Comparative physiology of salt and water stress

Alkalinity-salinity-sustainability: Decadal groundwater trends and its impact on agricultural water quality in the Indian Peninsula

Groundwater degradation due to alkalinity and salinity threatens irrigation-dependent agriculture, particularly in the Indian Peninsula. Over-extraction, erratic monsoons, and intensive farming have worsened groundwater quality, impacting soil health and crop productivity. The study examines long-term (2002-2022) spatio-temporal variations in pH, electrical conductivity (EC), and bicarbonate (HCO₃-) datasets, integrating them with Gravity Recovery and Climate Experiment (GRACE)-derived groundwater anomalies and rainfall variability through the Standardized Precipitation-Evapotranspiration Index (SPEI) employing hierarchical clustering. It further compares these variations with irrigation indices assessing sodium (Na) hazards and water suitability to identify critical hotspots for water sustainability. From 2002 to 2022, groundwater in the Indian Peninsula has shifted towards neutral to slightly alkaline conditions, with declining alkalinity in previously high-alkaline regions (mid-Gangetic plains) and increasing salinity in arid zones. Rising EC, driven by irrigation return flows and groundwater over-extraction, alongside fluctuating HCO₃- levels, highlights the growing impact of agricultural and climatic stressors on water quality. From 2012 to 2022, groundwater levels (GWLs) declined sharply in mid-Gangetic plains due to over-extraction. The issue was further exacerbated by worsening drought conditions as revealed by SPEI. Increasing mineral undersaturation has led to rising fluoride (F-) and hardness issues, and deteriorating irrigation indices indicate worsening salinity and Na hazards. Expanding clusters of high-risk states underscore the need for targeted groundwater management strategies. Future research should explore adaptive irrigation practices and policy measures to mitigate groundwater quality decline and sustain agricultural productivity.

Genomic and Physiological Basis of Structural and Foliar Trait Variation in Tropical Species Pterocarpus officinalis: Implications for Restoration in Future Drier Climates

Tropical wetlands are some of the most threatened ecosystems in the world. Pterocarpus officinalis exists in swampy wetlands in riparian and fresh-water coastal areas across the neotropics, supporting biodiversity and storm surge and flooding protection as well as water filtration. In Puerto Rico, P. officinalis-dominated forests have been severely declining in recent decades, mainly due to land development. Reversing this trend in the face of climate change and projected sea level rise via ecological restoration may benefit from understanding phenotypic traits suitable for future climates. Currently, there are no seed sourcing guidelines for restoration, due to the understudied nature of the species. The goals of our study were to examine population structure and the genomic basis of variation in structural and physiological foliar traits. Seeds were collected from twelve seed sources spanning the natural distribution of P. officinalis in Puerto Rico. Water use efficiency related foliar traits were measured in well-watered conditions from seedlings grown in a nursery experiment. A total of 109 seedlings were whole-genome resequenced from 12 seed sources. Our results indicate strong foliar trait variation despite very little genetic differentiation among seed sources within the island, suggesting a relatively small number of genes might be involved in water-use efficiency traits. Eleven out of thirteen foliar traits varied significantly across seed sources. Trait variation was associated with either longitude, elevation, mean annual precipitation, or isothermality. Seedlings across seed sources were observed to have different strategies for managing water use. Candidate loci identified using Genome-Wide Association Studies were associated with signal transduction, transcription regulation, DNA and RNA methylation, transport, and primary and secondary metabolism. Restoration of this species is key in maintaining ecosystem services. Our study identified seed sources that may be successful in drier restoration conditions and match future arid climates.

Alleviating Plant Density and Salinity Stress in Moringa oleifera Using Arbuscular Mycorrhizal Fungi: A Review

Moringa oleifera (LAM) is a multipurpose tree species with extensive pharmacological and ethnomedicinal properties. Production of important medicinal plants is facing decline under changing climatic conditions, which brings along exacerbated abiotic stresses like salinity and intraspecific competition, particularly high planting densities. Increasing plant density is seen as a strategy to increase production; however, the intraspecific competition and a lack of arable land limit productivity. Salinity has been estimated to harm approximately six percent of the Earth's landmass. This leads to a loss of over 20% of agricultural output annually. These stressors can significantly curtail moringa's growth and yield potential. Literature designates that Arbuscular Mycorrhizal Fungi (AMF), ubiquitous soil microorganisms forming symbiotic associations with plant roots, offer a promising avenue for mitigating these stresses. This narrative review aims to investigate the utilization of AMF to alleviate the detrimental effects of salinity and high planting density on Moringa oleifera. The different adaptive strategies M. oleifera undergoes to mitigate both stressors are explored. The review found that AMF inoculation enhances plant tolerance to these stressors by improving nutrient acquisition, water relations, and activating stress response mechanisms. By facilitating improved nutrient and water absorption, AMF enhance root architecture, modulate ROS scavenging mechanisms, and promote optimal biomass allocation, ensuring better survival in high-density plantings. Furthermore, AMF-mediated stress alleviation is linked to enhanced physiological efficiency, including increased chlorophyll content, root-shoot biomass balance, and ion homeostasis. This review is important because it could provide insights into a sustainable, natural solution for improving the resilience of Moringa oleifera under adverse environmental conditions, with potential applications in global agriculture and food security. Future research should prioritize identifying and characterizing moringa-specific AMF species and evaluate the long-term efficacy, feasibility, and economic viability of AMF application in real-world moringa cultivation systems to fully harness the potential of AMF in moringa cultivation.

Cadmium contamination impairs alkaline tolerance in sugar beet by inhibiting carbon fixation and tryptophan metabolism

The contamination of cadmium (Cd) may overlap with alkali stress, exerting a synergistic effect on crop growth. This study examined the morphological and physiological responses of sugar beet seedlings irrigated with Cd solution (50 mM CdCl2) to alkali stress (400 mM NaHCO3). Under alkali stress, the presence of Cd exacerbated the reduction in plant growth, the maximum quantum yield of photosystem II (Fv/Fm), chlorophyll content, and osmoregulatory substances (proline, soluble sugars). Cd augmented the concentration of MDA, O2·-, and H2O2, while reducing the expression of BvPOX. Concurrently, glutathione content, ascorbate peroxidase (APX) activity, and the glutathione transferase gene (BvGST) expression were also inhibited by Cd. Cd constrained the ribulose-5P content under alkali stress and the expression of the glyceraldehyde-3-phosphate dehydrogenase gene (BvGAPDH), thereby inhibiting the Calvin cycle. Additionally, the expression of the alcohol dehydrogenase gene (BvADH) was reduced, leading to decreased sucrose and starch content. Cd also accelerated pectin metabolism. Furthermore, Cd inhibited the expression of key genes involved in melatonin synthesis (aromatic-L-amino-acid/L-tryptophan decarboxylase gene, BvDDC/BvTDC and acetylserotonin O-methyltransferase gene, BvASMT), resulting in restricted tryptophan metabolism. This study provides insights into the inhibition of carbon fixation and tryptophan metabolism induced by Cd, its effects on the growth of beets under alkaline stress conditions.

Saline irrigation improves survival of forage sorghum but limits growth and increases toxicity

Moderately saline water has been proposed as a potential irrigation resource for crops such as forage sorghum (Sorghum bicolor × Sorghum bicolor nothosubsp. drummondii) in drought-prone regions. However, it is not yet fully understood how salinity affects growth and potential toxicity of sorghum. Sorghum produces the cyanogenic glucoside dhurrin, which can cause hydrogen cyanide (prussic acid) poisoning in grazing animals. To address this, two glasshouse experiments were conducted. Experiment 1 assessed tolerance of sorghum to a range of salt treatments (0, 12.5, 25, 50, 100 and 150 mM NaCl). Experiment 2 assessed whether moderately saline irrigation would relieve drought stress by growing sorghum under three treatments: no watering (drought), watering with freshwater, or watering with 50 mM NaCl. All treatments lasted 7 weeks. In Experiment 1, salinities as low as 25 mM NaCl significantly reduced biomass, despite sorghum being able to exclude sodium from entering transpiring leaves at NaCl concentrations up to 50 mM. Foliar concentrations of dhurrin positively correlated with salinity and exceeded the safe threshold for cattle of ≥12.5 mM NaCl. In Experiment 2, moderately saline water effectively alleviated drought stress of sorghum, with significant reductions in growth and photosynthesis in the drought treatment compared to the 50 mM NaCl treatment. While sorghum's survival and growth may be boosted by moderately saline irrigation during droughts, its cyanogenic glucoside concentrations should be monitored to ensure safety for grazing animals.

