Drought Stress Treatment Research Articles

Melatonin induces drought tolerance by modulating lipoxygenase expression, redox homeostasis and photosynthetic efficiency in Arachis hypogaea L.

Melatonin (N-acetyl-5-hydroxy tryptamine), a multipotent biomolecule is well known for its ability to confer tolerance to several abiotic and biotic stresses. The regulation of melatonin-mediated drought tolerance in drought-distinguished varieties can be different due to discriminating redox levels. The present study was focused on assessing the effects of melatonin priming against polyethylene glycol (PEG)-induced stress with respect to the antioxidant system, photosynthetic parameters, lipoxygenase expression, JA and ABA levels in drought-sensitive (Kadiri-7) and drought-tolerant (Kadiri-9) varieties. Exogenous melatonin alleviated the drought stress effects in sensitive variety (Kadiri-7) by increasing the endogenous melatonin content with an improved antioxidant system and photosynthetic attributes. The primed stressed plants of the sensitive variety exhibited reduced expression and activity of the chlorophyll degrading enzymes (Chl-deg PRX, pheophytinase and chlorophyllase) with a concomitant increase in chlorophyll content in comparison to unprimed controls. Interestingly, melatonin priming stimulated higher expression and activity of lipoxygenase (LOX) as well as enhanced the expression of genes involved in the synthesis of jasmonic acid (JA) including its content in drought stressed plants of the sensitive variety. The expression of NCED3 (involved in ABA-biosynthesis) was upregulated while CYP707A2 (ABA-degradation) was downregulated which corresponded with higher ABA levels. Contrastingly, priming caused a decrease in endogenous melatonin content under drought stress in tolerant variety (Kadiri-9) which might be due to feedback inhibition of its synthesis to maintain intracellular redox balance and regulate better plant metabolism. Furthermore, the higher endogenous melatonin content along with improved antioxidant system, photosynthetic efficiency and LOX expression associated with the increased levels of JA and ABA in unprimed stressed plants of the tolerant variety (Kadiri-9) is pointing towards the effectiveness of melatonin in mediating drought stress tolerance. Overall, exogenous melatonin alleviated the adverse effects of drought stress in sensitive variety while having no add-on effect on drought stress responses of tolerant variety which is inherently equipped to withstand the given duration of drought stress treatment.

Morphological and physiologic response of black rice M5 gamma ray irradiation to drought stress

Drought stress is one of the factors that affect plant growth, both in terms of morphology and physiology. Bantul M4 local black rice produces crops that have high proline content and low production. This study aims to examine the response to morphology, physiology and selection of M5 black rice irradiated by gamma rays which are tolerant to drought stress. This research was conducted in the Taman Keceh screen house, Wonogiri Regency at an altitude of 141 masl from June to September 2021. This study used a non-replicated experimental design with drought stress treatment using 50% and 100% water gravimetry. Observation of morphological characters by measuring plant height, number of productive tillers, and flowering age. Observation of physiological characters by measuring stomatal conductance, and transpiration. The results showed that the morphological response decreased plant height, increased the number of productive tillers, and accelerated flowering time. Physiological response to narrow stomatal conductance, transpiration.

