Levels Of Drought Stress Research Articles

Differences in species composition between calcareous and siliceous herbaceous communities are primarily explained by competition in favourable climates

Difference in vegetation composition between communities from calcareous and siliceous soils might be due to high competition on siliceous soils for species from calcareous origin, and high rock‐induced drought stress on calcareous soils for species from siliceous origin. We tested the hypothesis that, with increasing climate stress, competition should decrease on siliceous rock for species of calcareous origin and drought stress increase on calcareous rock for species of siliceous origin because of decreasing community biomass with increasing cold or drought stress. This question is of high interest for predicting changes in species distribution with climate change since bedrock type and climate change are both complex factors that are likely to interact with climate. We set up a transplant removal experiment in contrasting climate conditions of the south of France, warm and wet temperate, warm and dry Mediterranean, and cold temperate in the Alps and the Pyrenees. In each climate condition, three targets (two species and one population from a third species) from each origin were transplanted with and without neighbours on the two rock types and during two years with different levels of drought stress. Variation in the effects of neighbours and rock‐induced drought stress on transplant survival with and without neighbours were analysed with linear modelling at each site, separately, and with ANCOVA in the whole design. Competition was the highest on siliceous rock in the more favourable climate conditions but for species of siliceous origin. The lower competition found for species of calcareous origin was likely due to the occurrence of allelopathic effects that decreased the negative effect of neighbours as measured with the removal method. The rock‐induced drought stress was the highest on calcareous rock, in particular for species of siliceous origin. Thus, the decrease in competition intensity on siliceous rocks with increasing climate stress was more important for species from siliceous than calcareous origin. Additionally, the importance of the rock‐induced drought stress was relatively low in the most stressful climate conditions as compared to the overwhelming importance of climate drought stress over the two years of our experiment, which likely induced a collapse of the positive effect of growing on a siliceous rock.

THE IMPACT OF SEED SIZE ON INITIAL DROUGHT STRESS RESILIENCE AND YIELD IN WHEAT CULTIVATION

Wheat yield is affected severely by drought in this era of changing climate patterns, including high temperatures and altered precipitation patterns. Drought is among the most challenging environmental stressors, limiting wheat cultivars' growth, productivity, and performance. The current study was conducted during the rabi season 2022 at the Research Area, Department of Agronomy, University of the Punjab, Lahore, Pakistan. Therefore, the present study evaluated the potential of diverse seed sizes to advance wheat crop growth, development, and yield when subjected to different drought levels. The study comprised two experiments. The first was a lab experiment that included different drought levels (DL), DL0: 0.0 bar, DL1: -2 bar, DL2: -4 bar, and DL3: -6 bar (drought levels were induced by solutions of PEG-6000 at different concentrations) and three wheat seed size classes, i.e., bold grain (>38 g), medium grain (<33 g), and small grain (<25 g). In the field experiment, drought stress levels were DL0 (regular irrigation), DL1 (first irrigation at 30 days), DL2 (first irrigation at 45 days), and DL3 (first irrigation at 60 days). Seed sizes included W1 (bold >38 g), W2 (medium <33 g), and W3 (small <25 g). Drought severity increased with DL1 to DL3. The outcomes of the field experiment revealed that varying levels of drought stress and seed size classes significantly affected parameters such as emergence time, growth traits, biomass allocation, tiller count, plant height, and grain and biomass outcomes. Bold seeds contributed to higher biomass and grain yield, while severe drought decreased yields. Notably, the Harvest Index was affected, indicating bold seeds allocate more biomass to grains. In conclusion, proper seed size selection, favouring bold seeds, can enhance resilience to drought, benefiting wheat cultivation in water-scarce regions.

