Effects Of Water Deficit Stress Research Articles

Interactive effects of mycorrhizal, Azospirillum and nitrogen+phosphorus with limited irrigation on yield and morpho-physiological traits of evening primrose (Oenothera biennis L.) in arid and semi-arid regions

Evening primrose (Oenothera biennis L.) is a valuable medicinal plant known for its oil, which is rich in gamma-linolenic acid. However, the productivity and quality of evening primrose can be significantly affected by drought stress, a common challenge in arid and semi-arid regions. Water deficit stress not only limits plant growth and development but also affects physiological and biochemical processes. To mitigate the adverse effects of drought, the use of chemical and biological fertilizers has been explored. Mycorrhizal fungi and Azospirillum are known for their ability to enhance plant resilience to abiotic stresses, including drought, by improving nutrient uptake and promoting plant growth. Nitrogen and phosphorus (N+P) are essential nutrients that play crucial roles in plant metabolism and stress tolerance. This study aimed to assess the impact of mycorrhizal fungi, Azospirillum, and N+P on evening primrose under drought conditions. One experiment was conducted in two locations, Tehran (semi-arid) and Varamin (arid) in 2014 and 2015, using a greenhouse for growing plants and through field transplantation. Using a split factorial design within a randomized complete block layout, three irrigation regimes (50 %, 40 %, and 30 % of field capacity) constituted the main plots, while the subplots included three chemical fertilizer treatments (none, 50 %, and 100 % of N+P) and four biological fertilizer treatments (non-inoculated and inoculated with mycorrhizal fungi and Azospirillum) in factorial combinations. The study revealed that drought, both moderate and severe, resulted in reduced plant height, shoot dry weight, leaf area index, seed yield, harvest index, phosphorus content, relative water content, and oil yield. Notably, the highest water use efficiency occurred under moderate water deficit stress. Severe water deficit stress, however, led to the highest root dry weight, root ratio to shoot dry weight, and catalase activity. The application of chemical and biological fertilizers alleviated the negative effects of water deficit stress on plant growth and yield. Evening primrose water use efficiency increased under moderate water deficit stress, particularly when coupled with the application of chemical (N+P) and biological (mycorrhizal fungi and Azospirillum) fertilizers. The study emphasized the positive impact of mycorrhizal and Azospirillum inoculation on enhancing evening primrose growth under water deficit stress.

Effect of Water Deficit Stress on Reproductive Stage of Durum Wheat Near Isogenic Lines Carrying the NAM-B1 Gene

Background In wheat, the NAC family plays a crucial role in conferring cellular responses to different abiotic stresses, particularly drought. The functional NAM-B1 allele in durum wheat accelerates senescence, while its homologous genes contribute to improved water deficit stress tolerance. Therefore, the main objective of this study was to investigate the role of the NAM-B1 gene in durum wheat subjected to water deficit stress at two reproductive stages. Materials and Methods Three Near-Isogenic Lines carrying a functional NAM-B1 allele and their recurrent parent, Langdon (LDN), were used in this study. The study assessed NILs and LDN performance under varied water conditions (well-watered, 60%, and 80% water deficit of pot capacity) during flag leaf and anthesis stages. The agronomic performance of the three NILs and LDN was assessed for 16 traits, including plant height, grain yield, and thousand kernel weight. Additionally, physiological measurements, including stomatal resistance, chlorophyll content (SPAD values), and chlorophyll fluorescence (Fv/Fm) were taken. Results Significant genotypic effects were observed on seven agronomic traits, while 15 traits were influenced by the water stress treatment. The NILs exhibited accelerated maturity and a shorter grain-filling period, which were particularly pronounced under stress conditions. Severe water deficit resulted in reduced grain weight and thousand-grain weight in tested genotypes. Interestingly NILs carrying functional NAM-B1 showed taller plants and had higher tiller and spike numbers when compared to LND. Significant genotypic effects were observed for seven traits, and water stress treatments affected 15 traits. The NILs exhibited accelerated maturity and reduced grain weight under severe water deficit. Physiological measurements showed genotype and water-deficit differences, with NIL #504 displaying higher SPAD values, particularly under stress conditions, and a significant genotype X treatment effect was observed for stomatal resistance at the anthesis stage. Discussion Limited treatment × genotype interactions for most traits highlight the complexity of drought tolerance in the tested lines, which might be attributed to its quantitative nature influenced by multiple genes. The study emphasizes the necessity for future research to explore the role of other NAM-related genes in response to water deficit stress and their interactive effects with the NAM-B1 gene at different growth stages in wheat plants subjected to diverse stress conditions. Conclusion In conclusion, this study reveals pronounced genotypic effects, particularly in agronomic traits, such as maturation rate and grain filling period, under severe water deficit stress. Future studies are needed to understand the genetic mechanisms mediated by NAM-B1 genes in accelerating maturity in response to stress.

