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Article

Role of Endogenous Hormone Dynamics in Regulating the Development of Suaeda salsa L. Under Salt Stress

by
Jinxiu Hao
1,2,
Yanyan Wang
3,
Xinzhi Feng
1,
Wenxuan Mai
2,
Dong Zhang
2,
Ke Zhang
2,
Wentai Zhang
1,* and
Ahmad Azeem
2,*
1
College of Resources and Environment, Xinjiang Agricultural University, Urumqi 830052, China
2
Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
3
College of Resources and Environment, Yili Normal University, Yining 835000, China
*
Authors to whom correspondence should be addressed.
Agronomy 2025, 15(12), 2859; https://doi.org/10.3390/agronomy15122859
Submission received: 11 November 2025 / Revised: 3 December 2025 / Accepted: 8 December 2025 / Published: 12 December 2025
(This article belongs to the Special Issue Agro-Environmental Sustainable Exploitation of Halophyte, Medicinal and Aromatic Species from Marginal Areas—2nd Edition)
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Abstract

Soil salinization severely constrains agricultural productivity and ecosystem sustainability. Suaeda salsa L. is a representative halophyte and demonstrates strong adaptability and potential for saline–alkali land restoration. To elucidate its physiological responses to salt stress, pot experiments were conducted under four salinity levels, namely CK (0 mM NaCl), LS (800 mM NaCl), MS (1600 mM NaCl), and HS (2400 mM NaCl), with 20 replicates per treatment, and the dynamics of endogenous hormone were analyzed using targeted metabolomics. The soil salinity levels were prepared by adding NaCl solutions of different molarities to achieve the desired salinity treatments. Results showed that low to moderate salinity (CK-LS: 0–800 mM) promoted growth performance, whereas higher salinity (HS: 2400 mM) significantly inhibited biomass accumulation, plant height, and stem diameter (p < 0.01). Salinity markedly affected nutrient accumulation in Suaeda salsa, with Na increasing up to 222%, K decreasing by 17–33%, Ca by 7–21%, Mg by 35–46%, and S by 45–56% across growth stages, while Fe remained unchanged. Under increasing salinity, stress-related hormones such as abscisic acid, jasmonic acid, salicylic acid, and indole derivatives were upregulated, while gibberellins decreased markedly. Zeatin and its derivatives showed significant increases under MS (p < 0.01). Correlation analysis indicated positive associations of abscisic acid and zeatin with growth traits, and negative correlations for gibberellins (R > 0.6). These findings suggest that Suaeda salsa adapts to saline conditions by modulating hormone-mediated ion balance, osmotic regulation, and defense metabolism, thereby optimizing growth and biomass allocation under salt stress.

1. Introduction

Almost 10% of the arable land all over the world has been affected by salinity, according to the Food and Agriculture Organization of the United Nations (FAO) [1,2]. As global warming intensifies, the area of saline–alkali land is expanding at a rate of 1.0 × 106 to 1.5 × 106 hm2 per year [3]. China is the world’s third-largest country in terms of saline–alkali land area, with about 550 million mu of exploitable resources that are widely distributed and highly diverse, offering great development potential [4]. However, in arid and semi-arid regions, salt stress has become one of the primary factors restricting agricultural development. Excessive accumulation of salt in the soil leads to the deterioration of soil physical and chemical properties, inhibits normal plant growth, and in severe cases, causes plant death [5,6], thereby posing a serious challenge to the sustainable development of regional agriculture. Studies show that about 20% of the world’s arable land and 33% of irrigated agricultural areas have been affected by salinity [7]. By 2050, over half of the world’s arable land is projected to be affected by severe salt stress [8]. At present, traditional saline–alkali land utilization models generally suffer from problems such as low resource use efficiency and high maintenance costs. It is imperative to establish an efficient and sustainable resource utilization system centered on bioremediation technology [9]. Therefore, biological measures, as an economical and environmentally friendly soil improvement approach, show broad application prospects in saline–alkali land management.
Salt stress generally exerts a pronounced negative impact on plant growth and development, primarily manifested as growth inhibition, root damages [9], and physiological or metabolic disorders [10,11]. However, under such adverse conditions, halophytes can effectively regulate salt absorption, transport, and perform compartmentalization through mechanisms such as dilution, salt secretion, and salt exclusion, thereby maintaining normal physiological functions [12]. Among them, Suaeda salsa, as a typical halophyte, can adapt to high-salt environments through physiological mechanisms, such as organ fleshing, ion compartmentalization, and osmotic regulation, and store the absorbed salt in its body, thereby effectively reducing soil salinity [12]. In addition, due to its wide distribution and high biomass, Suaeda salsa can be used as an important material for bioremediation of saline–alkali land.
At present, research on the response mechanism of Suaeda salsa growth and development to soil salinity has been relatively systematic and in depth. It is known that the growth potential of Suaeda salsa has a non-linear response to the soluble salt content of soil, which is mainly due to its differential absorption and the utilization efficiency of salt and nutrients [13]. In saline soil with a salt concentration higher than 0.2%, the stem mass ratio of Suaeda salsa shows a decreasing trend, which leads to a reduction in the overall biomass of the plant [14]. However, this result contrasts with a report showing that maximum biomass was obtained under hydroponic conditions at approximately 1.0% NaCl [15]. This suggests that soil, as a complex growth medium, regulates the growth of Suaeda salsa differently from nutrient solution systems [16]. Therefore, it is speculated that the growth differences in Suaeda salsa in soils with different salinization levels may be closely related to the changes in its endogenous hormone levels.
Plant endogenous hormones can enhance the plant’s ability to adapt to saline environments by regulating physiological processes such as salt absorption, distribution, and excretion [17]. For example, abscisic acid (ABA), indoleacetic acid (IAA), gibberellins (GA), cytokinins (CK), brassinolides (BR), and methyl jasmonate (MeJA) are all involved in the plant’s stress resistance response [18]. Among them, abscisic acid (ABA) enhances the activity of sodium potassium pump-related enzymes, such as plasma membrane H+-ATPase, which helps regulate intracellular ion homeostasis [19,20]. This regulation improves the root’s tolerance to salt stress. In contrast, cytokinin (CK) indirectly influences root architecture by promoting cell division and elongation [21]. It also affects ion absorption and distribution within the rhizosphere environment [22,23]. Despite the existing research, the molecular and physiological mechanisms by which endogenous hormones finely regulate plant salt tolerance remain poorly understood. Given the increasing severity of salt stress, it is essential to investigate the response patterns and regulatory networks of plant hormones in saline–alkali soils. Therefore, this study aims to systematically analyze the dynamic changes in various endogenous hormones in Suaeda salsa under salt stress and explore hormone regulatory pathways that can effectively alleviate the inhibitory effects of salt stress on plant growth. This study provides valuable insights for developing salt-tolerant plant resources and improving plant adaptation to saline environments.

