Search Results (140)

Accelerating aridity and desertification driven by global climate change pose growing threats to dryland forest plantations, making it essential to understand transpiration dynamics across developmental stages for both forest-hydrology theory and the sustainable management of protective shelterbelts. This study compared transpiration characteristics, stomatal conductance (g_s), and water-regulation strategies between a 41-year-old mature stand and a 13-year-old young stand of Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) on the southern margin of Horqin Sandy Land during the 2024 growing season, using thermal-dissipation sap-flow measurements combined with meteorological monitoring and water-potential sampling. Mean individual-tree daily transpiration in the mature stand (2.36 mm·d⁻¹) was approximately 2.6 times that of the young stand (0.90 mm·d⁻¹), yet the young stand showed a disproportionately stronger sap-flow response to small rainfall events. Sap flow in both stands was jointly driven by vapor pressure deficit (VPD) and photosynthetically active radiation, with a near-synchronous lag of ±10 min and tight canopy-atmosphere coupling (decoupling coefficients: 0.177 and 0.256, respectively), indicating transpiration was predominantly governed by stomatal regulation. Stomatal conductance declined with rising VPD in both stands, with a steeper decline in the mature stand. Water-potential analysis revealed pronounced anisohydric behavior in the mature stand (σ = 2.643, R² = 0.765, p < 0.01), and near-strict anisohydric regulation in the young stand (σ = 0.919, R² = 0.105, p > 0.05), indicating high tree-level hydraulic variability and precluding a definitive classification along the iso/anisohydric continuum for this developmental stage. Both g_s and transpiration increased with tree size, contradicting the hydraulic limitation hypothesis. These findings elucidate distinct water-use strategies between the young and mature Mongolian pine stands in this paired design and provide a physiological basis for stage-differentiated, precision water management of dryland shelterbelt plantations. Full article

Continuous sap-flow monitoring is a key approach for understanding water-use strategies of shelterbelt species in semi-arid sandy lands. This study investigated two tree species (Populus alba var. pyramidalis Bge. and Pinus sylvestris var. mongholica Litv.) and two shrub species (Salix psammophila C. Wang & C. Y. Yang and Atraphaxis bracteata Losinsk.) in the Zhanggutai region, southern Horqin Sandy Land. Sap flow, environmental variables, and precipitation were continuously measured during the 2019–2020 growing seasons. Stomatal conductance (g_s) and its sensitivity to vapor pressure deficit (VPD) were evaluated. Precipitation dropped from 302.3 mm in 2019 to 106.3 mm in 2020. Daily sap flow peaked mid-season and declined by 21.9%–29.2% during 2020. VPD and solar radiation were primary drivers with narrow response lags. Trees exhibited higher g_s and stronger stomatal sensitivity than shrubs, showing steeper declines as VPD rose, which indicates key drought adaptation and protective mechanisms. Conversely, shrubs maintained a moderate and more stable g_s profile throughout the growing season. In 2020, soil water deficits may force stomatal closure, causing a pronounced drop in baseline g_s and a subsequent decline in sensitivity across all species. This widespread environmental decoupling indicates a critical shift from an atmospheric demand-limited regime during the wet year to a supply-limited regime during the drought year. Overall, trees demonstrated more pronounced stand-scale hydroclimatic sensitivity than shrubs. Given the persistent water consumption by shrubs, our results suggest tree species may offer advantages in later forest restoration stages. Nevertheless, further studies integrating biomass growth and ecosystem water balance are needed to optimize sustainable shelterbelt management. Full article