Morphological and biochemical responses of selectedOcimumspecies under drought

SummaryIntroduction:Drought stress is known to change biochemical activities resulting in altered plant growth and development.Objective:Due to the shortage of research evidence in a certain taxa of basil, it is imperative to examine the relationship between drought stress and morphological changes as well as essential oil accumulation.Methods:An open field experiment was conducted in 2020 to determine the effects of drought stress on the morphological and biochemical responses of selectedOcimumspecies. Five basil species, namelyO. basilicum‘Genovese’,O. basilicum‘Ohre’,O. × africanum,O. americanum,O. selloi, andO. sanctum‘Krishna’ were grown under irrigated (control) and non-irrigated (drought stress treatment) plots with two block replications.Results:The result showed that irrigation had a positive effect on production. Consequently, fresh and dry biomass yields were higher on irrigated plots by 39% and 33%, respectively. No significant changes were detected between the treatments in essential oils (EO) yield and EO composition of major compounds. However, a slight increase in camphor (O. × africanum), nerol (O. americanum), and trans-β-caryophyllene (O. sanctum‘Krishna’) ratios were observed under irrigation treatments. On the other hand, drought stress increased EO content, polyphenol content, and antioxidant capacity. Furthermore, drought stress had a positive effect on the ratios of 1,8-cineole (O. × africanum), and eugenol (O. sanctum‘Krishna’). There is only a slight increase in EO content under drought stress, which is not comparable to the significant yield reduction recorded. Morphological and biochemical variations were also detected among basil species. Accordingly, higher biomass (616.33 g/plant) and EO yield (3.72 ml/100 g) among the species were obtained fromO. basilicum‘Genovese’ andO. × africanum, respectively.Conclusion:Irrigation is imperative for maximizing biomass and EO yield of tested basil species.

Physiological Responses and Identification of Drought- Responsive miRNAs in Oil Palm Seedlings under Drought Stress ConditionsResilient Forests

Global climatic change poses a considerable risk to Malaysia’s booming oil palm industry as theinflorescence initiation and differentiation in oil palms are affected by drought stress. As a result, theproportion of female flowers significantly decreases, leading to reduced fruit bunch productivity. Hence, itis crucial for plantation companies to understand the physiological response of different oil palm genotypesto drought stress in ensuring that suitable genotypes are selected for stable yield production. Therefore, thisstudy aimed to understand the physiological and biochemical responses of oil palm seedlings under droughtstress conditions and to identify drought-responsive miRNAs in different oil palm progenies. Drought stresstreatment was imposed on 3-month-old seedlings consisting of two oil palm genotypes, Deli dura x pisifera(BC21) and URT-Calabar (EB8), by withholding irrigation for 20 days. Physiological measurements suchas fluorescence parameter (Fv/Fm) and stomatal conductance (gs) were then carried out weekly. Biochemicalassays were also performed to measure the chlorophyll content and proline concentration. Finally, advancedmolecular techniques were conducted to identify drought-responsive miRNA from drought stress samples.Based on the results, the decreased soil volumetric water content (vwc) resulted in a reduced plant growthrate with low biomass in drought stress BC21T (37%) and EB8T (31%). In addition, the increased prolinecontent in both genotypes by 3.9-fold for BC21T and 1.8-fold for EB8T confirmed the stress condition intreated seedlings. Furthermore, significant differences in gs and Fv/Fm were recorded earlier in BC21 (6days, 14 days) compared to EB8 (14 days, 20 days). The earlier gs reduction indicated that BC21 was moresensitive to drought stress than EB8. Meanwhile, bioinformatics analysis of small RNA sequencing readsidentified 151 conserved miRNAs in both genotypes, with 58 out of 77 identified as novel miRNAs weredifferentially expressed. Apart from that, nine miRNAs were identified as responsive to drought treatmentin both genotypes and played an essential role in various biological processes. Overall, this study providesvaluable insights into exploring oil palm physiological responses to drought and miRNA expressionpatterns, which may facilitate future research on developing drought tolerant markers.

Drought stress alters iron accumulation in Sorghum bicolor seeds

Sorghum ( Sorghum bicolor L.) is a cultivated food crop with iron-rich seeds that thrives in semi-arid areas. Although the mechanism of iron transport has been investigated in detail at the molecular level, the effects of drought stress on its regulation remain unclear. We cultivated sorghum in a chamber without (control) and with drought stress to determine iron accumulation in seeds. The drought stress treatment significantly increased the iron content by approximately 2-fold in seeds and decreased it by 0.6-fold in leaves. The results of RNA-sequencing leaves indicated that drought stress impaired the expression of genes involved in photosynthesis. This agreed with the finding that drought stress significantly reduced plant biomass. The expression of genes encoding vacuole iron transporter and ferritin were increased under drought stress. These expression profiles were confirmed by quantitative polymerase chain reaction, which indicated that expression of genes encoding the vacuole iron transporter and ferritin was significantly increased in leaves and seeds under drought stress. Furthermore, photosynthesis impaired by drought stress might trigger a disturbance in iron homeostasis. Therefore, increased vacuolar transporters and ferritin transcription might be important for safely storing excess iron. Our data suggested that maintaining iron homeostasis via vacuole iron transporters and ferritin enhances iron accumulation in seeds under drought stress. • Sorghum bicolor is drought stress-tolerant and has iron-enriched seeds • Drought stress enhanced iron accumulation in seeds • Drought stress affected genes associated with iron transport/homeostasis • Drought stress increased vacuole iron transporter and ferritin gene expression • Iron homeostasis might involve iron accumulation in drought-stressed seeds

