Search Results (48)

Maize cultivation in tropical Oxisols during the second growing season faces significant climatic risks, where spatial heterogeneity in soil water retention often dictates economic viability. This study integrated a trimodal sensing approach, combining multispectral, thermal, and LiDAR data, with proximal physiological measurements to map isohydric responses and yield variability. Conducted in the Brazilian Cerrado, the research monitored a one-hectare maize field using UAV-based sensors alongside ground truth evaluations of gas exchange, leaf water potential, and soil moisture. Results revealed high yield variability (6.6 to 13.4 Mg ha⁻¹) primarily governed by clay content-mediated water availability. Maize exhibited strict isohydric behavior, maintaining homeostatic leaf water potential through preventive stomatal closure, which limited CO₂ assimilation in zones with lower water retention. A significant statistical decoupling was observed between plant height and final grain yield, as water stress impacted reproductive stages more severely than vegetative growth. Furthermore, the Temperature Vegetation Dryness Index (TVDI) served as a robust proxy for biomass vigor rather than mere water deficit. These results confirm that yield variability in tropical Oxisols was not a product of hydraulic failure, but rather a consequence of carbon limitation necessitated by the crop’s conservative hydraulic management to maintain leaf water potential within safe thresholds. Full article

Urban roadside environments are characterized by altered microclimate and soil conditions that impose recurrent drought stress on trees, affecting their physiological performance and adaptive capacity. Understanding species-specific physiological and structural responses to drought stress is crucial for selecting tree species that are suitable for urban environments. In the present study, we investigated the species-specific and temporal (monthly) patterns of the in situ leaf physiological status and structural traits of two riparian tree species, Quercus robur L. and Carpinus betulus L., cultivated as urban roadside trees in Novi Sad, Serbia, throughout the growing season (from June to September). This was achieved by assessing leaf gas exchange and rapid light curves of chlorophyll a fluorescence together with leaf structural traits. Under drought stress, Q. robur exhibited sustained photosynthetic activity and transpiration rates due to reduced stomatal sensitivity, indicative of a more anisohydric behavior with respect to its water relations strategy. In contrast, C. betulus exhibited tighter stomatal regulation and showed lower assimilation rates accompanied by reduced cooling capacity, indicating stricter, more conservative water-balance management indicative of isohydric species. Fluorescence indices revealed contrasting behavior: C. betulus showed enhanced NPQ values accompanied by a decline in photosynthetic efficiency, while Q. robur exhibited lower NPQ, suggesting better maintenance of photosynthetic performance and electron transport in PSII under the observed drought stress. These patterns were further supported by higher stomatal density combined with smaller stomatal size, indicating faster stomatal response rates in C. betulus compared to Q. robur. Overall, these results suggest that C. betulus is a more promising riparian tree species for urban landscapes, particularly under drought-prone conditions and predicted climate changes, in comparison to Q. robur. Full article

Historically, certain physiological behaviours were typically attributed to genetic factors. However, some grape varieties exhibit different responses depending on crop management and environmental conditions. The present study examines whether the physiological responses of grapevines traditionally attributed to genotypic traits (near-isohydric or near-anisohydric behaviour) can instead be substantially modified by canopy architecture. The objective was to determine how canopy management influences water relations (leaf water potential—Ψ_L), physiological plant responses (water use efficiency (WUE), stomatal conductance (gs), transpiration (E) and photosynthetic (A) rates), and radiation interception efficiency (εi), particularly under warm Mediterranean conditions. To test this, two training systems were evaluated in a Syrah vineyard: a vertical shoot position (VSP1) and a sprawl (S1) system with 12 shoots·m⁻¹, under the same irrigation regime. The results showed that under stressed conditions (high vapor pressure deficit [VPD] and relatively lower Ψ_L, from −1.4 to −0.6 MPa), the S1 system—despite a similar leaf area index, LAI—exhibited lower gs values than those of the VSP1 system (10–30%), with plants closing their stomata to reduce water consumption and prevent their dehydration caused by steep E rates. Meanwhile, the VSP vines exhibited higher gs values (isohydric-like response), indicating higher E rates, which reduced their WUE and intrinsic water-use efficiency (IE). This strategy (similar to the anisohydric one) allowed the S1 treatment to obtain higher WUE and interception radiation efficiency (εi) ratios, even at low Ψ_L (more efficient), produced by the higher canopy demand (more exposed surface area [SA]). These contrasting behaviours indicate that sprawl systems can enhance radiation interception and WUE compared with vertical systems under semiarid Mediterranean conditions. 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