Response of Grafted Olive (Olea europaea L. Cv. Coratina) to Water Deficit Conditions

Drought is one of the most damaging abiotic stresses; water deficit problem is increasingly occurring due to global climate change and negatively affects crop growth and productivity. Grafting on tolerate rootstocks is a promise approach to mitigate negative impacts of drought stress and ensure production sustainability. The present study was carried out to investigate the effect of water deficit stress on Coratina olive plants grafted on the following cultivars as rootstocks (Coratina, Koroneiki, Manzanillo, Picual and Sorani). Three water levels based on soil field capacity (FC) (100, 50% and 25% of FC) were used for water deficit treatments. Water deficit decreased shoot growth, stem diameter, leaves number and area, shoot and root weight. Leaf analysis showed marked decrease in total chlorophyll content while proline, total sugars and phenolic content increased with increasing water deficit level. The studied grafting combination differed in their response to water deficit treatments; Coratina grafted on Sorani and Koroneiki recorded higher values of growth parameters and accumulated higher amount of osmolytes (proline and total sugars) and phenolic compared to other grafted olive plants.

Genotypic responses to phosphorus and water management in winter wheat: Strategies to increase resource use efficiency and productivity

The phosphorus (P) addition can be helpful in the mitigation of the adverse effects of water deficit stress. However, the efficiency of wheat in utilizing both components has not been assessed in field conditions. This research aims to assess the effects of P and water addition on phosphorus use efficiency (PUE) and water productivity (WP) in field conditions for select wheat cultivars co-adapted to climate-induced agronomic challenges. Three wheat cultivars were selected based on their PUE and water WP from a previous experiment. The trials were conducted in field conditions over two consecutive years, from 2020 to 2021 (Season 1) and 2021–2022 (Season 2). The plants were grown on an andisol with a soil P concentration of 10 mg P kg−1 and 30 mg P kg−1. Two irrigation treatments were imposed: Well-watered (+W) and dryland (-W). The plants were sampled at three stages: tillering (Z25), anthesis (Z65), and ripening (Z95). At the end of the phenological cycle, grain yield components, grain yield, grain quality, PUE, and WP were evaluated. Phosphorus addition promotes plant growth, especially in the early vegetative stages, by enhancing tiller development and nutrient and water uptake. These effects were critical during the anthesis and ripening stages, enhancing yield components and higher grain production. Differential responses were observed across cultivars, underscoring the genotype-specificity in PUE and WP. Seasonal water deficit stress modulated these effects, highlighting a more complex genotype-environment-nutrient interaction. The water addition promoted PUE and WP, suggesting a synergy between the two components. Among the cultivars, Chevignon outperformed in grain yield, PUE, and WP. However, while phosphorus, water, and environmental factors influenced grain quality, the genetic background of the cultivar was the primary determinant of these components. This study advocates for implementing individual nutrient management strategies tailored to the specific cultivar and adaptable to environmental conditions under climate change.

Soil Properties and Yield of Peppermint (Mentha Piperita L.) in Response to Different Nitrogen Fertilizers Under Water-Deficit Conditions