Early monitoring of drought stress in safflower (Carthamus tinctorius L.) using hyperspectral imaging: A comparison of machine learning tools and feature selection approaches

Early detection of drought stress is essential for preventing permanent plant damage and minimizing yield loss. This study utilized hyperspectral imaging at the leaf level to visualize drought stress in safflower plants (Carthamus tinctorius L.). Three safflower genotypes, Palenus, A82, and IL-111, were cultivated under three irrigation levels. Stress conditions were simulated by depleting 50%, 70%, and 90% of soil water content, representing unstressed (US), mild stress (MS), and severe stress (SS) conditions, respectively. Hyperspectral images of leaf samples were captured before any visible signs of water scarcity emerged. Classification analysis was performed using the full mean spectral data with partial least squares discriminant analysis, soft independent modeling of class analogy (SIMCA), support vector machines, and artificial neural network (ANN) classifiers. Feature selection methods were applied to extract the most informative wavebands, and ANN was used to build predictive models. Spatial analysis involved pixel-wise classification using both unsupervised (k-means clustering) and supervised (best classifiers) approaches. ANN outperformed other classifiers using the entire spectral data, effectively distinguishing US, MS, and SS classes in the Palenus, A82, and IL-111 genotypes, achieving F1-scores of 92.22%, 96.01%, and 96.47%, respectively. Among the feature selection methods, SIMCA-based features excelled in monitoring stress conditions in the Palenus and A82 genotypes. In supervised spatial analysis, ANN models clearly depicted the progression of stress in leaves across different genotypes. This study demonstrates the potential of hyperspectral imaging to differentiate various levels of drought stress in safflower, an important oilseed crop.

Sweet corn (Zea mays L.) seed performance enhanced under drought stress by chitosan and minerals coating.

Sweet corn (Zea mays L.) var. Saccharata is a tropical and semitropical annual cereal with low germination, poor vigor, and weak seedling establishment in the soil. In order to enhance the physical properties of sweet corn and examine the effects of seed coating on the morphological, biochemical, and physiological characteristics of sweet corn seedlings under drought stress conditions, we conducted a factorial experiment in greenhouse conditions. Seed coating was carried out using a mixture of vermiculite (V), kaolin (K), and perlite (P) in a ratio of 3:1.5:2. The main factors of the greenhouse experiment comprised three levels of coating treatment (chitosan 0.5% + V10K2.5P5 (gr), NaAlg 1% + V10K2.5P5 (gr), and non-coated seeds as a control) along with drought stress at four levels (0, -0.3, -0.6, and -0.9bar). In greenhouse conditions, the growth indexes of sweet corn seedlings were studied under increasing levels of drought stress. The results showed that as drought stress levels increased, certain growth indicators such as seedling emergence and seedling emergence rate, soluble protein, chlorophyll total content, nitrogen, and phosphorus content decreased. On the other hand, mean emergence, proline, potassium, soluble sugars, malondialdehyde, and hydrogen peroxide were increased. The study found that the highest seedling emergence percentage occurred in the coating treatment of chitosan 0.5% + V10K2.5P5 (gr) at all levels of drought stress. Overall, seed coating with the Chitosan 0.5% + V10K2.5P5 (gr) treatment improved the performance of sweet corn seeds and reduced the negative effects of drought stress by increasing seedling emergence and establishment.

Effect of Drought Stress on Agronomic Traits and Total Leaf Proteins in Different Bottle Gourd [<i>Lagenaria siceraria</i> (Molina) Standl.] Genotypes

Breeding drought-tolerant genotypes using genetic and biochemical tools is an important mitigation strategy to improve stress response and yields in bottle gourd [<em>Lagenaria siceraria</em> (Molina) Standl.]. This current study evaluated the variations among bottle gourd genotypes for potential breeding purposes by establishing the relationship between agronomic traits and the protein profile required for the plants’ resilience against drought stress. The study assessed 12 bottle gourd accessions grown under non-stressed (NS) control conditions and different levels of drought stress (DS) induced by withholding irrigation for 7, 14, and 21 days, using a 12 × 2 × 3 factorial experiment in a randomized complete block design with 3 replicates. Agronomic traits such as the total number of male and female flowers per plant, sex ratio, fruit number and fruit yield per plant (FYPP), and total protein analysis were determined in bottle-gourd plants immediately after the period of stress. Results showed significant differences (<em>p</em><em> </em>< 0.001) among the genotypes × environmental effect for most agronomic traits except the number of days to first flower (DTFF). Among the genotypes, BG-70 and BG-78 recorded the highest FYPP under drought stress conditions, with BG-70 showing similar results even under NS conditions. A positive correlation was found among all the agronomic traits and the total protein contents of the genotypes, especially after 14 days of drought stress. Overall, the results implied that the significant improvements in agronomic traits and unique protein expressions observed in BG-70 and BG-78 potentially confer tolerance to drought stress. Moreover, the high and unique proteins found in all genotypes (BG-48, BG-58, BG-52, BG-70, BG-78, and BG-81) warrant further research on their interaction with the stress, especially when coupled with improved agronomic traits, which could assist in identifying drought stress tolerant genotypes.

