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Article

Evaluation of Sesuvium portulacastrum (L.) L. as a Halophytic Candidate for the Phytoremediation of Industrial Wastewater

by
Tamanna Taskeen
1,
Sanket Chandrakant Patil
1,
Ravishanker Patil
1,
Ganesh Chandrakant Nikalje
2,* and
Suprasanna Penna
1,*
1
Amity Institute of Biotechnology (AIB), Amity University Maharashtra, Panvel, Mumbai 410206, India
2
Department of Botany, Seva Sadan’s R. K. Talreja College of Arts, Science and Commerce, Ulhasnagar 421003, India
*
Authors to whom correspondence should be addressed.
Sustainability 2026, 18(11), 5439; https://doi.org/10.3390/su18115439
Submission received: 22 February 2026 / Revised: 12 April 2026 / Accepted: 16 April 2026 / Published: 28 May 2026
(This article belongs to the Special Issue Plant Biotic and Abiotic Stresses: Issues of Plant Health and Sustainable Food Security)
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Abstract

This study evaluated the phytoremediation potential of the halophytic plant Sesuvium portulacastrum (L.) L. for treating industrial wastewater (IWW) in a hydroponic system over a nine-day exposure period. After treatment, the physicochemical analysis of IWW revealed a significant decrease in chemical oxygen demand (COD), biological oxygen demand (BOD), TSs (total solids), total dissolved solids (TDSs), TSSs (total suspended solids), ammonia, phosphate, and nitrate. The COD and BOD were reduced by 90.7% and 82.9%, respectively. The metal analysis indicated a significant decrease in Fe (95%), Mn (87.4%), and Al (93.9%) and complete removal of Ni, Pd, and Zn. The plant stress responses were assessed through the estimation of photosynthetic pigments (Chlorophyll-a, Chlorophyll-b, Total chlorophyll), phenolic and flavonoid contents, and antioxidant activity. Total chlorophyll declined from 1.449 mg/g (control) to 1.20 mg/g on Day 3, followed by partial recovery to 1.25 mg/g by Day 9, indicating physiological acclimatization. Total phenolic content reached 14 mg GAE/g in leaves and 12 mg GAE/g in stems on Day 6, while Total flavonoid content increased from ~70 µg/g (control) to 115 µg/g on in leaves. The metabolic profiling using GC-MS/MS revealed distinct time- and tissue-specific metabolic responses, with 53 metabolites identified in roots and 62 metabolites in leaves. The major differentially accumulated metabolites were sucrose, pinitol, talose and psicose, with peak accumulation at Day 6. A biphasic metabolic response pattern, characterized by early stress perception followed by adaptability, was observed. Phytotoxicity assays using Vigna radiata demonstrated improved germination from 15% (untreated IWW) to 95% after treatment. Overall, the study highlights the strong phytoremediation potential of halophyte S. portulacastrum as an environmentally friendly alternative for industrial wastewater remediation.