ABSTRACT Drought and lack of nutrients (including nitrogen) limit crop production in arid and semi-arid regions, including Iran. In order to investigate the combined effect of nitrogen fertilizer sources (organic and chemical) under low water stress on soil properties, biological yield and peppermint essential oil, a three-year experiment was conducted during the spring and summer of the years (2017–2019) in the semi-arid region of Iran. The experiment was conducted as split plots in the form of randomized complete blocks with three replications. Experimental treatments include three irrigation regimes (irrigation after draining 25, 40 and 55% of usable water in the root zone) as the main factor and six fertilizer treatments based on plant nitrogen requirements (100% Chemical, No fertilizer, 50% Chemical + 50% Azocompost, 100% Vermicompost, 100% Azocompost, 50% Chemical + 50% Vermicompost) as sub-factors. The results showed that water-deficit conditions decreased organic carbon, total nitrogen content, soil phosphorus and potassium and biological yield and increased the percentage of peppermint essential oil. Also, in most of the treatment compositions of irrigation regime, the application of organic fertilizer (especially pure vermicompost and azocompost treatments) or combination with chemical fertilizer the increase organic carbon, macronutrients (nitrogen and phosphorus) and micro (iron and zinc) in soil solution, causing improved biological yield and essential oil content and moderated the effects of water-deficit stress on peppermint. These practical measures can help save water and fertilizer consumption while promoting the production of healthy medicinal products over the course of three years.

Saving water under water deficit conditions by application of Xyway LFR@FMC: Greenhouse studies

Triazole fungicides are often referred to as "stress protectants" due to their ability to enhance the abiotic stress tolerance of plants. Xyway LFR@FMC (flutriafol) is a triazole and at-plant applied fungicide. The Xyway LFR@FMC fungicide that has been introduced into corn production system starting 2020 have been observed to improve plant performance under drought stress conditions. In this study, we accessed the potential of Xyway LFR@FMC product in altering the ability of corn (Zea mays L.) plants to control transpiration rates under water deficit-stressed (DS) conditions. Plants were grown under greenhouse conditions treated with Xyway LFR@FMC at 0.56, 0.77, and 1.11 L ha−1 in experiment 1 and 1.11 and 1.26 L ha−1 rates in experiment 2. Plants treated with 1.11 L ha−1 reduced the amount of water loss in response to DS and had the highest fraction of transpirable soil water (FTSW) thresholds. There was an increase in shoot hydraulic conductance (Kshoot) by 1.11 L ha−1 in both experiments. Plants treated with 0.77 and 1.11 L ha−1 had higher LWP rates compared to other treatments under DS conditions. In conclusion, the most likely chemical ingredient in Xyway LFR@FMC fungicide triggering the transpiration control response was flutriafol. This is the first report that early stomatal closure under soil drying conditions can be induced by the application of Xyway LFR@FMC fungicide. Application of at-plant fungicide, Xyway LFR@FMC has potential to reduce the negative effect of water-deficit stress in corn along with improving plants growth and physiological performance.

Mitigation of water stress in broccoli by soil application of humic acid

The main challenge to plant productivity is water scarcity, which is predicted to get worse with climate change, particularly in arid and semi-arid areas. Humic acid could improve plant tolerance to mitigate drought damage, which is an effective strategy to improve crop production and agriculture sustainability under limited water conditions in these regions, but its effective application rates should also be established. Thus, two field experiments were carried out at the Qaha Vegetable Research Farm in Qalubia Governorate, Egypt, during the two seasons of 2020–21 and 2021–22 on clay soil. The present study investigated the effect of three rates of humic acid application (0, 4.8, and 9.6 kg ha-1) on growth, yield, and quality of broccoli cv. Montop F1 hybrid under well-watered and drought conditions. Drought was induced by missing alternate irrigation. Soluble humic acid as potassium-humate was applied three times with irrigation water at the time of the first three irrigations of drought treatment. Water-stressed plants had a decrease in growth, yield, leaf chlorophyll, and nutrient content, while they showed an increase in the contents of leaf proline and curd dry matter and total soluble solids as well as water use efficiency, in both seasons. Soil application of humic acid was effective in mitigating the adverse effects of water deficit stress on the growth and yield of broccoli. Water-stressed plants had the highest WUE value (9.32 and 9.36 kg m3−1 in the first and second seasons, respectively) when the maximal humic acid rate was applied. Humic acid at a high level (9.6 kg ha−1) had the most promising results and represents an opportunity that must be applied to improve broccoli yield and its production sustainability in arid and semiarid regions.