Pinus (~113 species, generally early-seral) and Quercus (~435 species, generally late-seral), currently co-occur over a wide range of climates and biomes in the Northern Hemisphere. Climate change is expected to threaten the coexistence dynamics of pine and oak species. Here, we analyze the responses of Pinus and Quercus to water stress, with the objective of determining how they vary globally in their responses to drought at the genus level. The results show that pines tend to tightly close stomata before stress becomes severe and may deplete their stored carbon; on the other hand, oaks begin stomatal control at a lower water potential and hence do not suffer from carbon depletion. Pines exhibit a wider hydraulic safety margin (average: 3.33 MPa) than oaks (average: 1.41 MPa) because of lower Ψ₅₀ (average: −3.62 MPa) and earlier stomatal closure (average: −2.19 MPa). For oaks, stomatal closure and Ψ₅₀ occur at −2.61 MPa and −3.07 MPa, respectively. We discuss and show that these contrasting drought responses are consistent with their seral roles. While the difference in the basic strategies to drought in the two genera is unmistakable, the species studied are still too few to make convincing generalizations. Research is also needed on other components related to drought adaptations. Full article

To survive in saline environments, plants establish complex symbiotic relationships with soil microorganisms, including halotolerant arbuscular mycorrhizal fungi (AMF). The main objective of this study was to uncover how inoculation with a consortium of halotolerant AMF influences recretohalophyte Limonium species tolerance to long-term salinity, at physiological and molecular levels. In this study, the physiological performance, ultrastructure of leaf epidermal cells, and expression of seven genes involved in salinity response were studied in Limonium daveaui and Limonium algarvense plants exposed to 200 mM NaCl and inoculated with an AMF consortium, dominated by Rhizoglomus invernaius. An isohydric response was observed for both species after one year in salinity. Inoculation with AMF led to higher stomatal conductance for plants in non-saline conditions and improved photosystem II efficiency under salinity. In L. algarvense, inoculation enhanced stomata and salt gland epidermal area under tap water. While salinity significantly increased salt gland, stomata and pavement cells areas but not cell size. In L. daveaui, AMF led to an increased salt gland density as well as salt gland size under saline conditions. In both species, salinity increased the expression of Na⁺/H⁺ antiporter AtSOS1, aquaporin TIP5, and salt gland development related genes LbTRY, Lb7G34824 and Lb4G22721GIS2. The expression of such genes was significantly reduced in AMF-inoculated plants under salinity. Besides, higher levels of gene expression were observed in L. algarvense than in L. daveaui. Overall, our findings highlight the protective role of halotolerant AMF and emphasize their potential as sustainable effective bio-inoculants for enhancing plant salinity tolerance. Full article

Miscanthus is considered a promising candidate for the cultivation of marginal land. This land poses unique challenges, and experiments have shown that the “establishment phase” is of paramount importance to the long-term yield performance of miscanthus. This experiment analyzes novel miscanthus hybrids and how their establishment on marginal land can be improved through agronomic interventions. Experiments took place at two sites in Germany: at Ihinger Hof, with a very shallow soil profile and high stone content, and at Reichwalde, where the soil was repurposed river sediment with low organic matter, high stone content, and a compacted lower horizon. These marginal conditions functioned as test cases for the improvement of miscanthus establishment agronomy. Four hybrids (Miscanthus x giganteus, Gnt10, Gnt43, and Syn55) and agronomic treatments such as plastic mulch film, miscanthus mulch, inoculation with mycorrhizal fungi, and fertilization were tested in two years at both sites in 2021 and 2022. Specific weather conditions and the timing of planting were strong determinants of establishment success and no single treatment combination was found that consistently increased the establishment success. Plastic mulch films were found to hinder rather than help establishment in both these locations. Chipped miscanthus mulch caused nitrogen immobilization and stunted plant growth. At Ihinger Hof the novel seed-based miscanthus hybrid Gnt43 produced twice the biomass of other hybrids (7 t ha⁻¹) in the first growing season. Gnt10 yielded well in 2021 and showed impressive tolerance to water stress in the summer of 2022. No treatment combination was found that consistently increased the establishment success of miscanthus hybrids across sites and years. Novel genotypes consistently outperformed the standard commercial miscanthus hybrid Miscanthus x giganteus. Gnt10 may be a promising candidate for the cultivation of water-stress-prone marginal lands, due to its isohydric behavior and high yield potential. Full article