Genome-wide identification of CA genes in cotton and the functional analysis of GhαCA4-D, GhβCA6-D and GhγCA2-D in response to drought and salt stresses

Carbonic anhydrases (CAs) are critical metalloenzymes, widely exist in organisms, which involve in many physiological processes, including response to adverse environmental conditions. Although CA genes have been comprehensive identified and analyzed in numerous plants, there are a few of reports in cotton. Therefore, we conducted an exhaustive research for CA genes from two tetraploid cotton species and their ancestral species. A total of 138 CA genes were found, and 45 of them belonged to Gossypium hirsutum. Phylogenetic relationships and sequences analysis showed that CA genes were categorized into three distinct subtypes: α-type, β-type and γ-type. The exon numbers of β-type members were highly variable. Various types of cis-elements, including drought inducibility, were identified in CA genes, suggesting that CA genes might be involved in the regulation of drought stress response. qRT-PCR was applied to assess the gene expression level in various tissues under drought stress. The results indicated that the expression levels of GhαCA4-D, GhβCA1-A, GhβCA1-D, GhβCA3-D and GhβCA6-D were significantly higher in leaves than that in stems and roots. The expression of GhαCA4-A, GhαCA8-A, GhαCA4-D, GhβCA3-D, GhβCA6-D and GhγCAL1-D was significantly upregulated in roots at severe drought treatment. The functions of GhαCA4-D, GhβCA6-D and GhγCA2-D were analyzed using virus-induced gene silencing (VIGS) technology. Compared to the controls, GhγCA2-D-silenced upland cotton seedlings were more sensitive to salt stress. However, the drought tolerance of GhαCA4-D and GhβCA6-D silenced plants was significantly decreased. Stomatal density, width and area were significantly higher in TRV:GhβCA6-D compared to TRV:00 inoculated plants. GhαCA4-D silenced plants were susceptible to oxidative stress, and silencing GhαCA4-D induced leave cell death. Our results will assist to make clear the regulatory mechanism of CA genes under abiotic stress.

Inheritance of Some Salt Tolerance-Related Traits in Bread Wheat (Triticum aestivum L.) at the Seedling Stage: A Study of Combining Ability

The worldwide rise in soil salinization is among the most critical consequences of climate change, posing a significant threat to food security. Wheat (Triticum aestivum L.), a staple crop of paramount importance worldwide, encounters significant production limitations due to abiotic stressors, particularly salinity. Consequently, the development and cultivation of salt-tolerant wheat genotypes have emerged as an essential strategy to sustain agricultural productivity and safeguard global food security. The aim of the present study was to investigate the effect of salinity (150 mM) on the performance and combining ability of 10 hybrid combinations (F2) and their parents that were obtained through a line × tester mating design at the seedling stage. Morphological, physiological, and biochemical traits were assessed under both control and salt-stress conditions. Among the assessed traits, SFW emerged as the strongest predictor of salt tolerance, demonstrating the highest correlation with MFVS and the greatest contribution in the regression model. The results highlighted distinct responses among the studied genotypes. Hybrid H5 demonstrated particular promise, surpassing the performance of the superior parent for Na+, K+, K+/Na+ and proline (Pro). Furthermore, tester T1 emerged as a good combiner for proline (Pro), total soluble sugars content (Sug), chlorophyll content (Chl) and root length (RL) under saline conditions. In contrast, under control conditions, line L1 and testers T2, T3, and T5 exhibited superior performance, demonstrating significant general combining ability (GCA) effects for four traits simultaneously. Hybrid H4 emerged as outstanding under salt stress, exhibiting favorable specific combining ability (SCA) effects for Na+, K+/Na+ ratio, root length (RL), relative water content (RWC), and total soluble sugars content (Sug). Under normal conditions, hybrids H7 and H10 exhibited significantly superior performance across three traits simultaneously. Non-additive genetic effects predominantly influenced the studied traits under both conditions. The parental and hybrid combinations show promise for incorporation into breeding programs designed to improve salt tolerance under the specific conditions studied.

Comparative physiological and co-expression network analysis reveals potential hub genes and adaptive mechanisms responsive to NaCl stress in peanut (Arachis hypogaea L.)

BACKGROUND

Salt stress has become a major threat to peanut yield and quality, and salt stress is particularly detrimental to seedling growth. Combined analysis of the physiology and transcriptomics of salt-tolerant variety (NH5) and salt-sensitive variety (FH23) under 200 mM NaCl stress was conducted to identify the key factors influencing the differences in salt tolerance and to investigate the potential regulatory mechanisms and hub genes associated with salt tolerance in peanuts.

RESULTS

Malondialdehyde (MDA) content and electrolyte leakage rate were significantly increased under prolonged NaCl stress, with the increase in FH23 being even more pronounced. NH5 maintained intracellular osmotic homeostasis by accumulating free proline and soluble protein content. In addition, NH5 exhibited higher antioxidant enzyme activity. The net photosynthetic rate (Pn) of NH5 and FH23 decreased by 64.24% and 94.49% after 96 h of stress. The intercellular CO2 concentration (Ci) of NH5 significantly decreased by 7.82%, while that of FH23 increased by 42.74%. This suggests that non-stomatal limiting factors were the primary cause of the decline in photosynthesis observed in FH23. Transcriptome analysis revealed the presence of 12,612 differentially expressed genes (DEGs) in response to salt stress, with FH23 exhibiting a greater number than NH5. The number of upregulated genes was significantly higher than that of downregulated genes at 24 h of salt stress, whereas the number of downregulated genes exceeded that of upregulated genes at 48 h. Subsequently, Weighted Gene Co-expression Network Analysis (WGCNA) was performed in conjunction with physiological data. Twenty-four hub genes of salt response were identified, which encoded delta-1-pyrroline-5-carboxylate synthase, aldehyde dehydrogenase, SNF1-related protein kinase, magnesium transporter, temperature-induced lipocalin-1, and ERF transcription factors.

CONCLUSION

A regulatory network for potential salt tolerance in peanuts has been constructed. The findings revealed distinct mechanisms of response to salt tolerance and identified candidate genes for further investigation.

Differences in growth, ionomic and antioxidative enzymes system responded to neutral and alkali salt exposure in halophyte Haloxylon ammodendron seedlings

Soil salinity and alkalinity severely suppress plant growth and crop yields. This study compared the effects of neutral and alkaline salt exposure, both individually and mixed, on metal content and morphophysiological responses in halophyte Haloxylon ammodendron. Our results showed that alkaline salt exposure more considerably inhibited the growth and photosynthesis of H. ammodendron than neutral salt exposure. Under neutral salt conditions, Na accumulated significantly, while K and Fe absorption was hindered. In contrast, under alkaline salt stress, Na accumulation was more pronounced, leading to a greater inhibition of K absorption. Additionally, Ca accumulation was promoted, while the transport of Fe, Mg, and Cu from root to shoot was suppressed. Alkaline salt stress also induced more severe osmotic stress, triggering a stronger accumulation of soluble sugars to counteract it. Furthermore, seedlings under alkaline stress showed higher levels of REL, H2O2, and MDA, but lower activities of SOD, POD, CAT, and APX, indicating increased oxidative damage. These findings suggest that H. ammodendron can adapt well to neutral salt stress through efficient antioxidant enzyme systems and osmotic stress regulation. In contrast, alkaline stress severely inhibits the absorption and transport of mineral elements and disrupts the balance of antioxidant enzymes. Besides, the deleterious effects of neutral-alkaline salt mixed stress were significantly less than those of alkaline stress alone, indicating a reciprocal enhancement between neutral and alkaline salt stress was occurred.

Dynamic molecular regulation of salt stress responses in maize (Zea mays L.) seedlings

Introduction

Maize ranks among the most essential crops globally, yet its growth and yield are significantly hindered by salt stress, posing challenges to agricultural productivity. To utilize saline-alkali soils more effectively and enrich maize germplasm resources, identifying salt-tolerant genes in maize is essential.

Methods

In this study, we used a salt-tolerant maize inbred line, SPL02, and a salt-sensitive maize inbred line, Mo17. We treated both lines with 180 mmol/L sodium chloride (NaCl) for 0 days, 3 days, 6 days, and 9 days at the three-leaf growth stage (V3). Through comprehensive morphological, physiological, and transcriptomic analyses, we assessed salt stress effects and identified hub genes and pathways associated with salt tolerance.

Results

Our analysis identified 25,383 expressed genes, with substantial differences in gene expression patterns across the salt treatment stages. We found 8,971 differentially expressed genes (DEGs)-7,111 unique to SPL02 and 4,791 unique to Mo17-indicating dynamic gene expression changes under salt stress. In SPL02, the DEGs are primarily associated with the MAPK signaling pathway, phenylpropanoid biosynthesis, and hormone signaling under salt treatment conditions. In Mo17, salt stress responses are primarily mediated through the abscisic acid-activated signaling pathway and hormone response. Additionally, our weighted gene co-expression network analysis (WGCNA) pinpointed five hub genes that likely play central roles in mediating salt tolerance. These genes are associated with functions including phosphate import ATP-binding protein, glycosyltransferase, and WRKY transcription factors.

Discussion

This study offers valuable insights into the complex regulatory networks governing the maize response to salt stress and identifies five hub genes and pathways for further investigation. These findings contribute valuable knowledge for enhancing agricultural resilience and sustainability in saline-affected environments.

Systems genomics of salinity stress response in rice

Populations can adapt to stressful environments through changes in gene expression. However, the fitness effect of gene expression in mediating stress response and adaptation remains largely unexplored. Here, we use an integrative field dataset obtained from 780 plants of Oryza sativa ssp. indica (rice) grown in a field experiment under normal or moderate salt stress conditions to examine selection and evolution of gene expression variation under salinity stress conditions. We find that salinity stress induces increased selective pressure on gene expression. Further, we show that trans-eQTLs rather than cis-eQTLs are primarily associated with rice's gene expression under salinity stress, potentially via a few master-regulators. Importantly, and contrary to the expectations, we find that cis-trans reinforcement is more common than cis-trans compensation which may be reflective of rice diversification subsequent to domestication. We further identify genetic fixation as the likely mechanism underlying this compensation/reinforcement. Additionally, we show that cis- and trans-eQTLs are under balancing and purifying selection, respectively, giving us insights into the evolutionary dynamics of gene expression variation. By examining genomic, transcriptomic, and phenotypic variation across a rice population, we gain insights into the molecular and genetic landscape underlying adaptive salinity stress responses, which is relevant for other crops and other stresses.