PENGARUH CEKAMAN KEKERINGAN TERHADAP PERTUMBUHAN DAN HASIL DUA VARIETAS KEDELAI (Glycine max (L.) Merril) PADA TANAH ULTISOL

This study aims to determine the interaction between drought stress and varieties on the growth and yield of two soybean varieties. This study used a randomized block design (RBD) in a factorial pattern consisting of (two) factors, namely: The first factor two soybean varieties with the notation (V) consisting of two types, namely: Anjasmoro variety (V1) and Detap-1 variety (V2). second factor is level of drought stress with the notation (K) consisting of three levels: control water supply 100% field capacity (K0), 25% field capacity (K1), 50% field capacity (K2) and 75% field capacity (K3). Each treatment was repeated three times so there were 72 experimental units. The observed variables were plant height, total leaf area, stem diameter, number pods, number filled pods, number root nodules, number effective root nodules, not effective, dry weight of plants, dry weight seeds and harvest index. The results of this study indicate the varietal treatment had no significant effect on all observed variables except for the variable plant height, number of leaves and total leaf area, the drought stress treatment had significant effect all observed variables except for the variable number leaves and harvest index. The best growth was obtained in the Detap-1 variety treatment and the drought stress treatment, namely control or water supply of 100% field capacity.

Transcriptomics Analysis Reveals a More Refined Regulation Mechanism of Methylation in a Drought-Tolerant Variety of Potato.

Whether DNA methylation modification affects the gene transcription and expression of potatoes under drought stress is still unknown. In this study, we used comparative transcriptomics to explore the expression pattern of related genes of the drought-tolerant variety Qingshu 9 (Q) and the drought-sensitive variety Atlantic (A) under drought stress and DNA methylation inhibitor treatment. The results showed that there was a significant difference in the number of DEGs between the two varieties' responses to mannitol and 5-azad C, especially when they were co-treated with two reagents, and the gene expression of Q was more sensitive to mannitol after two hours. Furthermore, we found that these differentially expressed genes (DEGs) were significantly enriched in DNA replication, transcription, translation, carbohydrate metabolism, photosynthesis, signal transduction, and glutathione metabolism. These results indicate that the difference in the background of methylation leads to the difference in drought resistance of the two varieties. The complexity of the DNA methylation of variety Q might be higher than that of variety A, and the method of methylation regulation is more refined. This study systematically expands the understanding of the molecular mechanism wherein DNA methylation regulates the response to drought stress.

Overexpression of CpADC from Chinese Cherry (Cerasus pseudocerasus Lindl. ‘Manaohong’) Promotes the Ability of Response to Drought in Arabidopsis thaliana

