Severe Water Stress Research Articles

Seed osmopriming with polyethylene glycol (PEG) enhances seed germination and seedling physiological traits of Coronilla varia L. under water stress.

Water stress can adversely affect seed germination and plant growth. Seed osmopriming is a pre-sowing treatment in which seeds are soaked in osmotic solutions to undergo the first stage of germination prior to radicle protrusion. Seed osmopriming enhances germination performance under stressful environmental conditions, making it an effective method to improve plant resistance and yield. This study analyzed the effect of seed osmopriming with polyethylene glycol (PEG) on seed germination and physiological parameters of Coronilla varia L. Priming treatments using 10% to 30% PEG enhanced germination percentage, germination vigor, germination index, vitality index, and seedling mass and reduced the time to reach 50% germination (T50). The PEG concentration that led to better results was 10%. The content of soluble proteins (SP), proline (Pro), soluble sugars (SS), and malondialdehyde (MDA) in Coronilla varia L. seedlings increased with the severity of water stress. In addition, under water stress, electrolyte leakage rose, and peroxidase (POD) and superoxide dismutase (SOD) activities intensified, while catalase (CAT) activity increased at mild-to-moderate water stress but declined with more severe deficiency. The 10% PEG priming significantly improved germination percentage, germination vigor, germination index, vitality index, and time to 50% germination (T50) under water stress. Across the water stress gradient here tested (8 to 12% PEG), seed priming enhanced SP content, Pro content, and SOD activity in Coronilla varia L. seedlings compared to the unprimed treatments. Under 10% PEG-induced water stress, primed seedlings displayed a significantly lower MDA content and electrolyte leakage than their unprimed counterparts and exhibited significantly higher CAT and POD activities. However, under 12% PEG-induced water stress, differences in electrolyte leakage, CAT activity, and POD activity between primed and unprimed treatments were not significant. These findings suggest that PEG priming enhances the osmotic regulation and antioxidant capacity of Coronilla varia seedlings, facilitating seed germination and seedling growth and alleviating drought stress damage, albeit with reduced efficacy under severe water deficiency.

Comparative effects of drought stress on three olive cultivars focusing on older leaves

Drought is one of the main abiotic stresses to which plants are exposed during their growth and development under both natural and agricultural conditions. Water shortage can seriously affect also xerophytic species such as olive (Olea europaea L.), despite the numerous anatomical, morphological, and physiological adaptations to drought developed over time. Until now, the olive physiological responses to drought stress have been studied mainly on young leaves, i.e. on leaves formed after or during water stress, while very few studies have been conducted taking into consideration leaves already existing before stress (older leaves). In this work, in order to investigate the effect of drought on 1-year-old leaves (old leaves), young plants of three Italian olive cultivars, namely ‘Degli’, ‘Leccino’, and ‘Maurino’, were subjected to moderate water stress (30 days irrigated with 10 % of the pot capacity, T1); subsequently, the same plants were exposed at severe water stress (30 days, without water supplying, T2). The results indicate that the stress tolerance of cultivars can be due to several favorable morpho-anatomical traits, such as higher percentage of palisade tissue (about 50 %) and uniform size of starch grains pre and post stress event. ‘Maurino’ stood out for its ability to cope with the imposed drought condition, maintaining an acceptable water status all over the experiment, and sustaining vegetative growth. Moreover, this olive cultivar showed a stability in the size of starch inclusions, all over the experiment. On the contrary, ‘Degli’ and ‘Leccino’ showed several negative changes under drought conditions, i.e. less growth of main branches, smaller starch grains size, marked reduction of photosynthetic activity, and reduction of leaf succulence, showing a less adaptive behaviour to water stress. Our work provides a more complete insight on olive older leaves response to drought.

Rice mutants, selected under severe drought stress, show reduced stomatal density and improved water use efficiency under restricted water conditions.