Mitigating the effects of water-deficit stress on potato growth and photosynthesis using mycorrhizal fungi and phosphate-solubilizing bacteria

AbstractBiofertilizers, such as arbuscular mycorrhiza fungi and phosphate-solubilizing bacteria (PSB), have been reported to enhance plant growth under water stress conditions. This study aimed to investigate the effect of different biofertilizers on potato photosynthesis and growth under water deficit stress. The experiment was conducted over two crop years (2019 and 2020) using a randomized complete block design with three replications. Four irrigation intervals (70, 90, 110 and 130 mm of cumulative evaporation) and six biofertilizer treatments (PSB, Funneliformis mosseae [FM], Rhizoglomus fasciculatum [RF], PSB + FM, PSB + RF and no use) were applied. Severe moisture stress (130 mm evaporation) compared to no stress (70 mm evaporation) increased substomatal carbon dioxide concentration. The application of biofertilizers improved tuber yield under severe moisture stress, with FM showing the highest increase (62.9%), followed by RF (59.8%) and PSB (48.4%). The use of PSB along with mycorrhizae led to a significant decrease in mycorrhizal colonization percentage at all irrigation levels. The highest percentage of colonization and net photosynthesis was obtained from the application of both mycorrhizal species under irrigation conditions after 70 mm of evaporation. The application of PSB alone resulted in a 14.6% increase in the transpiration rate, additionally, the use of mycorrhiza led to an 18.7% increase in stomatal conductivity compared to no-biofertilizer. The results suggest that the simultaneous use of PSB and mycorrhizae can be effective in mild moisture stress, but in severe moisture stress, the use of mycorrhizal species alone is more effective.

Effects of Water Deficit Stress at the Tillering Stage of Direct Seeded Rice (Oryza sativa L.)

The ten rice varieties viz. NAUR-1, Purna, GNR-6, NVSR-2227, NVSR-3093, NVSR-2285, NVSR-2278, NVSR-2852, NVSR-2601, and NVSR-2927 were grown in kharif season for observing their efficiency in terms of yield under a deficit of water at tillering stage. The effects of short-term water stress on various morpho-physiological and biochemical traits viz. leaf area index, number of panicles, chlorophyll content, number of stomata, relative water content, abscisic acid, proline, glycine betaine, ascorbic acid, and harvest index content were studied and they were observed higher in Purna as compared to other nine varieties. However, Plant height and Ionic leakage were recorded lower in Purna as compared to other varieties. The abscisic acid as well as proline and glycine betaine content recorded maximum in Purna which might help in keeping hydration in cells during water deficit stress. Thus, with short-term water deficit stress at tillering stage, the variety Purna would be better in terms of breeding for tolerant variety as well as yield among ten rice varieties.

Soil Manuring and Genetic Variation Conjunctively Surmount the Partial Drought Stress in Wheat (Triticum aestivum L.)

Crop growth is negatively influenced under water-stress conditions, which is among the most yield-limiting factors significantly decreasing crop yield. This study evaluated the effect of water-deficit stress on physiological, bio-chemical and yield attributes of wheat (Triticum aestivum L.) under both constantly wet and water-stressed conditions on two wheat varieties (UJALA-14, SARC-4). Further, the combined impacts of crop genetic variability and organic manuring in soil was studied for overcoming the partial drought stress in wheat. Treatments of different levels of irrigation water alone or with farmyard manure (FYM) @ 20 Mg ha‒1 were compared as: constantly wet irrigation (control), irrigation intensity equal to field capacity (FC), ½ FC + FYM, and ¼ FC + FYM. Crop growth, physiological and chlorophyll as well as sodium and potassium contents were measured. The findings of current study exhibited that shortage of water had negative effects on growth, physiological, bio-chemical and yield attributes of wheat. Genotype SARC-4 exhibited superior growth response having constantly wet and field capacity condition, on the other hand UJALA-14 gave better growth response under water stress conditions of ½ FC and ¼ FC when treated with FYM amendment. It is concluded that partial drought stress developed tolerance in wheat genotypes particularly in UJALA-14, which was strengthened with organic amendment. Combined use of drought tolerant varieties and application of FYM as a fertilizer is very effective way to enhance crop yield.

