Moderate Water Stress Conditions Research Articles

Divergences in leaf CO2 diffusion conductance and water use efficiency of soybean coping with water stress and its interaction with N addition

Drought and nitrogen (N) additions have been shown to affect plant photosynthesis, but the effect of their interaction on CO2 diffusion conductance (i.e., stomatal conductance, gsc, mesophyll conductance, gm) and water use efficiency (WUE) at the leaf level (i.e., instantaneous water use efficiency, WUEins; intrinsic water use efficiency, WUEint) has rarely been reported. Herein, we examined the interactive effects of drought and N addition on gsc and gm and WUE (i.e., WUEins and WUEint) in soybean (Glycine max (Linn.) Merr.) and analysed the interaction mechanisms mitigating water stress based on leaf anatomy and molecular activity. Drought decreased gsc,gm and WUEins, but N addition had a positive interactive effect with water stress on leaf physiological traits. The variables gsc, gm and WUEins were significantly increased by the additions of 7.5 and 15.0 g urea m−2 under moderate water stress (MW) conditions (P < 0.05), but they decreased under the interaction effect of SW and N addition. The decreased Tcw and increased Sm and Sc under the water stress × N addition interaction positively affected gm, and the increased SS dominated the gsc increase. In addition, these positive effects were further enhanced with increased AQP, CA and Rubisco activities and a decrease in the ABA content. Accordingly, moderate soil N additions of 7.5 and 15.0 g urea m−2 greatly mitigated the negative effects of droughts, especially the MW effects, by enhancing CO2 diffusion conductance and WUE.

Operational blue water footprint and water deficit assessment of coal-fired power plants: case study in Malaysia

Freshwater is an essential resource used to generate electricity at coal-fired power plants. Previous literature has shown that a few states in Malaysia will face a high risk of water stress. Hence, coal-fired power plants located at risk states are exposed to potential water risk. This study aims (i) to determine the operational blue water footprint at coal-fired power plant from 2009 until 2020; (ii) to assess the water stress index at Perak, Negeri Sembilan and Johor; and (iii) to compare the water deficit impact across three states. This study accounted the operational water footprint using Water Footprint Assessment Global Manual. The study boundary focuses on water consumption of generating electricity at operational level. The water stress index was assessed based on ratio of water demand and water availability at Perak, Negeri Sembilan and Johor watershed. Next water deficit impact was determined to compare the impact of operational blue water footprint on local water resources. Data for this study were collected from the state’s water authority, published literature, national reports, and statistics. Result of this study found the average operational blue water footprint recorded by coal-fired power plant located at Perak is 0.11 m3/MWh followed 0.09 m3/MWh (Johor) and 0.04 m3/MWh (Negeri Sembilan). Water stress index at Perak and Negeri Sembilan shows moderate water stress, whereas Johor indicates low water stress index. The water deficit result shows Perak has the highest total water deficit at 12,542,824 m3H2Oeqn from 2009 to 2020. This is due to moderate water stress condition at Perak and the total blue water footprint of coal-fired power plant at Perak is 67% and 42% more as compared to Negeri Sembilan and Johor, respectively. The result from this study is useful in enhancing understanding of water consumption pattern at coal-fired power plant and its impact on state’s water resources for future electricity scenarios.

Managing Water Stress in Olive (Olea europaea L.) Orchards Using Reference Equations for Midday Stem Water Potential

The irrigation surface of olive orchards has increased over recent decades. In zones affected, deficit irrigation scheduling is a must. The aim of this work was to study water stress management based on reference equations for midday stem water potential. An experiment was conducted over three seasons in Seville (Spain) from 2020 to 2022. A young hedgerow olive orchard (cv Manzanilla de Sevilla) was irrigated using three different treatments: Control (full irrigated), RDI, and Rainfed, in a completely randomized design (six replications). The midday stem water potential and leaf conductance were measured throughout the three seasons. Stem water potential was more sensitive to water stress than leaf conductance and showed a clearer impact and rehydration. Individual data of stem water potential were grouped according to leaf conductance reduction. The relationship of these stem water potentials and temperature or vapor pressure deficit was significant, linear, and aligned to published baselines. Scattering in these equations increased when the leaf conductance reduction was greater. These reference equations would be useful to define moderate water stress conditions in the most sensitive processes, such as vegetative or fruit growth. Definition of severe water stress conditions would be better established with constant values.

