Different Levels Of Drought Stress Research Articles

Critical thresholds for nonlinear responses of ecosystem water use efficiency to drought

Climate change is expected to lead to greater variability in precipitation and drought in different regions. However, the responses of ecosystem carbon and water cycles (i.e., water use efficiency, WUE) to different levels of drought stress are not fully understood. Here, we examined the relationship between WUE and precipitation anomalies and identified the critical drought threshold (DrCW) above which WUE showed substantial decrease. The results revealed that 85.56 % of the study area had nonlinear WUE responses to drought stress; that is, the WUE decreased sustainably and steeply when the precipitation deficit exceeded the DrCW. DrCW indicates inflection points for changing ecosystem responses from relatively resistant to vulnerable to drought stress, thus providing an instructive early warning for intensifying suppressive impacts on vegetation growth. Additionally, DrCW varies across aridity gradients and among vegetation types. Based on the DrCW at the pixel level, the future eco-drought is projected to increase in >67 % of the study area under both the SSP2&RCP4.5 and SSP5&RCP8.5 scenarios by the end of the 21st century. Our study elucidates the response of the ecosystem function to drought and supports the development of accurate ecosystem adaptation policies for future drought stress.

Categorization of Sugar Beet Varieties for Water Saving in Sandy Soils Using Factor Analysis Scores

AbstractWater shortage in dry and semi-arid regions is a major agricultural challenge. This study investigated the performance of ten imported monogerm sugar beet varieties under continuous deficiency irrigation using a drip system on a private farm in the Wadi El-Natrun region, El-Beheira Governorate, Egypt, during two growing seasons, 2021/2022 and 2022/2023. The study utilized a novel method, a crossbar graph, to effectively visualize statistical data. The results showed significant interaction effects between sugar beet varieties and water deficit levels for all traits, indicating varying responses of the varieties to different levels of drought stress (75% and 55%). Drought stress levels (75% and 55%) had an adverse effect on the root yield of the ten varieties of sugar beet that were investigated. The exploratory factor analysis was applied to investigate and describe the relationship between ten different varieties of sugar beet and water stress treatments. Varieties Symbol, Stikhiyn, Volua, and Klara were characterized as moderate and tolerant with high performance, and they received the highest score in factor analysis. These varieties are recommended for cultivation under moderate and severe stress conditions. Factor analysis scores can be used as selection criteria for sugar beet varieties.

Effect of drought stress on natural rubber biosynthesis and quality in Taraxacum kok-saghyz roots.

Taraxacum kok-saghyz (TKS) is a potential source of natural rubber (NR) that can be grown in temperate regions with limited water availability. However, the effect of drought stress on NR production and properties in TKS isn't well studied. This study examined how different levels of drought stress (30, 60 and 90%) influenced the NR content, molecular weight (Mw), glass transition temperature (Tg), gene expression, and biochemical parameters in TKS roots. The results showed that drought stress didn't significantly change the NR content, but increased the Mw and the expression of CPT and SRPP genes, which are involved in NR biosynthesis. The NR from TKS roots (TNR) had a high Mw of 994,000 g/mol and a low Tg of below -60°C under normal irrigation, indicating its suitability for industrial applications. Drought stress also triggered the accumulation of proline, H2O2, MDA, and antioxidant enzymes (CAT, APX, GPX) in TKS roots significantly, indicating a drought tolerance mechanism. These findings suggest that TKS can produce high-quality NR under drought stress conditions and provide a sustainable alternative to conventional NR sources.

Metabolite-mediated adaptation of crops to drought and the acquisition of tolerance.

Drought is one of the major and growing threats to agriculture productivity and food security. Metabolites are involved in the regulation of plant responses to various environmental stresses, including drought stress. The complex drought tolerance can be ascribed to several simple metabolic traits. These traits could then be used for detecting the genetic architecture of drought tolerance. Plant metabolomes show dynamic differences when drought occurs during different developmental stages or upon different levels of drought stress. Here, we reviewed the major and most recent findings regarding the metabolite-mediated plant drought response. Recent progress in the development of drought-tolerant agents is also discussed. We provide an updated schematic overview of metabolome-driven solutions for increasing crop drought tolerance and thereby addressing an impending agricultural challenge.

