the soil, the local microclimate, as well as the physiological and health status of the plants. The paper presents the results obtained in the period 2018-2022 at RIFG Pitesti-Mărăcineni, in the monitoring of some harmful agents, using independent analog or digital devices, automatic or semi-automatic weather stations with software for real-time data collection and processing, forecasting and warning modules of the risk of attack. These assets allowed the highlighting of the dynamics of some of the damaging agents in fruit growing, the professional scheduling and carrying out of phytosanitary actions in bearing orchards, the reduction of the allocated resources consumption and the protection of the environment.

Identifying physiological traits related with drought tolerance and water‐use efficiency in floral hemp (Cannabis sativa L.)

AbstractHemp (Cannabis sativa L.) is a reemerging crop that was once deeply rooted in many global civilizations. Due to climate change and the increasing risk of water‐deficit situations, it is important to use water judiciously. Hemp production has interested many producers; however, due to its past illegal status, there is a lack of research‐based knowledge about the physiological parameters that are affected by drought and which parameters could be responsible for drought tolerance. Therefore, our objective was to study and understand the effects of different drought intensities and timings on physiological parameters such as water‐use efficiency (WUE), photosynthesis, stomatal conductance, and fluorescence parameters and determine if cultivar variation exists as this could mean the possibility of selection for drought‐tolerant cultivars. In addition, we tested if carbon isotope discrimination can be used to predict whole plant WUE as this technique is quick and allows moderate throughput for selection. Hemp cultivars BaOx and Cherry Mom were grown in a greenhouse from July to October during 2021 and 2022 under different water stress intensities and timings. During the water stress period, WUE was determined by the gravimetric method and photosynthetic traits were measured using two portable gas analyzers (LI‐6800). Moderate water stress (30%–50% field capacity) was found to have the least effect on physiological parameters studied, while intense water stresses significantly reduced many physiological parameters such as photosynthesis, stomatal conductance (gs), and electron transport rate (ETR). It was found that the cultivar BaOx had a greater WUE than Cherry Mom. This was confirmed with carbon isotope discrimination measurements, which were demonstrated to estimate WUE accurately, and therefore, this technique could be used for germplasm screening. Drought first decreased gs, which caused the reduction in photosynthesis, although cultivar variation in these traits was not observed. Twenty days after drought, negative effects on fluoresce parameters such as ETR were observed with the cultivar Cherry Mon being more affected. This study states that hemp is negatively affected by different timings and intensities of drought; however, there is physiological variation in the response between cultivars. More research is needed to investigate the sources of genotypic variation in physiological parameters to find the sources of drought tolerance.

Interannual land cover and vegetation variability based on remote sensing data in the HTESSEL land surface model: implementation and effects on simulated water dynamics

Abstract. Vegetation largely controls land surface–atmosphere interactions. Although vegetation is highly dynamic across spatial and temporal scales, most land surface models currently used for reanalyses and near-term climate predictions do not adequately represent these dynamics. This causes deficiencies in the variability of modeled water and energy states and fluxes from the land surface. In this study we evaluated the effects of integrating spatially and temporally varying land cover and vegetation characteristics derived from satellite observations on modeled evaporation and soil moisture in the Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL) land surface model. Specifically, we integrated interannually varying land cover from the European Space Agency Climate Change Initiative and interannually varying leaf area index (LAI) from the Copernicus Global Land Services (CGLS). Additionally, satellite data on the fraction of green vegetation cover (FCover) from CGLS were used to formulate and integrate a spatially and temporally varying effective vegetation cover parameterization. The effects of these three implementations on model evaporation fluxes and soil moisture were analyzed using historical offline (land-only) model experiments at the global scale, and model performances were quantified with global observational products of evaporation (E) and near-surface soil moisture (SMs). The interannually varying land cover consistently altered the evaporation and soil moisture in regions with major land cover changes. The interannually varying LAI considerably improved the correlation of SMs and E with respect to the reference data, with the largest improvements in semiarid regions with predominantly low vegetation during the dry season. These improvements are related to the activation of soil moisture–evaporation feedbacks during vegetation-water-stressed periods with interannually varying LAI in combination with interannually varying effective vegetation cover, defined as an exponential function of LAI. The further improved effective vegetation cover parameterization consistently reduced the errors of model effective vegetation cover, and it regionally improved SMs and E. Overall, our study demonstrated that the enhanced vegetation variability consistently improved the near-surface soil moisture and evaporation variability, but the availability of reliable global observational data remains a limitation for complete understanding of the model response. To further explain the improvements found, we developed an interpretation framework for how the model development activates feedbacks between soil moisture, vegetation, and evaporation during vegetation water stress periods.