Cloning, sequence analysis, and functional study of the PeDof-4 gene in response to drought stress

DNA-binding with one finger (Dof) was a functionally important gene in plant stress tolerance processes. The cloned full-length (849bp) passion fruit PeDof-4 gene was sequenced, which encodes 282 amino acids with the molecular formula C1274H1983N375O408S14, molecular weight 29529.87 u, and theoretical isoelectric point pI of 8.96. Evolutionary tree analysis showed that the PeDof-4-encoded proteins had a high degree of identity with Dof-encoded proteins in other plants. Blastp of the PeDof-4 encoded proteins revealed a closer affinity to the proteins encoded by the Dof of Theobroma cacao. The relative expression of the PeDof-4 gene was higher at 50% of the relative soil moisture content in the fluorescence qPCR experiments under different levels of drought stress. Tissue-specific analysis showed that the highest expression of this gene was found in the roots. Overexpression of GUS gene under the PeDof-4 promoter inbidopsis thaliana showed that PeDof-4 could significantly respond to drought stress. Bangladesh J. Bot. 52(3): 653-663, 2024 (September) Special

Exploring the adaptive mechanisms and strategies of various populations of Sporobolus ioclados in response to arid conditions in Cholistan desert

This study explored the drought resistance mechanisms of different populations of Sporobolus ioclados (Poaceae), locally known as “Sawri,” “Drabhri” and “Dhrbholi” native to Africa and the Indian Subcontinent. These populations were grown in conventional nursery practices at Khawaja Fareed Government College in Rahim Yar Khan, Pakistan, and subsequently subjected to four distinct levels of drought within carefully monitored experimental settings. The experiment was conducted in a two-factorial design involving populations and drought treatments and was repeated three times. The physiological and morphological responses of S. ioclados, including plant height, number of roots, root length, flag leaf area, stomatal features, proline concentration and nitrogen content, displayed significant variability in response to the imposed drought stress. Drought resulted in increases in proline concentration and nitrogen content. The number of roots decreased, while the length and width of the stomata increased in various populations. A combination of advanced statistical techniques, such as ANOVA, PCA, HCA, and DFA, provided a comprehensive understanding of the mechanism of plant adaptation and the extent of population diversity within the species. The Yazman and Nwab Wala populations exhibited the highest rates of photosynthesis and stomatal conductance, while S. ioclados demonstrated notable drought tolerance at the T4 level of drought stress. A negative correlation was found between proline levels, nitrogen contents, and photosynthesis, suggesting that proline has a protective role in drought. The diverse adaptation strategies indicated by S. ioclados populations have revealed the potential of this species for afforestation and climate change mitigation in dry environments.

Combined application of biochar and peatmoss for mitigation of drought stress in tobacco

Drought poses a significant ecological threat that limits the production of crops worldwide. The objective of this study to examine the impact of soil applied biochar (BC) and peatmoss (PM) on the morpho-biochemical and quality traits of tobacco plants under drought conditions. In the present experiment work, a pot trial was conducted with two levels of drought severity (~ well-watered 75 ± 5% field capacity) and severe drought stress (~ 35 ± 5% field capacity), two levels of peatmoss (PM) @ 5% [PM+ (with peatmoss) and PM- (without peatmoss)] and three levels of rice straw biochar (BC0 = no biochar; BC1 = 150 mg kg− 1; and BC2 = 300 mg kg− 1 of soil) in tobacco plants. The results indicate that drought conditions significantly impacted the performance of tobacco plants. However, the combined approach of BC and PM significantly improved the growth, biomass, and total chlorophyll content (27.94%) and carotenoids (32.00%) of tobacco. This study further revealed that the drought conditions decreased the production of lipid peroxidation and proline accumulation. But the synergistic approach of BC and PM application increased soluble sugars (17.63 and 12.20%), soluble protein (31.16 and 15.88%), decreased the proline accumulation (13.92 and 9.03%), and MDA content (16.40 and 8.62%) under control and drought stressed conditions, respectively. Furthermore, the combined approach of BC and PM also improved the leaf potassium content (19.02%) by limiting the chloride ions (33.33%) under drought stressed conditions. Altogether, the balanced application of PM and BC has significant potential as an effective approach and sustainable method to increase the tolerance of tobacco plants subjected to drought conditions. This research uniquely highlights the combined potential of PM and BC as an eco-friendly strategy to enhance plant resilience under drought conditions, offering new insights into sustainable agricultural practices.