Effects of exogenous melatonin on the growth and photosynthetic characteristics of tomato seedlings under saline-alkali stress

Saline-alkali stress is a major abiotic stress factor that adversely affects the growth, development, and yield of crops by disrupting ion homeostasis, osmotic balance, and metabolic processes. This study was designed to explore the alleviating effect of melatonin on the growth and development of tomato plants under saline-alkali stress conditions and to screen for optimal concentrations to alleviate the stress. Tomato variety 'Condine Red' was used as the test material, and a total of six treatments were designed including no saline-alkali stress and no melatonin spray as control (CK), and foliar spraying of 0, 50, 100, 150, and 200 µmol·L- 1 melatonin under saline-alkali stress (75 mmol·L- 1), which were used to determine the growth and photosynthetic characteristics of tomato plants. The results showed that saline-alkali stress significantly inhibited plant height, stem diameter, root activity and biomass accumulation, significantly reduced the chlorophyll content of tomato leaves and the efficiency of photosynthetic electron transfer from primary quinone receptor QA to secondary quinone receptor QB, and caused significant deformation of the fast chlorophyll fluorescence induced kinetic curve (OJIP), inhibiting photosynthesis. Exogenous melatonin could improve tomato tolerance to saline-alkali stress, and the effect depended on the concentration. In this experiment, treatment with 100 µmol·L- 1 melatonin showed the strongest positive effect on the growth of tomato plants under saline-alkali stress according to the comprehensive evaluation of principal components. In addition, changes in photosynthetic chlorophyll fluorescence parameters and chlorophyll fluorescence induction curves after melatonin treatment highlighted that melatonin could improve the response of the photosynthetic system to saline-alkali stress by enhancing quenching of excess excitation energy and protecting the photosynthetic electron transport system. Collectively, exogenous melatonin pretreatment increased root activity, chlorophyll content and improved photosystem processes, thereby alleviating tomato growth under saline-alkali stress. The results of this study lay the foundation for the practical application of melatonin in saline-alkali stress.

Multi-omics analysis reveals key regulatory defense pathways in Ruppia sinensis in response to water salinity fluctuations

Seagrasses maintain cellular water balance by regulating ion concentrations and accumulating organic osmolytes, enabling them to survive in the fluctuating salinity of intertidal environments. However, the molecular mechanisms underlying seagrass responses to salinity changes remain relatively understudied. To address this, we conducted a multi-omics analysis of Ruppia sinensis under low, moderate, and high salinity conditions to uncover the mechanisms behind its adaptation to salinity fluctuations. Our research revealed that the transition from low to high salinity significantly altered the physiological characteristics of R. sinensis. Simultaneously, the species enhanced its ability to cope with and adapt to salinity fluctuations by increasing antioxidant enzyme activity. Integration of multi-omics data further indicated that under high salinity conditions, R. sinensis synthesizes more flavonoids to bolster its adaptive capacity. Additionally, the phenylpropanoid metabolic pathway appears to play a crucial role in the response of R. sinensis to changes in water salinity.

Environmental Stress and Resource Availability Affect the Maintenance of Genetic Variation in a Dominant Marsh Plant (Spartina alterniflora)

Changes in genetic variation, and particularly documented declines in genetic diversity, influence not only evolutionary potential but also current ecological function. Given this context, it is essential to understand what abiotic and biotic factors promote or disrupt the maintenance of genetic variation in natural populations. To address this knowledge gap in the context of salt marsh plants, we established a three-year field experiment, testing the independent and interactive effects of nutrient availability and physical stress on the maintenance of plant (Spartina alterniflora) genotypic diversity. We found that in environments with high physical stress (i.e., low marsh elevations), diversity declined over time. However, the addition of nutrients promoted the maintenance of Spartina genotypic diversity across the physical stress gradient. We also observed changes in genotypic composition and genetic divergence across environmental stress treatments, indicating variation among Spartina genotypes in their response to these factors. Our results suggest that tidal inundation acts a selective gradient within coastal marshes, altering genotypic diversity and composition across the landscape. Moreover, our work highlights that the effects of increasing inundation due to continued sea-level rise on the maintenance of diversity may be modulated by concomitant changes in nutrient inputs, with cascading effects on marsh structure and function.

Gene metabolite relationships revealed metabolic adaptations of rice salt tolerance

Environmental stresses, particularly salinity, pose significant challenges to global crop production, notably impacting the growth and yield of rice. Integrating gene expression and metabolomics data offers valuable insights into the molecular mechanisms driving salt tolerance in plants. This study examined the effects of high salinity on the roots and shoots of rice genotypes with contrasting tolerances: CSR28 (tolerant) and IR28 (sensitive) at the seedling stage. Our phenotypic and physiological assessments indicated significant differences in response to prolonged salinity exposure between the two genotypes. Notably, osmoprotectants, including amino acids and sugars, exhibited increased accumulation, whereas most organic acids showed a decline. Linear regression analyses established significant correlations between the levels of proline, myoinositol, catalase (CAT), and superoxide dismutase (SOD) and their respective encoding genes: OsP5CS2, OsIMP, OsNCA1a, and OsSOD-Fe. Furthermore, a relationship was identified between H2O2 content and the expression of glycolate oxidase (GLO), highlighting its role in initiating defense mechanisms under salinity stress. Our findings indicated specific metabolites and genes associated with distinct organs, genotypes, and timepoints that can serve as biomarkers for the development of new salt-tolerant rice varieties.

Arbuscular mycorrhizal fungi and salinity stress mitigation in plants

In recent decades, climate change has caused a decrease in rainfall, increasing sea levels, temperatures rising, and as a result, an expansion in salt marshes across the globe. An increase in water and soil salinity has led to a decline in the cultivated areas in different areas, and consequently, a substantial decrease in crop production. Therefore, it has forced scientists to find cheap, effective and environmentally friendly methods to minimize salinity's impact on crops. One of the best strategies is to use beneficial soil microbes, including arbuscular mycorrhizal fungi, in order to increase plant tolerance to salt. The findings of this review showed that salinity can severely impact the morphological, physiological, and biochemical structures of plants, lowering their productivity. Although plants have natural capabilities to deal with salinity, these capacities are limited depending on plant type, and variety, as well as salinity levels, and other environmental factors. Furthermore, result of the present review indicates that arbuscular mycorrhizal fungi have a significant effect on increasing plant resistance in saline soils by improving the soil structure, as well as stimulating various plant factors including photosynthesis, antioxidant defense system, secondary metabolites, absorption of water and nutrients.

Characteristics of soil water-heat-salt coupling and crop response relationships in saline soils under freezing saline water irrigation

Frozen saline water irrigation (FSWI) is a method of effectively utilizing saline water to alleviate water scarcity. However, the coupled relationships among water, heat, and salt in soil irrigated with frozen saline water and the key influencing factors of FSWI on crop growth have not been clarified. Here, we conducted two consecutive years of in situ field plot experiments that focused on the freeze-thaw period (FTP) and crop growth period (CGP). The study characterized changes in soil moisture, heat, salinity, and crop growth at different FSWI levels (0, 140, 180, and 220 mm; CK, FSWI140, FSWI180, and FSWI220, respectively). Structural equation modeling (SEM) was performed to reveal the key driving mechanisms and potential environmental factors affecting crop growth under FSWI. The results showed that the FSWI treatment significantly reduced the coefficient of variation (P < 0.05) of temperature (P < 0.05) and cumulative subzero temperature (FSWI220 best) of the deep soil (40-100 cm) during the FTP period, slowed down the accumulation of salts in the tillage soil due to the temperature change, and shortened the duration of the soil freezing and thawing cycle relative to the CK. In addition, secondary drenching during the ablation period promoted downward salt drainage from the till soil (FSWI180 best), which significantly increased (P < 0.05) the till soil water storage in the seedling stage (82%-93%). However, the salt accumulation effect (up to 10.3 kg m-2) was carried over to the CGP till soil (0-40 cm) when FSWI >180 mm. Moreover, FSWI180 promoted crop growth (seedling emergence, plant height, and stem thickness) and significantly increased yields by 23% (P < 0.05). SEM showed that FSWI promoted the effects of soil water storage, temperature, and salinity on crop yields (0.5 vs -0.14, 0.27 vs 0.12, and -0.38 vs 0.42, respectively) compared with the CK treatment. Soil water storage and soil salinity were the main influencing factors (total effects of 0.92 and -0.38, respectively). In conclusion, FSWI180 is a feasible method of freezing saline water to alleviate water shortage problems in arid areas.