Estimating cumulative evapotranspiration using superconducting gravimeter data: a study in Buenos Aires Province, Argentina

ABSTRACT A new method for estimating cumulative evapotranspiration using superconducting gravimeter data is presented. Evapotranspiration is computed from the classical water balance equation using precipitation data, estimated runoff, and water storage assessed from temporal variations of gravity. The gravity-based methodology is applied to a study site located at the Argentinian–German Geodetic Observatory (AGGO) in the flatland area of Buenos Aires Province (Argentina), which houses the only superconducting gravimeter in South America. For the period from April 2017 to May 2018, the cumulative evapotranspiration is estimated at 710.7 ± 25.7 mm. Evapotranspiration values are successfully compared with estimates provided by three methods, based on the water balance equation using soil moisture data, the numerical modelling of water flow in the unsaturated zone and the MODIS product (MOD16A2). The analysis of evapotranspiration also allows us to identify a period of soil water stress which is validated by soil moisture measurements.

Comparison of physiological and biochemical responses of local and commercial tomato varieties under water stress and rehydration

Water scarcity presents an increasingly urgent challenge with global implications for the production of irrigated vegetables. Among these crops, tomatoes stand out as one of the most widely cultivated. Given their vulnerability to water stress, it is crucial to ensure efficient and sustainable water management for tomato irrigation. This study aims to compare physiological and biochemical parameters among three local and three commercial resilient tomato varieties in response to water stress and rehydration. We subjected tomato plants to either two brief periods of water stress (WE1) or one extended period of water stress (WE2), followed by rehydration. Our results did not reveal significant differences in the response to water stress among the varieties, which could be attributed to their respective origins. Following rehydration, the plants quickly returned to their normal physiological values. An exploration of oxidative stress markers revealed that oxidative damage occurred solely during the second episode of water stress in WE1 plants, or towards the conclusion of the prolonged water stress period in WE2 plants. However, after rehydration, tomato plants returned to normal oxidative parameters values, indicating the absence of irreversible damage. Although the severe water stress did not compromise the viability of the plants, all treatments and varieties exhibited a predictable and substantial growth inhibition. In conclusion, the different tomato varieties studied exhibited similar responses to water stress, primarily characterized by the inhibition of gas exchange processes and heightened oxidative stress. Nonetheless, none of the plants suffered irreversible damage from this stress.

Differential tree demography mediated by water stress and functional traits in a moist tropical forest