In the context of global climate change, drought events significantly impact plants, and studying the response of plant sap flow to environmental factors is of great significance for plant protection and sustainable development. This article uses the thermal pulse method to obtain trunk sap flow data, combined with real-time monitoring of environmental factor data, to compare the differences in sap flow characteristics between the subsequently deceased and surviving Zanthoxylum planispinum var. dingtanensis during a natural drought event. Additionally, the xylem vulnerability curve of Z. planispinum was fitted through laboratory measurements to estimate its hydraulic safety margin ($HSM$). The results showed that: (1) Compared with the surviving individuals, the subsequently deceased Z. planispinum exhibited a higher and more fluctuating sap flow rate, maintaining a consistently higher transpiration rate even after the onset of drought. (2) As soil moisture decreased, the sap flow of surviving Z. planispinum was promptly constrained by soil water availability and remained at a low, conservative level. In contrast, the sap flow of the deceased individuals continued to be driven by meteorological factors, failing to downregulate transpiration. (3) The xylem vulnerability curve revealed a $P_{50}$ of −2.2 MPa. During the severe drought, the minimum field branch water potential (${\psi }_{min}$) dropped to −3.0 MPa, resulting in a negative $HSM$ ($HSM$ = −0.8 MPa). This suggests that the xylem tension severely breached the embolism threshold, likely triggering catastrophic hydraulic failure, which emerged as the primary driver of the observed mortality in Z. planispinum. Therefore, for plants with low $HSM$s, when they are subjected to drought stress accompanied by highly fluctuating sap flow—a condition indicating that water supply cannot match the transpirational demand—timely manual intervention (e.g., supplemental irrigation) may be considered to mitigate hydraulic risks and ensure survival. Full article

Maize (Zea mays L.) is the dominant cereal of continental Hungary, yet the Pannonian belt lost one-third of its planted area over the last decade (1150 kha to 770 kha in 2025). This study quantified how supplemental irrigation and biostimulants affect maize transpiration. Fourteen Dynamax Flow32-1K stem-heat-balance sensors recorded sap flow at 15 min resolution on the Sushi FAO 340 hybrid across seven irrigated–rainfed plot pairs at Karcag, Hungary. Measurements spanned a dry 2024 season (irrigation: 253 mm; precipitation: 7.9 mm; VPD_max: 1.71 kPa) and a wetter 2025 season (120 mm irrigation; 62.9 mm precipitation; mean VPD_max: 1.33 kPa). A Control-only mixed-effects model returned a year × irrigation interaction F(1, 84) = 106 (p < 10⁻¹⁵): irrigation raised transpiration by 77% in 2024 and lowered it by 12% in 2025. The VPD_max–transpiration coupling was inverted in 2024, the field signature of stomatal closure under soil-water limitation. The irrigated Big Compost plot reached a grain-based WUE of 97.5 kg mm⁻¹ versus 41.6 kg mm⁻¹ for the matched Control. This was a 2.3-fold within-2025 separation at similar per-plant transpiration. The irrigation response differed sharply between seasons. However, the amendment classes were tested in different years, and the irrigation dose differed between seasons (253 mm in 2024 versus 120 mm in 2025). The cross-class contrast is therefore exploratory, and every cross-year comparison is provisional. With one sensor per plot, the amendment ranking remains a hypothesis for a replicated, same-season, and same-dose follow-up. Full article

As urban areas expand, the sustainable management of municipal water becomes a critical challenge, especially in arid and semi-arid regions facing severe water scarcity. Accurate assessment of urban plant water requirements (PWR) is essential for developing sustainable landscape architecture and resilient green infrastructure. In this study, a new quantitative equation (PWR_q) was developed as a regional proof of concept to adjust reference evapotranspiration estimates for hyper-arid conditions. A Tree Morphology Coefficient (K_tm) is introduced to combine canopy features (form, height) and leaf traits (size, density) with an updated drought-resistance coefficient (K_dr). Field measurements of 277 mature trees, representing 27 native and introduced species in Riyadh and Jeddah, Saudi Arabia, were analyzed. The framework explicitly includes an empirical multiplier to account for extreme urban heat island (UHI) effects and aerodynamic canopy scaling. Instead of direct empirical validation, the PWR_q model was benchmarked against established reference indices: Water Use Classification of Landscape Species (WUCOLS) and Simplified Landscape Irrigation Demand Estimation (SLIDE), showing strong alignment with established categorical indices and structural traits. The results confirm that the morphology-based method effectively makes previously subjective classifications objective. Notably, the quantitative assessment found that the dominant introduced species require about 3.5 times more water than native species. As a proof of concept, future research should empirically validate these findings against direct physical measurements, such as sap flow sensors or lysimeters. The proposed framework presents a practical, objective decision-support tool for municipal policymakers and landscape architects to optimize species selection, implement nature-based solutions (NBS), and achieve long-term sustainability in urban greening. Full article