2. Materials and Methods

2.1. Experimental Design

This experiment was conducted at the Fukang Desert Ecological Station of the Chinese Academy of Sciences (87°45′~88°05′ E, 43°45′~44°30′ N) from 11 May to 30 August 2024, in a rain shelter. Each pot was washed then dried before the experiment. Each pot was filled with 3.75 kg of air-dried soil that had passed through a 5 mm sieve, to attain a height of 35 cm within the pot. Based on the soil salinity classification standard for saline–alkali land, four NaCl salinity treatments were established using NaCl solutions of 0 mM (CK), 800 mM (low salinity, LS), 1600 mM (moderate salinity, MS), and 2400 mM (high salinity, HS), which were prepared by dissolving 0, 18.75, 37.50, and 56.25 g of NaCl, respectively, in 400 mL of deionized water for each pot. Each treatment had 20 replicates [24]. To ensure adequate nutrient supply for plant growth, 1.98 g of urea (CO(NH2)2) and 1.44 g of potassium dihydrogen phosphate (KH2PO4) were dissolved in 75 mL of deionized water as base fertilizer and evenly applied to all pots, bringing the soil moisture content to 80% of field capacity. After 24 h, 10 intact seeds of Suaeda salsa were uniformly sown in each pot and covered with a 2 mm layer of air-dried soil. When the seedlings attained 6 cm height, three healthy seedlings of similar growth were retained in each pot. The required amounts of NaCl for the different treatments (0, 18.75, 37.50, and 56.25 g) were dissolved in deionized water and applied to the pots in equal portions four times at two-day intervals. Throughout the growth cycle, deionized water was replenished periodically using a weighing method to maintain the soil moisture content at 60% of field capacity.

2.2. Test Materials

The seeds of Suaeda salsa were collected from the Halophyte Botanical Garden (84°59′41.61″ E, 45°28′6.38″ N), Karamay, Xinjiang, China. Soil samples were obtained from a long-term abandoned cotton field at the Fukang Desert Ecological Station, Chinese Academy of Sciences (87°45′–88°05′ E, 43°45′–44°30′ N). The initial physical and chemical properties of the soil are shown in Table 1. The experiment was held within pots of the following size: 27 cm in height, 20 cm inner bottom diameter, and 25 cm inner top diameter (Figure 1).

