Drought stress is becoming a structural phenomenon in cropping systems challenged by climate change and soil fertility degradation. A balanced fertilization strategy based on nitrogen, phosphorus, and potassium as well as on silicon supplementation was tested as an efficient practice to improve maize tolerance to short-term drought stress. Three fertilization strategies (control: treatment with zero NPK fertilizer application; NPK: granular NPK fertilizer, and NPK + Si: granular NPK fertilizer enriched with 5% silicon) were evaluated under three irrigation regimes simulating three probable water deficit levels in the Mediterranean climate (I1, well-watered conditions: 80% of soil field capacity; I2, medium drought stress: 60% of soil field capacity; and I3, severe drought stress: 30% of soil field capacity). Drought stress was applied at V10 growth stage of maize and maintained for 15 days, then plants were rewatered according to the optimal irrigation regime. Results showed that medium and severe drought stress down-regulated maize plant growth and yield, especially under nutrient deficient conditions (control). Plants amended with NPK and NPK + Si recorded higher chlorophyll a pigment content (+ 22 to + 64%), stomatal conductance (+ 6 to 24%), and leaf relative water content (+ 7 to 23%) than those of the control, depending on the drought stress level. Silicon supplementation attenuated the down-regulation effects of drought stress on maize photosynthesis and biomass accumulation by improving stomatal conductance and electron transfer efficiency between PSII and PSI. Silicon supply improved the performance index for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors (PIabs) and reduced the dissipation energy flux (DIo/RC), responsible for the protection of PSII from photo-damage under drought stress, which resulted in significant enhancement of maize photosynthesis recovery and grain yield (+ 59 to 69%). Findings from the present study demonstrate that granular NPK-fertilizer fortified with silicon could be an efficient strategy to increase maize photosynthesis performance, plant growth, and productivity under short-term drought stress conditions.

Salinity is a major abiotic stress that negatively affects agricultural land, significantly reducing crop yields. It alters the fundamental structure of the soil, causing a decrease in porosity, reduced aeration, and impaired water movement. Piriformospora indica, multifaceted fungi can enhance plant tolerance under abiotic stress conditions. The present study examined the effects of Piriformospora indica on the growth of Solanum melongena L. under saline conditions in a greenhouse, assessing parameters such as proline accumulation, lipid peroxidation, chlorophyll content, stomatal behavior, antioxidant activity, and phenotypic traits under salt stress Results of the present study showed significant improvement in phenotypic traits of Piriformospora indica colonized plants under saline conditions. Solanum melongena L. plants treated with 200 mM NaCl had swollen, deformed guard cells and closed stomata, while colonized plants maintained normal stomatal structure and their stomata remained open. Additionally, untreated plants exhibited higher malondialdehyde levels, indicating greater lipid peroxidation, while Piriformospora indica-colonized plants showed reduced oxidative damage, increased chlorophyll content, and enhanced peroxidase activity under saline conditions. The salt tolerance mediated by Piriformospora indica likely involves lipid desaturation, activation of antioxidant enzymes to counter reactive oxygen species, enhanced metabolism, improved nutrient uptake, proline accumulation, and increased phytohormone production.