Kiwifruit (Actinidia deliciosa cv. Hayward) is a high-demand crop due to its nutritional value. Climate change increasingly challenges its cultivation, particularly under Mediterranean conditions, due to limited water resources. Therefore, the early detection of water stress onset is crucial for optimizing irrigation water use and enhancing kiwi productivity. In this context, advanced sensors capable of continuously monitoring critical hydrodynamic parameters, combined with machine learning approaches, offer a promising solution for reliable prediction of plant water status, supporting irrigation decision-making systems. This study develops and evaluates machine learning (ML) models to predict trunk water potential (Ψtrunk), integrating soil moisture, climatic variables, and plant-based measurements, including sap flow. Various machine learning models were evaluated including Ridge Regression, Lasso Regression, Random Forest, Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), and Light Gradient Boosting Machine (LightGBM), using soil moisture, trunk water potential (Ψtrunk), sap flow, and microclimatic variables (relative humidity, wind speed, temperature, solar radiation, vapor pressure deficit, and reference evapotranspiration). Among the tested models, XGBoost demonstrated the best performance, achieving an accuracy of approximately 0.80, followed by Ridge, Lasso and SVM, which showed similar accuracy. Full article

Urban trees are increasingly deployed as nature-based infrastructure to mitigate heat and manage stormwater, yet quantitative guidance on how species traits and site context shape transpiration remains fragmented. We conducted a systematic metadata analysis of seven field studies that measured daily transpiration rate in urban settings using heat-pulse methods. The units and spatial scales reported were harmonized with the sap flow density across active sapwood (J_s, g H₂O/${\mathrm{cm}}^2$/day) by converting reported stand transpiration and the outer 2 cm of sapwood sap flux using established Gaussian radial distribution functions for angiosperms and gymnosperms, which account for the non-linear decline in sap flux from the vascular cambium to the heartwood boundary. We then summarized distributions and tested group differences with Kruskal–Wallis and Dunn post hoc comparisons across wood anatomy, climate, soil texture, and planting configuration. Conifers exhibited significantly lower median $J_s$ (39.76 g/${\mathrm{cm}}^2$/day) than angiosperms, while the ring-porous group (median $J_s$ = 92.25 g/${\mathrm{cm}}^2$/day) and diffuse-porous groups (median $J_s$ = 96.70 g/${\mathrm{cm}}^2$/day) had similar distributions overall. Climate-modulated responses within wood anatomy groups differed, with diffuse-porous species exhibiting the highest median $J_s$ (152.59 g/${\mathrm{cm}}^2$/day) in semi-arid regions, ring-porous species maintaining comparatively stable median $J_s$ across climates (varying slightly between 80.72 and 99.32 g/${\mathrm{cm}}^2$/day), and conifers reaching their highest median $J_s$ (69.90 g/${\mathrm{cm}}^2$/day) in humid continental sites. Soil texture effects were consistent with moisture availability: sandy loam generally reduced $J_s$ relative to loam or silt loam for conifers and diffuse-porous species. Across anatomies, single trees transpired more than clustered trees or closed canopies. For example, planting as single trees increased median $J_s$ by 86% in conifers (from 33.01 to 61.37 g/${\mathrm{cm}}^2$/day) and by 45% in diffuse-porous species (from 81.31 to 118.25 g/${\mathrm{cm}}^2$/day). These results provide actionable ranges and contrasts to inform species selection and planting design for urban greening and runoff reduction, while highlighting data gaps for future research. Ultimately, by matching specific wood anatomies and planting configurations to local soil and climatic conditions, urban planners and ecohydrologists can strategically optimize urban forests to maximize targeted ecosystem services. Full article