This study investigates the impact of water stress on grapevines, specifically examining the role of rootstocks and aquaporins. Two experiments on potted plants were conducted in central Chile during the summer, under conditions of high water demand, involving various rootstock genotypes and combinations of Cabernet Sauvignon (CS) grafted onto rootstocks. Significant differences were observed among plants in terms of stem water potential, stomatal conductance, and growth rate. Notably, the CS/CS combination consistently displayed the slowest growth rate, regardless of the irrigation treatment. The study also analyzed the expression levels of plasma membrane intrinsic protein (PIP) and tonoplast intrinsic protein (TIP) aquaporins in the leaves of grafted plants. Specifically, VvPIP2;2 aquaporins showed reduced expression after 14 days without irrigation, whereas VvTIP1;1 and VvTIP2;1 expression levels correlated positively with g_s responses in grafted plants, suggesting their role in modulating water content in leaves under water stress. TIP aquaporins likely play a significant role in the differential responses of CS plants towards near-isohydric or anisohydric behavior. The CS/CS combination exhibited near-isohydric behavior, correlating with lower TIP aquaporin expression, while the combination of CS onto 1103P and 101-14 showed higher expression, indicating anisohydric behavior. The findings suggest that grafted plants are more resilient to water stress, supporting the idea that rootstocks can mitigate the effects of water stress on the scion. Full article

Research Highlights: Environmental abiotic stressors generate secondary stresses in plants, such as osmotic and oxidative stresses, which negatively influence their normal growth, development, and metabolism. Research about other non-enzymatic components with antioxidant capacity has recently focused on polyphenols. However, their role as indicators of drought and shade tolerance in woody species leaves and roots has been poorly explored or was limited to leaves only. Background and Objectives: Under a scenario of increasing drought, understanding the seedling responses in terms of total polyphenols and their antioxidant activity, in particular at the fine root system level, may help to elucidate the native–alien species interaction. Materials and Methods: At the beginning of July, 5-month-old native Quercus robur and alien Quercus rubra seedlings were transferred indoors to the growth chamber and subjected to progressive soil drying for 21 days. Results: The decrease in soil water content was more pronounced for Q. robur (9%) than for Q. rubra (34% of field capacity). Leaf water potential significantly decreased over time in Q. robur but did not differ from the control in Q. rubra. The total polyphenol concentration in Q. robur was markedly lower in the leaves and significantly higher in the fine roots than in Q. rubra. For the leaves, both species showed markedly higher values if well-watered, and the values significantly decreased in response to drought only in Q. rubra. In contrast, the fine root values for both species were markedly higher if droughted and decreased significantly in time only in Q. robur. Differently from the polyphenol concentration, the antioxidant capacity of Q. rubra was always higher in both the leaves and fine roots. Conclusions: The higher antioxidant activity of the alien species Q. rubra revealed by this work, combined with its isohydric behaviour, could further shed some light on our understanding of its competitive performance at the seedling stage against the native Q. robur. Full article

Mechanisms underlying grapevine responses to water(-deficient) stress (WS) are crucial for viticulture amid escalating climate change challenges. Reanalysis of previous transcriptome data uncovered disparities among isohydric and anisohydric grapevine cultivars in managing water scarcity. By using a self-organizing map (SOM) transcriptome portrayal, we elucidate specific gene expression trajectories, shedding light on the dynamic interplay of transcriptional programs as stress duration progresses. Functional annotation reveals key pathways involved in drought response, pinpointing potential targets for enhancing drought resilience in grapevine cultivation. Our results indicate distinct gene expression responses, with the isohydric cultivar favoring plant growth and possibly stilbenoid synthesis, while the anisohydric cultivar engages more in stress response and water management mechanisms. Notably, prolonged WS leads to converging stress responses in both cultivars, particularly through the activation of chaperones for stress mitigation. These findings underscore the importance of understanding cultivar-specific WS responses to develop sustainable viticultural strategies in the face of changing climate. Full article