Genome wide association study of Ethiopian barley for terminal drought stress tolerance under field and climate chamber conditions

AbstractIn order to detect markers for drought stress tolerance, field experiments in Ethiopia were conducted for three years at two naturally drought-prone locations and two optimum moisture locations using 239 Ethiopian barley landraces and 21 barley breeding lines. Furthermore, a climate chamber experiment applying drought stress at different water regimes (70% soil water capacity (WC) for control and 20% WC for drought stress conditions) after flowering was conducted for selected 196 accessions. Results revealed reduced grain biomass by 47% and 80% under field and climate chamber conditions, respectively, as well as significantly (p < 0.05) reduced days to maturity and plant height, in both experimental designs. Based on 10,644 SNP markers, GWAS was conducted to identify marker trait associations (MTA) for drought stress tolerance. For days to maturity, relative chlorophyll content, plant height, number of seeds per spike, thousand kernel weight, and harvest index under field and climate chamber drought stress treatments, 58 significant MTAs were identified. In total, 41.4% of the MTAs were located on chromosome 2H, of which one is very close to the Ppd-H1 flowering locus. These findings underpin the importance of this genome region for drought tolerance. Another MTA on chromosome 1H was detected for days to maturity under field drought stress treatment in the vicinity of the known flowering time ELF3 gene. Additionally, 13 and 3 Ethiopian landraces that tolerate severe and moderate drought stress in climate chamber and field experiments were identified, respectively, using drought indices. The results highlight the tolerance of Ethiopian landraces to different levels of drought stress as well as their potential to be considered in future barley improvement programs.

Screening some pine species from North America and dried zones of western Asia for drought stress tolerance in terms of nutrients status, biochemical and physiological characteristics

Drought due to climate change or reduced precipitation is one of the main factors limiting the growth and establishment of plants and is one of the most critical challenges facing humans. To investigate the effect of different levels of drought stress on some pine species, this research was carried out as a factorial experiment using two factors and a completely randomized design. It included five populations of four pine species (Pinus brutia Ten. var. eldarica, P. nigra Arnold, P. mugo, and P. banksiana Lamb (including populations 8310055 and 8960049), and three levels of irrigation (100%, 75%, or 50% FC, denoted as normal, mild or intense drought stress, respectively) with three replicates. The findings showed that, photosynthetic pigments, relative water content, visual quality, the content of nutrients, protein content, and fresh and dry weight all decreased significantly when plants were exposed to intense drought stress. However, raised proline levels, electrolyte leakage percentage, soluble sugars levels, and antioxidant enzyme activity. We detected a decline in most growth traits when comparing mild drought stress conditions to normal irrigation, yet acceptable quality seedlings when compared to intense drought stress. Intense drought stress had a substantial impact on many pine seedlings. PCA results showed that among different pine species, the level of resistance to drought is as follows: P. mugo> P. brutia var. eldarica> P. nigra> P. banksiana 8310055> P. banksiana 8960049. Our novel finding was that, P. mugo is a resistant species in arid and semi-arid regions, and P. banksiana species, especially its population of 8960049, is sensitive.

Exploitation of various physio-morphological and biochemical traits for the identification of drought tolerant genotypes in cotton