Polyamines (PA) play an important role in the growth, development and stress resistance of plants, and arginine decarboxylase (ADC) is one of the key enzymes in the biosynthetic pathway of polyamines. Previously, the transcriptional regulation of the 'Manaohong' cherry under the shelter covering was carried out, and the PA synthase-related genes, particularly the ADC gene, were differentially expressed as exposure to drought stress. However, the mechanisms of how ADC is involved in the response of cherry to abiotic stress (especially drought stress) are still unknown. In the present work, the full-length coding sequence of this gene was isolated and named CpADC. Bioinformatics analysis indicated that the coding sequence of CpADC was 2529 bp in length. Cluster analysis showed that CpADC had the highest homologies with those of sweet cherry (Prunus avium, XP_021806331) and peach (Prunus persica, XP_007200307). Subcellular localization detected that the CpADC was localized in the plant nucleus. The qPCR quantification showed that CpADC was differentially expressed in roots, stems, leaves, flower buds, flowers, and fruits at different periods. Drought stress treatments were applied to both wild-type (WT) and transgenic Arabidopsis lines, and relevant physiological indicators were measured, and the results showed that the putrescine content of transgenic Arabidopsis was higher than that of WT under high-temperature treatment. The results showed that the MDA content of WT was consistently higher than that of transgenic plants and that the degree of stress in WT was more severe than in transgenic Arabidopsis, indicating that transgenic CpADC was able to enhance the stress resistance of the plants. Both the transgenic and WT plants had significantly higher levels of proline in their leaves after the stress treatment than before, but the WT plant had lower levels of proline than that of transgenic Arabidopsis in both cases. This shows that the accumulation of proline in the transgenic plants was higher than that in the wild type under drought and high and low-temperature stress, suggesting that the transgenic plants are more stress tolerant than the WT. Taken together, our results reveal that, under drought stress, the increase in both expressions of CpADC gene and Put (putrescine) accumulation regulates the activity of ADC, the content of MDA and Pro to enhance the drought resistance of Arabidopsis thaliana.

Identification and Functional Analysis of bZIP Genes in Cotton Response to Drought Stress

The basic leucine zipper (bZIP) transcription factors, which harbor a conserved bZIP domain composed of two regions, a DNA-binding basic region and a Leu Zipper region, operate as important switches of transcription networks in eukaryotes. However, this gene family has not been systematically characterized in cotton (Gossypium hirsutum). Here, we identified 197 bZIP family members in cotton. The chromosome distribution pattern indicates that the GhbZIP genes have undergone 53 genome-wide segmental and 7 tandem duplication events which contribute to the expansion of the cotton bZIP family. Phylogenetic analysis showed that cotton GhbZIP proteins cluster into 13 subfamilies, and homologous protein pairs showed similar characteristics. Inspection of the DNA-binding basic region and leucine repeat heptads within the bZIP domains indicated different DNA-binding site specificities as well as dimerization properties among different groups. Comprehensive expression analysis indicated the most highly and differentially expressed genes in root and leaf that might play significant roles in cotton response to drought stress. GhABF3D was identified as a highly and differentially expressed bZIP family gene in cotton leaf and root under drought stress treatments that likely controls drought stress responses in cotton. These data provide useful information for further functional analysis of the GhbZIP gene family and its potential application in crop improvement.

Analysis of Rac/Rop Small GTPase Family Expression in Santalum album L. and Their Potential Roles in Drought Stress and Hormone Treatments.

Plant-specific Rac/Rop small GTPases, also known as Rop, belong to the Rho subfamily. Rac proteins can be divided into two types according to their C-terminal motifs: Type I Rac proteins have a typical CaaL motif at the C-terminal, whereas type II Rac proteins lack this motif but retain a cysteine-containing element for membrane anchoring. The Rac gene family participates in diverse signal transduction events, cytoskeleton morphogenesis, reactive oxygen species (ROS) production and hormone responses in plants as molecular switches. S. album is a popular semiparasitic plant that absorbs nutrients from the host plant through the haustoria to meet its own growth and development needs. Because the whole plant has a high use value, due to the high production value of its perfume oils, it is known as the "tree of gold". Based on the full-length transcriptome data of S. album, nine Rac gene members were named SaRac1-9, and we analyzed their physicochemical properties. Evolutionary analysis showed that SaRac1-7, AtRac1-6, AtRac9 and AtRac11 and OsRac5, OsRacB and OsRacD belong to the typical plant type I Rac/Rop protein, while SaRac8-9, AtRac7, AtRac8, AtRac10 and OsRac1-4 belong to the type II Rac/ROP protein. Tissue-specific expression analysis showed that nine genes were expressed in roots, stems, leaves and haustoria, and SaRac7/8/9 expression in stems, haustoria and roots was significantly higher than that in leaves. The expression levels of SaRac1, SaRac4 and SaRac6 in stems were very low, and the expression levels of SaRac2 and SaRac5 in roots and SaRac2/3/7 in haustoria were very high, which indicated that these genes were closely related to the formation of S. album haustoria. To further analyze the function of SaRac, nine Rac genes in sandalwood were subjected to drought stress and hormone treatments. These results establish a preliminary foundation for the regulation of growth and development in S. album by SaRac.