Compound extreme heat and drought stress alter the spatial gradients of protein and starch in wheat grains

The spatial gradients of protein and starch in wheat grains affected the grain milling characteristics and flour utilization. The increase in compound heat stress and drought stress (HDS) due to global climate change threatens wheat grain yield and quality parameters, but the impacts of extreme climate events on the gradients of protein and starch in wheat grains remain unclear. In this study, two-year, environment-controlled experiments with four heat stress levels (17/27, 21/31, 25/35, and 29/39°C) and three drought stress levels (30 %, 55 %, and 75 % field capacity) were conducted to investigate the effects of HDS on the gradients of protein and starch concentrations within the five grain layers. The results showed that HDS resulted in significantly greater protein concentrations, while resulting in lower starch concentrations in the wheat grain layers. Among the five layers, the endosperm layers exhibited the greatest increase in protein concentration under HDS, but the starch concentration under HDS decreased in the order of husk > aleurone > endosperm layer. HDS unevenly altered the protein and starch concentrations of the five grain layers. There was significant linear relationship between relative protein and starch concentration with accumulated heat degree days (AHDD). With a 1°C·d increase in AHDD, the protein concentration in the five grain layers increased by 1.17–2.19 %, while the starch concentration decreased by 0.62–0.90 %, depending on the drought stress levels. A significant linear relationship was also observed between the relative protein and starch concentrations and evapotranspiration (ET). A 1 mm increase in ET led to a protein concentration decrease of 0.58–0.76 % in P1-P5, with a corresponding starch concentration increase of 0.28–0.46 %, depending on cultivar and treatment stages. Our results indicate that HDS significantly impacts the grain quality parameters for the flour milling process and human diet and will provide important insights into adapting wheat quality to climate change.

How do drought and heat affect the response of soybean seed yield to elevated O3? An analysis of 15 seasons of free-air O3 concentration enrichment studies.

The coincidence of rising ozone concentrations ([O3]), increasing global temperatures, and drought episodes is expected to become more intense and frequent in the future. A better understanding of the responses of crop yield to elevated [O3] under different levels of drought and high temperature stress is, therefore, critical for projecting future food production potential. Using a 15-year open-air field experiment in central Illinois, we assessed the impacts of elevated [O3] coupled with variation in growing season temperature and water availability on soybean seed yield. Thirteen soybean cultivars were exposed to a wide range of season-long elevated [O3] in the field using free-air O3 concentration enrichment. Elevated [O3] treatments reduced soybean seed yield from as little as 5.3% in 2005 to 35.2% in 2010. Although cultivars differed in yield response to elevated [O3] (R), ranging from 17.5% to -76.4%, there was a significant negative correlation between R and O3 dosage. Soybean cultivars showed greater seed yield losses to elevated [O3] when grown at drier or hotter conditions compared to wetter or cooler years, because the hotter and drier conditions were associated with greater O3 treatment. However, year-to-year variation in weather conditions did not influence the sensitivity of soybean seed yield to a given increase in [O3]. Collectively, this study quantitatively demonstrates that, although drought conditions or warmer temperatures led to greater O3 treatment concentrations and O3-induced seed yield reduction, drought and temperature stress did not alter soybean's sensitivity to O3. Our results have important implications for modeling the effects of rising O3 pollution on crops and suggest that altering irrigation practices to mitigate O3 stress may not be effective in reducing crop sensitivity to O3.

Inter-subspecies diversity of maize to drought stress with physio-biochemical, enzymatic and molecular responses.