Rice is among the least water-use-efficient crops, and rice plants utilise most of their water uptake for transpirational cooling via stomata. To improve water-use efficiency (WUE) in rice, reducing stomatal density and size could help optimise transpiration and photosynthesis. In this study, we compared two series of purple rice stomata mutants: the Stomatal Model Mutant (SMM) identified by microscopic observation of flag-leaf stomata, and the Drought-selected Model Mutant (DMM) generated through screening under severe water stress. After undergoing two rounds of severe water stress between -60 to -80 Ym, right before the R1-2 reproductive stage, three DMMs were selected based on their rapid recovery rate and % filled-grain percentage. The three DMMs displayed 618-697 stomatal units per mm2, similar to the SMMs low-density stomata mutant (JHN 8756 (LD)). Furthermore, the four SMMs, three DMMs and the Jao Hom Nin wild type (JHN WT) were treated with two restricted water condition schemes from seedlings to harvest. The total amount of irrigation and precipitation during the experiment was 78.1 L/plant (69.1 mm/plant) for the less restricted water condition (LR) and 47.5 L/plant (42 mm/plant) for the more restricted water condition (MR). Water condition treatments had no effects on stomatal density and stomatal index. In contrast, genotypes and restricted water condition schemes affected plant height, tillers/plant, % filled grains and shoot dry weight (SDW). The three DMMs and the JHN 8756 (LD), the SMM's low-density stomata mutant, displayed greater resilience towards more restricted water conditions than the SMMs and the JHN wild type. Particularly, DMMs were tolerant to more restricted water condition treatments, showing no SDW penalties. Together, the DMMs and the JHN 8756 (LD) displayed higher WUE under these conditions of more restricted water conditions. A rigorous screening process to distinguish tolerant mutants with a rapid drought recovery rate from severe water stress could pave the way to isolate more mutants with better stomatal functionality and resilience in preparation for imminent climate changes.

Comprehensive evaluation of early-age hydration and compressive strength development in seawater-mixed binary and ternary cementitious systems

Seawater-mixed concrete (SWC) is a proposed solution for catering to the needs of developing nations facing extremely severe water stress. Recent research works advocate the feasibility of producing SWC by adding supplementary cementitious materials (SCMs) and alternative reinforcements without reducing the engineering properties of the same. However, limited information is available for optimising the type and amount of SCMs in binary and ternary blended SW-mixed cementitious systems for achieving desirable strength development and early-age hydration. A comprehensive study to understand the evolution of heat of hydration and strength up to 28 days was conducted on 31 binder compositions mixed with both fresh water (FW) and seawater (SW). Fly ash, slag, metakaolin, and limestone are the supplementary cementitious materials used with CEM I as a primary binder at a replacement level between 10 and 70%. Isothermal calorimetry results revealed an increase in total heat of hydration and a reduction in setting time with SW-mixed cement pastes compared to their FW-mixed counterparts. Similarly, a significant increase in strength between 0 and 50% was observed in SW-mixed cement pastes. Suitable binder combinations showing an increase in compressive strength and not a significant reduction in strength compared to the CEM I reference mix were identified using the strength improvement factor approach. Binary and ternary blended cementitious, consisting of fly ash, slag, and metakaolin at different replacement levels, are amongst the chosen binder combinations.

تأثير جسيمات النانو من السيليكون على مكونات الفوتوكيمياء (النشاط البيولوجي) والخصائص الفسيولوجية لنبات الكزبرة تحت ضغط الماء

The present study was accomplished to scrutinize the efficiency of Nano silicon (NSi) as a foliar spray on (Coriander sativum) plants under water stress conditions during 2021/2022 season. Coriander plants were subjected to three water levels (100, 70 and 30% of field capacity). Plant leaves were sprayed with NSi in three different concentrations (3, 5 and 10 ppm) 14 days after germination. The results revealed that Coriander plants growth was significantly decreased under water stress, while NSi treatment showed a significantly enhanced plant growth (length and number of leaves per plant). Regarding biochemical constituents activity, total of alkaloids, phenol, flavonoids and fatty acids increased under water stress. Also, nutrient elements (P & Mg and Na) increased. Plant hormones such as gibberellic acid (GA3) and ascorbic acid (vitamin C) significantly decreased under both 70% and 30% FC, while abscise acid (ABA) increased. In the interim, the three different concentrations of NSi significantly improved carbohydrates concentration and adjustment of osmotic stress. Application of NSi at different concentrations significantly improved nutrients contents (N, P, K, Mg, Ca, Fe, Zn, Mn) mainly under moderate and severe water stress (70%, 30% FC). Generally, the profound concentration of NSi tested during the experiment was 5 ppm for ameliorating water stress. The present investigation showed that the application of NSi might be a promising method to enhance the plant growth, biochemical ingredients and crop productivity of Coriander plants grown under water stress conditions.