BackgroundDrought is one of the limiting factors for quality and quantity of cotton lint in tropical and sub-tropical regions. Therefore, development of drought tolerant cotton genotypes have become indispensable. The identification of drought tolerant genotypes is pre-requisite to develop high yielding cultivars suitable for drought affected areas.MethodsForty upland cotton accessions were selected on the basis of their adaptability and yield. The collected germplasm accessions were evaluated at seedling stage on the basis of morphological, physiological and biochemical parameters. The experiment was conducted under controlled conditions in greenhouse where these genotypes were sown under different levels of drought stress by following factorial under completely randomized design. The data were collected at seedling stages for root and shoot lengths, relative leaf water content, excised leaf water losses, peroxidase content and hydrogen peroxide concentrations in leaf tissues.ResultsThe biometrical analysis revealed that germplasm is significantly varied for recorded parameters, likewise interaction of genotypes and water stress was also significantly varied. The cotton germplasm was categorized in eight clusters based on response to water stress. The genotype Cyto-124 exhibited lowest H2O2 content under drought conditions, minimum excised leaf water loss under stress environment was exhibited by genotypes Ali Akber-802 and CEMB-33. Overall, on the basis of morphological and biochemical traits, SL-516 and Cyto-305 were found to be drought tolerant. Genotypes 1852 − 511, Stoneville 15–17 and Delta Pine-55 showed low values for root length, peroxidase activity and higher value for H2O2 contents. On the basis of these finding, these genotypes were declared as drought susceptible. ConclusionThe categorization of cotton germplasm indicating the differential response of various parameters under the control and drought stress conditions. The recorded parameters particularly relative leaf water contents and biochemical assays could be utilized to screen large number of germplasm of cotton for water deficit conditions. Besides, the drought tolerant genotypes identified in this research can be utilized in cotton breeding programs for the development of improved cultivars.

Adaptation of rhizosphere bacterial communities of drought-resistant sugarcane varieties under different degrees of drought stress.

Sugarcane is highly sensitive to changes in moisture, and increased drought severely restricts its growth and productivity. Recent studies have shown that plant growth-promoting microorganisms are essential to reduce the adverse effects of environmental stresses, especially drought. However, our knowledge about the dynamics of rhizosphere microbial community structure in sugarcane under varying degrees of drought stress is limited. We analyzed the effects of different degrees of drought stress on the rhizosphere microbial communities of Zhongzhe 1(ZZ1) and Zhongzhe 6(ZZ6) with differences in drought resistance, by combining soil enzyme activity, nutrient content, and physiological and morphological characteristics of sugarcane roots. The results showed that rhizosphere bacterial community began to change at a field capacity of 50%, enriching the sugarcane rhizosphere with drought-resistant bacteria. The core strains of ZZ1 and ZZ6 rhizosphere enrichment were mainly Streptomycetales, Sphingomonadales, and Rhizobiales. However, compared to ZZ1, the changes in rhizosphere bacterial abundance in ZZ6 were primarily associated with the abundance of Streptomycetales as drought levels increased. Rhizobiales and Streptomycetales, enriched in the rhizosphere of ZZ6 under drought, were positively correlated with root tip number and total root length (TRL), increasing the distribution area of roots and, thus, improving water and nutrient uptake by the roots thereby enhancing the resistance of sugarcane to drought stress. This research enhances our understanding of the composition of the rhizosphere microbial community in sugarcane under different levels of drought stress and its interaction with the roots, thereby providing valuable insights for enhancing drought resistance in sugarcane. IMPORTANCE Drought stress is expected to further increase in intensity, frequency, and duration, causing substantial losses in sugarcane yields. Here, we exposed sugarcane to varying degrees of drought treatment during growth and quantified the eventual composition of the resulting sugarcane rhizosphere bacterial community groups. We found that sugarcane rhizosphere under mild drought began to recruit specific bacterial communities to resist drought stress and used the interactions of root tip number, total root length, and drought-resistant strains to improve sugarcane survival under drought. This research provides a theoretical basis for the rhizosphere microbiome to help sugarcane improve its resistance under different levels of drought stress.