2.3. Sampling and Measurement

Plant and soil samples were collected from groups of five pots at the seedling stage (30 days), vegetative stage (45 days), flowering stage (85 days), and fruiting stage (100 days) (Figure 1). Morphological parameters (plant height, stem diameter) were measured before harvesting with the help of measuring tape. At the vegetative and flowering stages, the apical meristems of each plant were collected, rapidly placed in cryovials, flash-frozen in liquid nitrogen, and then stored at −80 °C for subsequent determination of endogenous hormone levels. The remaining samples were first blanched in an oven at 105 °C for 30 min, then dried at 75 °C for 48 h until constant weight was attained. After drying, the plant samples were pulverized using a ball mill and then microwave-digested with a mixed acid solution of HNO3 and H2O2. The contents of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), and iron (Fe) were determined using inductively coupled plasma optical emission spectrometry (ICP-OES; 735E, Agilent, Santa Clara, CA, USA).
Soil samples were air-dried then sieved through 2 mm and 1 mm sieves for later use. Soil pH and electrical conductivity (EC) were determined by deionized water extraction (pH, 1:2.5 w/v; EC, 1:5 w/v) using a pH meter (S20, Mettler Toledo, Greifensee, Switzerland) and an electrical conductivity meter (DDSJ-308A, Shanghai INESA Scientific Instrument Co., Shanghai, China), respectively. Total dissolved salt (TDS) was determined by the residue drying method. Available nitrogen (AN) was determined using a flow analyzer (BRAN LUEBBE AA3, SEAL Analytical, Norderstedt, Germany). Available phosphorus (AP) was determined using the molybdenum–antimony colorimetric method (UV-1800, Shimadzu, Kyoto, Japan). Available potassium (AK) was determined using atomic absorption spectrometry (Thermos Electron Corporation, Waltham, MA, USA).

2.4. Statistical Analysis

Normality of the data was checked through the Shapiro test before further analysis. This study employed one way analysis of variance (ANOVA) to analyze the significance of differences in soil TDS, biomass, growth parameters, and concentrations of Na, K, Ca, Mg, S, and Fe at different growth stages of Suaeda salsa. Multiple comparison tests were conducted using the least significant difference (LSD) method. All statistical analyses were performed using Microsoft Excel 2021 (Microsoft Corp., Redmond, WA, USA) and SPSS ver. 29.0 (IBM Corp., Armonk, NY, USA). All graphs were made in OriginPro 2022 (OriginLab Corp., Northampton, MA, USA). To minimize the impact of systematic errors on the analysis results, the raw data underwent prepossessing steps including deviation filtering, missing value imputation, and standardization. The results of multivariate analysis of variance (ANOVA) were used to screen deferentially expressed metabolites (DEMs) (p < 0.05), and Spearman’s correlation analysis was further performed on the deferentially expressed metabolites (|R| > 0.6, p < 0.05) to explore their association with physiological indicators.

3. Results and Analysis

3.1. Changes in Soil Physicochemical Properties Under Salt Stress

Different salt treatments significantly affected soil physicochemical properties at different sampling periods (Table 2). Soil pH remained within the range of 8.2 to 8.4 at all growth stages, with no significant differences among treatments. Electrical conductivity (EC) and soil soluble salts (TDSs) increased significantly with increasing salt concentration, reaching a peak at the HS treatment (p < 0.01). Available nitrogen content was relatively low during the seedling and fruiting stages, but increased significantly during the vegetative and flowering stages. It also showed an increasing trend with increasing salt gradient, reaching the highest value at the HS treatment (171.4 mg/kg during seedling stage and 187.6 mg/kg during fruiting stage, p < 0.01). Available phosphorus remained generally stable at all growth stages, with no significant differences among all treatments. The content of available potassium increased with increasing salt concentration at all growth stages, with the high-salt treatment groups, MS and HS, at the flowering stage and fruiting stage being significantly higher than the low-salt group (p < 0.01).

3.2. Effects of Salt Stress on the Growth Traits of Suaeda Salsa in Saline–Alkali Soil

Under salt stress, the dry weight, plant height, and stem diameter of Suaeda salsa gradually increased with the growth process, but significant differences were observed among different salt concentration treatments (Figure 2). Dry weight gradually increased with plant development at each growth stage. The CK and LS salt treatments showed significantly higher values than the control and high-salt treatments, whereas the HS salt treatment was significantly lower than the other treatments at all stages. Plant height increased continuously throughout the growth cycle. The CK and LS salt treatments promoted plant height, significantly exceeding the control and high-salt treatments at the vegetative, flowering, and fruiting stages, while the HS salt treatment significantly inhibited plant height growth. Stem diameter gradually increased with growth stage, with the CK and LS salt treatments being significantly higher than the control, while the MS salt treatment showed no significant difference as compared to the control; however, the HS salt treatment was significantly lower than the other treatments.