HOUSEHOLD WATER INSECURITY EXPERIENCES (HWISE) SCALE: THE PROTOCOL OF CULTURAL ADAPTATION AND STATISTICAL VALIDATION

Annually Sri Lanka experiences substantial rainfall; but, the availability of water within the island nation is unbalanced. Lack of an appropriate system view, suitable national-level policy, and bimodal rainfall have resulted in Sri Lankans experiencing medium to high water stress. Considering the impact individual households have to endure due to the unavailability of water, the following study presents a protocol to culturally adapt and statistically validate the Household Water Insecurity Experiences (HWISE) scale to the Sinhala language. The protocol critically discusses the application of classical test theory (CTT) and item response theory (IRT) and documents all relevant steps for the scale validation process. Through this study protocol, the authors attempt to demonstrate the procedural rigor of the adaptation and validation process of the HWISE scale to the Sinhala language in Sri Lanka. The availability of a valid scale to evaluate household water insecurity experiences will assist public health experts, policymakers, and the government in understanding the nature and severity of water stress and the consequences across health, economic, and psychosocial contexts. Similarly, preventative interventions and key policies could be implemented to further support the initiatives of responsible authorities.<p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/soc/0758/a.php" alt="Hit counter" /></p>

Transpiration Dynamics of Esparto Grass (Macrochloa tenacissima (L.) Kunth) in a Semi-Arid Mediterranean Climate: Unraveling the Impacts of Pine Competition.

Macrochloa tenacissima (M. tenacissima), or esparto, is a perennial tussock grass that coexists with Pinus halepensis (P. halepensis) in semi-arid Mediterranean woodlands. This research was carried out to explore diurnal transpiration at leaf level in esparto grass under different levels of pine-esparto competition and in contrasting environmental soil water conditions. The measurement period spanned from the summer of 2020 to the spring of 2021. The relationship between transpiration and competition was conducted in open and closed P. halepensis stands, and the type of leaf (green, senescent) and the maturity of the esparto grass were taken into account. We observed a higher control of transpiration in green leaves, and the correlations between the transpiration and pine competition were noted exclusively in this type of leaf. Our results demonstrated a significant impact of pine competitors (closed stands) on the transpiration of esparto grass, particularly during seasons characterized by scenarios of high water demand: the summer drought period and the commencement of the growing and flowering period (spring). Furthermore, our findings revealed a greater response to transpiration in mature bushes compared to young ones under severe water stress, indicating a higher adaptation to drought by esparto as it ages. Although our results confirmed that PAR increased transpiration in all seasons and in both stands, which is attributable to the heliophilia of esparto grass, the site effects on transpiration could also be attributable to competition for water, especially during periods of drought. These results may have important implications for the dynamics and management of these semi-arid mixed woodlands, as well as the planning of reforestation programs aimed at restoring esparto grass formations.

Influence of high temperature and drought stress at jointing stage on crop physiological responses and growth in summer maize plants (Zea mays L.)

The combination of low precipitation and high temperature stresses at jointing stage can severely threaten maize production. However, to date, few studies have been conducted on the effects of combined stress on maize plants expression at jointing stage. In the current research, plant growth, root morphology, and yield components were determined after exposure to the single and combined stress of high temperature and drought stress. Leaf gas exchange, malondialdehyde (MDA) content and antioxidant enzymes activities were conducted to identify potential mechanisms of stress responses. The single stress of high temperature and drought significantly reduced the biomass of various organs and the total aboveground biomass, which reduced the yield of maize plants. High temperature substantially decreased aboveground biomass and yield under mild and severe water stress, which indicated that the inhibitory effects of combined stress were more significant than that of high temperature or drought individually. High temperature exacerbated the negative impacts of water stress on plants growth and yield as shown by the reduced leaf photosynthetic rate (Pn), probably related to the increasing MDA content. Leaf-level water use efficiency (WUE) was enhanced as the reduction in leaf transpiration (Tr) was greater than the decrease in leaf photosynthesis under high temperature, even for those plants were suffering water stress. High temperature, drought stress and their combination all greatly increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), but were ineffective in mitigating oxidative damage. The MDA content and antioxidant enzymes activities showed an increasing trend following 12 days of combined stress. This substantiated the irreversible damage induced by combination of high temperature and desiccation stresses. The combined stress optimized roots length, root volume, root surface area, and thinned the average root diameter, which improved the adaptation of maize to high temperature, drought and combined stress. This study has provided meaningful references for improved understanding the impacts of drought, high temperature, and concurrent events on the physiology and growth of maize plants during the jointing period.