The development of water-saving management relies on understanding the physiological response of crops to soil drought. The coordinated regulation of hydraulics and stomatal conductance in plant water relations has steadily received attention. However, research focusing on grain crops, such as winter wheat, remains limited. In this study, three soil water supply treatments, including high (H), moderate (M), and low (L) soil water contents, were conducted with potted winter wheat. Leaf water potential (Ψ_leaf), leaf hydraulic conductance (K_leaf), and stomatal conductance (g_s), as well as leaf biochemical parameters and stomatal traits were measured. Results showed that, compared to H, predawn leaf water potential (Ψ_PD) significantly reduced by 48.10% and 47.91%, midday leaf water potential (Ψ_MD) reduced by 40.71% and 43.20%, K_leaf reduced by 64.80% and 65.61%, and g_s reduced by 21.20% and 43.41%, respectively, under M and L conditions. Although g_s showed a significant difference between M and L, Ψ_leaf and K_leaf did not show significant differences between these treatments. The maximum carboxylation rate (V_cmax) and maximum electron transfer rate (J_max) under L significantly decreased by 23.11% and 28.10%, stomatal density (SD) and stomatal pore area index (SPI) under L on the abaxial side increased by 59.80% and 52.30%, respectively, compared to H. The leaf water potential at 50% hydraulic conduction loss (P₅₀) under L was not significantly reduced. The g_s was positively correlated with Ψ_MD and K_leaf, but it was negatively correlated with abscisic acid (ABA) and SD. A threshold relationship between g_s and K_leaf was observed, with rapid and linear reduction in g_s occurring only when K_leaf fell below 8.70 mmol m⁻² s⁻¹ MPa⁻¹. Our findings demonstrate that wheat leaves adapt stomatal regulation strategies from anisohydric to isohydric in response to reduced soil water content. These results enrich the theory of trade-offs between the carbon assimilation and hydraulic safety in crops and also provide a theoretical basis for water management practices based on stomatal regulation strategies under varying soil water conditions. Full article

The globally increasing frequency of extreme drought events exacerbates the contradiction between the supply of water and the demand for high-quality urban greening. However, the mechanism of the response of urban shrubs to drought stress remains unclear. In this study, three typical urban shrubs (Euonymus japonicus, golden vicary [Ligustrum × vicaryi], and Japanese purple barberry [Berberis thunbergii var. atropurpurea]) that are used for greening in northern China were exposed to three levels of water (full irrigation, natural rain-fed, and extreme drought) in different periods of the growing season (April to May, June to July, and August to September) to investigate the responses of leaf water potential and photosynthetic parameters. The main results were as follows: (1) all the leaf water potentials (Ψ) and photosynthetic parameters (P_n) showed a typical linear relationship along the water gradient in the middle of the growing season. Extreme drought decreased the photosynthetic rates by 1.26~11.03 μmol·m⁻²·s⁻¹ compared with the irrigated groups. However, the responses were less pronounced in the early and late growing seasons. (2) Different shrubs responded with different intensities and mechanisms. B. thunbergii var. atropurpurea showed clear anisohydric behavior throughout the whole growing season, while L. × vicaryi and E. japonicus showed stronger isohydric behavior during the early and late growing seasons. These findings are important to improve the sustainability of maintenance of ornamental plants from the scope of the efficient utilization of urban water resources. Full article

Trees in degraded forest areas are generally exposed to water stress due to harsh environmental conditions, threatening their survival. This study simulated the environmental conditions of a degraded forest area by constructing an artificial rainfall slope and observing the physiological responses of Pinus densiflora to control, mulching, and waterbag treatments. P. densiflora exhibited distinct isohydric plant characteristics of reducing net photosynthetic rate and stomatal transpiration rate through regulating stomatal conductance in response to decreased soil moisture, particularly in the control and waterbag treatments. Additionally, the trees increased photochemical quenching, such as Y(NPQ), to dissipate excess energy as heat and minimize damage to the photosynthetic apparatus. However, these adaptive mechanisms have temporal limitations, necessitating appropriate measures. Under extreme drought stress (DS45), mulching treatment showed 4.5 times and 2.2 times higher in PI_abs and SFI_abs than in the control, and after the recovery period (R30), waterbag and mulching treatment showed similar levels, while PI_abs and SFI_abs in the control were only 45% and 75% of those in the mulching and waterbag treatments, respectively. Specifically, mulching extended the physiological mechanisms supporting survival by more than a week, making it the most effective method for enhancing the planting ground in degraded forest areas. Although the waterbag treatment was less effective than mulching treatment, it still significantly contributed to forming better growth conditions compared to the control. These findings highlight the potential for mulching and waterbag treatments to enhance forest restoration efforts, suggesting future research and application could lead to more resilient reforested areas capable of withstanding climate change-induced drought conditions. Full article