Drought is the most significant factor limiting maize production, given that maize is a crop with a high water demand. Therefore, studies investigating the mechanisms underlying the drought tolerance of maize are of great importance. There are no studies comparing drought tolerance among economically important subspecies of maize. This study aimed to reveal the differences between the physio-biochemical, enzymatic, and molecular mechanisms of drought tolerance in dent (Zea mays indentata), popcorn (Zea mays everta), and sugar (Zea mays saccharata) maize under control (no-stress), moderate, and severe drought stress. Three distinct irrigation regimes were employed to assess the impact of varying levels of drought stress on maize plants at the V14 growth stage. These included normal irrigation (80% field capacity), moderate drought (50% field capacity), and severe drought (30% field capacity). All plants were grown under controlled conditions. The following parameters were analyzed: leaf relative water content (RWC), loss of turgidity (LOT), proline (PRO) and soluble protein (SPR) contents, membrane durability index (MDI), malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, the antioxidant enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Additionally, the expression of heat shock proteins (HSPs) was examined at the transcriptional and translational levels. The effects of severe drought were more pronounced in sugar maize, which had a relatively high loss of RWC and turgor, membrane damage, enzyme activities, and HSP90 gene expression. Dent maize, which is capable of maintaining its RWC and turgor in both moderate and severe droughts, and employs its defense mechanism effectively by maintaining antioxidant enzyme activities at a certain level despite less MDA and H2O2 accumulation, exhibited relatively high drought tolerance. Despite the high levels of MDA and H2O2 in popcorn maize, the up-regulation of antioxidant enzyme activities and HSP70 gene and protein expression indicated that the drought coping mechanism is activated. In particular, the positive correlation of HSP70 with PRO and HSP90 with enzyme activities is a significant result for studies examining the relationships between HSPs and other stress response systems. The discrepancies between the transcriptional and translational findings provide an opportunity for more comprehensive investigations into the role of HSPs in stress conditions.

Radiation synthesis of sodium alginate/gelatin based ultra-absorbent hydrogel for efficient water and nitrogen management in wheat under drought stress

The main focus of this study was on using radiation to make an ultra-absorbent hydrogel (UAH) from sodium alginate (SA) and gelatin (GL) biopolymers. This UAH can effectively handle water and nitrogen in wheat farming during drought stress. The hydrogel was synthesized by gamma irradiation-induced SA/GL/polyacrylamide crosslinking at 10–40 kGy. Varying SA/GL ratios affected swelling and the gel fraction of SA/GL/PAm hydrogels. The (SA/GL 17/83) hydrogel exhibited a 40.03 g/g swelling degree, while increasing SA content resulted in higher swelling, peaking at 75.5 g/g for (SA/GL 83/17). This indicated a synergistic interaction between SA and GL. The gel fraction also increased from 76.8 to 90.3%, with a higher GL content reflecting increased crosslinking. After multiple hydrolysis cycles, the hydrogel achieved 1293 (g/g) swelling and 36 days of water retention. When applied to wheat (Triticuma estivum) under drought stress, it significantly improved shoot length (18%), root length (43%), shoot fresh weight (49%), and shoot dry weight (51%) under extreme drought. The significant increases in protein and carbohydrate content in both shoots (up to 32% and 19%, respectively) and grains (up to 21% and 24%, respectively), along with the reduction in proline content (up to 38%), demonstrate that ultra-absorbent hydrogel (UAH) effectively enhances nitrogen content, photosynthesis, and overall plant health in wheat under varying drought stress levels. This novel SA/GL-based UAH holds promise for addressing water scarcity and agricultural challenges, offering a sustainable solution for water and nitrogen management under drought stress.

Exploring the impact of exogenous melatonin on agro-morphological characteristics, carvacrol, and rosmarinic acid production in Satureja rechingeri Jamzad under drought stress