Above-and below-ground feedback loop of maize is jointly enhanced by plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi in drier soil

Drought is a potent abiotic stressor that arrests crop growth, significantly affecting crop health and yields. The arbuscular mycorrhizal fungi (AMF), and plant growth-promoting rhizobacteria (PGPR) can offer to protect plants from stressful environments through improving water, and nutrient use efficiency by strengthening plant root structure and harnessing favorable rhizosphere environments. When Acaulospora laevis (AMF) and Bacillus subtilus (PGPR) are introduced in combination, enhanced root growth and beneficial microbial colonization can mitigate drought stress. To assess this potential, a pot experiment was done with maize (Zea mays L.) to explore the effects of A. laevis and B. subtilus under different water levels (well-watered = 80 %; moderate water stress = 55 %; and severe water stress = 35 %) on maize yield, soil microbial activities, nutrients contents, root, and leaf functioning. Plants exposed to severe drought stress hampered their root and leaf functioning, and reduced grain yield compared with control plants. Combined use of AMF and PGPR increased root colonization (104.6 %–113.2 %) and microbial biomass carbon (36.38 %–40.23 %) under moderate to severe drought conditions over control. Higher root colonization was strongly linked with elevated ACC (aminocyclopropane-1-carboxylic acid) production, subsequently enhancing water use efficiency (21.62 %–12.77 %), root hydraulic conductivity (1.9 %–1.4 %) and root nutrient uptake under moderate to severe drought conditions. Enhanced nutrient uptake further promoted leaf photosynthetic rate by 27.3 %–29.8 % under moderate and severe drought stress. Improving leaf and root physiological functioning enhanced maize grain yield under stressful environments. Furthermore, co-inoculation with AMF-PGPR reduced cellular damage by lowering oxidative enzyme levels and increasing antioxidative enzyme activities, improving plant performance and grain yield under stressful environments. Conclusively, the synergistic interaction of AMF with PGPR ensured plant stress tolerance by reducing cellular injury, facilitating root-leaf functioning, enhancing nutrient-water-use-efficiencies, and increasing yield under drought stress.

Efficacy and Differential Physiological–Biochemical Response of Biostimulants in Green Beans Subjected to Moderate and Severe Water Stress

Water stress is one of the main factors affecting the development of agricultural crops. An innovative alternative to improve tolerance to water stress is the application of biostimulants. In the present study, the efficacy and physiological and biochemical responses of different biostimulants were evaluated in beans under moderate and severe stress. The treatments consisted of three types of irrigation: FC100, without water stress; FC75, irrigation reduced by 25% (moderate water stress); and FC50, irrigation reduced by 50% (severe water stress). In the treatments with water deficits, foliar biostimulants were applied: zinc oxide nanoparticles plus chitosan, Codasil®, Osmoplant®, Stimplex® and salicylic acid. Foliar application of ZnO + chitosan nanoparticles benefited biomass accumulation and yield under moderate water stress (FC75) and Codasil® and Osmoplant® under severe water stress (FC50). Proline, free sugars and gas exchange were higher with the application of ZnO + chitosan nanoparticles under moderate water stress and with Codasil® and Osmoplant® under severe water stress. Depending on the severity of water stress, ZnO + chitosan nanoparticles, Codasil® and Osmoplant® are viable products to increase tolerance in green bean cv. Strike plants.