3.3. Effects of Salt Stress on Nutrient Absorption in Saline–Alkali Soil

Nutrient absorption in Suaeda salsa under salt stress exhibited significant dynamic changes. Different salt concentrations significantly affected the accumulation dynamics of major nutrient elements in Suaeda salsa (Figure 3). Potassium (K) content remained relatively stable or increased slightly at all growth stages, reaching 9.8 g/kg in the seedling stage under CK salt treatment, while attaining the highest value at the vegetative stage (approximately 13.5 g/kg), and decreasing slightly at HS (approximately 11.4 g/kg). Calcium (Ca) content decreased with increasing salt concentration, reaching approximately 25 g/kg in the seedling stage under CK, but decreasing to approximately 18 g/kg under HS. It remained at a low level (15–20 g/kg) during the flowering and fruiting stages. Sodium (Na) content increased significantly with increasing salt concentration, rising from approximately 80 g/kg in the seedling stage under CK to approximately 170 g/kg under HS. The concentration of magnesium (Mg) in the high-salt group was 18–22 g/kg, which further accumulated to 180–190 g/kg during the vegetative and flowering stages, which was more than twice that of the low-salt group. Mg content remained relatively stable under low-salt treatment (approximately 18–22 g/kg), but decreased significantly at all stages under the HS treatment (approximately 10–12 g/kg). Sulfur (S) content was highest in the seedling stage at the CK (approximately 5.8 g/kg), gradually decreasing with increasing salt concentration, and reaching only about 60% of that in the high-salt treatment. Iron (Fe) content fluctuated relatively little overall, increasing slightly from the vegetative stage to the flowering stage (approximately 0.4–0.6 g/kg), reaching a relatively high value (approximately 0.7 g/kg) during the fruiting stage under the MS treatment.

3.4. Effects of Salt Stress on Endogenous Hormones in Saline–Alkali Soil

Salt stress significantly affected the levels of endogenous hormones in Suaeda salsa at different growth stages (Figure 4). During the vegetative stage, abscisic acid (ABA) content increased significantly with increasing salt concentration. Zeatin and its derivatives showed significant increase under LS and MS salt treatments, while indoles and their derivatives showed significant increase under high-salt HS treatment. However, gibberellins and its derivative content decreased significantly. Furthermore, salicylic acid levels showed a continuous upward trend with increasing salt concentration, and were significantly higher in the MS and HS salt treatments than in the low-salt treatment. During the flowering stage, ABA content increased significantly with increasing salt concentration. Zeatin and its derivatives showed significant increases under LS and MS salt treatments, while indoles and their derivatives also showed significant increases. However, gibberellins and its derivatives did not show significant differences among treatments. Meanwhile, jasmonic acid accumulated significantly during the flowering stage with increasing salt concentration, and its content in the high-salt treatment was significantly higher than in the low-salt treatment.

3.5. Relationship Between Changes in Endogenous Hormones and Growth Traits of Suaeda salsa in Saline–Alkali Soil

Correlation analysis showed that the growth traits of Suaeda salsa were closely related to endogenous hormone levels. During the vegetative stage, plant height, stem diameter, and biomass were all significantly correlated with endogenous hormone levels (Figure 5). Plant height showed a highly significant positive correlation with gibberellins, zeatin, its derivatives, and abscisic acid (ABA), as well as a significant positive correlation with indole derivatives. Stem diameter showed a highly significant positive correlation with gibberellins, zeatin, its derivatives, and ABA, as well as a significant negative correlation with indole derivatives. Biomass showed a highly significant positive correlation with gibberellins, zeatin, its derivatives, and ABA, as well as a significant positive correlation with indole derivatives. During the flowering stage, plant height showed a highly significant positive correlation with zeatin, its derivatives, and ABA, as well as a significant positive correlation with indole derivatives. Stem diameter showed a highly significant positive correlation with zeatin, its derivatives, and ABA, as well as a significant positive correlation with indole derivatives. Biomass also showed a highly significant positive correlation with zeatin, its derivatives, and ABA.