Unravelling the photosynthetic dynamics and fluorescence parameters under ameliorative effects of 24-epibrassinolide in wheat (Triticum aestivum L.) grown under heat stress regime

An experiment was performed at the Banaras Hindu University, India to study the effect of terminal heat stress on photosynthetic dynamics and fluorescence parameters of wheat genotypes and ameliorative effects of epibrassinolide by taking two genotypes with four concentrations as foliar spray at two growth stages of wheat. The highest values were observed in plots foliar sprayed with 1.0 µM 24-epibrassinolide (T1) under normal conditions (D1) where the genotype Sonalika (V1) performed significantly well w.r.t. the parameters viz. steady-state fluorescence (Fs) 116.22, quantum efficiency of PSII 0.59, maximum fluorescence (Fm) 776.5, normalized stress detection ratio (Fv/Fo) 4.47, maximum potential quantum efficiency of PSII (Fv/Fm) 0.82.Whereas under heat stress condition (late sown D2), there was significant reduction in these parameters in both the genotypes which was improved by the application of epibrassinolide suggesting its potential role in improving the photoinhibition process by raising the efficiency of PSII. Overall, the calibrated application of 24-epibrassinolide was found to be a potent growth regulator involved in the positive modulation of heat stress tolerance in wheat, coupled with improved photosynthetic efficiency in treated plots as compared to control.

Comparative Physiological and Transcriptomics Profiling Provides Integrated Insight into Melatonin Mediated Salt and Copper Stress Tolerance in Selenicereus undatus L

Selenicereus undatus L., (pitaya) is an important tropical fruit crop, and faces significant challenges from soil salinity and heavy metal toxicity. This study explores the role of melatonin (M) in enhancing stress tolerance in pitaya against salinity (S) and copper (Cu) toxicity, both individually and in combination (SCu). SCu stress reduced plant biomass by ~54%, while melatonin application mitigated stress effects and increased plant growth by ~73.26% under SCuM compared to SCu treatment. Antioxidant activities were also modulated by stress. Transcriptomic analysis revealed 21 differentially expressed genes (DEGs) common across stress treatments and 13 DEGs specific to combined melatonin with stress treatments involved in stress signaling, secondary metabolite biosynthesis, and photosynthesis. A weighted gene co-expression network analysis (WGCNA) identified four gene modules (brown, dark green, dark grey, and grey) significantly associated with phenotypic traits. A protein-protein interaction (PPI) network analysis highlighted 14 hub genes per module, including GH3, JAZ, PAL, CCR, and POD, implicated in MAPK signaling, phenylpropanoid biosynthesis, and hormone signaling pathways. Integration of DESeq2 and WGCNA identified 12 key stress-responsive genes strongly correlated with phenotypic traits. This study provides insights into regulatory mechanisms underlying stress responses and highlights candidate genes for developing stress-resilient S. undatus through breeding programs.

Systems genomics of salinity stress response in rice

Populations can adapt to stressful environments through changes in gene expression. However, the fitness effect of gene expression in mediating stress response and adaptation remains largely unexplored. Here, we use an integrative field dataset obtained from 780 plants of Oryza sativa ssp. indica (rice) grown in a field experiment under normal or moderate salt stress conditions to examine selection and evolution of gene expression variation under salinity stress conditions. We find that salinity stress induces increased selective pressure on gene expression. Further, we show that trans-eQTLs rather than cis-eQTLs are primarily associated with rice's gene expression under salinity stress, potentially via a few master-regulators. Importantly, and contrary to the expectations, we find that cis-trans reinforcement is more common than cis-trans compensation which may be reflective of rice diversification subsequent to domestication. We further identify genetic fixation as the likely mechanism underlying this compensation/reinforcement. Additionally, we show that cis- and trans-eQTLs are under balancing and purifying selection, respectively, giving us insights into the evolutionary dynamics of gene expression variation. By examining genomic, transcriptomic, and phenotypic variation across a rice population, we gain insights into the molecular and genetic landscape underlying adaptive salinity stress responses, which is relevant for other crops and other stresses.

Integrated Transcriptomic, Proteomic, and Metabolomic Analyses Revealed Molecular Mechanism for Salt Resistance in Soybean (Glycine max L.) Seedlings

Salt stress poses a significant challenge to plant growth and restricts agricultural development. To delve into the intricate mechanisms involved in soybean's response to salt stress and find targets to improve the salt resistance of soybean, this study integrated transcriptomic, proteomic, and metabolomic analyses to explore the regulatory networks involved in soybean salt tolerance. Transcriptomic analysis revealed significant changes in transcription factors, hormone-related groups, and calcium ion signaling. Notably, the biosynthetic pathways of cutin, suberine, and wax biosynthesis play an important role in this process. Proteomic results indicated salt-induced DNA methylation and the enrichment of phosphopyruvate hydrase post-salt stress, as well as its interaction with enzymes from various metabolic pathways. Metabolomic data unveiled the synthesis of various metabolites, including lipids and flavonoids, in soybean following salt stress. Furthermore, the integrated multiomics results highlighted the activation of multiple metabolic pathways in soybean in response to salt stress, with six pathways standing out prominently: stilbenoid, diarylheptanoid, and gingerol biosynthesis; carotenoid biosynthesis; carbon fixation in photosynthetic organisms; alanine, aspartate, and glutamate metabolism; thiamine metabolism; and pyruvate metabolism. These findings not only offer valuable insights into leveraging multiomics profiling techniques for uncovering salt tolerance mechanisms but also identify candidate genes for soybean improvement.

The varying responses of leaves and roots and the link between sugar metabolic genes and the SWEET family in Dendrobium officinale under salt stress

BACKGROUND

Dendrobium officinale Kimura et Migo is a perennial epiphytic herb in traditional Chinese medicine, showing remarkable resistance to salt stress. Water-soluble sugars serve as important osmoprotectants and play crucial roles in plant stress responses. Previous studies have primarily focused on sugar metabolism in individual tissues under stress, resulting in a limited understanding of the regulatory differences between tissues and the relationship between sugar metabolism and transport.

RESULTS

A variety of salt-responsive genes were identified through transcriptome analysis of D. officinale. GO and KEGG enrichment analyses revealed functional differences among the differentially expressed genes (DEGs) between leaves and roots. Expression analysis indicated that sugar metabolic genes and D. officinale Sugars Will Eventually be Exported Transporters (DoSWEETs) displayed distinct expression patterns in leaves and roots under salt stress. Most sugar metabolic genes were up-regulated in the leaves and down-regulated in the roots in response to salt, while DoSWEETs predominantly responded in the roots. Specifically, DoSWEET2a, 6a, 12a, 14, and 16 were confirmed via RT-qPCR. Additionally, positive correlations were observed between certain genes (scrK, INV, SUS) and DoSWEETs, with INV (LOC110096666) showing a strong positive correlation with all detected DoSWEETs in both leaves and roots.

CONCLUSIONS

Our findings not only illustrated the distinct responses of leaves and roots to salt stress, but also highlighted the relationship between sugar metabolic genes and DoSWEETs in adapting to such stress. This enhances our understanding of the differential responses of plant tissues to salt stress and identified candidate genes for salt-resistance breeding in D. officinale.

Functional and biotechnological cues of potassium homeostasis for stress tolerance and plant development

Potassium (K+) is indispensable for the regulation of a plethora of functions like plant metabolism, growth, development, and abiotic stress responses. K+ is associated with protein synthesis and entangled in the activation of scores of enzymes, stomatal regulation, and photosynthesis. It has multiple transporters and channels that assist in the uptake, efflux, transport within the cell as well as from soil to different tissues, and the grain filling sites. While it is implicated in ion homeostasis during salt stress, it acts as a modulator of stomatal movements during water deficit conditions. K+ is reported to abate the effects of chilling and photooxidative stresses. K+ has been found to ameliorate effectively the co-occurrence of drought and high-temperature stresses. Nutrient deficiency of K+ makes leaves necrotic, leads to diminished photosynthesis, and decreased assimilate utilization highlighting the role it plays in photosynthesis. Notably, K+ is associated with the detoxification of reactive oxygen species (ROS) when plants are exposed to diverse abiotic stress conditions. It is irrefutable now that K+ reduces the activity of NADPH oxidases and at the same time maintains electron transport activity, which helps in mitigating the oxidative stress. K+ as a macronutrient in plant growth, the role of K+ during abiotic stress and the protein phosphatases involved in K+ transport have been reviewed. This review presents a holistic view of the biological functions of K+, its uptake, translocation, signaling, and the critical roles it plays under abiotic stress conditions, plant growth, and development that are being unraveled in recent times.

Characterisation of a major QTL for sodium accumulation in tomato grown in high salinity

Soil salinity is a serious concern for tomato culture, affecting both yield and quality parameters. Although some genes involved in tomato salt tolerance have been identified, their genetic diversity has been rarely studied. In the present study, we assessed salt tolerance-related traits at juvenile and adult stages in a large core collection and identified salt tolerance quantitative trait loci (QTLs) by genome-wide association study (GWAS). The results suggested that a major QTL is involved in leaf sodium accumulation at both physiological stages. We were able to identify the underlying candidate gene, coding for a well-known sodium transporter, called SlHKT1.2. We showed that an eQTL for the expression of this gene in roots colocalized with the above ground sodium content QTL. A polymorphism putatively responsible for its variation was identified in the gene promoter. Finally, to extend the applicability of these results, we carried out the same analysis on a test-cross panel composed of the core collection crossed with a distant line. The results indicated that the identified QTL retained its functional impact even in a hybrid genetic context: this paves the way for its use in breeding programs aimed at improving salinity tolerance in tomato cultivars.