Evapotranspiration (ET) is a critical component of the soil-plant-atmosphere continuum, significantly influencing the water and energy balance of ecosystems. However, existing studies on ET have primarily focused on the growing season or specific years, with limited long-term analyses spanning decades. This study aims to analyse the components of ET within the alpine ecosystem of the Heihe River Basin, specifically investigating the dynamics of vegetation transpiration (T) and soil evaporation (Ev). Utilizing the SPAC model and integrating meteorological observations and eddy covariance data from 2013 to 2022, we investigate the impact of solar radiation and vegetation dynamics on ET and its partitioning (T/ET). The agreement between measured and simulated energy fluxes (net radiation and latent energy flux) and soil temperature underscores the validity of the model's performance. Additionally, a comparison employing the underlying water use efficiency method reveals consistent T/ET values during the growing season, further confirming the model's accuracy. Results indicate that the annual average T/ET during the 10-year study period is 0.41 +/- 0.03, close to the global average but lower than in warmer, humid regions. Seasonal analysis reveals a significant increase in T/ET during the growing season (April to October), particularly in May and June, coinciding with the thawing of permafrost and increased soil moisture. In addition, the study finds that the leaf area index and canopy stomatal conductance exhibit a logarithmic relationship with T/ET, whereas soil temperature and downward longwave radiation show an exponential relationship with T/ET. This study highlights the importance of understanding the stomatal conductance dynamics and their controls of transpiration process within alpine ecosystems. By providing key insights into the hydrological processes of these environments, it offers guidance for adapting to climate change impacts.

Dry season droughts may increasingly threaten Mediterranean forests under climate change. While plants employ three desiccation avoidance strategies to avoid or delay dehydration damage, including reduced water loss, enhanced tissue water storage, and improved root water access, resource allocation competition may lead to trade-offs among these strategies that are not yet fully understood. We investigated six Mediterranean woody species by analysing: (1) twig hydraulic capacitance (0.32 - 2.81 mmol m(-2) MPa-1) representing tissue water storage capacity; (2) twig residual conductance (g(res)) at 25 degrees C (1.23 -7.73 mmol m(-2) s(-1)) reflecting water loss rate; and predawn water potential (Psi(PD)) and its difference from midday water potential (triangle Psi) at the end of the dry season as root water access indicators. Significant trade-offs in plant desiccation avoidance strategies were observed as g(res) positively correlated with triangle Psi (R-2 = 0.78, P = 0.02) and twig hydraulic capacitance negatively correlated with Psi(PD) (R-2 = 0.68, P = 0.04). Consequently, species with greater root water access exhibited lower tissue water storage capacity and higher g(res), potentially increasing mortality risk when soil moisture becames limiting. By inverting a plant desiccation model, we also demonstrated that minimum survival-required hydraulic capacitance and a novel risk index were both positively correlated with Psi(PD), consistent with historical mortality records. Additionally, despite temperature-dependent g(res) patterns which revealed species-specific responses, elevated temperatures amplified the risk index for all species.

Maize (Zea mays L.) is an important cereal crop grown in arid and semiarid regions of the world. During the reproductive phase, it is more frequently exposed to drought stress, resulting in lower grain yield due to oxidative damage. Selenium and zinc oxide nanoparticles possess inherent antioxidant properties that can alleviate drought-induced oxidative stress by the catalytic scavenging of reactive oxygen species, thereby protecting maize photosynthesis and grain yield. However, the effect of zinc selenide quantum dots (ZnSe QDs) under drought stress was not been quantified. Hence, the aim of this study was to quantify the (i) toxicity potential of ZnSe QDs and (ii) drought mitigation potential of ZnSe QDs by assessing the transpiration rate, photosynthetic rate, oxidant production, antioxidant enzyme activity and seed yield of maize under limited soil moisture levels. Toxicity experiments were carried out with 0 mg L-1 to 500 mg L-1 of ZnSe QDs on earthworms and azolla. The results showed that up to 20 mg L-1, the growth rates of earthworms and azolla were not affected. The dry-down experiment was conducted with three treatments: foliar spray of (i) water, (ii) ZnSe QDs (20 mg L-1), and (iii) combined zinc sulfate (10 mg L-1) and sodium selenate (10 mg L-1). ZnSe or Se applications under drying soil reduced the transpiration rate compared to water spray by partially closing the stomata. ZnSe application at 20 mg L-1 at the tasselling stage significantly increased the photosynthetic rate (25%) by increasing catalase (98%) and peroxidase (85%) enzyme activity and decreased the hydrogen peroxide (23%) content compared to water spray, indicating that premature leaf senescence was delayed under rainfed conditions. ZnSe spray increased seed yield (26%) over water spray by increasing the number of seeds cob-1 (42%). The study concluded that foliar application of ZnSe (20 mg L-1) could decrease drought-induced effects in maize.