Adaptabilities of Water Production Function Models for Rice in Cold and Black Soil Region of China

Crop water production function models (WPFMs) are required methods to study the relationships between yield and water consumption under regulated deficit irrigation (RDI). In this study, a pot experiment was established to study the effect of water deficit during both individual growth stages and across two consecutive growth stages of rice on yield, water consumption, and water use efficiency (WUE) in 2017 and 2018. Light, medium, and severe water deficits were set as 80~90%, 70~80%, and 60~70% of saturated soil moisture content, respectively. The accuracies of five WPFMs were tested based on the experimental results. The results showed that yields and WUE of a light water deficit were higher than those of medium and severe water deficits at each growth stage. The yields and WUE of light drought stress treatments in the flowering and milky stages were higher than the saturated soil moisture control by 4~7.4% and 5.3~20.6%, respectively. Water consumption decreased with increasing water deficit across two consecutive growth stages. The Minhas model had the highest simulation accuracy of the five WPFMs, with relatively lower AE, RMSE, Cv, CRM, and higher R2, which were 0.0002, 0.0634, 6.9965, 0.0002, and 0.9951 in 2017 and 0.0110, 0.0760, 8.9882, 0.0131, and 0.9923 in 2018, respectively. The sensitivity indices for the Minhas model more accurately reflected the sensitivity of rice yield to water deficit at different growth stages in 2017 and 2018, compared with the Jensen model, Stewart model, Blank model, and Singh model. Rice yield was most sensitive to water deficit at the jointing and booting stage. The results indicate that the Minhas model is the most suitable WPFM for guiding rice irrigation practices in cold and black soil regions of China.

PIN1 regulates epidermal cells development under drought and salt stress using single-cell analysis.

Over the course of evolution, plants have developed plasticity to acclimate to environmental stresses such as drought and salt stress. These plant adaptation measures involve the activation of cascades of molecular networks involved in stress perception, signal transduction and the expression of stress related genes. Here, we investigated the role of the plasma membrane-localized transporter of auxin PINFORMED1 (PIN1) in the regulation of pavement cells (PCs) and guard cells (GCs) development under drought and salt stress conditions. The results showed that drought and salt stress treatment affected the development of PCs and GCs. Further analysis identified the different regulation mechanisms of PIN1 in regulating the developmental patterns of PCs and GCs under drought and salt stress conditions. Drought and salt stress also regulated the expression dynamics of PIN1 in pif1/3/4/5 quadruple mutants. Collectively, we revealed that PIN1 plays a crucial role in regulating plant epidermal cells development under drought and salt stress conditions, thus contributing to developmental rebustness and plasticity.

Transcriptome Profiling of Stem-Differentiating Xylem in Response to Abiotic Stresses Based on Hybrid Sequencing in Cunninghamia lanceolata.