Improving drought tolerance and glycyrrhizin content of licorice plant by EPS-producing cyanobacteria

We evaluated the effects of two selected EPS-producing cyanobacterial strains for microbe-dependent drought tolerance in native licorice plant (Glycyrrhiza glabra) and addressed the mechanisms, which might be improved through these interactions. These bacteria were inoculated on the soils in a form of single strain (Anabaena sphaerica or Nostoc pruniforme) or two strains (Anabaena + Nostoc) in greenhouse conditions. The growth parameters, physiological and metabolical responses among treatments were investigated through assaying the antioxidants and glycyrrhizin contents in the plants grown in both normal condition and moderate water stress condition (FC 50%). The reduction of the ratio of root/shoot in response to drought (FC 50%) was correlated with amount of specific metabolites production, including glycyrrhizic acid (GA), glabridin (GB), liquiritin (LQ) and liquiritigenin (LG), especially in soil treated by Anabaena + Nostoc (P < 0.05). In water-deficient conditions, accumulation of GA in plants treared by Anabaena + Nostoc was boosted by 64% and 69% compared to Anabaena and the control, respectively. Besides, a significant increase in catalase activity (25%) was perceived in this treatment after exposure to drought stress. These results highlight the potential role of enzymatic antioxidants and the increase of GA content in responsing to the drought tolerance in licorice plant. Our findings suggest that using EPS-producing strains of Cyanobacteria is an efficient treatment to improve the drought tolerance in cultivation of medicinal plant in soil of arid and semi-arid regions.

A comparative study on impacts of water stress in turmeric varieties Acc 48 and Acc 79

Water stress created in turmeric varieties Acc 48 and Acc 79 by irrigating them in different intervals. Water stress influence on morpho-logical features, physio-logical and yield features of both the varieties was investigated. In this study irrigation treatments divided into three groups. Group A control receives water weekly once. For every two weeks once group B was irrigated and for every three weeks once group C was irrigated. Plants which are under heavy water stress showed gradual reduction in morphological, physiological and in yield parameters, i.e. ‘plant height, number of leaves, width of the leaf, fresh and dry weight of rhizome, Relative Growth Rate, Net Assimilation Rate’. Acc 48 &amp; Acc 79 morphological- parameters, physiological and yield parameters was slightly affected in moderate stress compared to control. Among the two Acc 48 resisted water stress in moderate stress condition than Acc 79. In heavy water stress condition, the two varieties severely affected compared to control and moderate stress. Among the two varieties Acc 48 was less affected. In all the treatments Acc 48 was less affected in all aspects except in thin and tuberous roots number. To cope up with water stress length of thin and tuberous roots of both the varieties were increased in heavy and moderate water stress condition. Irrigating turmeric two weeks once showed minor impact on plants than irrigating them three weeks once. In heavy water stress, plants was affected in all morphological, physiological and yield aspects.

Effect of Water Stress on the Yield of Indeterminate-Growth Green Bean Cultivars (Phaseolus vulgaris L.) during the Autumn Cycle in Southern Spain

Common bean is typically cultivated in the Mediterranean basin, an area where water scarcity could limit yield. This species has a broad range of food uses (seed or pod) and very diverse growth patterns (indeterminate or determinate), which hinders any deficit irrigation strategy. The aim of this work was to evaluate the response of the vegetative and reproductive growth stages to water stress in beans of indeterminate habit. During two consecutive Autumn seasons (2020 and 2021), two cultivars of green bean were grown in a greenhouse in Seville (Spain). The experimental design was a split plot with four replications. One of the factors considered was the cultivars Helda, and Perfección Blanca; and the other was the irrigation strategy: a control treatment, which received 100% of crop evapotranspiration, and a regulated deficit irrigation (RDI) treatment, with 30% of the water applied to the control. In both seasons, significant differences were found between cultivars, but irrigation only reduced branch development around 50%. Reproductive growth was not markedly affected, although a clear diminishing trend of approximately 25% was measured in P. Pod length and the number of non-commercial pods were not importantly impacted by irrigation in any of the cultivars. Moderate water stress conditions did not reduce the quality and quantity of the yield. Therefore, the current irrigation strategy could increase water savings with low or no yield reduction.