Crop management affects the anatomical and physiological characteristics of gladiolus floral stems. Particulary, shading screens are important in gladiolus production. The aim of the study was to evaluate the meteorological conditions, physiological indicators, stomatal characteristics, and quality of gladiolus flower stems grown in different seasons under shading screens and mulching. Field experiments were conducted during the four growing seasons: 1 (March-June 2019), 2 (August-November 2019), 3 (August-November 2020), and 4 (OctoberDecember 2021). Gladiolus cv. White goddess was grown in beds with and without mulch. Shading treatments included 35% black, silver, and red shading screens, and an unshaded control. Weather conditions during four growing seasons over two years were within the range of maximum and minimum temperatures suitable for the crop. The black and red shading screens resulted in higher stomatal density (374.9; 362.0 stomatal mm-2), which improved the photosynthetic rate of the leaf resulting in greater flower stem length (116.32 cm) and number of florets (19.00) in the red shading screen. The highest relative chlorophyll index (57.75) was recorded in season 2, which contributed to a greater accumulation of assimilates and resulted in longer stems and better-quality florets. Planting under a red shading screen and mulched soil produced longer stems (8.60 %; 9.05 %, respectively), and a greater number of florets in seasons 2 (8.43 %) and 4 (14.74 %), compared to growing unshaded control. The lowest percentage of damage to flower stems was found in the silver shading screen (3.6%) and mulched soil (6.7%). Long flower stems without damage to the sepals and petals, and with a large number of florets are of better quality, have greater ornamental value and are more attractive to flower consumers. Our results showed that planting in seasons 2 and 4, and using red shading screens and mulching soil, are sustainable and conservation soil-management practices to provide a favorable environment which allowed us to obtain high-quality gladiolus flowers. The results of this study are parameters for future research with different soil mulchings and shading screen colors.

Increasing heatwaves are threatening forest ecosystems globally. Leaf thermal regulation and tolerance are important for plant survival during heatwaves, though the interaction between these processes and water availability is unclear. Genotypes of the widely distributed foundation tree species Populusfremontii were studied in a controlled common garden during a record summer heatwave-where air temperature exceeded 48 degrees C. When water was not limiting, all genotypes cooled leaves 2 to 5 degrees C below air temperatures. Homeothermic cooling was disrupted for weeks following a 72- h reduction in soil water, resulting in leaf temperatures rising 3 degrees C above air temperature and 1.3 degrees C above leaf thresholds for physiological damage, despite the water stress having little effect on leaf water potentials. Tradeoffs between leaf thermal safety and hydraulic safety emerged but, regardless of water use strategy, all genotypes experienced significant leaf mortality following water stress. Genotypes from warmer climates showed greater leaf cooling and less leaf mortality after water stress in comparison with genotypes from cooler climates. These results illustrate how brief soil water limitation disrupts leaf thermal regulation and potentially compromises plant survival during extreme heatwaves, thus providing insight into future scenarios in which ecosystems will be challenged with extreme heat and unreliable soil water access.