4. Discussion

Soil salinity imposes complex and dynamic stress on halophytes like Suaeda salsa, affecting soil physicochemical properties, water availability, nutrient supply patterns, ion uptake and balance, and endogenous hormone signaling [25]. As salinity increases in our pot experiments, we observed significant rises in soil electrical conductivity (EC) and total dissolved solids (TDSs), along with decreases in soil solution osmotic potential. These changes reduce root zone water availability and limit rhizosphere water absorption. Such soil-mediated constraints translate into the classical low-salt promotion, high-salt inhibition growth pattern commonly observed in halophytes and other salt-tolerant species [26]. This overall trend is strongly supported by recent syntheses summarizing salt-stress responses in a wide range of plant taxa [27]. Under low salinity (LS, 800 mM), modest Na concentrations may act as osmotic regulators, helping to maintain cell turgor and contributing to fleshy tissue development typical of succulent halophytes [28]. This effect likely underlies the observed increases in plant height and aboveground biomass under low to moderate salt. Such beneficial osmotic regulation by Na within optimal ranges is supported by earlier works on salt-adapted plants [29].
However, once salinity exceeds a physiological threshold (≥1600 mM NaCl), negative effects become dominant. Osmotic stress, Na toxicity, and competitive inhibition of essential cation uptake (K, Ca, Mg) disrupt ionic homeostasis and water balance, reducing turgor and impairing stomatal conductance and photosynthesis [30]. These physiological disturbances ultimately lead to suppressed growth, weaker stems, and lower biomass accumulation [31]. The dramatic drop in K/Na and Ca/Na ratios, along with reduced Ca and Mg concentrations, indicates severe ionic imbalance, which is a hallmark of salt-induced nutrient deficiency and toxicity stress [32]. This ionic imbalance likely compromises cell wall stability, enzyme function, membrane integrity, and overall metabolic capacity, impairing growth and survival under high salt stress [33]. In some cases, under low K conditions, Na may partially substitute for K to maintain osmotic balance and support photosynthetic metabolism [34]. While such substitution has limitations and cannot compensate for the loss of Ca/Mg or the disruption to signaling and metabolic processes under severe salinity [35,36,37], it may still provide partial relief under moderate stress.
Hormonal regulation under salt stress: The growth-to-stress transition and interactions between ions and hormones. The findings reveal that soil salinity alters endogenous phytohormone profiles, with these changes affecting ion balance and plant growth [38,39]. Using targeted metabolomics, we observed that at low-to-moderate salinity, growth-promoting hormones (e.g., auxin (IAA), cytokinins such as zeatin) are relatively elevated and correlate positively with growth traits (height, dry weight, stem diameter), consistent with previous findings [9,40,41]. This suggests that under moderate salt, endogenous hormonal balance still supports growth, possibly through enhanced cell elongation, division, tissue differentiation, and root/shoot development, favoring biomass accumulation [42]. By contrast, under high salinity, there is a marked accumulation of stress responsive hormones such as abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA), concomitant with a clear suppression of growth-promoting hormones such as gibberellins (GAs) [37]. This shift reflects a physiological switch from a growth-oriented hormonal regime to a stress-adaptive regime, emphasizing survival, osmotic regulation, ionic homeostasis, antioxidative defense, and resource reallocation, rather than continued biomass production [36,37,38,39].
This interpretation is supported by recent reviews and mechanistic studies. Plant hormone networks under salt stress (ABA, cytokinin, auxin, GA, JA, SA, ethylene, etc.) exhibit extensive crosstalk, coordinating stress responsive genes, ion transporters, and osmotic and oxidative stress pathways [9,40,41]. Hormonal signaling integrates environmental cues and transcriptional regulators to mediate growth stress trade-offs through processes such as ROS regulation, stomatal closure, root remodeling, and ion compartmentalization [42,43,44]. Notably, suppression of GA signaling under high salinity is adaptive, and reduced GA biosynthesis or signaling enhances salt tolerance [45], as observed in GA-deficient or DELLA-stabilized mutants, suggesting that downregulating GA conserves energy and limits growth under unfavorable conditions [46,47]. Meanwhile, elevated ABA (and other stress hormones) modulates stomatal closure, water loss, ion transport (via activation of antiporters, ion channels, and vacuolar compartmentalization), and antioxidant responses, all of which contribute to cellular survival under ionic and osmotic stress [48].
In halophytes, like Suaeda salsa, this hormonal reprogramming appears particularly important. Unlike many glycophytes, halophytes already possess a baseline capacity for Na tolerance, succulence, and ion compartmentalization [47]. The shift from a growth supportive hormone profile toward a stress responsive one likely represents an adaptive reconfiguration that optimizes survival under incremental salinity increase, at the cost of growth, which is a trade-off that ensures long-term persistence in saline–alkali soils [49,50]. Thus, the positive correlations between cytokinins/zeatin (or IAA) and growth traits at low-to-moderate salt do not imply that such relationships remain valid at high salinity. The hormonal balance changes and stress protective signaling via ABA, JA, SA (and possibly others) become dominant, which explains the observed growth inhibition under high-salinity treatments [51,52]. Our data show that high salinity leads to accumulation of Na in plant tissues, concomitant with reduced uptake of essential cations (K, Ca, Mg). This ionic imbalance is a key factor in salt-induced toxicity and growth suppression. However, hormonal regulation likely plays a compensatory role [53].
Recent studies suggest that under salt or drought stress, hormonal signaling (ABA, JA, SA, auxin, cytokinins, ethylene, strigolactones, etc.) interacts with ion transporters, transcription factors, and ROS regulatory systems. These interactions help reconfigure root architecture, activate ion efflux or compartmentalization, adjust membrane transport, and enhance antioxidative defenses [54]. For example, ABA can induce expression of Na/H antiporters (e.g., vacuolar NHX) or plasma membrane Na transporters (e.g., SOS1 via Ca SOS pathway), promote K retention, and modulate Ca/Mg transport to maintain cell viability under ionic stress. Meanwhile, certain transcription factors (e.g., AP2/ERF, NAC, WRKY, bZIP) integrate hormonal and stress signals to orchestrate expression of osmoprotectant synthesis, ion transporters, antioxidant enzymes, and stress protective proteins [55].
In Suaeda salsa, Ca and Mg reductions under high salinity likely arise from competition with Na uptake. Simultaneously, upregulation of ABA, JA, and SA, coupled with GA downregulation and auxin/cytokinin rebalancing, indicates a hormone-mediated adaptive response that conserves energy, maintains ion homeostasis, and activates defense and ion compartmentalization mechanism [56,57]. This interpretation aligns with the concept of a coordinated ion hormone growth regulatory network as central to salt-stress adaptation in halophytes and other tolerant species [58]. Therefore, rather than viewing decreased Ca/Mg simply as a passive consequence of ionic competition, it is more appropriate to consider it as part of an integrated adaptive response, regulated in part by hormonal signaling, which is an interpretation consistent with modern frameworks of salt-stress physiology [59,60].