Productivity and Feed Quality Performance of Napier Grass (Cenchrus purpureus) Genotypes Growing under Different Soil Moisture Levels.

In the semi-arid and arid environments of Sub-Sharan Africa, forage availability throughout the year is insufficient and highly limited during the dry seasons due to limited precipitation. Thus, the identification of drought stress-tolerant forage cultivars is one of the main activities in forage development programs. In this study, Napier grass (Cenchrus purpureus), an important forage crop in Eastern and Central Africa that is broadly adapted to produce across tropical environments, was evaluated for its water use efficiency and production performance under field drought stress conditions. Eighty-four Napier grass genotypes were evaluated for their drought stress tolerance from 2018 to 2020 using agro-morphological and feed quality traits under two soil moisture stress regimes during the dry season, i.e., moderate (MWS) and severe (SWS) water stress conditions, and under rainfed conditions in the wet season (wet). Overall, the results indicated the existence of genotype variation for the traits studied. In general, the growth and productivity of the genotypes declined under SWS compared to MWS conditions. High biomass-yielding genotypes with enhanced WUE were consistently observed across harvests in each soil moisture stress regime. In addition, the top biomass-yielding genotypes produced the highest annual crude protein yield, indicating the possibility of developing high-feed-quality Napier grass genotypes for drought stress environments.

Effect of Trichoderma asperellum on Wheat Plants' Biochemical and Molecular Responses, and Yield under Different Water Stress Conditions.

Eight Trichoderma strains were evaluated for their potential to protect wheat seedlings against severe (no irrigation within two weeks) water stress (WS). Considering the plant fresh weight and phenotype, T. asperellum T140, which displays 1-aminocyclopropane-1-carboxylic acid deaminase activity and which is able to produce several phytohormones, was selected. The molecular and biochemical results obtained from 4-week-old wheat seedlings linked T140 application with a downregulation in the WS-response genes, a decrease in antioxidant activities, and a drop in the proline content, as well as low levels of hydrogen peroxide and malondialdehyde in response to severe WS. All of these responses are indicative of T140-primed seedlings having a higher tolerance to drought than those that are left untreated. A greenhouse assay performed under high nitrogen fertilization served to explore the long-term effects of T140 on wheat plants subjected to moderate (halved irrigation) WS. Even though all of the plants showed acclimation to moderate WS regardless of T140 application, there was a positive effect exerted by T. asperellum on the level of tolerance of the wheat plants to this stress. Strain T140 modulated the expression of a plant ABA-dependent WS marker and produced increased plant superoxide dismutase activity, which would explain the positive effect of Trichoderma on increasing crop yields under moderate WS conditions. The results demonstrate the effectiveness of T. asperellum T140 as a biostimulant for wheat plants under WS conditions, making them more tolerant to drought.

Maize response to combined heat and water stresses under varying growth conditions

AbstractIdentificationof agronomic practices that can ameliorate the negative effect of combined heat and water stress on maize plants is vital in food security strategy. The objective of this study was to evaluate the effect of heat and water stress on the growth of maize (Zea mays L.) under variable growth conditions. A repeated greenhouse factorial experiment laid out in a completely randomized design with four replications was performed. The factors were maize variety, water stress, soil amendment, and soil type. The results showed a depressive effect of water stress on the maize leaf area, chlorophyll content, stem diameter, dry biomass yield, and harvest index. These attributes decreased as the severity of the water stress increased with harvest index dipping by 30.3 and 92.9% in moderate water stress (MS) and terminal water‐stress (TS) plants, respectively. Sandy clay loam soil gave higher maize growth and yield attributes than loamy sand soil. The varied growth conditions imposed by the different water stresses, soil types, and soil amendments elicited different responses from the three maize varieties. Mean stability analyses/ranking identified ZM1523 and WE5323 as the top‐performing varieties under poultry manure amendment for both non‐stress and MS conditions, whereas under TS their performance improved in combined poultry manure/mineral fertilizer and mineral fertilizer treatments. Similarly, WE3128 gave its best performance under mineral fertilizer amendment for non‐stress, MS, and TS conditions. Therefore, under combined heat and water stress conditions, the interaction of maize variety, soil type, and soil amendment should be considered to guarantee a high maize yield.

Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars

In recent years, the area dedicated to modern irrigated almond plantations has increased significantly in Spain. However, the legal irrigation allocations are lower than the maximum water requirements of the crop in most cases. Therefore, almond growers are forced to implement regulated deficit irrigation strategies on their farms, applying water stress in certain resistant phenological periods and avoiding it in sensitive periods. Given the need to monitor the water status of the crop, especially in the most sensitive periods to water stress, the objective of this work was to evaluate the sensitivity of two UAV-based crop water status indicators to detect early water stress conditions in four almond cultivars. The field trial was conducted during 2020 in an experimental almond orchard, where two irrigation strategies were established: full irrigation (FI), which received 100% of irrigation requirements (IR), and regulated deficit irrigation (RDI), which received 70% of IR during the whole irrigation period except during the kernel-filling stage when received 40% IR. The UAV flights were performed on four selected dates of the irrigation season. The Crop Water Status Index (CWSI) and the Normalized Difference Vegetation Index (NDVI) were derived from thermal and multispectral images, respectively, and compared to classical water status indicators, i.e., stem water potential (Ψstem), stomatal conductance (gs), and photosynthetic rate (AN). Of the four flights performed, three corresponded to mild water stress conditions and a single flight was performed under moderate water stress conditions. Under mild water stress, CWSI was not able to capture the differences between FI and RDI trees that were observed with Ψstem. Under moderate stress conditions, CWSI was sensitive to the water deficit reached in the trees and showed significant differences among both irrigation treatments. No differences were observed in the CWSI and NVDI response to water stress among cultivars. Although NDVI and CWSI were sensitive to water stress, the low signal intensity observed in NDVI makes this index less robust than CWSI to monitor crop water stress. It can be concluded that UAV-based CWSI measurements are reliable to monitor almond water status, although for early (mild) levels of water stress, Ψstem seems to be the preferred option.

Prediction of Olive Tree Water Requirements under Limited Soil Water Availability, Based on Sap Flow Estimations

The forecast of irrigation requirements in commercial olive orchards in the era of climate change is at the forefront of scientific research. Simplified models that are based on monitoring soil and plant water status, along with microclimatic variables are well established. In the present study, an attempt was made to correlate the olive tree sap fluxes and the theoretical grass water losses, as expressed by reference evapotranspiration (ETo) in mild to moderate water-stress conditions. The water flow in the soil–plant–air continuum was monitored using soil water and thermal dissipation probes (TDP), which have a comparatively low cost and satisfactory reliability, while microclimatic variability was monitored by a meteorological station placed within the experimental orchard. The assessment of water stress was conducted via a stress coefficient (Ks), which was determined according to soil water availability, and validated with measurements of pre-dawn water potential and stomatal conductance. The results suggest the existence of an exponential correlation (R2 = 0.869) between daily plant transpirational losses and reference evapotranspiration, while the methodology’s applicability is verified by the validation process (R2 = 0.804 and RMSE = 0.579 L per day).

Response of in vitro-regenerated Myrtus communis L. shoots to PEG-induced water stress

Myrtle ( Myrtus communis L.) is an evergreen and aromatic plant species with therapeutic and ornamental values . The effect of water stress induced by three concentrations of Polyethylene glycol (PEG), 0% (control), 3% (3%PEG) and 6% (6% PEG) was evaluated on in vitro -regenerated myrtle shoots. After 30 days of culture, all regeneration, growth and physiological parameters were measured at the end of the experiment. Murashige and Skoog (MS) medium contained 1.5 mgl -1 6-benzyladenine (BAP) and 0.2 mgl -1 Naphthaleneacetic acid (NAA) was optimized for the in vitro experiment. Increasing PEG concentration in the culture media resulted in fewer regenerated shoots, and higher rate of browning in the apical tissues. Chlorophylls and total carotenoids content significantly decreased in the shoots treated with PEG, however there were no significant differences in the pigment content under moderate or severe water stress conditions. PEG-induced water stress resulted in reduced plant growth and relative water content of newly-formed shoots. Lipid peroxidation and electrolyte leakage were lower in myrtle shoots treated with 6%PEG than 3%PEG, but they were still higher than that of the control. Proline accumulation significantly increased under 3%PEG treatment, while a little difference were observed between proline content under 6%PEG and the control. Apoptosis did not occur in the myrtle shoots grown under moderate or severe stress treatments which correlated with more increased Catalase and Superoxide dismutase activities in response to higher stress levels. The results showed a possible contribution of enzymatic antioxidant system in myrtle when counteracting severe water stress. • PEG-induced stress significantly decreased growth, water content, and pigments of in vitro -regenerated myrtle shoots. • Shoots showed a higher lipid peroxidation and electrolyte leakage under the PEG treatment than PEG-free control. • Proline accumulation significantly raised in myrtle only under mild water stress condition (3%PEG). • A higher increase of antioxidant enzymes might have a possible contribution in a lower apoptosis under stress condition.