In an increasingly dry environment, it is crucial to understand how tree species use soil water and cope with drought. However, there is still a knowledge gap regarding the relationships between species-specific stomatal behaviour, spatial root distribution, and root water uptake (RWU) dynamics. Our study aimed to investigate above- and below-ground aspects of water use during soil drying periods in four temperate tree species that differ in stomatal behaviour: two isohydric tracheid-bearing conifers, Scots pine and Norway spruce, and two more anisohydric deciduous species, the diffuse-porous European beech, and the ring-porous Downy oak. From 2015 to 2020, soil-tree-atmosphere-continuum parameters were measured for each species in monospecific forests where trees had no access to groundwater. The hourly time series included data on air temperature, vapor pressure deficit, soil water potential, soil hydraulic conductivity, and RWU to a depth of 2 m. Analysis of drought responses included data on stem radius, leaf water potential, estimated osmotically active compounds, and drought damage. Our study reveals an inherent coordination between stomatal regulation, fine root distribution and water uptake. Compared to conifers, the more anisohydric water use of oak and beech was associated with less strict stomatal closure, greater investment in deep roots, four times higher maximum RWU, a shift of RWU to deeper soil layers as the topsoil dried, and a more pronounced soil drying below 1 m depth. Soil hydraulic conductivity started to limit RWU when values fell below 10-3 to 10-5 cm/d, depending on the soil. As drought progressed,oak and beech may also have benefited from their leaf osmoregulatory capacity, but at the cost of xylem embolism with around 50 % loss of hydraulic conductivity when soil water potential dropped below -1.25 MPa. Consideration of species -specific water use is crucial for forest management and vegetation modelling to improve forest resilience to drought.

A new sustainable approach was aimed to explore the damage caused to legume grown in cadmium (Cd) polluted soil. Owing to the importance of chickpea (Cicer arietinum L.) as a source of protein which is exposed to Cd that imposes severe health hazards. A greenhouse pot experiment was designed to evaluate the potential of Rhizobium application in the amelioration of cadmium stress (Cd; 50 and 100 mg kg(- 1) soil) on chickpea cultivar namely Pusa-BG372 on growth (plant length; plant dry biomass; leaf area; and nodule number), photosynthetic pigments (total chlorophyll and carotenoids), stress biomarkers (malondialdehyde, MDA; superoxide radicles; cell viability), defense (proline, superoxide dismutase, SOD; peroxidase, POD; catalase, CAT; stomatal behaviour), and the major enzymes involved in nitrate assimilation (nitrate reductase; NR) and Calvin Cycle (carbonic anhydrase; CA). Among the different tested concentrations, 100 mg kg(-1) of Cd reduced the growth, photosynthetic variables, biochemical enzymes activity and increased oxidative stress under Cd stress. However, chickpea plants supplemented with Rhizobium-inoculation under the Cd toxicity revealed significantly increased chlorophyll, carotenoid, and proline contents, activity of CA, NR, and antioxidant enzymes. Aside from improved antioxidant enzyme performance and lower lipid peroxidation, cell viability and stomatal functioning were also improved in Rhizobium-inoculated plants. These observations depicted that application of Rhizobium inoculation to seeds could be useful approach to assist stress tolerance against Cd in crop plants grown in Cd contaminated sites.

Key messageThe high-wood-density species displays greater water limitation tolerance, as it maintains leaf transpiration under drought conditions.AbstractThe relationship between environmental conditions and plant hydraulic safety is essential to understand species' strategies to minimize damage to their hydraulic structure yet maintain function. In the Brazilian semi-arid, the relationships between rainfall seasonality, hydraulic conductivity, wood density, stomatal conductance, and phenology in different species still needs to be clarified. To better understand these relationships, we selected two deciduous trees species with contrasting wood density: (1) Commiphora leptophloeos (Mart.) J.B. Gillett (low wood density) and (2) Cenostigma pyramidale (Tul.) E. Gagnon & G. P. Lewis (high wood density) from the Caatinga dry forest of northeast Brazil. We tracked monthly measurements of whole-tree hydraulic conductivity, leaf stomatal conductance, leaf transpiration rate, xylem water potential, and phenology. We found that the low-wood-density species had a higher whole-tree hydraulic conductivity and an early leaf flush and fall. In addition, lower leaf transpiration rate and higher water storage capacity maintained high xylem water potential and stomatal conductance values, especially in the rainy season. On the other hand, the high-wood-density species had a lower whole-tree hydraulic conductivity and higher leaf transpiration rate, even during the dry season. These results point to the divergent hydraulic strategies employed by each species, further suggesting opposing hydraulic safety pathways during drought.