Regulation of hydrogen rich water on strawberry seedlings and root endophytic bacteria under salt stress

Salt stress could lead to plant growth barriers and crop yield reduction. Strawberries are sensitive to salt stress, and improving salt tolerance is important for strawberry production. This study aimed to explore the potential of hydrogen-rich water (HRW) to enhance salt tolerance in strawberries. Through pot experiments, we investigated how HRW affects plant growth, ion absorption, osmotic stress, oxidative stress, antioxidant enzyme levels, hormone levels, and root endophytic bacteria in strawberry seedlings under salt stress. The results showed that under 100 mM NaCl treatment, 50% and 100% HRW treatments significantly increased strawberry biomass by 0.29 g and 0.54g, respectively, wherein, 100% HRW significantly increased the shoot and root length by 15.34% and 24.49%, respectively. In addition, under salt stress the absorption of K+ by strawberry seedlings was increased with the HRW supplement, while the absorption of Na+ was reduced. Meanwhile, HRW treatment reduced the transfer of Na+ from root to shoot. Furthermore, under salt stress, HRW treatment increased the relative water content (RWC) by 12.35%, decreased the electrolyte leakage rate (EL) by 7.56%. HRW modulated phytohormone levels in strawberry seedlings, thereby alleviating the salt stress on strawberries. Moreover, HRW was found to promote plant growth by altering the diversity of bacteria in strawberry roots and recruiting specific microorganisms, such as Tistella. Our findings indicate that HRW could help restore the microecological homeostasis of strawberry seedlings, thus further mitigating salt stress. This study provides a novel perspective on the mechanisms by which HRW alleviates salt stress, thereby enriching the scientific understanding of hydrogen's applications in agriculture.

Fermentation broth of a novel endophytic fungus enhanced maize salt tolerance by regulating sugar metabolism and phytohormone biosynthesis or signaling

Soil salinization is a major environmental factor that severely affects global agriculture. Root endophytes can enter root cells, and offer various ecological benefits, such as promoting plant growth, improving soil conditions, and enhancing plant resistance. Su100 is a novel strain of endophytic fungus that was characterized from blueberry roots. In this study, we focused on evaluating the effects of Su100 secretion on maize growth. The results demonstrated that maize treated with Su100 fermentation broth (SFB) exhibited significantly stronger salt tolerance than the control. It is worth mentioning that the treated root system not only had an advantage in terms of biomass but also a change in root structure with a significant increase in lateral roots (LRs) compared to the control. Transcriptome analysis combined with hormone content measurements indicated that SFB upregulated the auxin signaling pathway, and also caused alterations in brassinosteroids (BR) and jasmonic acid (JA) biosynthesis and signaling pathways. Transcriptome analyses also indicated that SFB caused significant changes in the sugar metabolism of maize roots. The major changes included: enhancing the conversion and utilization of sucrose in roots; increasing carbon flow to uridine diphosphate glucose (UDPG), which acted as a precursor for producing more cell wall polysaccharides, mainly pectin and lignin; accelerating the tricarboxylic acid cycle, which were further supported by sugar content determinations. Taken together, our results indicated that the enhanced salt tolerance of maize treated with SFB was due to the modulation of sugar metabolism and phytohormone biosynthesis or signaling pathways. This study provided new insights into the mechanisms of action of endophytic fungi and highlighted the potential application of fungal preparations in agriculture.

Does succulence in woody plants delay desiccation, and is stored water used to maintain physiological function during drought conditions?

Succulence is a trait that describes water storage in plant organs and tissues regardless of life form. Plants use the stored water to maintain physiological function and delay desiccation. However, it is unclear whether succulence in leaves, stems and roots of woody plants delays desiccation, whether it provides 'utilizable water' to maintain physiological function, or buffers changes in water status in drying soils through capacitance. We conducted a pot dry-down experiment with nine shrub species to determine whether woody plants with greater leaf, stem, or root succulence have greater shoot utilizable water or capacitance. We also investigated whether greater succulence delays desiccation, represented by cumulative VPD, until evapotranspiration ceased or until utilizable water was exhausted. Greater leaf and stem succulence were strongly related to greater shoot utilizable water and capacitance. However, desiccation time was not delayed in plants with greater total shoot succulence, utilizable water, or capacitance. Instead, woody plants with greater root succulence had longer desiccation times. This suggests that woody plants use aboveground succulence to maintain physiological function and water status during drought, whereas root succulence extends desiccation time. Our study improves the mechanistic understanding of how woody plants use stored water to survive in dryland ecosystems.

Rice growth and yield responses to saline water irrigation are related to Na+/K+ ratio in plants

Rice growth and yield response to salinity can be influenced by the duration and the timing of salt stress. The present study tested the effects of saline water irrigation from vegetative growth to maturity on rice growth and yield and ion concentrations in the straw and root and related them to changes in soil salinity and soil solute potential. The treatments consisted of five levels of saline water irrigation (electrical conductivity ~0.25 (control), 4, 6, 8, and 10 dS m-1) with two rice cultivars (BRRI dhan67 and BRRI dhan99) grown in pots in a rain shelter. Grain weight per pot, dry straw weight, and root weight were significantly reduced with increasing water salinity, but BRRI dhan99 was less affected. With prolonged saline water irrigation, salt concentration increased in the soil and lowered the soil solute potential. Increased saline water induced higher concentrations of Na+ in the straw (527-1200 mmol kg-1 at 4-10 dS m-1) relative to the root. By contrast, higher Cl- concentrations accumulated in the root than in the straw. The decrease of K+ in the straw and root for increasing salinity was inconsistent, but the Na+/K+ ratio sharply increased in the straw with higher water salinity. The increased Na+/K+ explained most grain weight loss due to higher salinity (R2 = 0.93) followed by Na+ (R2 = 0.87) and Cl-1 (R2 = 0.53). We conclude that the prolonged saline water irrigation has a cumulative effect on root zone salinity and solute potential that depresses grain yield in rice by increasing the Na+/K+ ratio in plants.

Genome-wide identification of alcohol dehydrogenase (ADH) gene family in oilseed rape (Brassica napus L.) and BnADH36 functional verification under salt stress

BACKGROUND

Alcohol dehydrogenase (ADH) is an enzyme that binds to zinc, facilitating the interconversion of ethanol and acetaldehyde or other corresponding alcohols/aldehydes in the pathway of ethanol fermentation. It plays a pivotal role in responding to environmental stress. However, the response of the ADH family to abiotic stress remains unknown in rapeseed.

RESULT

In this study, we conducted a comprehensive genome-wide investigation of the ADH family in rapeseed, encompassing analysis of their gene structure, replication patterns, conserved motifs, cis-acting elements, and response to stress. A total of 47 ADH genes were identified within the rapeseed genome. Through phylogenetic analysis, BnADHs were classified into four distinct clades (I, II, IV, V). Prediction of protein domains revealed that all BnADH members possessed a GroES-like (ADH_N) domain and a zinc-bound (ADH_zinc_N) domain. Analysis of promoter sequences demonstrated that BnADHs contained numerous cis-acting elements associated with hormone and stress responses, indicating their widespread involvement in various biological regulatory processes. Expression profiling under different concentrations of salt stress treatments (0%, 0.4%, 0.8%, 1.0% NaCl) further highlighted the significant role played by the BnADH family in abiotic stress response mechanisms. Overexpression of BnADH36 in rapeseed significantly improved the salt tolerance of rapeseed.

CONCLUSION

The features of the BnADH family in rapeseed was comprehensively characterized in this study, which could provide reference to the research of BnADHs in abiotic stress response.

Cerium Oxide Nanoparticles (CeO2 NPs) Enhance Salt Tolerance in Spearmint (Mentha spicata L.) by Boosting the Antioxidant System and Increasing Essential Oil Composition

Salinity represents a considerable environmental risk, exerting deleterious effects on horticultural crops. Nanotechnology has recently emerged as a promising avenue for enhancing plant tolerance to abiotic stress. Among nanoparticles, cerium oxide nanoparticles (CeO2 NPs) have been demonstrated to mitigate certain stress effects, including salinity. In the present study, the impact of CeO2 NPs (0, 25, and 100 mg L-1) on various morphological traits, photosynthetic pigments, biochemical parameters, and the essential oil profile of spearmint plants under moderate (50 mM NaCl) and severe (100 mM NaCl) salinity stress conditions was examined. As expected, salinity reduced morphological parameters, including plant height, number of leaves, fresh and dry weight of leaves and shoots, as well as photosynthetic pigments, in comparison to control. Conversely, it led to an increase in the content of proline, total phenols, malondialdehyde (MDA), hydrogen peroxide (H2O2), and antioxidant enzyme activities. In terms of CeO2 NP applications, they improved the salinity tolerance of spearmint plants by increasing chlorophyll and carotenoid content, enhancing antioxidant enzyme activities, and lowering MDA and H2O2 levels. However, CeO2 NPs at 100 mg L-1 had adverse effects on certain physiological parameters, highlighting the need for careful consideration of the applied concentration of CeO2 NPs. Considering the response of essential oil compounds, combination of salinity stress and CeO2 treatments led to an increase in the concentrations of L-menthone, pulegone, and 1,8-cineole, which are the predominant compounds in spearmint essential oil. In summary, foliar application of CeO2 NPs strengthened the resilience of spearmint plants against salinity stress, offering new insights into the potential use of CeO2 NP treatments to enhance crop stress tolerance.