INFLUENCE OF CALCIUM CARBONATE AND KAOLIN ON GROWTH, DROUGHT RESISTANCE INDEX AND PHYSIOLOGICAL TRAITS OF PAULOWNIA (PAULOWNIA TOMENTOSA, THUNB.) SEEDLINGS UNDER DROUGHT STRESS CONDITIONS

Two pot experiments were carried out at lath house in the Nursery of Ornamental Plants, Hort. Dept., Zagazig Univ., Egypt during the two spring consecutive seasons of 2018/2019 and 2019/2020 to study the effect of water stress (irrigation at 100, 75 and 50 % from field capacity), antioxidants type [(distilled water as control, 4 g/l of calcium carbonate (CC) and 30 g/l of kaolin (Ka)] as foliar applications and their interaction treatments on growth parameters, physiological traits, drought resistance percentage and some chemical constituents of paulownia seedlings. Plant height, stem diameter, leaf number per plant, dry weight of leaves per plant, drought resistance index, wood density and total chlorophyll content decreased significantly with increasing drought treatments from 100% to 50 % field capacity. However, water stress significantly increased soluble sugar content and proline content in leaves compared to full irrigation treatment. Furthermore, using each calcium carbonate or kaolin significantly increased all abovementioned parameters compared to control (sprayed with distilled water) in both seasons. Generally, it could conclude that 30g/l Ka showed a uniform influence in alleviating of Paulownia tomentosa growth inhibition and its wood density under moderate water stress condition with increasing in drought resistance percentage to reach 105.68 and 102.09 % in the first and second seasons, respectively.

Physiological responses of orange trees subject to regulated deficit irrigation and partial root drying

Variations in climate, crop, and field conditions have caused different results in applying regulated deficit irrigation (DI) and partial root drying irrigation (PRD) for citrus. In this study field grown, Washington Navel orange trees were exposed to RDI and PRD practices at two reduced irrigation levels: 80% and 50% of full water requirement under a semi-arid climate. Applying DI-80 and PRD-80 resulted in a moderate water stress condition for the experimented trees and saved ~ 15% of the seasonal irrigation without significant yield reduction (~ 3 to 5%). Applying DI-50 and PRD-50 saved up to 40% of the seasonal irrigation, but the trees experienced a severe water stress condition with ~ 28% yield reduction in DI-50 and 19% in PRD-50 trees. The fruit weight was not significantly affected by the irrigation techniques, and the yield reduction in DI treatments was attributed to the fruitlet abscission and the lower number of fruits per tree. A higher leaf water potential, more controlled vegetative growth and greater yield resulted from the trees irrigated at 80% irrigation level. Internal fruit composition was equally enhanced in DI and PRD fruits and was more notable at the 50% irrigation level. A more effective drought management mechanism was found in the PRD-treated trees and was more notable and beneficial in the severe water stress level. In high water stress conditions, the soil water content (SWC) had a more remarkable impact on controlling the stomatal response compared to vapor pressure deficit (VPD), while in low water stress conditions, the effect of VPD was more evident.