Cunninghamia lanceolata (C. lanceolata) belongs to Gymnospermae, which are fast-growing and have desirable wood properties. However, C. lanceolata's stress resistance is little understood. To unravel the physiological and molecular regulation mechanisms under environmental stresses in the typical gymnosperm species of C. lanceolata, three-year-old plants were exposed to simulated drought stress (polyethylene glycol 8000), salicylic acid, and cold treatment at 4 °C for 8 h, 32 h, and 56 h, respectively. Regarding the physiological traits, we observed a decreased protein content and increased peroxidase upon salicylic acid and polyethylene glycol treatment. Superoxide dismutase activity either decreased or increased at first and then returned to normal under the stresses. Regarding the molecular regulation, we used both nanopore direct RNA sequencing and short-read sequencing to reveal a total of 5646 differentially expressed genes in response to different stresses, of which most had functions in lignin catabolism, pectin catabolism, and xylan metabolism, indicating that the development of stem-differentiating xylem was affected upon stress treatment. Finally, we identified a total of 51 AP2/ERF, 29 NAC, and 37 WRKY transcript factors in C. lanceolata. The expression of most of the NAC TFs increased under cold stress, and the expression of most of the WRKY TFs increased under cold and SA stress. These results revealed the transcriptomics responses in C. lanceolata to short-term stresses under this study's experimental conditions and provide preliminary clues about stem-differentiating xylem changes associated with different stresses.

Essential oil composition, physiological and morphological variation in Salvia abrotanoides and S. yangii under drought stress and chitosan treatments

Several Salvia species are among the most valuable aromatic herbs used for industrial and pharmaceutical applications. Hence, under greenhouse trial conditions, the effects of chitosan treatment (0, 100, and 200 mg L−1) and water deficiency stress on the morphological, physiological, and biochemical features of two Salvia species were examined. Significant changes were seen in chlorophyll a, root volume, dry and fresh weight, and H2O2 concentration as a result of drought stress. Significant influence of chitosan was found for all studied parameters except root length and malondialdehyde (MDA) content. Hydrogen peroxide (H2O2), proline, and MDA were elevated, while photosynthetic pigments decreased under drought stress. The highest essential oil (EO) content (2.20% d.b.) was recorded under moderate stress condition in the absence of chitosan treatment. Using chitosan topically, it is possible to offset the impact of water scarcity on EO content decline and enhance EO compositions. The compensatory effects of chitosan application under stress conditions were observed on the abundance of EO constituents, such as 1,8-cineol, camphor, bornyl acetate, α-bisabolol, α-cadinol, and α-humulene. Moreover, present results suggested that chitosan application can alleviate the drought damage in studied Salvia species.

The interaction between drought stress and nodule formation under multiple environments in chickpea.

Environmental stresses, particularly drought, limit symbiotic nitrogen fixation in legumes, resulting in decreased yielding capacity. Drought is one of the most important constraints limiting yield potential in crops and it is the major abiotic stress that can cause more than 70% yield loss in chickpea. In this study, a total of two hundred four chickpea (Cicer arietinum L.) genotypes were selected to study the interaction between drought stress and nodule formation. This interaction was assessed by using morphological, yield and yield components. The field experiments were laid out in two locations (Terbol and Kfardan stations, Bekaa valley, Lebanon) using Alpha lattice design with two replications and two watering treatments (irrigation and rainfed) during 2016 and 2017 seasons. Parameters that were measured include days to 50% flowering (DFL), day to maturity (DM), plant height (PLH), nodule biomass (NB), nodule fresh weight (NFW), nodule dry weight (NDW), grain yield (GY), Biological yield (BY), 100 seed weight (100SW) and drought tolerance stress (DTS). The results indicated a significant variation between genotypes, environments and other morphological, yield and yield components traits. Drought stress reduced significantly the yield and the nodule’s characteristics, biological and grain yield. The genotypes with the highest levels of drought tolerance, such as IG70399, IG8256, IG71832, IG70270, and IG70272, showed a minimal decrease in yield and nodule biomass. Nodule observations significantly and positively correlated with GY (0.36-0.38) under drought stress treatment. The correlation values for nodule characteristics with DFL and DM were higher under drought stress compared to irrigated conditions. This is a comparative study between drought stress and nodule formation traits associated with morphological, yield and yield components traits.

Neglecting acclimation of photosynthesis under drought can cause significant errors in predicting leaf photosynthesis in wheat.