Effects of zinc-nano oxide, salicylic acid and sodium nitroprusside on physiological properties, antioxidant enzyme activities and secondary metabolites of Viola odorata under drought stress

One of the most important abiotic stresses and limiting factors (closing pores, lack of CO2 entry, reduced photosynthesis, and reduced yield) of plant products around the world is water-deficit stress. This study aimed to examine the water deficit stress and foliar application with anti-stress compounds (ASC) on characteristics of Viola odorata. The study was carried out as a factorial experiment based on a randomized complete design. The factors consisted of water deficit and the foliar application of ASC at six levels [zinc-nano oxide (ZnO, 1000 and 1500 mg l–1), salicylic acid (SA, 200 and 300 mg l–1), and sodium nitroprusside (SNP, 200 and 300 μM)], and the control. The water deficit reduced the leaf water potential, cell membrane stability, and the shoot and root fresh weight but increased electrolyte leakage and soluble sugar accumulation. However, foliar applications, particularly SA and SNP, positively affected the measured parameters. The activities of superoxide dismutase and guaiacol peroxidase at all three field capacity levels were higher in the plants treated with SA and SNP than in the control and plants treated with ZnO. In sum, using 200 mg l–1 of SA as a foliar application, in addition to improvement of the growth and developmental conditions of the aromatic violet plant, moderated the adverse effects of water deficit stress and increased the plant resistance to water deficit stress. Based on the results, the application of SA, SNP, and ZnO reduced electrolyte leakage and enhanced the plant’s resistance to water deficit by increasing the compatible osmolyte accumulation and antioxidant enzyme activity.

Effect of water deficit stress during fruit cultivation on the carbon stable isotopes of organic acids in Japanese apricots and liqueur prepared from these fruits

ABSTRACT The objective of this study was to assess the impact of water deficit stress during fruit cultivation on the δ 13C values of citric acid and malic acid in Japanese apricots at different ripeness stages and their resulting liqueurs. Our experiments show that water deficit stress increases the δ 13C values of citric acid and malic acid in tree-ripened fruits, counteracting the typical decrease during ripening. However, water deficit treatment has a minimal effect on the δ 13C values of organic acids in green fruits. Regardless of fruit ripeness or water status, the δ 13C values of organic acids in fruits are directly reflected in the resulting liqueurs. Overall, water deficit stress during fruit cultivation has the potential to promote similarity in the δ 13C values of organic acids across fruits at different ripeness levels, reducing variations among liqueurs derived from fruits of varying ripeness levels.

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.

MITIGATION OF WATER DEFICIT STRESS IN WHEAT BY FOLIAR FEEDING OF POTASSIUM

An experiment was conducted at the research field of Crop Physiology and Ecology Department, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur, Bangladesh during November 2021 to March 2022 to investigate the ameliorative effect of foliar application of potassium on wheat under non-irrigated water deficit stress condition, The treatments viz., well water (WW), water deficit stress (WDS) and foliar application of 2.23% K2SO4 under WDS were placed as main plot treatment and two wheat varieties (BARI Gom 28 and BARI Gom 32) were placed as sub plot treatment in split plot design following three replications. The interaction effect of growing conditions and wheat varieties significantly influenced the physiological traits, yield components and yield of wheat. Imposed water deficit stress significantly reduced different physiological traits, yield and yield attributes except proline content of flag leaf of wheat. Foliar application of potassium alleviated the adverse effect of water deficit stress in different degrees and improved the studied traits under stress condition. Foliar application of potassium was found more effective in BARI Gom 28 than that of BARI Gom 32. Foliar potassium increased grain yield by 7.43% and 3.56% in BARI Gom 28 and BARI Gom 32, respectively under water deficit stress condition. It can be concluded that additional foliar feeding of potassium along with recommended potassium could alleviate adverse effect of water deficit stress and improve productivity of wheat under drought environment.

Using Deficit Irrigation Strategies and Organic Mulches for Improving Yield and Water Productivity of Mango under Dry Environment Conditions

