Relative Water Content Research Articles

ACC deaminase producing bacteria alleviate the polyethylene glycol induced drought stress in black gram (Vigna mungo L.) by enhancing nutrient uptake and soil respiration activity

The present study aimed to exploit ACC deaminase (ACCD) producing drought-tolerant bacteria to mitigate drought stress (PEG stress) and simultaneous enhancement of the essential nutrients (N and P), relative water content (RWC), and chlorophyll pigment. In this study, 80 previously isolated ACCD-producing bacteria were screened for drought tolerance, and the results showed that 13.75 % (11isolates) were tolerant to up to -0.73 MPa. Further, screening of these drought tolerant ACCD producers revealed that the 11 isolates produced siderophore (96.82–99.67 %), indole-3-acetic acid like substances (15.15–70.55 µg/mL), and phosphate solubilization (39.33–142.67 µg/mL). Furthermore, pot studies (2000 ppm PEG stress) revealed an enhanced root (40.97–174.24 %) and shoot length (14.06–194.86 %) in inoculated plants compared to the control plants. In addition, inoculated plants also enhanced the uptake of nitrogen (35.10–42.61 mg/g) and phosphorus (2.67–3.68 mg/g), relative water content (55.26–83.33 %), chlorophyll (15.83–47.25 mg/g) and ACCD production in the soils (2.03–5.51 µmol/mL). The inoculated bacteria also enhanced the soil respiration activity such as dehydrogenase enzyme (65.31–144.48 µg/g), fluorescein diacetate hydrolysis (19.27–55.25 µg/g), and alkaline phosphatase (611.53–1011.53 µg/g). In conclusion, IPTS 7 (Rhodococcus kroppenstedtii) and CWN 5 (Bacillus altitudinis) can be used to mitigate drought stress and mobilize essential nutrients (N and P).

Physio-biochemical Behavior and Health Effects of Pepper Plants Subjected to Lead Stress and Their Responses to Remediating Agents as Microbial Activity and Phosphorus

This work assessed the alleviating effects of bacteria (Bacillus subtilis) and phosphorus as environmentally friendly materials on the cultivation of pepper plants in polluted soil with lead (Pb) in forms of PbSO4, and Pb(NO3)2 at rates of 0, 1000, 2000 and 3000 µg Pb/g soil. Pot experiments were conducted to study the growth parameters, some physiological factors, biochemical constituents, and yield attributes, as well as the tolerance index (TI), translocation factor (TF), bioconcentration factor (BCF), and health effects [daily intake of heavy metals (DIM), health risk index (HRI), and carcinogenic risk (CR)]. Increasing the Pb concentration of all Pb salt used in soil severely affected the plant vegetative growth parameters. In comparison with other Pb salt forms, Pb(NO3)2 salt had a strong inhibitory impact. Additionally, the photosynthetic pigments in leaves were negatively impacted by all Pb salt forms. The application of Pb in all salt forms led to changes in the leaf water deficit (LWD), osmotic pressure, and membrane integrity and decreased the total water content, relative water content (RWC), transpiration rate, and leaf succulence. Pollution with Pb salts considerably decreased the yield constituents and various chemical properties of pepper, more so in the presence of Pb nitrate than in the presence of Pb sulfate type. A comparison of the concentration of Pb presence of Pb nitrate was greatly increased than the Pb sulfate in the whole plants. The safe limit of 0.3 mg/kg was exceeded by the Pb concentration in pepper fruits (6.3 and 4.3 mg/kg) cultivated in Pb-contaminated soil [with Pb(NO3)2 and PbSO4, respectively]. Additionally, Pb sulfate had a greater detrimental effect on Pb uptake in several plant organs than other Pb salt forms. The TI of pepper plants treated with salt types was >60% with PbSO4 (75.6%), whereas it was <60% with Pb(NO3)2 (35.2%). The BCF values of pepper plants in the polluted Pb soils varied from 0.10 to 0.41, indicating a moderate accumulator plant. At every level of Pb contamination with all Pb salt types, the sequence of Pb TF values was as follows: roots (TFr) > shoots (TFsh) > fruits (TFf), with TF values < 1. When compared with TFr and TFsh, TFs for shoot to fruits (TFf) had the lowest values (range, 0.07–0.22). The DIM, HRI, and CR values of pepper plants revealed that the Pb of fruit of stressed pepper plants is within safe limits. In addition to reducing the detrimental effects of intolerable Pb levels (2000 and 3000 µg Pb/g soil) on the majority of the aforementioned characters, adding Bacillus bacteria as a bio-agent and phosphorus as a chemo-agent to Pb-polluted soils also stimulated growth, increased yield, controlled plant water relations, protected photosynthetic pigments, and sharply decreased the Pb accumulation in plant organs. The Bacillus bacteria application resulted in some superior characteristics, such as root length, leaf number, leaf length, leaf area, leaf area index, fresh biomass, dry biomass, photosynthetic pigments, quantity yield attributes, reduction Pb accumulation in all plant organs, TI, TFr, TFf, BCF, in health effects trials, whereas phosphorus application improved plant height, leaf width, RWC, LWD, osmotic pressure, total soluble solids, acidity, total carbohydrates, total protein, and TFsh.