Salinity is a major constraint limiting the yield of tomatoes. However, grafting strategies may help to overcome the salt toxicity of this important horticultural species if appropriate rootstocks are identified. The present study aimed to test a new rootstock, JUPAFORT1, obtained by crossing the glycophyte Solanum lycopersicum (cv. Poncho Negro) with the halophyte wild-related species Solanum chilense to improve the salinity tolerance of the Chilean tomato landrace Old Limachino Tomato (OLT). Intact OLT plants were exposed to 0, 80, or 160 mM of NaCl for 21 days at the vegetative stage and compared with self-grafted (L/L) and Limachino plants grafted on JUPAFORT1 rootstock (L/R) under a completely randomized design. JUPAFORT1 increased OLT scion vigor in the absence of salt but did not significantly increase fresh weight under stress conditions. However, JUPAFORT1 confers to the scion an anisohydric behavior contrasting with the isohydric behavior of L and L/L plants as indicated by measurements of stomatal conductance; L/R plants were able to maintain their metabolic status despite a slight decrease in the leaf’s relative water content. JUPAFORT1 rootstock also enabled the maintenance of photosynthetic pigment concentrations in the scion in contrast to L and L/L plants, which exhibited a decrease in photosynthetic pigments under stress conditions. L/R plants encountered oxidative stress at the highest stress intensity (160 mM of NaCl) only, while L and L/L plants suffered from oxidative damage at a lower dose (80 mM of NaCl). L/R plants behaved as includer plants and did not sequester Na⁺ in the root system, in contrast to L and L/L, which behaved as excluder plants retaining Na⁺ in the root system to avoid its translocation to the shoots. The expression of genes coding for ion transporters (HKT1.1, HKT1.2, LKT1, SKOR, SOS2, and SOS3) in the root system was not modified by salinity in L/R. In contrast, their expression varied in response to salinity in L and L/L. Overall, L/R plants exhibited higher physiological stability than L/L or L plants in response to an increasing NaCl dose and did not require additional energy investment to trigger an adaptative response to salinity. This suggests that the constitutive salinity tolerance of the halophyte S. chilense was maintained in the interspecific rootstock. JUPAFORT1 issued from S. lycopersicum x S. chilense may thus improve salt-stress resilience in OLT tomatoes. Additional studies are required to identify the molecular components involved in the root-to-shoot signaling pathway in this promising material. Full article

Citrus orchards in semi-arid regions are increasingly exposed to drought conditions due to climate change. This study compared the physiological and growth responses of ‘W. Murcott’ tangor (WM) grafted onto Citrus macrophylla (M), Swingle citrumelo (SC), C-35 citrange (C35), or bitter citrandarin (C22) rootstock subjected to two irrigation treatments: daily irrigation to replace 100% of the water lost daily by evapotranspiration (ET; control treatment) or daily irrigation to replace 75% of the water lost daily by ET (water deficit treatment). For trees in each treatment, leaf gas exchange, relative chlorophyll content, chlorophyll fluorescence, midday stem water potential, trunk cross-sectional area, and shoot length were measured 46 days after treatments were initiated. The results showed that WM on SC or C22 rootstock exhibited isohydric behavior, where decreased stomatal conductance limited transpiration in the water deficit treatment. WM on M rootstock exhibited an anisohydric response in the water deficit treatment, where there was no stomatal control of water loss by transpiration. Among the rootstocks tested for WM, the most tolerant to soil water deficit was SC, whereas trees on M rootstock were the most negatively affected by soil water deficit. Full article