The effect of melatonin on physiological, biochemical, and enzymatic properties and the expression of antioxidant genes under different irrigation regimes in wheat

A split-plot experiment was conducted based on a randomized complete block design with four replications in two years to study the effect of melatonin on the biochemical properties and the gene expression related to antioxidant enzyme activity in bread wheat. Irrigation levels (normal (FC = 80%)), mild stress (FC = 60%), and severe stress (FC = 40%)) were assigned to the main plots, and melatonin foliar applications (zero, 50, 100, 150, and 200 μM) were assigned to Subplots. Results showed that, with the intensification of water stress, the 1000 kernel weight decreased, and the activity of ascorbate peroxidase enzyme and flavonoid content increased. Also, the level of 100 μM melatonin had the highest 1000 kernel weight, flavonoid content, and ascorbate peroxidase enzyme activity. In this study, the highest number of grains per spike, biological yield, grain yield, chlorophyll a, chlorophyll b, carotenoids, and the lowest amount of malondialdehyde recorded for foliar treatment with 50 μM of melatonin under normal irrigation conditions and the highest proline content, total phenol, superoxide dismutase, and catalase were allocated to the 100 μM melatonin foliar treatment under severe water stress conditions. The synergistic effect of water deficit stress and melatonin foliar application increased the activity and expression level of genes related to antioxidant enzymes. So, the content of superoxide dismutase (21.30% and 65.16% respectively) and catalase (50.60% and 54.44% respectively) enzyme activity increased significantly under 100- and 150-mM melatonin foliar application in water severe water stress compared to the corresponding control treatment. Furthermore, mentioned melatonin levels increased the gene expression levels of superoxide dismutase (16.67% and 38.19% respectively), ascorbate peroxides (73.76% and 47.57% respectively), polyphenol oxidase (39.32 and 51.15%) and catalase (39.95% and 50.0% respectively) under an extreme water shortage compared with corresponding control treatment. In general, the application of 100- and 150-mM melatonin induced resistance to water deficit stress in wheat by increasing the expression of antioxidant genes.

Impacts of cultivar and management practices on the diversity and population dynamics of mites in soybean crops.

The objective of this study was to evaluate the diversity and population dynamics of mites in soybean crops with different cultivars and management practices. The study was conducted in two soybean production fields in the municipalities of Mato Queimado (L1) and Três de Maio (L2), Rio Grande do Sul state, Brazil. Two transgenic cultivars were used, and insecticide applications varied among treatments. Sampling began at the V2 stage, with 60 leaves/area/collection that were sorted, mites were collected and identified using dichotomous keys. A total of 18,100 mites belonging to 12 species were found. Among the species, Tetranychus urticae Koch, Mononychellus planki (McGregor), and Tetranychus ludeni Zacher (Tetranychidae) were the most abundant, whereas the most abundant predatory mites were the phytoseiids Neoseiulus californicus McGregor and Neoseiulus idaeus Denmark and Muma, with N. idaeus being more abundant and present in all areas. The acarofauna was influenced by environmental conditions and management practices. Neoseiulus idaeus was commonly associated with populations of M. planki, T. ludeni, and T. urticae. Neoseiulus californicus tolerated pesticide use but was affected by severe water stress, whereas N. idaeus tolerated periods of low relative humidity and high temperatures.

Co-inoculation of mycorrhizal fungi and plant growth-promoting rhizobacteria improve growth, biochemical and physiological attributes in Dracocephalum kotschyi Boiss. under water deficit stress.