Candida albicans (C. albicans) is an opportunistic fungal pathogen capable of causing a wide range of infections, including mucosal and systemic candidiasis. In the oral cavity, fungi represent a minor component of the microbiome but can significantly contribute to morbidity, particularly under conditions of dysbiosis or immunosuppression. Treatment remains challenging due to increasing multidrug resistance. This study investigates the in vitro antifungal potential of Viroelixir, a standardized polyphenol blend derived from green tea and pomegranate and enriched in catechins (including epigallocatechin gallate, EGCG), ellagitannins (notably punicalagin), ellagic acid, and flavonoids, with particular focus on its potential anti-virulence mechanisms. Methods: The effect of Viroelixir on C. albicans growth was assessed using MTT assay, optical density measurements, colony formation, carbohydrate quantification, and pH variation analysis. Biofilm formation, morphological transition, ROS production, necrosis, virulence gene expression, adhesion, and host immune responses were also evaluated. Results: Viroelixir significantly inhibited C. albicans growth and reduced colony formation compared with untreated controls. The formulation also inhibited biofilm formation and markedly reduced pseudohyphal development, reaching up to 94% reduction under specific treatment conditions. Flow cytometry analysis showed an increase in dead fungal cells, reaching approximately 88% following exposure to Viroelixir at the highest tested concentration. In addition, Viroelixir reduced the transcript levels of several virulence-associated genes, including SAP1–SAP9 and EAP1. In epithelial cell co-culture models, pre-treatment of C. albicans with Viroelixir reduced fungal adhesion and attenuated epithelial inflammatory responses, including IL-6, IL-8, and hBD-2 production, and was associated with reduced activation of the TLR4-NF-κB signaling pathway. Conclusions: These findings suggest that the antifungal and anti-virulence effects observed may be associated with the polyphenolic compounds present in the Viroelixir formulation, highlighting its potential as a promising in vitro antifungal candidate against C. albicans. Full article

Under recurring droughts, the southwestern U.S. loses a significant proportion of precipitation as evapotranspiration (ET), suggesting an opportunity to reduce ET via forest thinning. To better understand the potential impacts of thinning on the forest hydrologic cycle, we used sap flow sensors and Bowen ratio stations to measure ET in thinned and non-thinned ponderosa pine (Pinus ponderosa Douglas ex C. Lawson) stands in northern Arizona during the wet year of 2023, where thinning removed 42% of overstory basal area. Although our study site had experienced prolonged drought in previous years, heavy winter snowfall made 2023 a wet year. We correlated sap flow with environmental variables and used principal component analysis to identify the primary drivers of ponderosa pine water use in thinned and non-thinned stands. Results showed that after accounting for tree size, thinned stands had ~20% (~5 L day⁻¹) higher individual-tree water use at daily and weekly temporal scales than non-thinned stands. At the stand level, thinning decreased overstory ET (OET) but increased understory ET (UET), indicating a reallocation of outgoing water fluxes in the water balance. As a result, total ET (sum of OET and UET) decreased from 584 to 516 mm year⁻¹. In the semi-arid forest, this decrease in total ET of 68 mm year⁻¹ (~12% reduction) indicates an ecohydrologically meaningful outcome of forest thinning. In both stands, tree water use was strongly regulated by environmental variables, primarily atmospheric variables such as air temperature and vapor pressure deficit. Overall, our results suggest that thinning can still promote an improved stand-level forest water balance during a wet year and thus may enhance forest resilience under projected increases in heat and aridity in the southwestern U.S. Full article