Effectiveness of manganese foliar spraying to mitigate salt stress in ornamental cabbage: Insights into morphological, physiological biochemical adaptations and mTERF gene responses

Salinity has been the subject of research for many years. However, salt stress studies on ornamental plants have increased recently. It is very important to determine the responses of bedding flowers, which are widely used in landscaping, to salt stress, and to strengthen the defense against stress. Ornamental cabbage (Brassica oleareacea L.) is widely used bedding flower in winter. The aim of this study was determining the effects of foliar application of manganese (Mn) on morphological, physiological, biochemical, and molecular parameters in ornamental cabbage ('Pigeon Purple F1′) under salt stress. Plants were irrigated with 4 different irrigation solutions which containing 0 [control], 75, 150 and 300 mM NaCl concentrations and Mn (4000 ppm) was sprayed to the leaves on 0, 7th and 14th days of the salt stress application. The application of manganese did alleviate the negative effects of salinity on shoot fresh weight and shoot dry weight in 75 mM NaCl plants. Ion leakage for 0 and 75 mM NaCl decreased with foliar spraying of Mn, but relative water content of plants did not change with Mn application. Lipid peroxidation (7.6 %) and H2O2 (hydrogen peroxide) (21.3 %) contents increased with Mn foliar spraying. Superoxide dismutase (SOD) and peroxidase activity did not change with Mn application under salinity. The highest catalase activity obtained from 150 mM (13.81 Unit g−1 leaf) and 300 mM NaCl (16.00 Unit g−1 leaf) which treated with Mn. Root Na content was lower with Mn-treated plants when compared control plants under salt stress. Foliar spraying of Mn significantly increased the K content of the plants. Furthermore, Na/K and Na/Ca ratios which are important indicators for salt stress also decreased by Mn application under saline conditions. In addition, m TERF genes were measured by using the q-RT PCR. In most cases, mTERF expression was slightly induced by salinity, while manganese application generally led to downregulation of mTERFs.

Aspectos ecofisiológicos e produção de biomassa de genótipos de soja sob condições de estresse por alagamento do solo

ABSTRACT The objective of this study was to evaluate the ecophysiological aspects and biomass production of three soybean genotypes subjected to soil flooding in the vegetative and/or reproductive stages. The design adopted was completely randomized with 5 replications, in a 3 x 3 factorial arrangement, with three soybean genotypes: PELBR 17-46, PELBR 15-7016, and 75I77RSF IPRO; and three water treatment conditions: soil flooding for 10 days in the vegetative period + 10 days in the reproductive period; soil flooding for 10 days only in the reproductive period, and the control treatment, where the soil was maintained at 70% of field capacity. There was a reduction in the relative water content for the PELBR 15-7016 and PELBR 17-46 genotypes in the vegetative/reproductive stages and in the reproductive stage, while for the 75I77RSF IPRO there was no difference. The levels of chlorophyll a, chlorophyll b, and total chlorophyll were reduced only for the PELBR 15-7016 and 75I77RSF IPRO genotypes. The dry matter in the leaves and roots was lower for PELBR 17-46 and PELBR 15-7016 when subjected to stress in the R2 soybean stage and for the grain production. PELBR 17-46 and PELBR 15-7016 genotypes are more susceptible to stress, while the 75I77RSF IPRO showed mechanisms to overcome waterlogging stress.