Because of swift climate change, drought is a primary environmental factor that substantially diminishes plant productivity. Furthermore, the increased use of chemical fertilizers has given rise to numerous environmental problems and health risks. Presently, there is a transition towards biofertilizers to enhance crops' yield, encompassing medicinal and aromatic varieties. This study aimed to explore the impacts of plant growth-promoting rhizobacteria (PGPR), both independently and in conjunction with arbuscular mycorrhizal fungi (AMF), on various morphological, physiological, and phytochemical characteristics of Dracocephalum kotschyi Boiss. This experimentation took place under different irrigation conditions. The irrigation schemes encompassed well watering (WW), mild water stress (MWS), and severe water stress (SWS). The study evaluated the effects of various biofertilizers, including AMF, PGPR, and the combined application of both AMF and PGPR (AMF + PGPR), compared to a control group where no biofertilizers were applied. The findings of the study revealed that under water-stress conditions, the dry yield and relative water content of D. kotschyi Boiss. experienced a decline. However, the application of AMF, PGPR, and AMF + PGPR led to an enhancement in dry yield and relative water content compared to the control group. Among the treatments, the co-application of AMF and PGPR in plants subjected to well watering (WW) exhibited the tallest growth (65 cm), the highest leaf count (187), and the most elevated chlorophyll a (0.59 mg g-1 fw) and b (0.24 mg g-1 fw) content. Regarding essential oil production, the maximum content (1.29%) and yield (0.13 g plant -1) were obtained from mild water stress (MWS) treatment. The co-application of AMF and PGPR resulted in the highest essential oil content and yield (1.31% and 0.15 g plant-1, respectively). The analysis of D. kotschyi Boiss. essential oil identified twenty-six compounds, with major constituents including geranyl acetate (11.4-18.88%), alpha-pinene (9.33-15.08%), Bis (2-Ethylhexyl) phthalate (8.43-12.8%), neral (6.80-9.32%), geranial (9.23-11.91%), and limonene (5.56-9.12%). Notably, the highest content of geranyl acetate, geranial, limonene, and alpha-pinene was observed in plants subjected to MWS treatment following AMF + PGPR application. Furthermore, the co-application of AMF, PGPR, and severe water stress (SWS) notably increased the total soluble sugar (TSS) and proline content. In conclusion, the results indicate that the combined application of AMF and PGPR can effectively enhance the quantity and quality of essential oil in D. kotschyi Boiss., particularly when the plants are exposed to water deficit stress conditions.

Classification of Tropical Forage Grass Varieties Under Moderate and Severe Water Stress using Naïve Bayes and Kernel Density Estimation

The selection of forage grasses that are more adapted to adverse conditions, such as water scarcity or dry rain periods, is extremely important. Mainly due to the severe climate changes, and the search for more sustainable ways of farming. Forage grasses form the basis of the diet of beef cattle and are also used as a source of biofuels, for erosion control and soil improvement. This work presents a machine learning methodology to obtain classification models for nine forage cultivars, subject to moderate and severe water stress. The Naïve Bayes algorithm is used together with the Kernel Density Estimation method to obtain the densities used in the classification models. Before learning the models, the grouped cross-validation technique and also the grid search are used to search for the best set of hyperparameters. The best accuracy and precision results are 0.88 and 0.90, respectively. It is observed that the classification performance depends on the cultivars used in the training and test sets. At the end, the estimated probability densities are also analyzed by comparing them with some statistics obtained for each variable and water stress or control environments.

Estimation of grain protein content in commercial bread and durum wheat fields via traits inverted by radiative transfer modelling from Sentinel-2 timeseries

Wheat (Triticum spp.) is crucial to food security. Grain protein content (GPC) is key to its nutritional and economic value and is controlled by genetic and agronomic factors, soil properties and weather. GPC prediction from remote sensing could reduce nitrogen (N) losses, help management decisions, and improve profit. However, GPC prediction is complex because multiple plant traits influence GPC and their effects change through the growing season. Traits with known physiological links to GPC, which can be retrieved from imaging spectroscopy, include leaf area index (LAI), chlorophyll (Ca+b), and stress indicators. Further inspection of these and other traits retrieved from satellite data can advance research relevant to precision agriculture. Sentinel-2 (S2) timeseries (TS) were acquired for 6,355 ha of commercial dryland bread (T. aestivum) and durum (T. durum) wheat fields in south-east Australia through two consecutive years with dissimilar rainfall. Wheat growers provided ∼ 92,000 GPC data points from harvester-mounted protein monitors. For each, Ca+b, leaf dry matter, leaf water content (Cw) and LAI were retrieved from the S2 images by radiative transfer model inversion. A gradient boosted machine learning algorithm was applied to analyse these traits’ importance to GPC and to predict GPC in 30% of samples unseen by the algorithm in training. The strongest relationships between predicted and observed GPC (R2 = 0.86, RMSE = 0.56 %), in a model built from five S2 images across a season, were better than those from single-date hyperspectral (HS). In severe water stress, LAI was the main predictor of GPC early in the season, but this switched to Cw later. Trait importance was more evenly distributed in milder conditions. S2 TS had a clear accuracy advantage over single-date S2 and HS, especially in benign conditions, emphasising the potential of S2 TS for large-scale GPC monitoring.