Abstract Climate‐induced changes in tree mortality, recruitment and growth have been extensively observed in forests worldwide. However, there is still a lack of quantitative understanding regarding how tree demography responds to environmental factors, particularly different water conditions, and how plant functional traits contribute to interspecific differences in this response. Using data collected from a forest monitoring plot, meteorological observations and trait measurements on Barro Colorado Island in Panama—one of the most studied sites, we investigated the mortality, recruitment, growth and population dynamics of 165 tree species from 1990 to 2014 and examined the influence of functional traits in determining the interspecific differences in tree demography. We also employed parametric accelerated failure time models to assess the impact of environmental conditions, functional traits and individual tree characteristics on tree survival time. We find that water stress drives the temporal dynamics of tree demography. During the high water stress period, the increase in mortality rates and decrease in recruitment rates caused negative population changes for species. In contrast, the increase in recruitment rates and decline in mortality rates during the low water stress period positively affected the population of species. Wood density and P50 (xylem water potential at 50% loss of maximum hydraulic conductivity) are significantly correlated with species‐level mortality, recruitment and growth rates, indicating that traits related to resource allocation and hydraulic safety dictate the interspecific differences in demographic rates. Our results demonstrate that water stress and traits related to resource allocation and hydraulic safety jointly mediate tree demography in this tropical forest. High mortality and low recruitment under high water stress may especially cause a decline in fast‐growing species. Therefore, timely recovery of recruitment under favourable water conditions is crucial for the forest dynamics. Read the free Plain Language Summary for this article on the Journal blog.

Cobalt Combined with Potassium Humate as Beneficial Applications in Alleviating Water Stress Impacts on Groundnut During Sensitive Growth Stages

Enhancing plant nutrition during critical periods of water stress is a paramount objective. As such, this study aims to examine the effects that arise from implementing water stress regimes during the sensitive growth phases of groundnut. Furthermore, we will explore the impact of applying cobalt and potassium humate individually or in combination, either through foliar application (KH-F) or soil amendments (KH-S), to mitigate the adverse effects on nutrient accumulation, yield, and irrigation water use efficiency (Iwue). A field experiment was conducted between 2021 and 2022 using a split-split plot design. In the main plots, an additional control of full irrigation requirement scheme (IR100) was implemented, along with three other schemes: the first involved applying 75% of the irrigation requirement during the development stage (IRD75), the second applied 75% during the flowering till pod stage (IRF75), and the third involved applying 85% from the development stage till the pod stage (IR85). In the subplots, cobalt was applied at rates of 0 and 7.5 mg l−1 to the plants. The sub-sub plots were further divided to investigate the effects of KH-F and KH-S. Plants that experienced water stress during the flowering stage were found to be more vulnerable. However, when treated with KH-S, there were significant improvements in yield compared to KH-F treatment. This effect was particularly pronounced under the IRF75 irrigation scheme. Interestingly, there was an antagonistic relationship observed between cobalt and iron or manganese, in contrast to other nutrients. When KH-S was applied in combination with cobalt, it showed the potential to enhance various characteristics and increase the uptake of iron or manganese. The highest yield, nutrient accumulation, and Iwue were achieved through the combined application of cobalt and KH-S, along with adopting the IR85% irrigation scheme.

Impact of shading on evapotranspiration and water stress of urban trees

AbstractEvapotranspiration of urban street trees is essential in mitigating urban heat islands due to its cooling effect. However, current shifts in rainfall and temperature regimes towards drier and hotter periods in Central Europe have caused substantial water stress for street trees. Quantifying and subsequently managing these changing dynamics as well as estimating evapotranspiration and water availability is necessary but at the same time extremely challenging in urban environments. Both dynamics are influenced by soil sealing and complex shading patterns of the surrounding street canyon, which vary on a small spatial scale as a function of the canyon layout and orientation. In the present study, the diurnal patterns of six typical urban shading types for street trees were derived by considering a large set of street orientations, widths and tree positions within the street canyon. A shading model was integrated into a hydrological urban tree model to assess the impact of those shading types on diurnal patterns of radiation and evapotranspiration rates calculated using the Penman–Monteith approach and the resulting soil moisture conditions for several vegetation seasons and water‐supply scenarios. The modelling results showed that the six shading patterns significantly influenced the simulated hourly, daily and seasonal potential and actual evapotranspiration rates and water availability. Shaded trees have a substantially reduced, simulated water stress period, regardless of initial water supply, and are able to provide a longer‐lasting cooling function during dry periods due to higher evapotranspiration rates later in the summer season.