Satureja rechingeri Jamzad (known as “Jatra” in Persian), which belongs to the Lamiaceae family, is a rich source of essential oil particularly carvacrol, and rosmarinic acid. Drought stress has a detrimental impact on the physiological and biochemical parameters of plants, leading to a decline in plant productivity. Melatonin (MT), a new plant growth regulator found abundantly in plants, has been found to enhance the plant's internal resistance to various environmental stresses. The present study aimed to examine the impact of exogenously applied MT on the agro-morphological, physio-biochemical, and phytochemical traits of S. rechingeri plants cultivated under different levels of drought stress. The results indicated that plants treated with 200 µM MT obtained the highest plant height, length and width of leaf, fresh, dry and drug weight under different drought stress levels. The highest values of relative water content (RWC) (93.5%) and chlorophyll content (15.4 mg/g FW) were recorded by MT 200 µM and 100 µM, respectively, in 100% FC. Drought stress treatments (40, 60, and 80% FC) without foliar spray of MT significantly enhanced the H2O2 content, electrolyte leakage, and malondialdehyde content in leaves, whereas MT treatment under drought stress significantly decreased the above parameters. The lowest H2O2 content (11.5 nmol/g), electrolyte leakage (3.08%), and malondialdehyde content (0.78 µM/g) were obtained by 200 µM MT at 100% FC. In contrast, drought stress treatment increased the total phenol content (TPC), rosmarinic acid (RA), essential oils (EOs) content and yield, and carvacrol. The maximum values of TPC (28.1 mg GAE/g DW), EOs content (3.63%) and yield (0.96%), and carvacrol (95.66%) were achieved by 200 µM MT at 40% FC. The highest RA content (7.43 mg GAE/g DW) was recorded in 100 µM MT at 40% FC. Thus, foliar spray MT has the potential to enhance plant growth through the mitigation of reactive oxygen species (ROS)-induced oxidative harm, as well as the augmentation of photosynthesis pigments, secondary metabolites such as phenolics, EOs levels, overall antioxidant scavenging capacity, and the preservation of RWC during periods of drought stress.Graphical

Nitrogen facilitation was maintained in sown Mediterranean forage mixtures despite drought stress conditions with concurrent general benefits upon plant aboveground water status and yield

There is an urge to optimise the sustainability and resilience of grasslands, especially in light of the extreme weather risks posed by climate change. Plant sown diversity could contribute to mitigating these risks by improving resource use efficiency as well as reducing reliance on fertilisation. We established a field experiment to determine forage swards’ performance in terms of water use, nitrogen (N) use, and dry matter (DM) yield in a semi-arid Mediterranean area which faced a severe drought period. Most variables were tested over three growing seasons, whilst DM yield had an extra year of sampling in which two levels of N fertilisation were tested. Following the Generalised Diversity-Interactions modelling approach, we manipulated the composition and evenness of forage swards including a grass (Festuca arundinacea), a legume (Medicago sativa), and a non-legume forb (Cichorium intybus). Communities were grown as monocultures or mixtures of three species according to a simplex design, which allowed us to estimate separately the two components of the diversity effect: the individual species effects and that due to species interactions. Models were tested both with sown proportions (Pi0) and realised proportions (PiR). The Pi0 models indicated a major beneficial effect of mixtures in contrast to the average monoculture performance for all studied variables. In contrast, PiR models revealed that some of the effects in Pi0 models are indeed explained by the growing proportion of M. sativa over time. However, beneficial interaction effects are still found in PiR models, especially concerning N2 fixation (with δ15N as proxy), which was maintained regardless of the drought stress level experienced by the swards. All things considered, mixed swards merit attention as a valuable nature-based solution that can optimise N management (by boosting N2 input through fixation) as well as water use. This would result in well-nurtured swards with a better ability to cope with drought stress and maintain productivity.

Rice Growth and Leaf Physiology in Response to Four Levels of Continuous Drought Stress in Southern China