Performance of coal slime-based silicon fertilizer in simulating lead-contaminated soil: Heavy metal solidification and multi-nutrient release characteristics

High-ash coal slime-based silica fertilizer (CSF) has the potential to provide mineral nutrients and passivate lead (Pb) in the soil to ensure the sustainable development of the coal industry and agriculture. This study investigated the performance and passivation mechanism of CSF, which contains potassium tobermorite and potassium silicate as the main components for soil improvement. Leaching experiments showed that low-crystalline muscovite was the only crystalline phase for CSF etching and that the silicon (Si), calcium (Ca), and potassium (K) in CSF had significant citric solubility. Soil cultivation and planting trials confirmed the ability of CSF to neutralize soil acidity, increase available soil Si and K, improve exchangeable Ca content, reduce the bioefficacy of Pb (exchangeable Pb by 19-75 % and carbonate-bound Pb by 6-18 %), and increase residual state Pb content. Compared to untreated Pb-contaminated soil, the 0.4 % CSF treatment reduced Pb in Chinese cabbage (Brassica rapa) by 25 % and increased plant biomass, Ca, and K by 37 %, 36 %, and 4 %, respectively. At the same time, soil pH increased by 0.58, and residual state Pb increased by 5 %. In CSF-treated soils, lead silicate is the dominant form of Pb present in the residual state. First-principle calculations showed that Pb3Si2O7 (cohesion energy -1.98 eV) formed by the passivation of Pb by CSF had greater stability in the soil compared to lead carbonate (PbCO3) (cohesion energy -1.38 eV) and lead sulfate (PbSO4) (cohesion energy -1.41 eV). This work shows the promising application of coal slime mineral fertilizers prepared using hydrothermal methods for soil improvement.

Mitigation strategy of saline stress in Fragaria vesca using natural and synthetic brassinosteroids as biostimulants

Bassinosteroids (BRs) can induce plant defence responses and promote plant growth. In this work, we evaluated the effect of a natural (EP24) and a synthetic (BB16) brassinosteroid on strawberry (Fragaria vesca ) plants exposed to saline stress. Treated plants showed higher shoot dry weight and root growth compared to untreated control plants. In BR-treated plants, crown diameters increased 66% and 40%, leaf area 148% and 112%, relative water content in leaves 84% and 61%, and SPAD values 24% and 26%, in response to BB16 and EP24, respectively. A marked stomatal closure, increased leaflet lignification, and a decrease in cortex thickness, root diameter and stele radius were also observed in treated plants. Treatments also reduces stress-induced damage, as plants showed a 34% decrease in malondialdehyde content and a lower proline content compared to control plants. A 22% and 15% increase in ascorbate peroxidase and total phenolic compound activities was observed in response to BB16, and a 24% increase in total flavonoid compound in response to both BRs, under stress conditions. These results allow us to propose the use of BRs as an environmentally safe crop management strategy to overcome salinity situations that severely affect crop yield.

Unravelling wheat genotypic responses: insights into salinity stress tolerance in relation to oxidative stress, antioxidant mechanisms, osmolyte accumulation and grain quality parameters

BACKGROUND

Salt stress is a prominent abiotic stressor that imposes constraints on grain yield and quality across various crops, including wheat (Triticum aestivum). This study focused on assessing the genetic diversity of 20 wheat genotypes categorized as tolerant, moderately tolerant, and sensitive with three genotypes of unknown tolerance. To address salinity stress-related problems, different morpho-physiological, osmoprotectant, biochemical, yield, and grain quality-related parameters were analyzed under control (pH 8.0, EC 3.9) and saline-sodic (pH 9.4, EC 4.02) conditions in field.

RESULTS

Findings revealed noteworthy variations among the genotypes in response to salinity stress. Greater accumulation of Na+ and lower K+ content were observed in response to salt stress in the sensitive varieties HD1941 and K9162. Proline, a stress indicator, exhibited significantly (p ≤ 0.05) greater accumulation in response to salinity stress, particularly in the tolerant cultivars KRL210 and KH65. Salt stress induced the most significant decrease (p ≤ 0.05) in spike length, thousand-grain weight, and hectolitre weight coupled with increased protein content in sensitive varieties, resulting in diminished yield.

CONCLUSION

Correlation analysis of parameters under salinity stress showed that SOD, proline, and K+ contents can be used as the most efficient screening criteria for salinity stress during early developmental stages. Principal component analysis revealed that DBW187, DBW303, and DBW222 varieties were tolerant to salinity stress and exhibited an effective antioxidant system against salinity. This study will facilitate salt-tolerant wheat breeding in terms of the identification of tolerant lines by screening for limited traits in a wide range of germplasms.

Exogenous Uniconazole promotes physiological metabolism and grain yield of rice under salt stress

Introduction

Salt stress severely inhibit plant growth and development. Uniconazole has been considered to significantly increase plant stress tolerance. However, the mechanism by which Uniconazole induces salt tolerance in rice seedlings and its impact on yield is still unclear.

Methods

In this study, the effects of exogenous Uniconazole on morphogenesis, physiological metabolism, and yield of rice seedlings under salt stress were analyzed using the salt-tolerant rice variety HD961 and the salt-sensitive rice variety 9311.

Results

The results showed that salt stress significantly inhibited rice growth, disrupted the antioxidant system and pigment accumulation, and reduced photosynthesis, and yield. There were corresponding percent decreases of 13.0% and 24.1% in plant height, 31.6% and 55.8% in leaf area, 65.7% and 85.3% in root volume, respectively for HD961 and 9311. spraying However, compared to salt stress, the US treatment increased the percentage to 4.7% and 139.0% in root volume, 7.5% and 38.0% in total chlorophyll, 4.5% and 14.3% in peroxidase (POD) of leaves, 14.4% and 54.2% in POD of roots, 18.7% and 22.7% in catalase (CAT) of leaves, and 22.6% and 53.9% in CAT of roots, respectively, for HD961 and 9311. In addition, it also significantly enhanced photosynthesis at the reproductive stage, promoted the transport of carbohydrate to grains. And US treatment significantly increased the percentage to 9.0% in panicle length, 28.0% in panicle number per hole, 24.0% in filled grain number, 3.0% in 1000-grain weight, and 26.0% in yield per plant, respectively, for HD961, compared to salt stress.

Discussion

In summary, applying Uniconazole at the seedling stage can alleviate the damage induced by NaCl stress on rice by regulating the physiological metabolism of rice plants. This reduces the negative effects of salt stress, enhance salt tolerance, and boost rice production.

Challenges of Salinity Intrusion and Drought Stress on Olive Tree Cultivation on Mljet Island

Understanding genotype-specific responses to environmental stressors is vital for developing resilience strategies that ensure sustainable olive cultivation and productivity. In this work, cultivar 'Oblica' and several olive genotypes from the island of Mljet (Croatia) were exposed to short-term (21 days) salinity and drought treatments. In contrast to other olive genotypes, genotype M29 as well as cultivar 'Oblica' managed to maintain growth and chlorophyll a levels under salinity stress to the same level as the control. Drought, however, significantly reduced the growth parameters in all olive trees. Cultivar 'Oblica' accumulated the greatest amount of Na+ ions in the leaves compared to olive genotypes from the island of Mljet, demonstrating superior resistance by translocating Na+ to leaf vacuoles. The observed reduction in K+ content in the roots of olive trees under all treatments suggests a generalized stress response. On the other hand, effective Ca2+ uptake has been identified as a crucial energy-saving strategy that olive trees use to cope with brief periods of salinity and drought. The proline content and activities of superoxide dismutase (SOD) and guaiacol peroxidase (GPOX) varied among the olive trees, highlighting the importance of antioxidative capacities and stress adaptation mechanisms. According to the obtained results, stress-resistant olive genotypes like 'Oblica' and M29 show potential for breeding resilient varieties.

Overexpression of rice lectin receptor-like kinase, OsLec-RLK, confers salinity stress tolerance and increases seed yield in pigeon pea (Cajanus cajan (L.) Millsp.)

KEY MESSAGE

OsLec-RLK overexpression enhances cell signalling and salt stress tolerance in pigeon pea, enhancing seed yield and harvest index and thus, enabling marginal lands to increase food and nutritional security. Lectin Receptor-like kinases (Lec-RLKs) are highly effective cell signaling molecules that counteract various stresses, including salt stress. We engineered pigeon pea by overexpressing OsLec-RLK gene for enhancing salt tolerance. The OsLec-RLK overexpression lines demonstrated superior performance under salt stress, from vegetative to reproductive phase, compared to wild types (WT). The overexpression lines had significantly higher K+/Na+ ratio than WT exposed to 100 mM NaCl. Under salt stress, transgenic lines showed higher levels of chlorophyll, proline, total soluble sugars, relative water content, and peroxidase and catalase activity than WT plants. Membrane injury index and lipid peroxidation were significantly reduced in transgenic lines. Analysis of phenological and yield attributes confirmed that the OsLec-RLK pigeon pea lines maintain plant vigor, with 10.34-fold increase in seed yield (per plant) and 4-5-fold increase in harvest index of overexpression lines, compared to wild type. Meanwhile, the overexpression of OsLec-RLK up-regulated the expression levels of histone deacetylase1, acyl CoA, ascorbate peroxidase, peroxidase, glutathione reductase and catalase, which were involved in the K+/Na+ homeostasis pathway. This study showed the potential of OsLec-RLK gene for increasing crop productivity and yields under salt stress and enabling the crops to be grown on marginal lands for increasing food and nutritional security.