Multi-omics reveals the sugarcane rhizosphere soil metabolism-microbiota interactions affected by drought stress

Drought is considered one of the most damaging stresses affecting crop productivity. Although rhizosphere bacterial communities contribute to improved crop resistance, little is known about the dynamics of these communities in sugarcane under various drought conditions. The rhizosphere bacterial community structure results from a series of complex interactions and feedback between plant roots, bacteria, and the soil physicochemical environment. Therefore, in the current study, we assessed the impact of root phenomes, soil metabolites, soil nutrients, and other multi-omics factors on rhizosphere bacterial community structure under different levels of drought stress. The results showed that different degrees of drought stress may strongly affect bacterial community structure and function by affecting rhizosphere soil metabolite composition. Specifically, sugarcane under mild drought may improve soil nutrient availability and provide an abundant carbon source for bacteria through diversifying rhizosphere soil metabolites (maybe via root exudation). In addition, rhizosphere bacteria may also produce derived metabolites to cross-feed other rhizosphere bacteria to stabilize the bacterial community under mild drought. When drought stress intensifies, the hosts recruit specific bacterial populations to resist drought stress by releasing metabolites and reducing community diversity through this recruitment. In particular, we found that Streptomyces had the greatest contribution to the stress-related microbiota recruited by sugarcane under high drought stress levels. This may be an important target for sugarcane drought-resistance microbiome engineering. This study provides a novel theoretical foundation for improving the stress resistance of sugarcane under different drought stress levels by optimizing the bacterial community.

Unearth of small open reading frames (sORFs) in drought stress transcriptome of Oryza sativa subsp. indica

Drought is a major abiotic stress that influences rice production. Although the transcriptomic data of rice against drought is widely available, the regulation of small open reading frames (sORFs) in response to drought stress in rice is yet to be investigated. Different levels of drought stress have different regulatory mechanisms in plants. In this study, drought stress was imposed on four-leaf stage rice, divided into two treatments, 40% and 30% soil moisture content (SMC). The RNAs of the samples were extracted, followed by the RNA sequencing analysis on their sORF expression changes under 40%_SMC and 30%_SMC, and lastly, the expression was validated through NanoString. A total of 122 and 143 sORFs were differentially expressed (DE) in 40%_SMC and 30%_SMC, respectively. In 40%_SMC, 69 sORFs out of 696 (9%) DEGs were found to be upregulated. On the other hand, 69 sORFs out of 449 DEGs (11%) were significantly downregulated. The trend seemed to be higher in 30%_SMC, where 112 (12%) sORFs were found to be upregulated from 928 significantly upregulated DEGs. However, only 8% (31 sORFs out of 385 DEGs) sORFs were downregulated in 30%_SMC. Among the identified sORFs, 110 sORFs with high similarity to rice proteome in the PsORF database were detected in 40%_SMC, while 126 were detected in 30%_SMC. The Gene Ontology (GO) enrichment analysis of DE sORFs revealed their involvement in defense-related biological processes, such as defense response, response to biotic stimulus, and cellular homeostasis, whereas enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways indicated that DE sORFs were associated with tryptophan and phenylalanine metabolisms. Several DE sORFs were identified, including the top five sORFs (OsisORF_3394, OsisORF_0050, OsisORF_3007, OsisORF_6407, and OsisORF_7805), which have yet to be characterised. Since these sORFs were responsive to drought stress, they might hold significant potential as targets for future climate-resilient rice development.

Spermine mitigates the adverse effects of water deficit by strengthening antioxidant enzymes and anthocyanin pathway-related gene expressions