1. Introduction

Industrial activities have led to significant water pollution worldwide, with an estimated 300–400 megatons of industrial waste discharged into water bodies annually [1]. Heavy metals, petroleum hydrocarbons, and untreated industrial effluents contaminate water resources, posing serious risks to human health and the environment. Rapid Industrial development has generated widespread environmental concerns on a global scale. Studies from the United States have shown that even small-scale mining operations can cause significant ecological damage, including water pollution and a marked reduction in stream invertebrate diversity [2]. However, industrial pollution remains one of the major contributors to global water contamination. The rapid industrial growth observed over the past decade has further intensified this problem, as untreated wastewater discharged into rivers poses a significant threat to both human health and ecosystem stability [3].
Most untreated industrial effluents are discharged into nearby water bodies, particularly rivers and streams, leading to soil and groundwater contamination in surrounding areas and degrading the agricultural productivity and ecological health [4]. Once pollutants enter waterways, they can contaminate drinking water sources, harm aquatic ecosystems by poisoning fish and other organisms, and ultimately affect human health [1]. Proper management and treatment of industrial wastewater are therefore essential to mitigate these adverse impacts. While several industries employ physical and chemical treatment methods due to their efficiency, these approaches have notable limitations [5]. Although large industries often possess wastewater treatment facilities, small-scale industries frequently lack such infrastructure due to financial constraints and low profit margins. As a result, inadequate management of industrial wastewater remains a widespread issue [6,7].
The impacts of industrial wastewater pollution are multifaceted. Physically, it can degrade water quality by increasing turbidity and reducing dissolved oxygen levels. Biologically, pollutants can bioaccumulate along the food chain, leading to elevated concentrations of heavy metals in higher trophic levels [4]. In contrast, biological treatment methods offer several advantages, including efficiency in removing organic pollutants, energy savings, environmental sustainability, and operational flexibility [2]. The use of microorganisms in wastewater treatment represents a cost-effective and eco-friendly approach, contributing to improved water quality and ecosystem health [8]. These methods are particularly effective in targeting a wide range of organic pollutants, including complex compounds resistant to chemical degradation. Microorganisms such as bacteria and fungi degrade organic contaminants into simpler, less toxic end products, including carbon dioxide, water, and microbial biomass [9]. Through this process, wastewater is effectively treated and rendered less hazardous to the environment [10].
Phytoremediation is another sustainable approach for environmental cleanup, utilizing plants to absorb, metabolize, and detoxify contaminants from soil, water, and air, offering significant potential for pollution mitigation [11]. Several aquatic plant species, including halophytes, have been successfully used in the remediation of heavy metals and other pollutants [11]. S. portulacastrum (Family- Aizoaceae) is a promising candidate due to its higher tolerance to heavy metals and other pollutants [12,13,14,15]. Its overall phytoremediation potential makes it suitable for industrial wastewater detoxification. The present study investigates the phytoremediation efficiency of S. portulacastrum against metallic, organic, and inorganic contaminants under hydroponic conditions, and evaluates the phytotoxicity of treated industrial wastewater on seed germination and plant survival.

2. Materials and Methods

S. portulacastrum plants were collected from their natural habitat at the Mankhurd–Vashi Creek, Mumbai, Maharashtra, India (19°02′53.9″ N, 73°06′41.0″ E; Mumbai, Maharashtra, India) and maintained under laboratory conditions. Nodal cuttings were grown hydroponically in plastic containers (1000 mL capacity) supplemented with 170 mM NaCl and maintained for 20 days to induce root formation. After acclimatization, plants were exposed to industrial wastewater (IWW). Samples were collected at different exposure durations (3, 6, and 9 days). Control plants (Day 0) were maintained under identical hydroponic conditions with 170 mM NaCl but without exposure to industrial wastewater, ensuring that observed responses were attributable to IWW treatment rather than salinity differences.

2.1. Phytodegradation of Industrial Wastewater (IWW)

IWW samples were collected from the Kasarda River flowing through the Taloja industrial area in Navi Mumbai, India (19°03′45.2″ N, 73°06′41.0″). Actively growing, rooted plants obtained from hydroponic culture were exposed to the industrial wastewater in a separate experimental setup. Exposure durations were set at 3, 6, and 9 days, while the control group (0 days) consisted of plants not exposed to IWW. All experiments were conducted in triplicate (n = 3). A parallel no-plant control (IWW-only) was not included in the present experimental design. Therefore, the potential contribution of abiotic processes such as sedimentation, precipitation, or adsorption cannot be independently quantified within this study.

2.2. Characterization of IWW

To assess the composition of the industrial wastewater, physicochemical parameters, including Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Solids (TSs), Total Suspended Solids (TSSs), Total Dissolved Solids (TDSs), silicates, sulfates, and ammonia, were estimated. Heavy metal contamination in the effluent was analyzed using Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES; Agilent Technologies 5100 Santa Clara, CA, USA) following the method of Watharkar et al. [16]. Pre- and post-exposure analyses of IWW were performed using standardized methodologies and identical instrumentation to ensure analytical consistency and accuracy. COD was determined using the dichromate reflux method (APHA, 5220B). BOD5 was measured by incubating diluted samples at 20 °C for 5 days in the dark (APHA 5210B). Samples were preserved at 4 °C and analyzed within 24 h. Dilution and pH adjustment (to 7.0 ± 0.2) were performed where required.