Exploring the growth and physiological response mechanisms of rice under continuous drought stress circumstances can provide a significant scientific foundation and technological assistance for meeting drought difficulties, improving drought resistance and rice (Oryza sativa L.) output, and ensuring food security. In this study, a rice field experiment was conducted under a rain shelter with five different treatments set up: P1 (drought stress from tillering stage), P2 (drought stress from jointing–booting stage), P3 (drought stress from heading–flowering stage), P4 (drought stress from grain filling stage), and CK (adequate water management throughout the growth stage). Continuous drought stress from different growth stages with four levels (mild, medium, moderate, and severe). The results showed that the effects of different drought stress treatments on rice growth varied significantly. Compared with the CK treatment, plant height was reduced by 12.10%, 8.14%, 3.83%, and 1.06% in the P1, P2, P3, and P4 treatments, respectively, and the number of tillers was reduced by 23.83%, 18.91%, 13.47%, and 8.68%, respectively. With the increase in drought stress levels, SPAD values and Rubisco activity of rice leaf continued to decrease; SOD activity showed a decreasing trend, but the decreasing trend of POD and CAT activities was not significant, while MDA content showed an increasing trend. For yield components, continuous drought stress significantly reduced spike length of rice by an average of 3.5%, effective number of spikes by 18.9%, thousand grain weight by 3.7%, grain number per spike by 11.6%, and fruiting rate by 1.8%, respectively, compared to CK treatments during the growth period. In general, continuous drought stress during the early growth period affected the effective spike number and the grain number per spike. Continuous drought stress after the grain filling stage had the least effect on yield (17.62% of yield reduction), and water use efficiency (1.76 kg m−3) was much higher than other treatments. These researchers’ findings provide insight into how rice physiology and growth react to continuous drought stress, which is significant for agricultural operations.

Morfologi Bawang Merah (Allium ascalonicum L.) Pada Cekaman Kekeringan Terhadap Aplikasi Asam Salisilat

Shallots are the vegetable crop with the highest production in Indonesia. However, the problem with cultivating shallots is that they are not resistant to environmental stress such as drought. The decrease in soil water content to 60% of available water has caused a drought stress effect on shallot plants. The strategy that can be used to limit the harmful effects of lack of water on shallots is the application of salicylic acid. Salicylic acid plays an important role that enhances plant growth and development under drought stress conditions by reducing cell membrane damage in water-stressed plant leaves by reducing cellular lipid peroxidation and H2O2 accumulation. This research aimed to study the growth, yield and physiological responses of shallots under drought stress conditions with the application of salicylic acid. This research was carried out in the greenhouse of the Faculty of Agriculture, University of North Sumatra, Medan from April to June 2024. This research used a factorial randomized block design with 2 treatment factors. The first factor of antioxidant spraying consisted of 4 levels, namely 0 mM (control), 0.5 mM, 1 mM and 1.5 mM. The second factor was the level of drought stress (percentage of soil water content) which consisted of 3 levels, namely 80%, 60% and 40% FC. The results showed that drought stress decreased plant height, number of leaves, number of tillers, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight. Meanwhile, application of salicylic acid up to 1 mM could increas shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight.

Influence of Salicylic Acid under Different Levels of Drought Stress on Growth, Yield, and Chemical Content in Sesame Crop.

Influence of Salicylic Acid under Different Levels of Drought Stress on Growth, Yield, and Chemical Content in Sesame Crop.

Mitigation of drought-induced stress in sunflower (Helianthus annuus L.) via foliar application of Jasmonic acid through the augmentation of growth, physiological, and biochemical attributes

Drought stress poses a significant threat to agricultural productivity, especially in areas susceptible to water scarcity. Sunflower (Helianthus annuus L.) is a widely cultivated oilseed crop with considerable potential globally. Jasmonic acid, a plant growth regulator, plays a crucial role in alleviating the adverse impacts of drought stress on the morphological, biochemical, and physiological characteristics of crops. Experimental detail includes sunflower varieties (Armani Gold, KQS-HSF-1, Parsun, and ESFH-3391), four drought stress levels (0, 25%, 50%, and 75% drought stress), and three levels (0, 40ppm, 80ppm) of jasmonic acid. The 0% drought stress and 0ppm jasmonic acid were considered as control treatments. The experimental design was a completely randomized design with three replicates. Drought stress significantly reduced the growth in all varieties. However, the exogenous application of jasmonic acid at concentrations of 40ppm and 80ppm enhanced growth parameters, shoot and root length (1.93%, 19%), shoot and root fresh weight (18.5%, 25%), chlorophyll content (36%), photosynthetic rate (22%), transpiration rate (40%), WUE (20%), MDA (6.5%), Phenolics (19%), hydrogen peroxide (7%) proline (28%) and glycine betaine (15–30%) under water-stressed conditions, which was closely linked to the increase in stomatal activity stimulated by jasmonic acid. Furthermore, JA 80 ppm was found to be the most appropriate dose to reduce the effect of water stress in all sunflower varieties. It was concluded that the foliar application of JA has the potential to enhance drought tolerance by improving the morphological, biochemical, and physiological of sunflower.