Foliar applied potassium nanoparticles (K-NPs) and potassium sulfate on growth, physiological, and phytochemical parameters in Melissa officinalis L. under salt stress.

Salinity stress significantly constrains agricultural productivity and vegetation decline worldwide, particularly in Iran. Potassium, the second most prevalent nutrient in plants, is well known to be essential for cell metabolism. Here, the effects of potassium fertilizer in two biogenic nanoparticles (K-NPs) and conventional (potassium sulfate) forms (0.1 mg/ml) on Melissa officinalis L. under salinity (0, 50, 100, and 150 mM) were investigated. The results demonstrated that stress markers (electrolyte leakage, malondialdehyde, and hydrogen peroxide) increased as salinity levels increased. Plant growth parameters (shoot and root length, fresh and dry weight of shoot and root) and physiological and photosynthetic parameters (stomatal conductance, relative water content, chlorophyll fluorescence, and photosynthetic pigments) were reduced in salinized plants. The highest reduction in fresh weight root, dry weight root, fresh weight shoot, dry weight shoot, root length, and shoot length was recorded under 150 mM NaCl by 30.2%, 51.6%, 30.5%, 24.7%, 26.4%, and 21%, respectively. In contrast, bulk potassium sulfate and K-NPs increased these parameters. Furthermore, K-NPs improved M. officinalis tolerance to NaCl toxicity by enhancing the content of osmolytes such as proline, soluble sugars, and antioxidant enzymes, improving antioxidant contents such as phenols, tannins, anthocyanins, and flavonoids; increasing total protein; and lowering stress markers in plant tissues. Given the results of the physiological, biochemical, and phytochemical parameters obtained from this study, it can be stated that K-NPs, in comparison to the conventional form of potassium fertilizer, exhibit a greater potential to mitigate damages caused by salinity stress in M. officinalis plants.

Water Use Strategies and Shoot and Root Traits of High-Yielding Winter Wheat Cultivars under Different Water Supply Conditions

Drought is the most important factor limiting winter wheat yield in the North China Plain (NCP). Choosing high-yielding cultivars is an important measure to minimize the negative effects of drought stress. Field studies were conducted with 10 cultivars in the 2020–2022 seasons under three irrigation treatments (I0, without irrigation; I1, irrigated at jointing stage; I2, irrigated at jointing and anthesis stages) in the NCP to examine the water use strategies and root and shoot traits of high-yielding cultivars under different water supply conditions. The results showed that yield variation among cultivars was 21.2–24.6%, 23.7–25.9% and 11.6–15.3% for the I0, I1 and I2 treatments, respectively. Under water deficit conditions (I0 and I1), high-yielding cultivars reduced water use during vegetative stages and increased soil water use during reproductive stages, especially water use from deeper soil layers. Those cultivars with higher root length density (RLD) in deep soil layers exhibited higher water uptake. Each additional millimeter of water used after anthesis from the 100–200 cm soil layers increased grain yield by 23.6–29.6 kg/ha and 16.4–28.5 kg/ha under I0 and I1, respectively. This water use strategy enhanced dry matter accumulation after anthesis, decreased canopy temperature (CT) and increased relative leaf water contents (RLWC), which ultimately improved grain yield. For winter wheat grown under I2, cultivars that decreased water use after anthesis had higher water productivity (WP). Root length (RL), root weight (RW) and root:shoot ratio were each negatively correlated with grain yield, while above-ground biomass was positively correlated with grain yield. Therefore, higher dry matter accumulation and smaller root systems are two important traits of high-yielding cultivars under sufficient water supply conditions (I2) in the NCP.