Assessment of physiological traits of common bean cultivars in response to water stress and molybdenum levels

Molybdenum is an essential micronutrient that regulates plant growth, development, and responses to abiotic environmental stresses. However, little is known about the joint effects of water stress, molybdenum, and cultivar on physiological traits of field-grown common bean. Therefore, a split-plot factorial design was used to determine the main and interaction effects of Water stress (3 levels: 55–60, 90–95 and 120–125 mm evaporation from class A pan), Molybdenum (2 levels: control and 80 g per ha), and Cultivar (2 levels: Akhtar and COS-16) on physiological traits and grain yield of common bean. The results indicated that leaf area index (LAI), chlorophyll index, relative water content (RWC) and grain yield decrease with increasing water stress. Spraying molybdenum to the plants increased LAI, RWC, and grain yield, but the extent of the increase varied with cultivar. The positive effect of molybdenum also varied with the magnitude of water stress, and it was higher in severe water stress condition compared to that in normal irrigation and moderate water stress conditions. Of the two cultivars, COS-16 gave significantly higher grain yield than Akhtar cultivar, but Akhtar was superior in terms of physiological traits. The study demonstrated that the application of Molybdenum under water stress may cause an increase in N uptake and the efficiency of its use, that consequently increases the chlorophyll index and grain yield of common bean cultivars.

Genotypic Variation in Potato Growth and Yield Response to Water Stress During two Production Seasons in Northwest Ethiopia

Water stress during low-rainfall periods (Mesino and Belg) constrains the potato from meeting full yield potential in northwest Ethiopia. Farmers tend to grow local varieties in these seasons but these varieties have not been tested for their water stress tolerance. Therefore, the present study was conducted to evaluate major Ethiopian local varieties for their drought tolerance under controlled conditions in two growing seasons, and to compare these with a few selected varieties from outside sources. Nine local varieties and six new varieties were tested in the screen house at Adet Agricultural research center in both Mesino and Belg seasons for their response to moderate water stress conditions during 2014. All varieties were grown under two water regimes (well-irrigated and stressed) maintained by monitoring soil moisture. The results showed that, averaging across varieties, the marketable tuber yield losses due to water stress in Mesino (residual production) and Belg seasons were 28% and 67%, respectively. Substantial differences between varieties in growth and yield response to both growing season and water stress were also observed. In the Mesino season, although no variety out-yielded the main local variety, ‘Siquare’, under drought conditions, “Belete”, “CIP-395109.34”, “Abadamu” and “Granola” had showed the lowest water stress susceptibility index (SSI) and higher marketable tuber yield in stress condition. In the Belg season, ‘Granola’ followed by ‘Abadamu’ and “Gera” had the highest marketable tuber yields under both irrigated and stress conditions and the lowest water stress susceptibility index. Traits associated with high marketable yield potential and stability under stress condition include: high harvest index, increased root length, relatively few deformed and small sized tubers under stress. The results indicated potential for improving dry season potato production in Ethiopia by utilizing both selected local and new varieties.

Coupling Hyperspectral Remote Sensing Data with a Crop Model to Study Winter Wheat Water Demand

Accurate information of crop growth conditions and water status can improve irrigation management. The objective of this study was to evaluate the performance of SAFYE (simple algorithm for yield and evapotranspiration estimation) crop model for simulating winter wheat growth and estimating water demand by assimilating leaf are index (LAI) derived from canopy reflectance measurements. A refined water stress function was used to account for high crop water stress. An experiment with nine irrigation scenarios corresponding to different levels of water supply was conducted over two consecutive winter wheat growing seasons (2013–2014 and 2014–2015). The calibration of four model parameters was based on the global optimization algorithms SCE-UA. Results showed that the estimated and retrieved LAI were in good agreement in most cases, with a minimum and maximum RMSE of 0.173 and 0.736, respectively. Good performance for accumulated biomass estimation was achieved under a moderate water stress condition while an underestimation occurred under a severe water stress condition. Grain yields were also well estimated for both years (R2 = 0.83; RMSE = 0.48 t∙ha−1; MRE = 8.4%). The dynamics of simulated soil moisture in the top 20 cm layer was consistent with field observations for all scenarios; whereas, a general underestimation was observed for total water storage in the 1 m layer, leading to an overestimation of the actual evapotranspiration. This research provides a scheme for estimating crop growth properties, grain yield and actual evapotranspiration by coupling crop model with remote sensing data.