2.3. Pigment Analysis

Chlorophyll content in S. portulacastrum was estimated using a spectrophotometric method [17,18] with dimethyl sulfoxide (DMSO) as the extraction solvent, following the protocol of Hiscox and Israelstam (1979). Approximately 100 mg of fresh leaf tissue was homogenized in 10 mL of DMSO. To minimize turbidity interference, the extract was centrifuged at 10,000 rpm for 10 min, and the supernatant was used for absorbance measurements. The homogenate was incubated at 65 °C for 4 h and then cooled to room temperature. Absorbance was recorded at 663 nm and 645 nm, with DMSO serving as the blank. Chlorophyll a, chlorophyll b, and total chlorophyll contents were calculated using standard equations [18]. Chlorophyll levels were monitored at regular intervals (Day 0, Day 3, Day 6, and Day 9) to evaluate the effects of industrial wastewater stress, providing an effective assessment of plant stress responses over time.

2.4. Phytochemical Analysis

2.4.1. Determination of Total Phenolic Content (TPC)

A spectrophotometric assay, as described by Molole et al. [18], was used to quantify the total phenolic content in methanolic extracts of both control and stressed S. portulacastrum. Fresh leaf tissues were collected from control plants (0 day, not exposed to IWW) and IWW-treated plants (3, 6, and 9 days). For extraction, 500 mg of fresh leaf tissue was homogenized in 10 mL of methanol and centrifuged at 10,000 rpm for 10 min at 4 °C. The supernatant was collected and used for phenolic estimation. Briefly, 200 µL of the methanolic extract was mixed with 1 mL of Folin–Ciocalteu reagent (diluted 1:10 with distilled water) and incubated in the dark for 5 min. Subsequently, 800 µL of 7.5% (w/v) sodium carbonate (Na2CO3) was added, followed by incubation in the dark for 90 min. Absorbance was measured at 765 nm. A standard curve was prepared using gallic acid, and the phenolic content was expressed as milligrams of gallic acid equivalents per gram of fresh weight (mg GAE g−1 FW).

2.4.2. Determination of Total Flavonoid Content (TFC)

The total flavonoid content of methanolic extracts from fresh leaf and stem tissues of S. portulacastrum was determined for both control (Day 0) and IWW-treated plants (Day 3, Day 6, and Day 9) following Molole et al. [18]. Approximately 500 mg of fresh plant tissue was homogenized in 10 mL of methanol and centrifuged at 10,000 rpm for 10 min at 4 °C. The supernatant was collected as the methanolic extract. Briefly, 200 µL of the extract was mixed with 600 µL of 95% ethanol, 40 µL of aluminium chloride, and 40 µL of potassium acetate (1 M), and then diluted with 1.12 mL of distilled water. After incubation in the dark for 30 min, absorbance was measured at 415 nm using ethanol as a blank. A standard curve was prepared using quercetin, and flavonoid content was expressed as milligrams of quercetin equivalents per gram of extract (mg QE g−1).

2.4.3. Antioxidant DPPH Activity

A modified DPPH assay was employed to determine the radical scavenging potential of S. portulacastrum methanolic extracts, following the method of Brand-Williams et al. [19] with minor modifications as described by Patil et al. [20]. The antioxidant capacity of the extracts was evaluated based on their ability to neutralize free radicals, reflecting their potential to mitigate oxidative stress. Methanolic extracts were prepared from fresh leaf and stem tissues collected from control (Day 0) and IWW-treated plants (Day 3, Day 6, and Day 9). A stock solution of DPPH (0.1 mM) was prepared in methanol and diluted to obtain an initial absorbance of 0.90 ± 0.02 at 515 nm, ensuring uniform radical concentration and assay reproducibility.
For the assay, 500 µL of the extract was mixed with the DPPH working solution and incubated in the dark for 30 min. Absorbance was measured at 517 nm using methanol as the blank. A control was prepared without the extract. The radical scavenging capacity (RSC) was calculated using the following formula:
%RSC = [(A(control) − A(sample))/A(control)] × 100

2.4.4. Reducing Sugar Content

The dinitrosalicylic acid (DNSA) method [21] was used to determine the reducing sugar content of S. portulacastrum extracts. Fresh leaf and stem tissues were collected from control (Day 0) and IWW-treated plants (Day 3, Day 6, and Day 9). For extraction, 500 mg of fresh tissue was homogenized in 10 mL of distilled water, sonicated for 10 min, and centrifuged at 10,000 rpm for 10 min at 4 °C. For the DNSA assay, 1 mL of the aqueous extract was mixed with 1 mL of distilled water and 2 mL of DNSA reagent. The mixture was heated in a boiling water bath for 10 min and cooled to room temperature, and absorbance was measured at 540 nm. A standard curve was prepared using glucose (dextrose), and reducing sugar content was expressed as milligrams of glucose equivalents per gram of fresh weight (mg GE g−1 FW).