Macro-Mineral Uptake, Relative Water Content, Retention Capability, and Tolerance Index of Sunn Hemp (Crotalaria juncea L.) under Salinity Stress at Early Seedling

Salt stress exerts adverse effects on yield by inhibiting or delaying seed germination and impeding seedling growth. Additionally, different salt concentrations have adverse effects on plant wet and dry weight and stem and shoot development. Crotalaria juncea L., the fastest-growing species within the Crotalaria genus, demonstrates a high degree of adaptability to both tropical and subtropical climates. To assess the tolerance of sunn hemp to salinity during the germination and early seedling stages, several indicators were determined at different (0, 50, 100, 150, 200, 250, and 300 mM) salt concentrations. Germination was conspicuously absent at salt concentrations of 250 mM and 300 mM. Notably, seedling characteristics, such as shoot length, root length, root fresh weight, seedling fresh weight, retention capability of the shoot, and the relative water content, experienced adverse effects with escalating salt concentrations. Intriguingly, the apex of seedling and root dry weights manifested at the pinnacle of salt concentration at 200 mM. Despite the discernible influence of heightened salt concentrations during the nascent seedling stage, the tolerance index was quantified at 100 mM, 150 mM, and 200 mM. Analyzing the study results through the lens of macro-minerals revealed an augmentation in Na and Cl content concomitant with increasing salt concentrations.

Effects of Na2CO3 simulated alkali stress on tradeoff strategies of individual and clonal traits of Leymus chinensis​​​​​​​

Alkali stress is a significant challenge across the globe which is posing serious threat to crop production and food security. This study was carried out to study the effect of different levels of alkali stress on growth and physiological traits of Leymus chinensis. The study was comprised of different levels of alkali stress; control (CK; 0 mmol·L-1), 25 and 50 mmol·L-1. The results showed that imposition of 50 mmol·L-1 alkali stress substantially reduced the photosynthetic capacity, relative water contents and accumulation of carbon (C), nitrogen (N) and phosphorus (P) in plant parts. Further, 50 mmol·L-1 alkali stress also reduced the above and below ground biomass, and severely inhibited the root growth. Moreover, increase in concentration of alkali stress inhibited clone components, tillering, tillering bud, and internode bud of Leymus chinensis. In conclusion the increasing concentration of alkali stress can reduce the growth and biomass production and nutrient accumulation of Leymus chinensis.

Partial root-zone drying combined with nitrogen treatments mitigates drought responses in rice

Drought is a major stress affecting rice yields. Combining partial root-zone drying (PRD) and different nitrogen fertilizers reduces the damage caused by water stress in rice. However, the underlying molecular mechanisms remain unclear. In this study, we combined treatments with PRD and ammonia:nitrate nitrogen at 0:100 (PRD0:100) and 50:50 (PRD50:50) ratios or PEG and nitrate nitrogen at 0:100 (PEG0:100) ratios in rice. Physiological, transcriptomic, and metabolomic analyses were performed on rice leaves to identify key genes involved in water stress tolerance under different nitrogen forms and PRD pretreatments. Our results indicated that, in contrast to PRD0:100, PRD50:50 elevated the superoxide dismutase activity in leaves to accelerate the scavenging of ROS accumulated by osmotic stress, attenuated the degree of membrane lipid peroxidation, stabilized photosynthesis, and elevated the relative water content of leaves to alleviate the drought-induced osmotic stress. Moreover, the alleviation ability was better under PRD50:50 treatment than under PRD0:100. Integrated transcriptome and metabolome analyses of PRD0:100 vs PRD50:50 revealed that the differences in PRD involvement in water stress tolerance under different nitrogen pretreatments were mainly in photosynthesis, oxidative stress, nitrogen metabolism process, phytohormone signaling, and biosynthesis of other secondary metabolites. Some key genes may play an important role in these pathways, including OsGRX4, OsNDPK2, OsGS1;1, OsNR1.2, OsSUS7, and YGL8. Thus, the osmotic stress tolerance mediated by PRD and nitrogen cotreatment is influenced by different nitrogen forms. Our results provide new insights into osmotic stress tolerance mediated by PRD and nitrogen cotreatment, demonstrate the essential role of nitrogen morphology in PRD-induced molecular regulation, and identify genes that contribute to further improving stress tolerance in rice.

Effect of Irrigation Cuttings at Different Growth Stages and Spraying with Citrullus Colocynthis Extract on the Leaf Water Balance of two Cultivars of Zea Mays L.