Water stress significantly affects the diurnal variation of solar-induced chlorophyll fluorescence (SIF): A case study for winter wheat

Remote sensing of Solar-induced chlorophyll fluorescence (SIF) has been widely used in estimating Gross Primary Productivity (GPP) and detecting stress in terrestrial ecosystems. Water stress adversely impacts the growth, development, and productivity of a plant. Recently, the characterizing and understanding of the diurnal cycling of plant functioning and ecosystem processes has been explored using SIF. However, the diurnal response of SIF to different levels of water stress remains unclear. This study conducted field experiments on winter wheat by subjecting it to different levels of water stress including well-watered (CK) and, mild, moderate, and severe water stress (D1, D2, D3), and collected the spectral data using an automated SIF measurement system. The results observed the strong SIF-PAR (photosynthetically active radiation) correlations and that these relationships gradually decoupled with increasing water stress, which further decreased the accuracy of temporal upscaling of far-red SIF from an instantaneous to daily scale. To quantify the characteristics of diurnal far-red SIF, five indices including peak time, peak value, curve opening coefficient (leading coefficient of the parabola), and left/right slopes of the peak were proposed. The results demonstrated that diurnal far-red SIF was characterized by an earlier peak time, decreasing peak value, wider curve opening, and flattening right slope from the CK plot to the D3 plot. There were certain mechanisms linking the different indices, for example, between peak size and opening coefficient. Furthermore, the response of far-red SIF to water stress was most pronounced at noon. SIF/PAR exhibited a more significant response to varying water stress compared to far-red SIF, which mitigated the negative influence of PAR variations on diurnal SIF. These findings contribute to the monitoring of plant water dynamics at fine temporal scales.

Monitoring land subsidence induced by tectonic activity and groundwater extraction in the eastern Gediz River Basin (Türkiye) using Sentinel-1 observations

Alaşehir-Sarıgöl sub-basin (ASSB) in Türkiye faces severe water stress mainly due to intensive agricultural irrigation. This has led to declining groundwater levels, aquifer compaction, and subsequent land subsidence. This study aims to evaluate the roles of tectonic activity and groundwater withdrawal in land-subsidence and investigate additional factors like faults and soft soil thickness. The P-SBAS algorithm was applied, using 98 and 123 Sentinel-1 SAR images in ascending and descending orbits, respectively, from 2016 to 2020. Independent Component Analysis separated long-term displacements from seasonal variations in the InSAR time series data. InSAR analysis showed displacement rates up to −6.40 cm/year. Results reveal a direct correlation between InSAR displacement and soft soil thickness, highlighting aquitard layer compaction due to groundwater withdrawal and piezometric head depletion as the primary causes of land subsidence. It was not possible to disentangle the multi-year displacements with different rates, i.e., to isolate the displacements caused by tectonic activity from displacements due to the soft soil compaction induced by groundwater withdrawal. Nonetheless, the analysis identified two spatiotemporal displacement trends: one linked to long-term, linear plastic compaction of the aquitard due to groundwater withdrawal and the other involving long-term displacements with seasonal rebounds caused by yearly water level fluctuations.