Novelty and Practical Implications

Compared with many previous studies, especially those based on hydroponic culture, single-ion focus, or single-hormone measurements, this work offers several advances, and realistic soil-based salinity gradients. By using soil as the growth medium and applying graded NaCl treatments, this design more closely mimics natural saline–alkali environments (with their spatial heterogeneity, ionic competition, osmotic gradients, and physical constraints), rather than the artificially uniform conditions of hydroponics [61]. As well as the integration of targeted metabolomics (quantifying multiple endogenous hormones), plant growth, biomass, and morphological traits offer a comprehensive, multidimensional perspective on plant salt adaptation, revealing the coordination of hormonal networks with ion homeostasis in governing growth survival trade-offs [59]. It also offers mechanistic insight into the growth-to-stress transition threshold. This study identifies a salinity threshold beyond which growth-promoting hormonal and ionic balance collapses, and stress-responsive regulation predominates. Such threshold-based reconfiguration elucidates the dynamic physiological shift halophytes undertake to cope with increasing salt stress. Furthermore, this study moves beyond simplistic models (e.g., Na toxicity alone, or single-hormone effects) toward a system-level understanding of salt tolerance. Collectively, these features contribute novel empirical evidence to current salt-stress research and provide a refined conceptual model applicable to halophyte biology and saline–alkali land restoration.

5. Conclusions

1.
Salt stress significantly alters the growth environment and metabolic balance of Suaeda salsa in saline–alkali land. As the salt gradient increases, soil electrical conductivity and soluble salts continue to rise, and Na accumulates in the plant and inhibits the absorption of Ca, Mg, and other ions, thereby affecting overall nutrient homeostasis.
2.
Suaeda salsa showed a typical low-salt environment promotes growth and high salt inhibits growth response to salt stress. LS had growth-promoting effects, but MS and HS significantly inhibited growth traits such as plant height and biomass. The seedling and flowering stage were more sensitive to salt stress.
3.
Salt tolerance of Suaeda salsa is closely related to the dynamics of endogenous hormones. Salt stress promotes a significant increase in the content of IAA, ABA, JA, and SA, forming a defensive signaling core. At the same time, IAA maintains a high level in the medium-salt stage to maintain growth activity, while the decrease in GA content is consistent with the growth inhibition process.
4.
The salt tolerance mechanism of Suaeda salsa is characterized by a comprehensive regulatory model of “moderate salt stimulation hormone rebalancing homeostasis maintenance”. Hormone levels are significantly correlated with growth traits. The dynamic regulation of endogenous hormones is not only a key physiological strategy for salt adaptation, but also provides a theoretical basis for understanding the community-building advantages of halophytes in saline–alkali ecosystems and their potential application in saline–alkali land restoration.

Author Contributions

Conceptualization, J.H. and W.M.; methodology, J.H., W.M., A.A. and W.Z.; software, J.H. and K.Z.; validation, J.H., Y.W., X.F., D.Z. and A.A.; formal analysis, W.Z., Y.W., D.Z., K.Z. and A.A.; investigation, X.F., Y.W. and A.A.; resources, K.Z., Y.W., X.F. and D.Z.; data curation, W.M. and J.H.; writing—original draft preparation, J.H.; writing—review and editing, J.H., W.Z., A.A. and W.M.; visualization, Y.W. and X.F.; supervision, W.M., W.Z. and A.A.; project administration, W.M.; funding acquisition, W.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Chinese Academy of Sciences.