A study in the real world with a Randomised Complete Block Design (R.C.B.D.) utilising a split-split diagrams layout with three separate replicates was carried out at the research facility of the college's water resources and soil sciences department at the Agriculture faculty / University of Diyala in the autumn season 2022. The experiment included three stages of cutting off irrigation: male flowering, milky stage, and three concentration levels of Citrullus Colocoynthis extract. Two cultivars of Zea mays L. were used: AGN720 and JAMESON. The concentration levels were 50 ml L-1 and 100 ml L-1, respectively, and two cultivars were used: AGN720 and JAMESON Citrullus Colocoynthis extract has an anti-transpiration effect on the water balance of leaves and water use efficacy of Zea mays L. grown under water stress conditions. The most important results are as follows: the AGN720 variety recorded the best water use efficiency, with an increase of 9.04% compared to the JAMESON variety. Spraying the extract of Citrullus Colocoynthis as anti-transpiration at a concentrate level of 100 ml L-1 increased the capability of water retention, relative water content, and water use efficiency. The irrigation cut-off treatment in the milky phase stage had the best water use efficiency, saving 2.559 kg of grain m-3 water compared to the no-cut irrigation treatment.

Determination of Morpho-Physiological Traits for Assessing Drought Tolerance in Sugarcane

Drought is a significant constraint to sugarcane productivity. Therefore, understanding how different varieties of sugarcane respond to drought stress can facilitate breeding programs and set up criteria for selecting drought-tolerant varieties. In the present study, we examined eight morpho-physiological traits to distinguish 40 sugarcane genotypes categorized into four groups based on significant differences in cane yield under non-stressed conditions and reduction of cane yield under drought-stressed conditions. The study was conducted during the formative stage in a greenhouse, encompassing both control and drought conditions. Drought treatments resulted in significant changes and differences in the mean values of various morpho-physiological traits. The hierarchical clustering analysis, utilizing stay-green traits such as higher chlorophyll fluorescence ratio (Fv/Fm), leaf chlorophyll content (SPAD), leaf relative water content (RWC), and lower leaf rolling score (LR), leaf drying score (LD), and drought recovery score (DR), successfully grouped 40 sugarcane genotypes into four major clusters, similar to the previously categorized groups. Correlation analysis showed significant relationships among cane yield, reduction of cane yield under drought conditions, and the stay-green traits. Our results demonstrated that morpho-physiological traits contributing to the “stay-green” phenotypes could be useful as selection criteria for drought tolerance in sugarcane.

Growth, Physiological, and Biochemical Responses of a Medicinal Plant Launaea sarmentosa to Salinity

Launaea sarmentosa is a valuable medicinal plant with adaptability in saline areas, but it is still unclear how it responds to salinity. For the first time, the present study examined the plant’s changes under different soil salinities generated by 50, 100, 200, and 400 mM NaCl in order to elucidate its responses in terms of growth, photosynthesis, water uptake, osmotic adjustment, ion homeostasis, and oxidative stress defense to salinity. The results showed that the plant’s growth was enhanced by 50 mM NaCl with an 18.07% increase in dry biomass compared to the control, whereas higher salinity levels reduced its growth with a 6.39–54.85% decrease in dry biomass. The plant’s growth response indicates that it had tolerance to salinity levels up to 400 mM NaCl. The accumulation of photosynthetic pigments, including chlorophylls (a + b) and carotenoids, was enhanced under salinity, except for a reduced accumulation under 400 mM NaCl. Relative water content decreased while proline content increased in the salt-stressed plants. Moreover, the salt-stressed plants reduced their K+ and NO3− content along with increases in Na+ and Cl− content. The high salt stress level also caused oxidative stress in the plants, which was revealed through the accumulation of malondialdehyde and hydrogen peroxide content. In addition, the salt-stressed plants had increased total phenolic content and the activities of antioxidant enzymes such as catalase, peroxidase, and superoxide dismutase. These physiological and biochemical changes suggest that L. sarmentosa evolved adaptive mechanisms in photosynthesis, osmotic adjustment, ion homeostasis, and antioxidant defense for growing under salt stress.