Water deficit is regarded as one of the worst causes of low agricultural productivity. It disrupts morphophysiological and biochemical processes in plants. In the current research, spermine effectively induced defense responses to abiotic stresses. The foliar spray with spermine ameliorated the adverse impacts of water deficit on zinnia plants (Zinnia elegans L.). The aim of this study was to investigate the effects of foliar spraying of spermine on growth characteristics, enzyme antioxidants activity, gas exchange and genes expression related to the anthocyanin biosynthesis pathway (ABP) of zinnia plants grown under water-deficit treatments. The evaluations involved measuring growth characteristics (i.e. height, flower biomass, total plant biomass, fresh and dry plant weight, flower diameter, and vase life), photosynthesis and gas exchange (stomata conductivity, intracellular CO2, transpiration), water use efficiency (WUE), lipid peroxidation (MDA), enzymatic activity (POD and APX) and genes expression related to ABP (CHS, CHI, F3H, F3'H, ANS, 3GT, DFR and AT2). Spermine mitigated the adverse impacts of severe water-deficit on the growth characteristics, flower longevity, and WUE. Our results showed that spermine boosted antioxidant enzymes activity and reduced lipid peroxidation of zinnia under severe and moderate water-deficit. Real-time PCR analysis of genes related to ABP revealed that the early (CHI, CHS and F3H) and late (ANS and 3GT) biosynthetic genes were promptly induced by both water deficit and spermine treatments. We showed that DFR and AT2 genes were induced by different levels of drought stress, while the F3'H gene was expressed only by the exogenous application of spermine. Spermine decreased the MDA content and enhanced the water-deficit tolerance of zinnia plants by maintaining morphological integrity, gaseous exchange, chlorophyll index, WUE, APX, and POD enzyme activities, as well as gene expressions related to ABP. Spermine (3 mM) can be applied as a foliar treatment to alleviate the adverse impacts of water-deficit in zinnia plants.

Evaluation of yield and water use efficiency of quinoa under irrigation regimes, gamma aminobutyric acid, and vermicompost application

The current study was aim to evaluate the interaction effects of gamma aminobutyric acid (GABA) and vermicompost on yield and yield components of quinoa under different levels of drought stress. For this, two experiments were similarly designed as the factorial-split with four replicates for evaluating this hypothesis. Irrigation regimes (50, 75, and 100 % of plant water requirement (PWR)) as the main plot and vermicompost V (0, 5 t ha-1) × gamma aminobutyric acid GABA levels (0, 5, 10 mg l-1) as the subplot were designed. Severe drought stress had a significant effect on plant height. Plant height reduced 31.8 % after using 50 % of PWR compared to the control conditions. Although drought stress negatively affected the 1000 seed mass and seed yield, GABA foliar application alleviated these effects. After using 50 % of PWR, 10 mg l-1 of GABA increased the seed yield and harvest index up to 21.22 and 15.5 %, respectively, compared to the non-foliar application. The reduction in PWR from 100 to 50 % led to increasing in P and K concentrations, as well as sugar and proline contents. In the same conditions, the use of GABA or V had a significant effect on improving these traits. A similar trend was also recorded in relation to water use efficiency. Therefore, using 10 mg l-1 of GABA and 5 t ha-1 of V can be effective in alleviating water stress.

Probabilistic assessment of drought stress vulnerability in grasslands of Xinjiang, China.

In the process of climate warming, drought has increased the vulnerability of ecosystems. Due to the extreme sensitivity of grasslands to drought, grassland drought stress vulnerability assessment has become a current issue to be addressed. First, correlation analysis was used to determine the characteristics of the normalized precipitation evapotranspiration index (SPEI) response of the grassland normalized difference vegetation index (NDVI) to multiscale drought stress (SPEI-1 ~ SPEI-24) in the study area. Then, the response of grassland vegetation to drought stress at different growth periods was modeled using conjugate function analysis. Conditional probabilities were used to explore the probability of NDVI decline to the lower percentile in grasslands under different levels of drought stress (moderate, severe and extreme drought) and to further analyze the differences in drought vulnerability across climate zones and grassland types. Finally, the main influencing factors of drought stress in grassland at different periods were identified. The results of the study showed that the spatial pattern of drought response time of grassland in Xinjiang had obvious seasonality, with an increasing trend from January to March and November to December in the nongrowing season and a decreasing trend from June to October in the growing season. August was the most vulnerable period for grassland drought stress, with the highest probability of grassland loss. When the grasslands experience a certain degree of loss, they develop strategies to mitigate the effects of drought stress, thereby decreasing the probability of falling into the lower percentile. Among them, the highest probability of drought vulnerability was found in semiarid grasslands, as well as in plains grasslands and alpine subalpine grasslands. In addition, the primary drivers of April and August were temperature, whereas for September, the most significant influencing factor was evapotranspiration. The results of the study will not only deepen our understanding of the dynamics of drought stress in grasslands under climate change but also provide a scientific basis for the management of grassland ecosystems in response to drought and the allocation of water in the future.