Extreme climatic events, such as heat waves, cold snaps and drought spells, related to global climate change, have become more frequent and intense in recent years. Acclimation of plant physiological processes to changes in environmental conditions is a key component of plant adaptation to climate change. We assessed the temperature response of leaf photosynthetic parameters in wheat grown under contrasting water regimes and growth temperatures (Tgrowth ). Two independent experiments were conducted under controlled conditions. In Experiment 1, two wheat genotypes were subjected to well-watered or drought-stressed treatments; in Experiment 2, the two water regimes combined with high, medium and low Tgrowth were imposed on one genotype. Parameters of a biochemical C3 -photosynthesis model were estimated at six leaf temperatures for each factor combination. Photosynthesis acclimated more to drought than to Tgrowth . Drought affected photosynthesis by lowering its optimum temperature (Topt ) and the values at Topt of light-saturated net photosynthesis, stomatal conductance, mesophyll conductance, the maximum rate of electron transport (Jmax ) and the maximum rate of carboxylation by Rubisco (Vcmax ). Topt for Vcmax was up to 40°C under well-watered conditions but 24-34°C under drought. The decrease in photosynthesis under drought varied among Tgrowth but was similar between genotypes. The temperature response of photosynthetic quantum yield under drought was partly attributed to photorespiration but more to alternative electron transport. All these changes in biochemical parameters could not be fully explained by the changed leaf nitrogen content. Further model analysis showed that both diffusional and biochemical parameters of photosynthesis and their thermal sensitivity acclimate little to Tgrowth , but acclimate considerably to drought and the combination of drought and Tgrowth . The commonly used modelling approaches, which typically consider the response of diffusional parameters, but ignore acclimation responses of biochemical parameters to drought and Tgrowth , strongly overestimate leaf photosynthesis under variable temperature and drought.

Effects of drought and salt stress on seed germination of ephemeral plants in desert of northwest China

Seed germination is the most sensitive stage of plant life history. Studying its response to drought and salinity can analysis the response and adaptation characteristics of desert plants to the environment. In this experiment, the seeds of four common desert ephemeral plants in Xinjiang (Ixiolirion tataricum, Nepeta micrantha, Lepidium apetalum, and Plantago minuta) were used as materials. To study the germination characteristics of seeds under drought, we used salt stress, and coupled salt-drought stress under treatments and explored the germination recovery ability of rehydrated seeds after salt and drought stress treatments. The results showed that: (1) Under salt stress, the germination ability of four plant seeds was inhibited in different degrees. Overall, the degree of inhibition was proportional to the concentration of NaCl solution. (2) Drought stress slowed the seed germination process, and the greater the degree of stress, the more pronounced the slowdown; PEG treatment showed no significant effect on the germination of the four seeds at low concentrations and significant inhibition at medium and high concentrations. (3) The coupled salt-drought treatment significantly alleviated the stress effect of one factor and improved the germination characteristics of seeds. (4) Seeds that did not germinate under different concentrations of salt stress, drought stress, and coupled stresses rapidly recover germination when the stress was relieved or lifted. Ephemeral plants are sensitive to environmental changes, and this study aims to provide a reference basis for vegetation restoration and ecological rehabilitation in arid and semi-arid areas.

Leaf-transcriptome profiles of phoebe bournei provide insights into temporal drought stress responses.

Phoebe bournei (Hemsl.) Yang is used as a commercial wood in China and is enlisted as a near-threatened species. Prolonged droughts pose a serious threat to young seedlings (1-2 years old). A transcriptome sequencing approach, together with the measurement of growth parameters and biochemical analyses were used to understand P. bournei's drought responses on 15d, 30d, and 45d of drought stress treatment. The stem and root dry weights decreased significantly with drought stress duration. Activities of antioxidative enzymes i.e., peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) increased significantly with the increase in drought stress duration. A total of 13,274, 15,648, and 9,949 genes were differentially expressed in CKvs15d, CKvs30d, and CKvs45d, respectively. The differential expression analyses showed that photosystem I and II underwent structural changes, chlorophyll biosynthesis, and photosynthesis were reduced. The genes annotated as POD, SOD, and CAT were upregulated in drought-treated leaves as compared to control. Additionally, plant-hormone signal transduction, MAPK signaling-plant, phenylpropanoid biosynthesis, flavonoid biosynthesis, and starch and sucrose metabolism pathways showed large-scale expression changes in major genes. We also found that members of 25 transcription factor families were differentially expressed. Our study presents and discusses these transcriptome signatures. Overall, our findings represent key data for breeding towards drought stress tolerance in P. bournei.