Hydraulic redistribution (HR) in plants facilitates bidirectional water transport through the vascular system in response to soil water potential gradients, with implications for ecological facilitation. This study aimed to evaluate the efficacy and results obtained with high-precision weighing lysimeters in detecting HR in olive (Olea europaea L.) using a split-root experimental setup with potted trees. Sixteen pots, each containing half of a plant’s root system, were independently monitored for mass changes to quantify HR between irrigated and water-stressed compartments. The independent weighing of each pair of linked pots was a challenge, but the purpose-built precision lysimeter array effectively isolated weights despite mechanical connections between pot pairs. Results demonstrated measurable water redistribution via roots from irrigated to dry pots, with mass transfer from the irrigated side to the non-irrigated side of the plants, between 10 and 70 g. After irrigation, non-irrigated pots received by HR on average between 3 and 12% of the irrigation water applied in irrigated pots. This furthermore highlighted the potential of the lysimeters for precise quantification of plant-mediated water dynamics. It was observed that HR intensity peaked shortly after irrigation, some hours to one day, and diminished over time, with higher intensity during nocturnal periods or cloudy humid daily conditions of negligible or null evapotranspiration. These findings confirm previous observations with reverse sap flow sensors, now with a different experimental approach, which appears precise but only possible for potted plants, allowing further understanding of HR. Full article

Efficient apple orchard water management under climate variability requires understanding how fruit load and water supply regulate branch-scale water use to optimize irrigation, yield, and fruit quality. During the summer of 2014, sap flow (SF) and maximum daily shrinkage (MDS) were measured in one branch from six apple trees (Malus domestica Borkh. Cv. ‘Jazz™’) using the Compensation Heat Pulse method and diameter variation sensors in an orchard near Havelock North, New Zealand. One west-oriented branch per tree, with diameters of 1.5 to 2.3 cm, was monitored alongside midday stem (ψs) and leaf (ψl) water potentials, leaf gas exchanges, leaf area index (LAI), and fruit dry matter per branch at the end of the growing season. Half of the trees were subjected to irrigation withdrawal after day of year (DOY) 31 (non-irrigated treatment), resulting in a significantly lower midday stem water potential (ψs) by DOY 56 (−1.03 MPa). Pre-harvest, SF and MDS were tightly correlated (r² = 0.69), but this correlation decreased post-harvest (r² = 0.16) due to reduced fluctuations in both SF and branch variations (BV). SF was normalized per unit of leaf area, categorizing branches into high and low LAI: fruit dry matter ratio. SF values were approximately 2.2 times higher for FI pre-harvest and remained 2-fold higher post-harvest, associated with lower ψl and higher midday leaf transpiration for FI. MDS was identified as a better indicator of mild water deficit compared to SF, with both measurements responding effectively to midday vapor pressure deficit and reference evapotranspiration values. Overall, MDS proved to be a more sensitive indicator of mild water deficit than SF, while fruit load exerted a persistent influence on branch water use, highlighting the value of branch-scale measurements for improving irrigation management in apple orchards. Full article

Sap flow serves as the primary carrier for water, nutrients, and signaling molecules, playing a crucial role in fruit development by delivering these essential constituents to the fruit. While the efflux of sap from fruit to other organs (termed reverse sap flow) has been observed in plants, its underlying mechanisms remain unclear due to a lack of effective methodologies for comprehensive studies. Here, we pioneered the integration of real-time sap flow measurements from novel plant-wearable sensors with synchronized environmental monitoring, establishing a multimodal data framework to systematically decode the endogenous causes and exogenous triggers of reverse sap flow in watermelon plants. Our experimental results reveal that plant water supply–consumption imbalance is the core endogenous cause of reverse sap flow, which is induced by two external triggers in the natural environment: rapid light intensity surges and soil drought. Furthermore, a long-term drought stress experiment illustrates that reverse sap flow from the fruit enhances the drought resistance of plants by adjusting water redistribution within the whole plant. This study challenges the unitary view of fruit solely as a “sink” in the traditional source–sink theory, further refines the understanding of the source–sink paradigm, and provides a novel mechanism and insight for plant drought tolerance strategies. Full article