Chitosan-based Schiff base-metal (Fe, Cu, and Zn) complexes mitigate the negative consequences of drought stress on pomegranate fruits

Drought is one of the major environmental stresses that impairs fruit productivity and quality. The proper management of minerals can, however, assist plant to maintain their growth even under drought incidents, and is considered one of the encouraging approaches to refine the drought tolerance of plants. The beneficial effects of chitosan (CH)-based Schiff base-metal complexes (e.g., CH–Fe, CH–Cu and CH–Zn) in reducing the harmful impacts of different levels of drought stress on the growth and productivity of ‘Malase Saveh’ pomegranate cultivar were examined. All CH-metal complexes displayed favorable effects on the yield- and growth-related attributes of pomegranate trees cultivated under well-watered and different drought situations, with the best effects were observed with CH–Fe application. Specifically, leaves of CH–Fe-treated pomegranate plants showed higher concentrations of photosynthetic pigments [chlorophyll a (Chl a), Chl b, Chl a+b, and carotenoids by 28.0, 29.5, 28.6 and 85.7%, respectively] and microelements (Fe by 27.3%), along with increased levels of superoxide dismutase (by 35.3%) and ascorbate peroxidase (by 56.0%) enzymatic activities relative to those of CH–Fe-non-treated pomegranate plants under intense drought stress. CH–Fe-treated drought-stressed pomegranate leaves showed high increment of abscisic acid (by 25.1%) and indole-3-acetic acid (by 40.5%) relative to CH–Fe-non-treated pomegranates. The increased contents of total phenolics, ascorbic acid, total anthocyanins, and titratable acidity (by 24.3, 25.8, 9.3 and 30.9%, respectively) in the fruits of CH–Fe-treated drought-stressed pomegranates indicated the advantageousness of CH–Fe on the enhancement of fruit nutritional qualities. Collectively, our results prove the explicit functions of these complexes, particularly CH–Fe, in the control of drought-induced negative effects on pomegranate trees grown in semi-arid and dry areas.

Accumulation of Dehydrin Transcripts Correlates with Tolerance to Drought Stress in Sunflower

Present study was focused on the analyses of phenotypic traits (across field and laboratory trials) and transcriptional changes in cotyledons and roots of sunflower hybrids, exposed to different levels of drought stress. By comparing the level of dehydrins genes (DHNs) expression in tolerant and sensitive genotypes as response to drought and of the correlations between physiologic responses in laboratory and field screening, an efficient and easily manageable experimental test system for sunflower seedlings was established. Thus, DHNs genes (Rab18-like, Xero1 and COR47-like) differentially expressed under induced hydric stress could be used as a proceeding for estimation of plant drought survival, hence, improving the pre-screening trials in the breeding programs aimed on plant tolerance to water-deficit stresses.

Physiological and molecular responses of roots differ from those of leaves in spinach plants subjected to short-term drought stress

• Physiological and molecular responses of roots differ from those of leaves in spinach plants subjected to short-term drought stress. • Short-term drought stress triggers oxidative stress in roots but not in leaves. • Dehydrin and PLDα1 polypeptides with different molecular weights accumulate in roots and leaves. • Drought tolerance of roots and leaves might be associated with expression profiles of Dehydrin and PLDα1 polypeptides in these tissues. In this study, physiological responses as well as changes in expressions of specific proteins (dehydrin [DHN] and phospholipase Dα1 [PLDα1]) were determined in leaf and root tissues of Spinacia oleracea L.cv. Matador plants under different levels of drought stress. Spinach plants grown in the plant growth chamber were exposed to two levels of drought stress (Moderate Stress [MS]: 50% Field Capacity [FC] and Severe Stress [SS]: 25% FC) and compared with no stress conditions (Control: 100% [FC]) for a period of 10 days. Results revealed that the roots and leaves of spinach plants responded differently to drought stress, probably due to different antioxidant activities and accumulation of specific proteins (DHN and PLDα1). Moderate or severe drought stress did not alter the oxidation parameters in leaves of S. oleracea L. cv. Matador plants while significant changes associated with oxidative stress were observed in roots. Dehydrin polypeptides (75 and 50 kDa for leaves and 75 kDa for roots) and PLDα1 polypeptides (22 kDa in leaves; 52 kDa and 28 kDa in roots) have been observed to accumulate following drought exposure. The accumulation of these polypeptides was associated with physiological responses of spinach plants which provide evidence for their contribution to the acclimation process in early drought stress. These data suggest that tissues of spinach plant respond differently against different levels of drought stress and that the response is associated with altered expressions of DHN and PLDα1 polypeptides.