The effect of strobilurin on ethylene production in flowers, yield and quality parameters of processing tomato grown under a moderate water stress condition in Mediterranean area

This research was conducted in Southern Italy over two growing seasons to evaluate the effect of strobilurin application on the ethylene production of flowers (EF) and on the yield and quality parameters of processing tomato grown under moderate water deficit conditions. The following two irrigation regimes were applied: IR100, full irrigation that restores 100% of the maximum crop evapotranspiration (ETc) and IR75, which is 75% of the amount of water of IR100. Furthermore, from the beginning of flowering two fungicide treatments were applied three times: fungicide treatment without strobilurin (ST0) and strobilurin fungicide with an azoxystrobin based product (STaz). At full flowering, ethylene production in the flowers (EF) was determined. At harvest, the main yield and qualitative parameters were evaluated. The strobilurin treatment caused a significant decrease of EF, which was less evident in the first warmer year than in the second. This result was presumably because of the interference of high temperatures on the inhibition of ethylene synthesis described for the strobilurin. In contrast, the decrease of EF due to strobilurin treatment was more evident under IR75 than under IR100. Finally, the decrease in the number of marketable fruits with respect to the EF increase was lower under strobilurin treatment presumably because of the protective effect of this molecule on the flower drop. Further studies are needed to investigate this hypothesis in greater detail.

Delaying berry ripening of Bobal and Tempranillo grapevines by late leaf removal in a semi-arid and temperate-warm climate under different water regimes

Background and Aims Climate change is advancing grape ripening and decoupling sugar and phenolic maturity, impacting wine typicity. The aim of this study was to test whether late leaf removal (LLR) under different watering regimes delayed harvest of two Spanish red cultivars in a semi‐arid and temperate‐warm climate. Methods and Results In two trials carried out in eastern Spain with the Bobal and Tempranillo cultivars, vines were partially defoliated above the bunch zone shortly before veraison under rainfed and deficit irrigation conditions during two seasons. The rate of grape ripening in both cultivars was significantly affected by LLR under either watering regime, consequently delaying harvest. Vine water status and leaf photosynthetic rate were improved by LLR. The reduction in leaf area‐to‐fruit ratio resulting from the LLR treatments was found to be more limiting for the accumulation of anthocyanin than for TSS. Consequently, LLR negatively affected wine colour intensity. In addition, yield was constrained by LLR in Tempranillo due to a reduction in bunch and berry mass. Conclusions The reduction in the rate of accumulation of grape TSS provoked by LLR did not necessarily result in a more balanced berry maturity. The effectiveness of the LLR technique appears to depend on its final impact on leaf area‐to‐fruit ratio and vine water status, the cultivar photosynthetic compensation capacity and the environmental conditions. Significance of the Study Late leaf removal might not be effective for coupling anthocyanin and TSS in berries under moderate water stress conditions, given the observed reductions in red wine colour.

Reducing basal nitrogen rate to improve maize seedling growth, water and nitrogen use efficiencies under drought stress by optimizing root morphology and distribution

Frequent spring droughts and nitrogen (N) fertilizer overuse limit rain-fed maize production in Northeast China. However, the interactions between water-stress and N rates on maize seedling growth and root development remain elusive. In this study, a pot experiment was conducted with maize grown under three N rates (N omission, low and high N rates, i.e., N0, LN and HN) and severe water-stress (SS), moderate water-stress (MS) and well-watered (WW) conditions for 2-week from 4-leaf stage. Dry biomass (DM), leaf rolling performance, water use efficiency (WUE), N fertilizer use efficiency (NUE), root morphology and distribution were evaluated. It was showed that soil water levels and N rates had significant individual and interactive effects on most measured parameters. The dual stress of drought and N deficiency severely limited maize growth and N uptake. Nitrogen fertilization improved maize growth, N uptake and WUE under water-stress. However, compared with HN treatment, LN treatment had less water consumption, higher leaf relative water content and less leaf rolling symptom both under the MS and SS conditions. The reason is that LN enhanced root growth and elongation with more fine roots, especially in deep soil. Notably, maize plants in MS-LN treatment had an optimal root distribution characterized by higher root length density (0.30 cm cm−3), larger and deeper penetration scale throughout the soil layers, and thus showed fewer drought responses and obtained the highest WUE (4.1 g L−1) and NUE (17.2%) among all the water-stress treatments. In contrast, HN limited root growth and extension in deep soil and in turn increased water and N depletion, resulting in more serve leaf rolling and lower WUE and NUE. Therefore, reducing basal N rate is recommended to optimize root growth, morphology and distribution at the seedling stage in rain-fed maize production, to enhance drought resistance and improve WUE and NUE.