Comparison of lauric acid and 12-hydroxylauric acid in the alleviation of drought stress in peach (Prunus persica (L.) Batsch).

Water shortage is a key factor that can restrict peach tree growth. Plants produce fatty acids and the fatty acid derivatives lauric acid (LA) and 12-hydroxylauric acid (LA-OH), which are involved in abiotic stress responses, but the underlying stress response mechanisms remain unclear. In this study, physiological examination revealed that in Prunus persica (L.) Batsch, pretreatment with 50 ppm LA-OH and LA reduced drought stress, efficiently maintained the leaf relative water content, and controlled the relative conductivity increase. Under drought stress, LA-OH and LA treatments prevented the degradation of photosynthetic pigments, increased the degree of leaf stomatal opening and enhanced the net photosynthetic rate. Compared with drought stress, LA-OH and LA treatment effectively increased the net photosynthetic rate by 204.55% and 115.91%, respectively, while increasing the Fv/Fm by 2.75% and 7.75%, respectively, but NPQ decreased by 7.67% and 37.54%, respectively. In addition, the level of reactive oxygen species increased under drought stress. The content of O2 - in LA-OH and LA treatment decreased by 12.91% and 11.24% compared to CK-D, respectively, and the content of H2O2 decreased by 13.73% and 19.94%, respectively. At the same time, the content of malondialdehyde (MDA) decreased by 55.56% and 58.48%, respectively. We believe that the main reason is that LA-OH and LA treatment have improved the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). The application of exogenous LA increased the levels of soluble sugars, soluble proteins, proline and free amino acids under drought stress, and maintained the osmotic balance of cells. Compared with CK-D treatment, it increased by 24.11%, 16.89%, 29.3% and 15.04%, respectively. At the same time, the application of exogenous LA-OH also obtained similar results. In conclusion, exogenous LA-OH and LA can alleviate the damage to peach seedlings caused by drought stress by enhancing the photosynthetic and antioxidant capacities, increasing the activities of protective enzymes and regulating the contents of osmotic regulators, but the molecular mechanism is still in need of further exploration.

Effect of drought stress and inoculation treatments on nutrient uptake, essential oil and expression of genes related to monoterpenes in sage (Salvia officinalis)

To investigate the effect of inoculation of Piriformospora indica (P. indica) and Pseudomonas fluorescens (P. fluorescens) on some morphological and physiological traits, nutrient concentration, essential oil (EO) and gene expression in Salvia officinalis under drought stress (100, 70 and 40% Field Capacity (FC)) we designed a factorial experiment in a completely randomized design with three replications. The results showed that by increasing drought stress intensity, percentage of root colonization by P. indica, growth parameters, relative water content, chlorophyll index, essential oil yield, and nutrient concentration decreased. The highest and lowest values of dry herb yield (33.94 and 11.62 g pot−1), RWC (80.20 and 51.60 %), chlorophyll concentration (38.46 and 30.47), essential oil yield (0.22 and 0.20 ml pot−1) and P concentration (0.40 and 0.26 %) were observed in P. indica inoculated plants under well-watered conditions and non-inoculated plants in severe drought stress (40% FC), respectively. The Sabinene synthase (ss) gene expression rate enhanced notably under drought stress and the highest expression rate was obtained in the 40% FC in plants inoculated with P. fluorescens. In contrast, the expression of geranyl diphosphate synthase (gpps) and bornyl diphosphate synthase (bpps) decreased under drought stress. The highest amount of predominant compounds of essential oil including α-Thujone, 1,8-Cineole (36.48 and 13.26%) and Camphor (18.94%) were observed in bacterial inoculation treatment under drought level of 40% FC and non-inoculated plants in well-watered condition, respectively.