Molecular and Physiological Evaluation of Bread Wheat (Triticum aestivum L.) Genotypes for Stay Green under Drought Stress.

Water availability is considered as the main limiting factor of wheat growth illuminating the need of cultivars best adapted to drought situations for better wheat production and yield. Among these, the stay-green trait is thought to be related to the ability of wheat plants to maintain photosynthesis and CO2 assimilation, and a detailed molecular understanding of this trait may help in the selection of high-yielding, drought-tolerant wheats. The current study, therefore, evaluated the physiological responses of the selected wheat genotypes under pot-induced water stress conditions through different field capacities. The study also focused on exploring the molecular mechanisms involved in drought tolerance conferred due to the stay-green trait by studying the expression pattern of the selected PSI-associated light-harvesting complex I (LHC1) and PSII-associated LHCII gene families related to pigment-binding proteins. The results revealed that the studied traits, including relative water content, membrane stability index and chlorophyll, were variably and negatively affected, while the proline content was positively enhanced in the studied wheats under water stress treatments. Molecular diagnosis of the selected wheat genotypes using the expression profile of 06 genes, viz. TaLhca1, TaLhca2, TaLhca3, TaLhcb1, TaLhcb4 and TaLhcb6 that encodes for the LHCI and LHCII proteins, indicated variable responses to different levels of drought stress. The results obtained showed the relation between the genotypes and the severity of the drought stress condition. Among the studied genotypes, Chirya-1 and SD-28 performed well with a higher level of gene expression under drought stress conditions and may be used in genetic crosses to enrich the genetic background of common wheat against drought stress.

Physiological and biochemical assay of drought stress responses in eggplant (Solanum melongena L.) inoculated with commercial inoculant of Azotobacter chroococum and Azotobacter vinelandii

• Decreased RWC, g s values of plants under drought stress, and especially K, Ca and Mg accumulations and protein contents in the root increased significantly with rhizobacteria inoculation. • Higher levels of total phenolic compounds and proline were accumulated in inoculated plants compared to uninoculated plants. • Higher antioxidant enzymatic activities were observed in inoculated stressed plants, and MDA was reduced. • Results were found to be important in that the inoculant with Azotobacter chroococum and Azotobacter vinelandii has the potential to diminish the negative effects of drought stress in eggplant . The aim of this study is to examine the effects of commercial rhizobacteria inoculant on eggplant plants grown under drought stress conditions. Commercial inoculant containing Azotobacter chroococum and Azotobacter vinelandii rhizobacteria species was applied to eggplant plants by root inoculation and the plants were exposed to different levels of drought stress (moderate drought stress-MS and severe drought stress-SS). To determine the growth-promoting ability of inoculation with rhizobacteria, changes in plant morphology (shoot-root fresh and dry weights, shoot length and diameter) and physiology (relative water content-RWC, stomatal conductivity-g s , K, Ca, Mg and Na accumulations in shoot and root, photosynthetic pigment contents) were investigated. To determine the impacts of the inoculant on the potential of increasing the drought tolerance of eggplant, besides the enzyme activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), non-enzymatic antioxidant activities such as antochiyanin, total phenolic substance, proline were investigated. In addition, H 2 O 2 and malondialdehyde (MDA) contents were analyzed to resolve whether drought stress causes oxidative damage in eggplant. The increase in the severity of drought caused a decrease in plant growth and shoot-root fresh and dry weights. Nevertheless, these adverse effects of drought stress were alleviated by inoculation. Decreased RWC, g s values of plants under drought stress, and especially K, Ca and Mg accumulations and protein contents in the root increased significantly with inoculation. On the other hand, Chlorophyll (Chl) (Chl a , Chl b , Chl a + b ) and carotenoid contents were significantly increased in leaves under uninoculated MS and SS. Inoculation with rhizobacteria reduced the increase in photosynthetic pigment contents. Depending on the severity of stress, higher levels of total phenolic compounds and proline were accumulated in inoculated plants compared to uninoculated plants. However, higher SOD, CAT, and GR enzymatic activities were observed in inoculated stressed plants, and membrane lipid peroxidation was reduced. These results were found to be important in that the commercial bacterial inoculant has the potential to diminish the negative effects of drought stress in eggplant and supports the stress tolerance of the plant by mitigating the drought-related oxidative damage.