2.4.5. Sampling and Extraction for Metabolite Profiling by GC-MS/MS

Metabolic profiling of S. portulacastrum was performed using fresh leaf and stem tissues following the GC–MS-based extraction protocol originally described by Roessner et al. [22], with modifications as reported by Kulkarni et al. [23]. Approximately 500 mg of fresh leaf and stem tissues were ground in a porcelain mortar and pestle using pre-chilled methanol and incubated at room temperature for 30 min. The samples were then sonicated and centrifuged at 10,000 rpm for 10 min at 4 °C. The resulting supernatant was collected and used for further analysis. Metabolic analysis was conducted at 0, 3, 6, and 9 days of treatment using a Shimadzu QP2010 gas chromatograph coupled with a mass spectrometer (GC–MS), following Kulkarni et al. [23]. Samples (1 µL) were injected in split mode (1:10). Mass spectra were recorded over m/z 50–600. The ionization voltage was maintained at 70 eV. For gas chromatography, a Restek capillary column (XTI-5; 60 m × 0.25 mm; Restek, Bellefonte, PA, USA) was used under temperature-programmed conditions. The initial column temperature was set at 80 °C and held for 2 min, followed by a linear increase at 10 °C min−1 to 280 °C, where it was maintained for 7 min. The GC–MS interface temperature was set at 290 °C, and the injection port temperature at 280 °C. Helium was used as the carrier gas at a flow rate of 1 mL min−1, with a total run time of 30 min. Metabolite identification was performed by comparing retention times and fragmentation patterns with mass spectra available in the NIST spectral library (version 1.10 beta, Shimadzu, Kyoto, Japan) with ≥80% match. Peak areas were normalized using an internal standard (ribitol).

2.4.6. Phytotoxicity Assay

Twenty Vigna radiata seeds were placed in Petri dishes lined with moistened blotting paper and irrigated daily with IWW samples corresponding to 0, 3, 6, and 9 days of treatment. Germination percentage was recorded to evaluate initial phytotoxicity, while root and shoot growth of the germinated seeds were measured to assess effects on seedling development [24]. Prior to the germination experiment, seeds were visually inspected, and only healthy, undamaged seeds were selected to ensure uniformity in seed quality and a high germination rate (95%).

2.4.7. Statistical Analyses

MetaboAnalyst 6.0 software was used for all statistical analyses and data processing. Differences among treatments (0, 3, 6, and 9 days) were evaluated using one-way analysis of variance (ANOVA), followed by Tukey’s honestly significant difference (HSD) post hoc test (p < 0.05). In addition, an unpaired Student’s t-test (p < 0.01 and p < 0.05) was applied where appropriate. To examine overall variance patterns among treatments, Principal Component Analysis (PCA) was performed and visualized using score plots. For feature selection and discrimination among treatment groups, Partial Least Squares–Discriminant Analysis (PLS-DA) was conducted, along with Variable Importance in Projection (VIP) score analysis. Cluster analysis based on a correlation matrix was used to evaluate relationships and relative abundance of detected metabolites, and results were visualized using a heat map. The heat map highlighted variations across treatments, emphasizing significant changes in metabolite levels in response to industrial wastewater stress.