Aquaporin ZmTIP2;3 Promotes Drought Resistance of Maize through Symbiosis with Arbuscular Mycorrhizal Fungi

Arbuscular mycorrhizal fungi symbiosis plays important roles in enhancing plant tolerance to biotic and abiotic stresses. Aquaporins have also been linked to improved drought tolerance in plants and the regulation of water transport. However, the mechanisms that underlie this association remain to be further explored. In this study, we found that arbuscular mycorrhiza fungi symbiosis could induce the gene expression of the aquaporin ZmTIP2;3 in maize roots. Moreover, compared with the wild-type plants, the maize zmtip2;3 mutant also showed a lower total biomass, colonization rate, relative water content, and POD and SOD activities after arbuscular mycorrhiza fungi symbiosis under drought stress. qRT-PCR assays revealed reduced expression levels of stress genes including LEA3, P5CS4, and NECD1 in the maize zmtip2;3 mutant. Taken together, these data suggest that ZmTIP2;3 plays an important role in promoting maize tolerance to drought stress during arbuscular mycorrhiza fungi symbiosis.

GhMAPK3, a mitogen-activated protein kinase, enhance salt and drought tolerance in cotton (Gossypium hirsutum)

Multiple abiotic stresses, such as drought and high salinity, seriously limit cotton production. However, the mitogen-activated protein kinases (MAPKs) could play a critical role in responding to multiple environmental abiotic stresses. In this study, one of the MAPKs in cotton, GhMAPK3 (GH_D03G1517), was cloned and its role in drought and salt stress tolerance was investigated. The qRT-PCR assays demonstrated that GhMAPK3 predominantly expressed in leaf and root parts and showed higher expression under salt and drought stress. Subcellular localization assays revealed that GhMAPK3 was distributed in the nucleus and cytoplasm. The silenced of GhMAPK3 could decrease the tolerance of cotton plants under salt and drought stress via virus-induced gene silencing (VIGS) experiments. In GhMAPK3-slienced plants, the expression of stress-responsive genes has been revealed to be down-regulated levels, while the oxidants and antioxidant enzymes showed relatively higher levels and relatively lower levels, respectively. We further acquired three GhMAPK3 overexpression Arabidopsis lines, and they showed higher drought and salt tolerance than the wild-type (WT) plants, the chlorophyll content and relative leaf water content were found to be relatively stable through GhMAPK3 overexpressed plants under the abiotic stress. Further investigation revealed that GhMAPK3 showed a higher germination rate and longer root length under salt and drought stress. Overall, our findings revealed that the GhMAPK3 gene plays a prominent role in drought and salt tolerance and offers knowledge on crop genetic improvements.

Does jasmonic acid mitigate the adverse effects of salt stress on wheat through the enhancement of ascorbate biosynthesis and the induction of glutamate dehydrogenase activity?

AbstractBackgroundSalt stress is one of the most common abiotic stresses, reducing plant growth and productivity. Thus, the development of suitable management practices to minimize the deleterious effects of salt stress has become necessary.AimsThis study was conducted to investigate the possible mechanisms underlying salt tolerance conferred by jasmonic acid (JA).MethodsSalt‐stressed wheat seedlings were supplemented with 1 mM JA and/or 1 mM ibuprofen (IBU), an inhibitor of endogenous JA biosynthesis, in the culture medium.ResultsThe obtained results showed that salt stress significantly decreased shoot and root dry weight production and relative water contents. This was associated with a noteworthy reduction in leaf and root ascorbate (AsA) concentrations, as well as glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) activities. Exogenously supplied JA did not affect GS and GOGAT activities in leaves and roots of salt‐treated seedlings. However, noticeable enhancements were observed in growth, AsA concentrations, as well as GDH activities. Likewise, the inhibition of JA biosynthesis by IBU application was accompanied by a significant decrease in seedlings’ growth associated with a noticeable reduction in AsA concentrations and GDH activities. The decreases in growth and GDH activities were also obtained following inhibition of AsA biosynthesis by lycorine (Lyc) application. By contrast, increased GDH activities and enhanced growth were obtained following exogenous AsA supplementation, with or without JA biosynthesis inhibition.ConclusionsThe findings implied that exogenous JA enhanced AsA biosynthesis and induced GDH activity, which further promoted the growth of wheat seedlings in salt‐stressed conditions. Therefore, the stimulation of AsA biosynthesis and GDH activity through JA application in the rhizosphere may be suggested as a vital strategy for strengthening the salt tolerance of wheat plants, at least at the seedling stage.