Data Availability Statement

The data presented in this study are available upon request from the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Growth status of Suaeda salsa at different growth stages. (a) Seedling stage; (b) vegetative stage; (c) flowering stage; (d) fruiting stage. Note: CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
Figure 1. Growth status of Suaeda salsa at different growth stages. (a) Seedling stage; (b) vegetative stage; (c) flowering stage; (d) fruiting stage. Note: CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
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Figure 2. Growth dynamics of Suaeda salsa under salt stress: (a) dry weight; (b) plant height; (c) stem diameter. Note: vertical error bars represent ± standard error (N = 5). Different lowercase letters indicate statistically significant differences between different treatments at the same sampling time (p < 0.01). CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
Figure 2. Growth dynamics of Suaeda salsa under salt stress: (a) dry weight; (b) plant height; (c) stem diameter. Note: vertical error bars represent ± standard error (N = 5). Different lowercase letters indicate statistically significant differences between different treatments at the same sampling time (p < 0.01). CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
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Figure 3. Nutrient dynamics of Suaeda salsa under salt stress: (a) potassium (K), (b) calcium (Ca), (c) sodium (Na), (d) magnesium (Mg), (e) sulfur (S), and (f) iron (Fe). Note that vertical error bars represent ± standard error (N = 5). Different lowercase letters indicate statistically significant differences between different treatments at the same sampling time (p < 0.01) CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
Figure 3. Nutrient dynamics of Suaeda salsa under salt stress: (a) potassium (K), (b) calcium (Ca), (c) sodium (Na), (d) magnesium (Mg), (e) sulfur (S), and (f) iron (Fe). Note that vertical error bars represent ± standard error (N = 5). Different lowercase letters indicate statistically significant differences between different treatments at the same sampling time (p < 0.01) CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
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Figure 4. Effects of salt stress on endogenous hormones and secondary metabolism in Suaeda salsa. (a) Changes in endogenous hormones during the vegetative stage; (b) changes in endogenous hormones during the flowering stage; (c) changes in secondary metabolism during vegetative and flowering development stage. Note: CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
Figure 4. Effects of salt stress on endogenous hormones and secondary metabolism in Suaeda salsa. (a) Changes in endogenous hormones during the vegetative stage; (b) changes in endogenous hormones during the flowering stage; (c) changes in secondary metabolism during vegetative and flowering development stage. Note: CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM.
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Figure 5. Correlation between changes in endogenous hormones and growth traits in Suaeda salsa under salt stress (a) vegetative stage and (b) flowering stage. Note: Gibberellin and its derivatives (GA) include the main bioactive gibberellins such as Gibberellin1 (GA1), Gibberellin3 (GA3), and Gibberellin4 (GA4); Indole and its derivatives (IAA and related indole compounds) include indole-3-acetic acid (IAA), indoleacetyl glutamic acid (IAA-Glu), and indole-3-acetyl-L-aspartic acid (IAA-Asp); Zeatin and its derivatives (ZT) include zeatin (ZT) and its biosynthetically related cytokinins such as zeatin riboside (ZR), trans-zeatin (tZ), and isopentenyl adenine (iP). Asterisks indicate statistical significance: * p < 0.05; ** p < 0.01.