Effect of PEG-simulated Drought Stress on Seed Germination of Three Medicinal Liquorice (Glycyrrhiza) Species

Background: Glycyrrhiza is an important medicinal plant that has been in shortage in recent years because of high demand and exhaustive harvesting. Investigating the drought tolerance of liquorice species can inform the artificial cultivation of liquorice under different water conditions and help address the shortage. Methods: Seeds of G. uralensis, G. glabra and G. inflata were treated with different concentrations of polyethylene glycol (PEG)-6000 solutions to simulate different levels of drought stress. The germination process germination rate, germination index, vigour index, stress tolerance index and recovery germination percentage of seeds were measured. Drought tolerance was evaluated using the membership function. Result: Low concentrations of PEG promoted the seed germination of G. glabra and G. inflata, whereas high concentrations inhibited the seed germination of all three plants. The degree of inhibition increased with increasing PEG concentration. Under mild PEG stress, the drought tolerance of G. uralensis was highest and that of G. glabra was the lowest. However, under severe PEG stress, the drought tolerance of G. glabra was the highest and that of G. uralensis was the lowest. Therefore, seeds of G. uralensis should be sown in relatively moist soil and those of G. glabra in relatively arid soil.

Morpho-physiological responses of iaa9 tomato mutants to different levels of PEG simulated drought stress

Abstract. Suminar E, Budiarto R, Nuraini A, Mubarok S, Ezura H. 2022. Morpho-physiologicalresponsesof iaa9 tomato mutants to different levels of PEG simulated drought stress. Biodiversitas 23: 3115-3126.This study aimed to analyze the morphological and physiological responses of iaa9 mutants and its WT-MT to different levels of drought stress in in vitro growing medium. This study applied a completely randomized design with two factors, i.e., tomato genotypes and polyethylene glycol (PEG) - induced drought stress levels. The factor of varieties consisted of three levels, i.e., WT-MT as control (G1), iaa9-3(G2), and iaa9-5 (G3). The factor of PEG-induced drought stress also consisted of four levels, i.e., 0% PEG as control (PEG0), 5% PEG (PEG5), 10% PEG (PEG10), and 15% PEG (PEG15). The results observed 12 weeks after culture showed the variations of the morpho-physiological response of WT-MT and mutant genotypes to PEG-induced in vitro drought stress. The WT-MT showed a higher reduction in plantlet height, root number, and root length than mutants under severe drought conditions. The plantlet fresh and dry weight of iaa9-3and iaa9-5were higher than its WT-MT under no drought conditions. The total chlorophyll content of WT-MT was lower than iaa9-5due to the significant gain of chlorophyll-b on that mutant rather than its WT-MT. However, the analysis of principal components and correlation revealed the reduction of morphological size and leaf pigment content in response to drought stress, irrespective of genotype factor. These results suggest that in vitro selection techniques using PEG is useful for the initial screening of drought-tolerant tomato.