Many techniques have been and are being made to find alternatives to water-saving practices. Among them, Partial root drying (PRD), one effective approach, plays a major role in reducing the harmful effects of water deficit stress. Field experiments were carried out on mango trees for a private farm in Egypt over the course of two years, 2020/2021 to 2021/2022, in an area with sandy soil, hot summer conditions, and cold and rainy winter conditions. In the experiment that was carried out, the experimental design included using different irrigation strategies (I1, 100% full irrigation “FI”; I2, 75% FI; I3, 50% FI; and I4 (PRD), 50% FI) in the main plot and different amounts of organic mulch in the soil (L0, no layers of organic soil mulch, used as a control; L1, a single layer of organic soil mulch; L2, two layers of organic soil mulch; and L3, three layers of organic soil mulch) in subplots of the main plot in order to inspect the impact of the treatments on yield, water productivity, and energy usage under arid conditions. To meet the study’s objective, two field experiments were carried out at a private farm. Our results demonstrate a general decrease in water stress and salt accumulation inside the root-zone area with PRD and L3. During the 2020/2021 and 2021/2022 seasons the PRD strategy increased fruit yields by 3.7 and 7.3% and water productivity by 51.9 and 53.1%, respectively, compared with the control treatment (I1) while reducing the amount of applied irrigation water by 50%. The PRD strategy along with organic mulching showed superior results with respect to increasing mango yields and water productivity. In general, PRD can be used as a good technique to save water and energy by up to 50% while enhancing productivity, ultimately improving mango yields under arid climatic conditions. Thus, it may prove a good adaptation strategy for current and future water shortage scenarios involving climate change.

Application Methodology and Physiological Insights of Melatonin Hormone for Water Stress Alleviation in Black Pepper (Piper nigrum L.)

Black pepper is highly sensitive to water deficit stress especially during summer, resulting in significant losses in yield; therefore, strategies aimed at enhancing water stress tolerance are essential. Melatonin improves stress tolerance in plants; however, its method of application and optimum concentration in black pepper under water deficit stress remains unclear. Therefore, we conducted a two pot culture experiment during March and April, 2022 (var. Panniyur-1) to investigate the effects of foliar-sprayed and root-irrigated melatonin (50, 100 and 150 µM L-1) on the recovery per cent and physiological mechanism under water stress. The treatment details were, WW - Well-watered; WS - Water stressed; FM50 - Waterstress+50µM Melatonin (Foliar spray); FRM50 - Water stress + 50µM Melatonin (Foliar spray + Soil drenching @ 50ml/plant); FM100 - Water stress + 100µM Melatonin (Foliar spray); FRM100 - Water stress + 100µM Melatonin (Foliar spray + Soil drenching @ 50ml/plant); FM150 - Water stress + 150µM Melatonin (Foliar spray); FRM150 - Water stress + 150µM Melatonin (Foliar spray + Soil drenching @ 50ml/plant). The melatonin-induced enhanced stress tolerance could be attributed to improved recovery %, leaf relative water content, photosynthetic pigments, activity of antioxidant enzymes (SOD, POD, and CAT), and ultimately significantly relieved the inhibitory effects of water stress on leaves. After rehydration, melatonin-treated plants recovered more quickly than untreated plants. In addition, melatonin counteracted the water stress induced accumulation in proline content. Overall, the results of this study demonstrated that melatonin at 100 µM L-1 (Foliar spray and root irrigation) significantly alleviated the adverse effects of water deficit stress compared untreated plants. In addition, application of exogenous melatonin combined with root and foliar application is superior than foliar spraying alone.

Effect of climate change-induced water-deficit stress on long-term rice yield.

The water requirements of crops should be investigated to improve the efficiency of water use in irrigated agriculture. The main objective of the study was to assess the effects of water deficit stress on rice yields throughout the major cropping seasons. We analyzed rice yield data from field experiments in Taiwan over the period 1925-2019 to evaluate the effects of water-deficit stress on the yield of 12 rice cultivars. Weather data, including air temperatures, humidity, wind speed, sunshine duration, and rainfall were used to compute the temporal trends of reference evapotranspiration and crop water status (CWS) during rice growth stages. A negative CWS value indicates that the crop is water deficient, and a smaller value represents a lower water level (greater water-deficit stress) in crop growth. The CWS on rice growth under the initial, crop development, reproductive, and maturity stages declined by 96.9, 58.9, 24.7, and 198.6 mm in the cool cropping season and declined by 63.7, 18.1, 8.6, and 3.8 mm in the warm cropping season during the 95 years. The decreasing trends in the CWSs were used to represent the increases in water-deficit stress. The total yield change related to water-deficit stress on the cultivars from 1925-1944, 1945-1983, and 1996-2019 under the initial, crop development, reproductive, and maturity stages are -56.1 to 37.0, -77.5 to -12.3, 11.2 to 19.8, and -146.4 to 39.1 kg ha-1 in the cool cropping season and -16.5 to 8.2, -12.9 to 8.1, -2.3 to 9.0, and -9.3 to 8.0 in the warm cropping season, respectively. Our results suggest that CWS may be a determining factor for rice to thrive during the developmental stage, but not the reproductive stage. In addition, the effect of water-deficit stress has increasingly affected the growth of rice in recent years.