Determination of Yield and Quality Parameters in Pickling Hot Peppers Grown under Different Water Stress Conditions

Plants are exposed to various adverse environmental conditions throughout their growth period. In recent years, drought, which has occurred and necessitated different measures, ranks among these adverse conditions. At the same time, plants synthesize certain biochemical compounds in response to the adverse conditions they will encounter. These compounds not only strengthen the immune system but also provide resistance against various diseases, and they tend to increase under adverse environmental conditions that plants will face during cultivation. This study was conducted to determine the changes in yield and some biochemical components in pickling hot peppers (Capsicum Annuum L.) grown under different water stress conditions. Two different levels of water stress (%70 and %30 irrigation) were applied in addition to full irrigation (%100 irrigation). At the end of the research, while a yield of 269.42 g per plant was obtained in the control group (%100 irrigation), 150.14 g and 93.33 g of pickling hot peppers were harvested in each water stress treatment, respectively. Total phenolic compound levels increased with water stress; it was determined to be 0.827 mg-1g in the trial irrigated with full irrigation water, 1.170 mg-1g in plants exposed to mild water stress, and up to 1.536 mg-1g in the trial subjected to severe water stress. In addition, total flavonoids and antioxidant compound levels also increased with increasing water stress. The amounts of flavonoid compounds obtained from the trial groups were 0.146, 0.373, and 0.412 mg-1g, respectively, while the antioxidant levels determined by the DPPH method increased in quantity with increasing water stress, similar to other biochemical compounds. According to these results, it was determined that the yield of pickling hot peppers decreased in the case of water shortage that the plants would face in cultivation, but there was an increase in some biochemical compounds.

Assessment of isoprene and near-surface ozone sensitivities to water stress over the Euro-Mediterranean region

Abstract. Plants emit biogenic volatile organic compounds (BVOCs) in response to changes in environmental conditions (e.g. temperature, radiation, soil moisture). In the large family of BVOCs, isoprene is by far the strongest emitted compound and plays an important role in ozone chemistry, thus affecting both air quality and climate. In turn, climate change may alter isoprene emissions by increasing temperature as well as the occurrence and intensity of severe water stresses that alter plant functioning. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) provides different parameterizations to account for the impact of water stress on isoprene emissions, which essentially reduces emissions in response to the effect of soil moisture deficit on plant productivity. By applying the regional climate–chemistry model RegCM4chem coupled to the Community Land Model CLM4.5 and MEGAN2.1, we thus performed sensitivity simulations to assess the effects of water stress on isoprene emissions and near-surface ozone levels over the Euro-Mediterranean region and across the drier and wetter summers over the 1992–2016 period using two different parameterizations of the impact of water stress implemented in the MEGAN model. Over the Euro-Mediterranean region and across the simulated summers, water stress reduces isoprene emissions on average by nearly 6 %. However, during the warmest and driest selected summers (e.g. 2003, 2010, 2015) and over large isoprene-source areas (e.g. the Balkans), decreases in isoprene emissions range from −20 % to −60 % and co-occur with negative anomalies in precipitation, soil moisture and plant productivity. Sustained decreases in isoprene emissions also occur after prolonged or repeated dry anomalies, as observed for the summers of 2010 and 2012. Although the decrease in isoprene emissions due to water stress may be important, it only reduces near-surface ozone levels by a few percent due to a dominant VOC-limited regime over southern Europe and the Mediterranean Basin. Overall, over the selected analysis region, compared to the old MEGAN parameterization, the new one leads to localized and 25 %–50 % smaller decreases in isoprene emissions and 3 %–8 % smaller reductions in near-surface ozone levels.

Evaluation for Multiple Abiotic Stress Tolerance in Rice (Oryza Sativa) Genotypes

Abiotic stresses are the major constraints that affect the morphological, physiological and biochemical attributes of plants resulting in reduction of yield. Recently, combined occurrence of stresses has become a greater cause of concern in farmers’ fields. Hence, there is a need to identify genotypes that are tolerant to more than one stress. A study on physiological characterization for water and salinity stress was conducted in twenty rice genotypes during kharif 2022 at Regional Agricultural Research Station, Maruteru, Andhra Pradesh, India. Results showed that among all the treatments, root length, shoot length, root and shoot dry weight and chlorophyll content were greater under control followed by 1% mannitol, 2% mannitol and salinity stress. Visual scoring for water stress at seedling stage revealed that under mild water stress (1% M) in genotypes viz., CR4423-8, FL 478 and Pantara recorded 75-90% of survival and under severe water stress (2% M) 40-50% survival. Under salinity stress, the score 3 was recorded in FL 478 and 5 in Naveen, Pantara and CR 4423-75. For combined stresses, FL 478 and Pantara were identified as tolerant and can be suggested as donors.