3. Results

3.1. Impact of S. portulacastrum on the Physicochemical Profile of IWW

S. portulacastrum plants grown in industrial wastewater (IWW) for up to nine days (Figure 1) exhibited a visible change in the colour of the wastewater over the course of the experiment.
The results of the phytoremediation study revealed that ammonium, phosphate, and nitrate levels decreased in a time-dependent manner (Figure 2A). Similarly, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Solids (TSs), Total Suspended Solids (TSSs), and Total Dissolved Solids (TDSs) all showed a declining trend. COD and BOD were reduced by 90.7% and 82.9%, respectively, indicating a strong phytodegradation potential of the halophyte S. portulacastrum for reducing organic pollutant loads. A significant decrease was also observed in TS (49.4%), TDS (47.1%), and TSS (54.4%) (Figure 2B), suggesting efficient sedimentation and/or filtration of particulate matter. Furthermore, phosphate and nitrate levels decreased by 68.9% and 63.4%, respectively. Halophytes are known to possess specialized salt glands, succulent tissues, and ion compartmentalization mechanisms that facilitate the sequestration and stabilization of dissolved salts and suspended particulates [25,26]. The observed reductions in phosphate and nitrate indicate the plant’s ability to immobilize these nutrients, likely through root adsorption, precipitation, and metabolic assimilation, as reported in previous phytoremediation studies involving saline and industrial effluents [27].
Overall, these results suggest that S. portulacastrum is an efficient phytoremediator of IWW, with a strong capacity to reduce COD, BOD, TDS, and TSS [28]. The buffering effect observed in treated IWW may be attributed to ion exchange, carbonate precipitation, and organic acid regulation in the rhizosphere, processes commonly associated with constructed wetland-type phytoremediation systems [29].
The reduction in high metal concentrations in IWW treated with S. portulacastrum suggests its strong potential as an effective phytoremediator (Table 1). Data were analyzed using one-way ANOVA followed by Tukey’s HSD test (p < 0.05). Substantial decreases were observed in several major elements, including iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), and sodium (Na). Iron levels decreased from 9.67 mg L−1 to 0.4 mg L−1, representing a remarkable reduction of nearly 95%. Potassium levels decreased by 56.06%, followed by magnesium at approximately 53.58%. Sodium concentrations were reduced by 53.6%, declining from 725.28 mg L−1 to 336.6 mg L−1 after treatment.
Other metals, including aluminium (Al), chromium (Cr), and manganese (Mn), also showed significant reductions of 93.94%, 72.73%, and 87.37%, respectively. Notably, nickel (Ni), palladium (Pd), and zinc (Zn) were completely removed following phytoremediation, suggesting that S. portulacastrum can be useful for the phytoremediation of industrial effluents. Supporting this observation, Ayyappan et al. [30] reported that S. portulacastrum exhibits high bioaccumulation capacity for chromium, cadmium, copper, zinc, sodium, and chloride. Similarly, Kumawat et al. [31] also demonstrated the effectiveness of this species in treating wastewater from the Tapi River and various industrial sources in India containing elevated levels of heavy metals and organic pollutants. A shift in pH toward neutrality after treatment is also noteworthy, as extreme pH conditions contribute to wastewater toxicity and corrosivity. The observed buffering effect in treated IWW may be attributed to ion exchange, carbonate precipitation, and organic acid regulation in the rhizosphere—processes characteristic of wetland-type phytoremediation systems [28,29]. Overall, the comparison between untreated and treated IWW demonstrates statistically significant reductions in heavy metal concentrations after 9 days of phytoremediation using S. portulacastrum. The results are summarized in Table 1.
Highly significant reductions (p < 0.001) were observed for Al, Fe, K, Mg, Zn, and Na. Chromium (Cr) and manganese (Mn) showed significant reductions at p < 0.01, while reductions in nickel (Ni) and palladium (Pd) were significant at p < 0.05. In contrast, copper (Cu) showed no significant difference (p > 0.05), consistent with its relatively unchanged concentration in treated samples.
These findings validate the efficiency of S. portulacastrum in mitigating a wide range of metals from industrial effluents. Substantial reductions in iron (95%), sodium (53.6%), potassium (56.1%), magnesium (53.6%), aluminium (93.9%), chromium (72.7%), and manganese (87.4%) demonstrate the plant’s strong metal accumulation and sequestration potential. The complete removal of nickel, palladium, and zinc further highlights its applicability as a hyperaccumulator halophyte for industrial wastewater remediation. Compared to media-assisted systems, such as lanthanum-modified zeolite-based wetlands that enhance phosphorus removal and reduce clogging, and advanced catalytic systems, such as Ce–Fe2O3/Al2O3 electro-Fenton processes for simultaneous organic degradation and Cr(VI) reduction, plant-based systems offer a low-cost, solar-driven, and ecologically sustainable alternative [32,33]. In addition, advanced photocatalytic systems, such as Ag/AgBr/Bi24O31Cl10 S-scheme heterojunctions, achieve rapid degradation (85.7%) and substantial mineralization (69.8% TOC removal) of organic pollutants via ROS-mediated pathways [34], whereas the S. portulacastrum system in the present study demonstrates comparatively slower but sustainable, plant-driven multi-contaminant remediation.
Halophytes such as S. portulacastrum are highly efficient in metal uptake due to their extensive root systems, high biomass production, presence of metal-binding cell wall components, and efficient vacuolar sequestration mechanisms [35]. The significant removal of sodium observed in this study is also consistent with the plant’s inherent salt tolerance mechanisms, including Na+ compartmentalization, which are well characterized [36]. The absence of a significant reduction in copper content may be attributed to its low initial concentration, suggesting limited bioavailability rather than inefficiency in phytoremediation. Similar observations have been reported in studies on wastewater treatment using halophytes and aquatic macrophytes [25,37].