Chitosan from Mushroom Improves Drought Stress Tolerance in Tomatoes.

Chitosan is a derivative of chitin that is one of the most abundant biopolymers in nature, found in crustacean shells as well as in fungi cell walls. Most of the commercially available chitosans are produced from the exoskeletons of crustaceans. The extraction process involves harsh chemicals, has limited potential due to the seasonal and limited supply and could cause allergic reactions. However, chitosan has been shown to alleviate the negative effect of environmental stressors in plants, but there is sparse evidence of how chitosan source affects this bioactivity. The aim of this study was to investigate the ability of chitosan from mushroom in comparison to crustacean chitosan in enhancing drought stress tolerance in tomato plants (cv. MicroTom). Chitosan treatment was applied through foliar application and plants were exposed to two 14-day drought stress periods at vegetative and fruit set growth stages. Phenotypic (e.g., fruit number and weight), physiological (RWC) and biochemical-stress-related markers (osmolytes, photosynthetic pigments and malondialdehyde) were analyzed at different time points during the crop growth cycle. Our hypothesis was that this drought stress model will negatively impact tomato plants while the foliar application of chitosan extracted from either crustacean or mushroom will alleviate this effect. Our findings indicate that drought stress markedly decreased the leaf relative water content (RWC) and chlorophyll content, increased lipid peroxidation, and significantly reduced the average fruit number. Chitosan application, regardless of the source, improved these parameters and enhanced plant tolerance to drought stress. It provides a comparative study of the biostimulant activity of chitosan from diverse sources and suggests that chitosan sourced from fungi could serve as a more sustainable and environmentally friendly alternative to the current chitosan from crustaceans.

Maize ZmLAZ1-3 gene negatively regulates drought tolerance in transgenic Arabidopsis

BackgroundMolecular mechanisms in response to drought stress are important for the genetic improvement of maize. In our previous study, nine ZmLAZ1 members were identified in the maize genome, but the function of ZmLAZ1 was largely unknown.ResultsThe ZmLAZ1-3 gene was cloned from B73, and its drought-tolerant function was elucidated by expression analysis in transgenic Arabidopsis. The expression of ZmLAZ1-3 was upregulated by drought stress in different maize inbred lines. The driving activity of the ZmLAZ1-3 promoter was induced by drought stress and related to the abiotic stress-responsive elements such as MYB, MBS, and MYC. The results of subcellular localization indicated that the ZmLAZ1-3 protein localized on the plasma membrane and chloroplast. The ectopic expression of the ZmLAZ1-3 gene in Arabidopsis significantly reduced germination ratio and root length, decreased biomass, and relative water content, but increased relative electrical conductivity and malondialdehyde content under drought stress. Moreover, transcriptomics analysis showed that the differentially expressed genes between the transgenic lines and wild-type were mainly associated with response to abiotic stress and biotic stimulus, and related to pathways of hormone signal transduction, phenylpropanoid biosynthesis, mitogen-activated protein kinase signaling, and plant-pathogen interaction.ConclusionThe study suggests that the ZmLAZ1-3 gene is a negative regulator in regulating drought tolerance and can be used to improve maize drought tolerance via its silencing or knockout.

Deficit Irrigation with Silicon Application as Strategy to Increase Yield, Photosynthesis and Water Productivity in Lettuce Crops.