Figure 5. Correlation between changes in endogenous hormones and growth traits in Suaeda salsa under salt stress (a) vegetative stage and (b) flowering stage. Note: Gibberellin and its derivatives (GA) include the main bioactive gibberellins such as Gibberellin1 (GA1), Gibberellin3 (GA3), and Gibberellin4 (GA4); Indole and its derivatives (IAA and related indole compounds) include indole-3-acetic acid (IAA), indoleacetyl glutamic acid (IAA-Glu), and indole-3-acetyl-L-aspartic acid (IAA-Asp); Zeatin and its derivatives (ZT) include zeatin (ZT) and its biosynthetically related cytokinins such as zeatin riboside (ZR), trans-zeatin (tZ), and isopentenyl adenine (iP). Asterisks indicate statistical significance: * p < 0.05; ** p < 0.01.
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Table 1. Initial soil physical and chemical properties.
Table 1. Initial soil physical and chemical properties.
SoilpHECTDSDensityWHCOrganic
Matter		Quick-Acting
Nitrogen		Quick-Acting
Phosphorus		Quick-Acting
Potassium
(cm)(mS cm−1)(g kg−1)(g cm−3)(%)(g kg−1)(mg kg−1)(mg kg−1)(mg kg−1)
0–207.80.41.71.425.010.159.034.1664.1
Note: EC = electrical conductivity; TDS = total dissolved salts; WHC = field water-holding capacity.
Table 2. Soil physicochemical properties at different sampling periods.
Table 2. Soil physicochemical properties at different sampling periods.
Sampling
Period		TreatmentspHECTDSQuick-Acting NitrogenQuick-Acting PhosphorusQuick-Acting Potassium
(mS cm−1)(g kg−1)(mg kg−1)(mg kg−1)(mg kg−1)
Seedling
stage		CK8.3 ± 0.02 a0.7 ± 0.07 d2.8 ± 0.26 d114.8 ± 5.18 c31.8 ± 1.53 a446.8 ± 3.71 a
LS8.2 ± 0.03 ab2.4 ± 0.11 c7.2 ± 0.33 c120.4 ± 4.24 c33.7 ± 0.44 a463.9 ± 6.33 a
MS8.2 ± 0.42 ab3.7 ± 0.29 b11.7 ± 0.42 b158.6 ± 0.77 b30.2 ± 2.18 a460.5 ± 10.63 a
HS8.2 ± 0.24 b5.5 ± 0.29 a16.5 ± 0.94 a171.4 ± 4.61 a31.3 ± 2.21 a451.2 ± 8.31 a
Vegetative stageCK8.6 ± 0.06 a0.3 ± 0.03 d1.2 ± 0.08 d114.2 ± 5.64 c30.2 ± 1.45 a440.8 ± 10.81 b
LS8.3 ± 0.04 b2.2 ± 0.45 c6.3 ± 1.28 c142.0 ± 10.18 b31.0 ± 2.38 a465.3 ± 18.09 ab
MS8.2 ± 0.01 b4.0 ± 0.19 b11.2 ± 0.47 b164.5 ± 1.06 a35.8 ± 1.69 a489.6 ± 3.02 a
HS8.3 ± 0.03 b5.3 ± 0.10 a14.9 ± 0.29 a178.1 ± 5.28 a35.5 ± 2.75 a481.7 ± 18.27 ab
Flowering stageCK8.7 ± 0.05 a0.2 ± 0.17 d0.7 ± 0.04 d114.7 ± 2.97 c39.1 ± 9.34 a484.8 ± 11.44 a
LS8.8 ± 0.22 a1.7 ± 0.23 c5.0 ± 0.43 c127.5 ± 14.33 bc22.9 ± 2.97 b466.7 ± 22.38 a
MS8.4 ± 0.06 ab3.4 ± 0.42 b10.5 ± 0.52 b163.3 ± 1.83 ab28.7 ± 3.69 ab476.8 ± 11.23 a
HS8.3 ± 0.02 b5.1 ± 0.10 a14.1 ± 0.33 a180.7 ± 21.54 a34.9 ± 1.60 ab494.0 ± 5.73 a
Fruiting stageCK8.6 ± 0.07 a0.5 ± 0.05 d1.5 ± 0.16 d94.1 ± 10.12 c22.1 ± 2.27 ab447.6 ± 11.89 b
LS8.4 ± 0.05 b2.1 ± 0.16 c5.7 ± 0.45 c151.4 ± 9.44 b18.9 ± 1.92 b447.4 ± 4.57 b
MS8.3 ± 0.06 b3.6 ± 0.15 b9.9 ± 0.49 b172.0 ± 1.86 ab20.2 ± 1.81 b471.9 ± 5.52 ab
HS8.3 ± 0.02 b5.0 ± 0.41 a13.7 ± 1.15 a187.6 ± 19.41 a27.0 ± 2.20 a491.7 ± 11.79 a
Note: The value was mean ± standard error (N = 5). Different lowercase letters indicate statistically significant differences (p < 0.01). CK = control 0 mM, LS = low salinity 800 mM, MS = moderate salinity 1600 mM, and HS = high salinity 2400 mM. EC = electrical conductivity; TDS = total dissolved salts.
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Hao, J.; Wang, Y.; Feng, X.; Mai, W.; Zhang, D.; Zhang, K.; Zhang, W.; Azeem, A. Role of Endogenous Hormone Dynamics in Regulating the Development of Suaeda salsa L. Under Salt Stress. Agronomy 2025, 15, 2859. https://doi.org/10.3390/agronomy15122859

AMA Style

Hao J, Wang Y, Feng X, Mai W, Zhang D, Zhang K, Zhang W, Azeem A. Role of Endogenous Hormone Dynamics in Regulating the Development of Suaeda salsa L. Under Salt Stress. Agronomy. 2025; 15(12):2859. https://doi.org/10.3390/agronomy15122859

Chicago/Turabian Style

Hao, Jinxiu, Yanyan Wang, Xinzhi Feng, Wenxuan Mai, Dong Zhang, Ke Zhang, Wentai Zhang, and Ahmad Azeem. 2025. "Role of Endogenous Hormone Dynamics in Regulating the Development of Suaeda salsa L. Under Salt Stress" Agronomy 15, no. 12: 2859. https://doi.org/10.3390/agronomy15122859

APA Style

Hao, J., Wang, Y., Feng, X., Mai, W., Zhang, D., Zhang, K., Zhang, W., & Azeem, A. (2025). Role of Endogenous Hormone Dynamics in Regulating the Development of Suaeda salsa L. Under Salt Stress. Agronomy, 15(12), 2859. https://doi.org/10.3390/agronomy15122859

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