3.2. Biochemical and Metabolic Responses of S. portulacastrum

3.2.1. Photosynthetic Pigments

Data on chlorophyll pigments are presented in Figure 3. Statistical analysis was performed using one-way ANOVA followed by Tukey’s HSD test (p < 0.05). S. portulacastrum exhibited a total chlorophyll content of 2.5 mg g−1 in control plants (Day 0). Exposure to industrial wastewater (IWW) resulted in a significant reduction to 1.20 mg g−1 on Day 3 (17.18% decrease; p < 0.05), indicating early stress-induced degradation of photosynthetic pigments (Figure 3). Chlorophyll a showed a progressive decline from 1.95 mg g−1 in control plants to 1.45 mg g−1 on Day 3 (26.31% reduction; p < 0.05), further decreasing to 0.90 mg g−1 on Day 6 (52.63% reduction; p < 0.01) and remaining low at 0.80 mg g−1 on Day 9 (57.89% reduction; p < 0.01). This trend indicates a high sensitivity of chlorophyll a to IWW-induced oxidative stress. In contrast, chlorophyll b exhibited an adaptive response.
After an initial decline from 0.55 mg g−1 in control plants to 0.50 mg g−1 on Day 3 (16.67% reduction; p < 0.05), chlorophyll b content increased significantly to 0.90 mg g−1 on Day 6 (50% increase over control; p < 0.05) and remained elevated at 0.94 mg g−1 on Day 9 (41.67% increase; p < 0.05). Correspondingly, total chlorophyll content partially recovered to 1.77 mg g−1 by Day 9 (13.73% reduction compared to control; p < 0.05), suggesting physiological acclimatization under prolonged IWW exposure. This differential response indicates a compensatory mechanism in which enhanced chlorophyll b synthesis offsets chlorophyll a degradation, thereby maintaining pigment stability and supporting photosynthetic efficiency under stress conditions [25,38]. Oxidative stress may impair chlorophyll biosynthesis by inhibiting key enzymatic steps [38,39].

3.2.2. Total Phenolic Content and Flavonoid Content

The total phenolic content (TPC) of S. portulacastrum varied across tissues and exposure durations to industrial wastewater (IWW) (Figure 4A). Leaf tissues exhibited higher phenolic content (approximately 14 mg GAE g−1) compared to stem tissues (approximately 12 mg GAE g−1). Following IWW exposure, both leaf and stem tissues showed a slight decrease in TPC on Day 3, indicating an early stress response. By Day 6, TPC levels increased to approximately 14 mg GAE g−1 in leaves and 12 mg GAE g−1 in stems, suggesting activation of phenolic biosynthesis as part of the antioxidant defense system. In contrast, by Day 9, TPC decreased significantly in both tissues compared to control and earlier exposure periods, indicating possible metabolic depletion or resource reallocation under prolonged stress conditions.
The total flavonoid content (TFC) exhibited a pronounced tissue-specific response (Figure 4B). In leaf tissues, flavonoid levels increased from 70 µg g−1 in control plants to 100 µg g−1 on Day 3, peaking at 115 µg g−1 on Day 6, and then declining to 75 µg g−1 by Day 9. In contrast, stem TFC decreased progressively from 65 µg g−1 (control) to 62 µg g−1 (Day 3), 47 µg g−1 (Day 6), and 33 µg g−1 (Day 9), indicating that flavonoid accumulation was strongly upregulated in leaves during intermediate exposure, whereas stems exhibited reduced flavonoid production under prolonged IWW stress [40,41].
Phenolics and flavonoids play critical roles in plant defense by scavenging reactive oxygen species (ROS) and mitigating oxidative damage induced by heavy metals and organic contaminants [42]. The observed increase in TPC and TFC up to Day 6 suggests strong activation of antioxidant defense pathways in response to IWW exposure. However, the subsequent decline by Day 9, particularly in leaf tissues, may indicate depletion of metabolic reserves or a shift toward stress acclimation processes. Such biphasic antioxidant responses are characterized by early induction followed by stabilization or decline under prolonged pollutant exposure and have been widely reported in phytoremediation studies involving industrial effluents and heavy metal stress [43,44]. Statistical analysis using one-way ANOVA followed by Tukey’s HSD test confirmed that exposure duration had a significant effect on these biochemical parameters, highlighting the adaptive detoxification dynamics of S. portulacastrum under industrial wastewater stress.