Understanding how cultivated xerophytic shrubs physiologically regulate canopy water loss under anomalously wet conditions is crucial for predicting ecohydrological responses and for providing practical guidance in landscape restoration under the ongoing warming–wetting trend on the northern Loess Plateau. This study tested hypotheses concerning the hierarchy of atmospheric and soil-water controls on canopy transpiration (E_c), stomatal conductance (g_s), the strength of canopy–atmosphere coupling, and species-specific soil-water sensitivities and water-use strategies in Caragana korshinskii and Salix psammophila. Concurrent measurements of branch-level sap flow, meteorological variables, and soil water content (SWC) at multiple depths were conducted in two adjacent stands during the wet season of a climatically wet year (July–September 2017). Meteorological factors, particularly vapor pressure deficit (VPD), were the dominant drivers of daily E_c and g_s, whereas SWC exerted secondary but species-specific influences. Both shrubs were strongly coupled to the atmosphere, with consistently low decoupling coefficients (Ω ≈ 0.11–0.15) on daily scales. C. korshinskii maintained stable water use through access to deeper soil, whereas S. psammophila responded sensitively to fluctuations in shallow SWC. These contrasting patterns indicate depth-partitioned water-use strategies and a context-dependent continuum between isohydric and anisohydric behavior rather than fixed species traits. The findings support improved parameterization of shrub water use in ecohydrological models, more effective water-use management, and informed species selection and nursery practices for landscape restoration in semi-arid regions experiencing warming–wetting climatic shifts. Full article

This study aimed to evaluate the physiological responses and yield of Tahiti lime (Citrus latifolia) cultivated at high density under three soil moisture tension (SMT) levels: low (L = −0.010 MPa), medium (M = −0.035 MPa), and high (H = −0.085 MPa). Measurements included water status, sap flow, photochemical activity, gas exchange, and fruit yield during the dry and early rainy seasons. The leaf water potential (Ψ_L) and relative water content (RWC) were higher in the L and M treatments than in H, with an overall improvement at the onset of the rainy season. From the dry to the rainy season, sap flow decreased by 25.3, 16.0, and 1.9 L day⁻¹ in L, M, and H plants, respectively. Plants with higher soil water availability (L and M) maintained better water status during the dry season, which favored photochemistry and gas exchange, reflected in a greater shoot growth and fruit yield (54.5 and 53.4 kg plant⁻¹, respectively). In contrast, H SMT significantly reduced water relations and photosynthetic activity, leading to yield loss. Short-term rainfall (six days) was insufficient to restore physiological performance. Maintaining SMT around −0.035 MPa during the dry season optimizes yield while reducing water use. Full article

Vigor-reducing rootstocks are now commonly used in sweet cherry cultivation. However, their application in Hungary presents challenges due to the drier summer climate and limited availability of irrigation water. The aim of this study was to determine the water transport characteristics and potential drought tolerance of three vigor-reducing rootstocks that may be suitable for cherry production in Hungary. The stomatal conductance (gs), midday stem water potential (MSWP), and sap flow velocity were measured in four-year-old Carmen and Regina cherry trees grafted onto MaxMa 14, WeiGi 2, and GiSelA 6 rootstocks. Measurements were taken after harvest during a period of severe drought. Among the rootstocks studied, MaxMa 14 trees exhibited the lowest MSWP values, even after irrigation and during periods with a relatively adequate water supply. No significant or consistent differences in the gs values were observed between the rootstocks. However, the variation in the gs and MSWP values before and after irrigation was the greatest in MaxMa 14 trees and the smallest in GiSelA 6 trees. Furthermore, the sap flow velocity in MaxMa 14 trees showed no significant difference between the pre- and post-irrigation measurements, indicating stable water transport. In contrast, trees on GiSelA 6 and WeiGi 2 rootstocks exhibited significant differences between dry and irrigated conditions. Although MaxMa 14 showed lower MSWP values, its gs responded more dynamically to changes in the water availability, and it maintained consistent water transport parameters across both dry and wet conditions. Based on the evaluated parameters, GiSelA 6 and WeiGi 2 showed similar behavior. However, in regard to some traits—such as the dynamic change in stomatal conductance—WeiGi 2 appeared to be more similar to MaxMa 14. Our results suggest that MaxMa 14 may be the most adaptable to drought among the tested rootstocks. Full article