In regions where water is a limited resource, lettuce production can be challenging. To address this, water management strategies like deficit irrigation are used to improve water-use efficiency in agriculture. Associating this strategy with silicon (Si) application could help maintain adequate levels of agricultural production even with limited water availability. Two lettuce crop cycles were conducted in a completely randomized design, with a factorial scheme (2 × 3), with three irrigation levels (60%, 80% and 100%) of crop evapotranspiration (ETc), and with and without Si application. To explore their combined effects, morphological, productive, physiological and nutritional parameters were evaluated in the crops. The results showed that deficit irrigation and Si application had a positive interaction: lettuce yield of the treatment with 80% ETc + Si was statistically similar to 100% ETc without Si in the first cycle, and the treatment with 60% ETc + Si was similar to 100% ETc without Si in the second cycle. Photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate and total chlorophyll content increased under water-stress conditions with Si application; in the first cycle, the treatment with 80% ETc + Si increased by 30.1%, 31.3%, 7.8%, 28.46% and 50.3% compared to the same treatment without Si, respectively. Si application in conditions of water deficit was also beneficial to obtain a cooler canopy temperature and leaves with higher relative water content. In conclusion, we found that Si applications attenuate water deficit effects and provide a strategy to ameliorate the yield and water productivity in lettuce crops, contributing to more sustainable practices in agriculture.

Variation of Phenology of Flacourtia rukam in Two Different Habitats and Their Relation to Rainfall, Dry Days, and the Plant Water Status

Phenological shifts in the emergence of vegetative and generative parts, occur due to the response of plants to water received due to climate change. The rukam tree (Flacourtia rukam (Zoll & Moritzi)) is a local Indonesian plant with potential as an edible fruit and antioxidant agent, but its existence is increasingly rare. F. rukam can be found in Pasuruan, East Java, including Purwodadi Botanical Garden (PBG) as collected plants and Sekarmojo Village as cultivated plants. These populations show a shift in phenology, but this has never been studied. This study aimed to analyze the spatial variation of the phenology of two rukam populations and its relation to plant water status, rainfall quantity (RQ), and drought days (DD). This research was conducted on two individual trees at each location, was conducted from August 2020 to October 2022 using secondary data from BMKG, such as daily rainfall and the number of days without rain. Phenology was directly observed every week with an estimated abundance of numbers 1-4; plant water status was observed by calculating relative water content (RWC); soil physical analysis was carried out in mid-season. Data were analyzed by Mann-Whitney test and SEM WarpPLS. The results showed differences in phenology in the phases of leaf fall, flower buds, young fruit, and ripe fruit on the trees in the different locations. The decreased RQ in the past month significantly reduced the RWC value of F. rukam in both places, while the number of DD contributed to a decrease in the RWC value in PBG only, not in Sekarmojo. In both sites, decreasing the RWC of the rukam increased the abundance of fallen leaves and the chances of flowering. Rainfall and drought days affected plant phenology directly or indirectly through RWC mediation. In both places, RQ had a direct positive and significant effect on blooming flowers and new leaves but had negative effect on fallen leaves. While DD had a positive effect on leaf fall, flower formation, and fruit ripening, but had a negative effect on the appearance of young fruit (in PBG). Indirectly, RQ mainly affected several phenological parameters, while DD did not affect all phenological parameters.

Evaluation of Frost Tolerance in Sugar Beet Cultivars During Early Growth Stages

AbstractLate spring frost is the most hazardous abiotic stress affecting the survival of sugar beet seedlings. Therefore, it is very important to identify frost-tolerant cultivars during the early seedling development stage. In the study, the physiological and morphological responses of ten sugar beet cultivars (Ernestina, Isabella, Orthega, Serenada, Kuno, Taurus, Tuna, Mohican, Rodeo, and Smılodon) to frost stress at different growth stages (V1.1, V2.1, and V3.1) were evaluated. Seedlings were exposed to − 3 °C for 2 h at all stages. Percent damage (%), leaf chlorophyll content (SPAD), leaf surface temperature (°C), electrolyte leakage (%), leaf relative water content (%), and turgidity loss (%) were examined. The results showed that higher damage percentages were observed in earlier growth stages of sugar beet, with recorded values of 29.7% in V1.1, 15.4% in V2.1, and 3.6% in V3.1. A great genotypic variation was observed among the cultivars; electrolyte leakage increased from 15.6% in control to 52.6% in frost stress, and higher electrolyte leakage was obtained from frost-stressed plants. The relative water content of leaves increased only at stage V2.1, although frost decreased turgor loss. Sugar beet showed sensitivity to frost in earlier seedling growth stages, but their tolerance levels increased in later growth stages. The study revealed that electrolyte leakage is a reliable indicator for identifying sugar beet cultivars that exhibit tolerance to frost stress during early development.