Some physio-biochemical traits of sunflower (<em>Helianthus annuus</em> L.) as affected by arbuscular mycorrhizal fungi inoculation under different irrigation treatments

Plant-arbuscular mycorrhizal (AM) fungi association is one of the oldest symbiotic relationships between organisms. This relationship may be more important under stress conditions such as drought and can help the host plant tolerate drought. This study was conducted in 2016 and 2017 at the Agricultural Research Farm of Razi University, Kermanshah, Iran to evaluate the effect of AM fungi (AMF) inoculation (with either Funneliformis mosseae or Rhizophagus intraradices) on some physio-biochemical traits of three sunflower cultivars under different soil irrigation treatments (severe water deficit stress, mild water deficit stress and well-watered). In both years, water deficit conditions significantly reduced leaf relative water content (RWC), chlorophyll concentrations (a, b and total) and shoot phosphorus concentration (SPC) while simultaneously increasing shoot proline levels and malondialdehyde (MDA) concentrations. AMF inoculation had positive effects on RWC, chlorophyll concentrations and SPC irrespective of sunflower cultivar and irrigation treatment. Shoot proline concentration and MDA reduced more in AM than non-AM plants. In most cases F. mosseae performed better than R. intraradices in terms of plant performance. Moreover, the improvements caused by AM fungi were more evident under water deficit than well-watered condition. It may be concluded that AM inoculation can alleviate the negative effects of water deficit stress on some important physio-biochemical traits of sunflower grown in the field, and can be considered as a practical and economical approach to improve crop performance in environments exposed to water limitations.

Silicon Nutrition in Plants under Water-Deficit Conditions: Overview and Prospects

Drought is one of the major constraints for sustainable crop production worldwide, especially in arid and semiarid regions. The global warming and climate change scenario has worsened the dilemma of water scarcity, creating an immediate threat to food security. Conserving water resources and exploiting various strategies that enable plants to withstand water deficits need to be urgently addressed. Drought adversely affects plant growth by modulating a range of physio-chemical, metabolic, and molecular processes inside the plant body, which ultimately reduces crop productivity. Besides developing drought-tolerant cultivars, better nutrient management could be a promising strategy to enhance drought tolerance in crop plants. Silicon, a quasi-essential element, is known to play a vital role in improving crop performance under a range of biotic and abiotic stresses. This review discusses the potential of Si application in attenuating the adverse effects of water-deficit stress. Silicon enhances plant growth by improving seed germination, cell membrane stability, carbon assimilation, plant–water relations and osmotic adjustment (by accumulating soluble sugars, proline and glycine betaine). It triggers the activity of antioxidants, promotes the biosynthesis of phytohormones, enhances nutrient acquisition and regulates the activity of vital enzymes in plants under drought stress. Silicon also induces anatomical changes in the plant cell wall through the deposition of polymerized amorphous silica (SiO2-nH2O), thereby improving stem and leaf erectness and reducing lodging. Further, Si-mediated physiological, biochemical and molecular mechanisms associated with drought tolerance in plants and future research prospects have been elucidated.

Optimization of paclobutrazol dose for mitigation of water-deficit stress in rice (Oryza SativaL.)

The objective of the present study was to assess and optimize the paclobutrazol (PBZ) dose for mitigation of adverse effects of water deficit stress in rice. Paclobutrazol (PBZ), a triazole compound, has been proven to protect plants against abiotic stresses. As a result, an experiment was conducted with three rice varieties, namely N22, IR64 DTY1.1, and IR64, to identify the optimal dose under both mild and severe water deficit stress (WDS) at both vegetative and anthesis stages. Exogenous PBZ (30, 60, 90, and 120 ppm) was applied to plants just before imparting water deficit stress. The highest augmentation of relative water content (RWC), membrane stability index (MSI), total chlorophyll, chlorophyll stability index (CSI), and abscisic acid (ABA) was observed at 90 ppm of PBZ. Based on a curve-fitting analysis of the physiological responses of three rice cultivars to PBZ, the optimum dose was estimated to be around 100 ppm.