Selenium and its nanoparticles modulate the metabolism of reactive oxygen species and morpho-physiology of wheat (Triticum aestivum L.) to combat oxidative stress under water deficit conditions

BackgroundWheat (Triticum aestivum L.) is one of the most important cereal crop species worldwide, but its growth and development are adversely influenced by drought stress. However, the application of trace elements is known to improve plant physiology under water-limited conditions. In this study, the effects of drought stress on wheat plants were investigated, with a focus on potential mitigation by foliar application of selenium nanoparticles (Se(np)) and sodium selenate (Na2SeO4). The experiment was conducted in a net house using a completely randomized design with four replications. The treatments involved three levels of drought stress (mild, moderate, and severe) started at 30 days after sowing (DAS), with foliar sprays of Se(np) and Se (both 25 µM) initiated at 27 DAS and repeated 4 times at 7-day intervals until 55 DAS.ResultsDrought stress significantly reduced plant growth, whereas Se(np) and Se sprays enhanced it. Drought stress induced chlorophyll degradation, increased malondialdehyde and hydrogen peroxide levels, impaired membrane stability, and caused electrolyte leakage. Severe drought stress reduced the levels of antioxidants (e.g., proline, ascorbate, and glutathione by 4.18-fold, 80%, and 45%) and the activities of antioxidant enzymes (ascorbate peroxidase, dehydroascorbate reductase, and others). Conversely, treatment with Se(np) and Se restored these parameters, for example, 1.23-fold higher total chlorophyll content with Se(np) treatment, 26% higher APX activity with Se treatment, 15% lower electrolyte leakage with Se treatment in wheat plants under severe drought stress. This Se-associated enhancement facilitated rapid scavenging of reactive oxygen species and reduced methylglyoxal toxicity, thereby diminishing oxidative stress and positively affecting the morphophysiological and biochemical responses of the plants under drought.ConclusionsDrought-stressed wheat plants exhibited reductions in physiological processes, including water uptake and photosynthetic activity. However, Se(np) and Se applied at 25 µM mitigated the detrimental effects of drought. The application of Se(np) was notably more effective than the application of Se in mitigating drought stress, indicating the potential of the application of Se(np) as a sustainable agricultural practice under water-limited conditions.

Physiological and biochemical characteristics of milk thistle (Silybum marianum (L.) Gaertn) as affected by some plant growth regulators.

Milk thistle (Silybum marianum (L.) Gaertn) is a globally and widely used medicinal plant that contains silymarin. This plant has antioxidant, antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, and neuroprotective effects. Plant quality, yield, and phytochemicals, especially silymarin content, change under various conditions like drought stress. Therefore, this research studied plant growth regulators (PGRs) like salicylic acid, spermidine, and brassinosteroid to increase plant tolerance to drought stress. Experimental treatments include different levels of irrigation (25%, 50%, 75%, and 90% field capacity), and foliar spraying including salicylic acid (75 and 150 mg/L), spermine (70 and 140 mg/L), and brassinosteroid (1 and 1.2 μM), separately, and water as a control and a secondary factor. The results revealed that the highest amount of leaf phenolic compounds was observed in the highest drought stress level (25%) and 75 mg/L salicylic acid application. Furthermore, brassinosteroid at different concentrations and salicylic acid (75 mg/L) increased leaf flavonoid content compared to other treatments. In 50% field capacity, foliar application of salicylic acid (150 mg/L) significantly increased seed yield by approximately 75% compared to control under the same stress level. Brassinosteroid application (1 μM) under 75% field capacity significantly increased the seed's taxifolin amount by 159%. Additionally, salicylic acid noticeably increased the silychristin concentration. The concentration of silydianin in the seed has also been increased under drought stress and foliar spraying with PGRs. Compared to the control, using spermidine below 75% field capacity caused an increase in its concentrations by over seven times. The highest silybin A amount was obtained in 50% field capacity and foliar150 mg/L salicylic acid. Taxifolin, silychristin, silydianin, silybinin B, iso-silybinin A, and iso-silybinin B compounds were identified in the seed extract. Generally, foliar spraying using plant growth regulators increased the number of silymarin compounds under drought stress conditions and field cultivation conditions.