Evolution, identification, evaluation, and characterization of a stable salinity tolerant sugarcane variety CoG 7

From the fluff generated during 2005, after the preliminary experiments (2005-2007), a promising clone G2005047 has been identified. It showed moderate resistance to red rot (3.6 on a 9-scale scoring system), less susceptibility to shoot borer (13.25%) and internode borers (25.35%), and resistance to woolly aphid (0%). In the Advanced Yield Trials (2008-2011), it showed advantages over check for cane yield (CY) (11.79%), commercial cane sugar percent (CCSP) (0.35%), and sugar yield (SY) (20.33%). To ascertain its large-scale cultivation suitability, it has experimented under adaptive research trials (2012-2014) at farmers' fields. It exhibited 18.04%, 1.27%, and 19.55% supremacy over the check Co 86032 for CY, CCSP, and SY respectively. The stability of G2005047 under salinity was ascertained through a multi-environment-based experiment (2015-2017). AMMI (Additive Main-effects and Multiplicative Interactions) and GGE (Genotype × Genotype-Environment interaction) biplots were utilized. ANOVA revealed that the genotypic variation exerted the most significant effect followed by genotype × environment interaction and environment. G2005047 had the highest mean values for yield and quality traits with minimal ASV (AMMI stability value) (2.38:CY; 0.57: CCSP; & 0.58:SY) indicating its good-yielding ability and stability. AMMI I, AMMI II, and GGE biplots confirmed the stability of G2005047. In the jaggery quality assessment trials (2018 and 2019), it yielded 37.1% increased jaggery over the check. Also, the clone G2005047, exhibited moderate resistance to red rot disease, less susceptibility to shoot borer (13.25%) and internode borer (25.35%), and resistance against sugarcane woolly aphid (SWA). Due to supremacy for yield, quality, better performance under salinized situations, and tolerance to disease and pests, the clone G2005047 was released as a variety CoG 7 in 2022.

Effect of non-uniform root salt distribution on the ion distribution and growth of the halophyte Suaeda salsa

Soil salinity in the root rhizosphere is highly heterogeneous in natural environments. Suaeda salsa L. is a highly salt-adapted halophyte, but it is unclear how S. salsa responds to non-uniform salinity conditions. The results of the root-splitting experiment showed that the increase in root dry weight in the low salt side (50/350-50) root of S. salsa may be associated with relative increases in root morphology. The concentration of Na+, Cl-, K+, the Na+ efflux and the expression of SsSOS1 in the low salt side root were higher than that of uniform low salt treatment. The expression of SsPIP1-4, SsPIP2-1, SsNRT1.1 and SsNRT2.1 were upregulated, which increased water and NO3- uptake in the low salt side root compared to uniform low salt treatment. In conclusion, under non-uniform salt treatment, the increased Na+ efflux, water and NO3- uptake from the low salt side root can alleviate salt stress in S. salsa.

A novel Microbacterium strain SRS2 promotes the growth of Arabidopsis and MicroTom (S. lycopersicum) under normal and salt stress conditions

MAIN CONCLUSION

Microbacterium strain SRS2 promotes growth and induces salt stress resistance in Arabidopsis and MicroTom in various growth substrates via the induction of the ABA pathway. Soil salinity reduces plant growth and development and thereby decreases the value and productivity of soils. Plant growth-promoting rhizobacteria (PGPR) have been shown to support plant growth such as in salt stress conditions. Here, Microbacterium strain SRS2, isolated from the root endosphere of tomato, was tested for its capability to help plants cope with salt stress. In a salt tolerance assay, SRS2 grew well up to medium levels of NaCl, but the growth was inhibited at high salt concentrations. SRS2 inoculation led to increased biomass of Arabidopsis and MicroTom tomato in various growth substrates, in the presence and in the absence of high NaCl concentrations. Whole-genome analysis revealed that the strain contains several genes involved in osmoregulation and reactive oxygen species (ROS) scavenging, which could potentially explain the observed growth promotion. Additionally, we also investigated via qRT-PCR, promoter::GUS and mutant analyses whether the abscisic acid (ABA)-dependent or -independent pathways for tolerance against salt stress were involved in the model plant, Arabidopsis. Especially in salt stress conditions, the plant growth-promotion effect of SRS2 was lost in aba1, abi4-102, abi3, and abi5-1 mutant lines. Furthermore, ABA genes related to salt stress in SRS2-inoculated plants were transiently upregulated compared to mock under salt stress conditions. Additionally, SRS2-inoculated ABI4::GUS and ABI5::GUS plants were slightly more activated compared to the uninoculated control under salt stress conditions. Together, these assays show that SRS2 promotes growth in normal and in salt stress conditions, the latter possibly via the induction of ABA-dependent and -independent pathways.

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

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

Surviving the stress: Understanding the molecular basis of plant adaptations and uncovering the role of mycorrhizal association in plant abiotic stresses

Environmental stresses severely impair plant growth, resulting in significant crop yield and quality loss. Among various abiotic factors, salt and drought stresses are one of the major factors that affect the nutrients and water uptake by the plants, hence ultimately various physiological aspects of the plants that compromises crop yield. Continuous efforts have been made to investigate, dissect and improve plant adaptations at the molecular level in response to drought and salinity stresses. In this context, the plant beneficial microbiome presents in the rhizosphere, endosphere, and phyllosphere, also referred as second genomes of the plant is well known for its roles in plant adaptations. Exploration of beneficial interaction of fungi with host plants known as mycorrhizal association is one such special interaction that can facilitates the host plants adaptations. Mycorrhiza assist in alleviating the salinity and drought stresses of plants via redistributing the ion imbalance through translocation to different parts of the plants, as well as triggering oxidative machinery. Mycorrhiza association also regulates the level of various plant growth regulators, osmolytes and assists in acquiring minerals that are helpful in plant's adaptation against extreme environmental stresses. The current review examines the role of various plant growth regulators and plants' antioxidative systems, followed by mycorrhizal association during drought and salt stresses.

Halophytes and heavy metals: A multi-omics approach to understand the role of gene and genome duplication in the abiotic stress tolerance of Cakile maritima

PREMISE

The origin of diversity is a fundamental biological question. Gene duplications are one mechanism that provides raw material for the emergence of novel traits, but evolutionary outcomes depend on which genes are retained and how they become functionalized. Yet, following different duplication types (polyploidy and tandem duplication), the events driving gene retention and functionalization remain poorly understood. Here we used Cakile maritima, a species that is tolerant to salt and heavy metals and shares an ancient whole-genome triplication with closely related salt-sensitive mustard crops (Brassica), as a model to explore the evolution of abiotic stress tolerance following polyploidy.

METHODS

Using a combination of ionomics, free amino acid profiling, and comparative genomics, we characterize aspects of salt stress response in C. maritima and identify retained duplicate genes that have likely enabled adaptation to salt and mild levels of cadmium.

RESULTS

Cakile maritima is tolerant to both cadmium and salt treatments through uptake of cadmium in the roots. Proline constitutes greater than 30% of the free amino acid pool in C. maritima and likely contributes to abiotic stress tolerance. We find duplicated gene families are enriched in metabolic and transport processes and identify key transport genes that may be involved in C. maritima abiotic stress tolerance.

CONCLUSIONS

These findings identify pathways and genes that could be used to enhance plant resilience and provide a putative understanding of the roles of duplication types and retention on the evolution of abiotic stress response.

Salicylic acid-mediated alleviation of salt stress: Insights from physiological and transcriptomic analysis in Asarum sieboldii Miq

As global agriculture faces the pressing threat of salt stress, innovative solutions are imperative for sustainable agriculture. The remarkable potential of salicylic acid (SA) in enhancing plant resilience against environmental stressors has recently gained attention. However, the specific molecular mechanisms by which SA mitigates salt stress in Asarum sieboldii Miq., a valuable medicinal plant, remain poorly understood. Here, we evaluated the physiological and transcriptomic regulatory responses of A. sieboldii under salt stress (100 mM NaCl), both in the presence (1 mM SA) and absence of exogenous SA. The results highlighted that SA significantly alleviates salt stress, primarily through enhancing antioxidant activities as evidenced by increased superoxide dismutase, and peroxidase activities. Additionally, we observed an increment in chlorophyll (a and b), proline, total soluble sugar, and plant fresh weight, along with a decrease in malondialdehyde contents. Transcriptome analysis suggested consistency in the regulation of many differentially expressed genes and transcription factors (TFs); however, genes targets (GSTs, TIR1, and NPR1), and TFs (MYB, WRKY, TCP, and bHLH) possessed expressional uniqueness, and majority had significantly up-regulated trends in SA-coupled salt stress treatments. Further, bioinformatics and KEGG enrichment analysis indicated several SA-induced significantly enriched biological pathways. Specifically, plant hormone signal transduction was identified as being populated with key genes distinctive to auxin, cytokinin, ethylene, and salicylic acid signaling, suggesting their important role in salt stress alleviation. Inclusively, this report presents a comprehensive analysis encompassing gene targets, TFs, and biological pathways, and these insights may offer a valuable contribution to our knowledge of SA-mediated regulation and its crucial role in enhancing plant defense against diverse abiotic stressors.

Stigmasterol: An Enigmatic Plant Stress Sterol with Versatile Functions

Sterols play important structural and regulatory roles in numerous intracellular processes. Unlike animals, plants contain a distinctive and diverse variety of sterols. Recently, information has emerged showing that stigmasterol is a "stress sterol". Stigmasterol is synthesized via the mevalonate biosynthesis pathway and has structural similarity to β-sitosterol but differs in the presence of a trans-oriented double bond in the side chain. In plants, the accumulation of stigmasterol has been observed in response to various stresses. However, the precise ways that stigmasterol is involved in the stress responses of plants remain unclear. This comprehensive review provides an update on the biology of stigmasterol, particularly the physicochemical properties of this ethylsterol, its biosynthesis, and its occurrence in higher plants and extremophilic organisms, e.g., mosses and lichens. Special emphasis is given to the evolutionary aspects of stigmasterol biosynthesis, particularly the variations in the gene structure of C22-sterol desaturase, which catalyzes the formation of stigmasterol from β-sitosterol, in a diversity of evolutionarily distant organisms. The roles of stigmasterol in the tolerance of plants to hostile environments and the prospects for its biomedical applications are also discussed. Taken together, the available data suggest that stigmasterol plays important roles in plant metabolism, although in some aspects, it remains an enigmatic compound.

The impacts of pullulan soaking on radish seed germination and seedling growth under salt stress

Pullulan can not only provide a source of organic carbon but also has excellent properties. However, current research is mostly limited to the physical properties of the high-molecular-weight components of pullulan, and little is known about the application of its low-molecular-weight components. This study was designed to explore the impact of presoaking of radish seeds in a pullulan solution on seed germination and subsequent seedling growth under salt stress conditions. Pullulan soaking was found to enhance the germination rates of radish seeds subjected to salt stress, while also enhancing the aboveground growth of radish seedlings. Pullulan soaking resulted in increases in chlorophyll, soluble protein, and soluble sugar concentrations in the leaves of these seedlings, together with greater peroxidase activity and root activity as well as decreases in Na+ and malondialdehyde concentrations. This provides an important reference for the application of pullulan in plant protection.

Growth and non-structural carbohydrates response patterns of Eucommia ulmoides under salt and drought stress

Introduction

Salinity and droughts are severe abiotic stress factors that limit plant growth and development. However, the differences and similarities of non-structural carbohydrates (NSCs) responses patterns of trees under the two stress conditions remain unclear.

Methods

We determined and compared the growth, physiology, and NSCs response patterns and tested the relationships between growth and NSCs concentrations (or pool size) of Eucommia ulmoides seedlings planted in field under drought and salt stress with different intensities and durations.

Results and discussion

We found that drought and salt stress can inhibit the growth of E. ulmoides, and E. ulmoides tended to enhance its stress resistance by increasing proline concentration and leaf thickness or density but decreasing investment in belowground biomass in short-term stress. During short-term drought and salt stress, the aboveground organs showed different NSCs response characteristics, while belowground organs showed similar change characteristics: the starch (ST) and NSCs concentrations in the coarse roots decreased, while the ST and soluble sugar (SS) concentrations in the fine roots increased to enhance stress resistance and maintain water absorption function. As salt and drought stress prolonged, the belowground organs represented different NSCs response patterns: the concentrations of ST and SS in fine roots decreased as salt stress prolonged; while ST in fine roots could still be converted into SS to maintain water absorption as drought prolonged, resulting in an increase of SS and a decrease of ST. Significant positive relationships were found between growth and the SS and total NSCs concentrations in leaves and branches, however, no significant correlations were found between growth and below-ground organs. Moreover, relationships between growth and NSCs pool size across organs could be contrast.

Conclusion

Our results provide important insights into the mechanisms of carbon balance and carbon starvation and the relationship between tree growth and carbon storage under stress, which were of great significance in guiding for the management of artificial forest ecosystem under the context of global change.

Eco-evolutionary strategies for relieving carbon limitation under salt stress differ across microbial clades

With the continuous expansion of saline soils under climate change, understanding the eco-evolutionary tradeoff between the microbial mitigation of carbon limitation and the maintenance of functional traits in saline soils represents a significant knowledge gap in predicting future soil health and ecological function. Through shotgun metagenomic sequencing of coastal soils along a salinity gradient, we show contrasting eco-evolutionary directions of soil bacteria and archaea that manifest in changes to genome size and the functional potential of the soil microbiome. In salt environments with high carbon requirements, bacteria exhibit reduced genome sizes associated with a depletion of metabolic genes, while archaea display larger genomes and enrichment of salt-resistance, metabolic, and carbon-acquisition genes. This suggests that bacteria conserve energy through genome streamlining when facing salt stress, while archaea invest in carbon-acquisition pathways to broaden their resource usage. These findings suggest divergent directions in eco-evolutionary adaptations to soil saline stress amongst microbial clades and serve as a foundation for understanding the response of soil microbiomes to escalating climate change.

Juncus rigidus high biomass and cellulose productivity under wastewater salinity stress - A paradigm shift to the valorization of RO reject water

The use of water purifiers is intensively catching up and disposing of reverse osmosis reject water is of great concern. Reject water management using conventional methods is costly and harmful to the environment. To address this issue, the present study aims to utilize reverse osmosis reject wastewater using an eco-friendly approach. Juncus rigidus was treated with reject wastewater containing different salinity levels. Wastewater-treated plant dry biomass increased with increasing reject water salinity, and 625.3 g dry biomass recovered in treatment-B (~18,520 ppm). However, ~23,220 ppm wastewater salinity was lethal to the plants. The cellulose was extracted by alkali hydrolysis. The cellulose content in the wastewater-treated biomass was significantly higher in Treatment-B compared to both the control and Treatment-A (~12,744 ppm). The water salinity enhanced the cellulose (26.49 %) production in J. rigidus. Cellulose purity was confirmed using spectroscopic and thermogravimetric means. XRD shows highest crystallinity Index (77.29) with a d-spacing of 4.7 Å and 5.7 nm crystallite size in treatment-B. FTIR results reveal well-defined relevant peaks for OH, CH, CO, CH2, C-O-C, CO groups in treatment-B cellulose. Salinity impacts carboxyl groups in treatment B cellulose with a sharper and intense peak at 1644 cm-1 responsible for water absorption. Treatment-B exhibits higher thermal stability due to increased crystallinity. DSC shows endothermic depolymerization of cellulose with distinct peaks for different treatments. Morphological traits got better with increasing salinity with no adverse effect on cellulose. Salinity moderately affected the water absorption capacity of cellulose. All cellulose samples were devoid of gram-negative bacteria known by microbial test. This pioneering work underscores the plant's remarkable capacity not only to accomplish the circular economy by the valorization of wastewater obtained from various water purifiers for Juncus cultivation for cellulose production for diverse applications but also to generate income from wastewater.

Salinity-induced desertification in oasis ecosystems: challenges and future directions

Salinity-induced desertification is a pressing environmental issue that poses a significant threat to the sustainability of oasis ecosystems worldwide. These ecosystems are vital to the livelihoods of millions of people living in hyper-arid, arid and semi-arid regions, providing essential resources such as food, water and other necessities. However, overexploitation of natural resources, changes in land use and climate change have led to the degradation of these ecosystems, resulting in soil salinisation, waterlogging and other adverse effects. Combating salinity-induced desertification requires a comprehensive approach that addresses both the underlying causes of ecosystem degradation and the direct consequences for local communities. The strategy may include measures for sustainable land use, reforestation and water conservation. It is also essential to involve local communities in these activities and to ensure that their perspectives are heard. The aim of this article is to examine the causes and processes of salinity-induced desertification in oasis ecosystems and the implications for their sustainability. It also examines strategies that are being used to prevent desertification and promote sustainable oasis management. This article aims to raise awareness of this critical issue and to promote action towards a more sustainable future.

Salt tolerance in a neotropical orchid in the absence of local adaptation to salt spray

PREMISE

Salt tolerance has rarely been investigated regionally in the neotropics and even more rarely in Orchidaceae, one of the largest families. Therefore, investigating local adaptation to salt spray and its physiological basis in Epidendrum fulgens, a neotropical orchid species, brings important new insights.

METHODS

We assessed the degree of salt tolerance in E. fulgens by testing whether coastal populations are more tolerant to salt, which could point to local adaptation. To understand the physiological basis of such salt tolerance, we exposed wild-collected individuals to salt spray for 60 days, then measured leaf expansion, osmotic potential, sodium leaf concentration, chlorophyll leaf index, chlorophyll fluorescence, relative growth rate, and pressure-volume curves.

RESULTS

There is no local adaptation to salt spray since both inland and coastal plants have a high tolerance to salt stress. This tolerance is explained by the ability to tolerate high concentrations of salt in leaf tissues, which is related to the high succulence displayed by this species.

CONCLUSIONS

We showed an unprecedented salt tolerance level for an orchid species, highlighting our limited knowledge of that trait beyond the traditional studied groups. Another interesting finding is that salt tolerance in E. fulgens is linked to succulence, is widespread, and is not the result of local adaptation. We suggest that E. fulgens and its allied species could be an interesting group to explore the evolution of important traits related to tolerance to salt stress, like succulence.