3.2.3. IWW-Induced Specific Metabolites in the Stem and Leaf Samples of S. portulacastrum

GC–MS/MS-based metabolite profiling revealed a total of 53 and 62 metabolites in leaf and stem tissues, respectively (Figure 5). In leaf tissues, the major differentially accumulated metabolites (DAMs) included sucrose, which showed increased accumulation on Day 3 (1.50-fold) and Day 9 (1.06-fold). Additionally, pinitol was detected at both Day 3 and Day 9, while talose was specifically detected on Day 3. In stem tissues, sucrose (Day 3: 1.49-fold; Day 9: 0.47-fold) and pinitol (Day 3: 2.11-fold; Day 9: 0.93-fold) were identified as key DAMs (Figure 5b,c). Carbohydrate metabolism plays a crucial role in plant responses to environmental stress [45]. The increased accumulation of soluble carbohydrates, such as sucrose, observed in this study suggests an adaptive response of S. portulacastrum to industrial wastewater (IWW) stress. Soluble sugars function as osmoprotectants, maintaining cellular osmotic balance and membrane integrity under stress conditions. Moreover, sucrose also acts as a signaling molecule that regulates stress-responsive metabolic pathways, enabling plants to adjust their physiological and metabolic processes in response to environmental stress [45].
Among the detected metabolites, pinitol, a methylated cyclitol belonging to the sugar alcohol family, was particularly notable. Pinitol is widely recognized as a compatible solute that contributes to osmotic adjustment and protects cellular structures against salinity and oxidative damage [46]. Its increased accumulation in S. portulacastrum under IWW exposure suggests activation of metabolic pathways involved in stabilizing proteins and membranes while mitigating reactive oxygen species (ROS)-induced damage. The accumulation of pinitol observed in this study indicates stress imposition and adaptive metabolic reprogramming. Similar findings have been reported in halophytes such as Acrostichum aureum [47] and Mesembryanthemum crystallinum [48], which exhibit elevated pinitol levels under NaCl stress. Additionally, salt stress-induced accumulation of polyols, including D-pinitol, has been previously documented in S. portulacastrum [49].
The increased accumulation of additional sugars, including talose and psicose, further emphasizes the role of carbohydrate metabolism in stress adaptation [43]. Rare sugars are known to participate in carbon metabolism and redox homeostasis, thereby enhancing metabolic flexibility under stress conditions. The presence and differential accumulation of these metabolites indicate that S. portulacastrum adapts to stress through fine-tuning of carbohydrate metabolic pathways, enabling the maintenance of cellular homeostasis and metabolic activity during prolonged exposure to industrial wastewater. Overall, the observed alterations in sugars and sugar alcohols suggest that metabolic reprogramming of carbohydrate pathways is a key adaptive strategy in S. portulacastrum. The accumulation of osmoprotective metabolites such as sucrose and pinitol likely contributes to osmotic regulation, protection of cellular structures, and stabilization of metabolic processes, thereby enabling this halophytic species to tolerate industrial wastewater stress.
The distribution of metabolites detected in the stem of S. portulacastrum across four exposure durations (0, 3, 6, and 9 days) is presented in Figure 5a. The overlapping regions represent metabolites shared among different treatment groups. Two metabolites were common across all four conditions, indicating their stable presence irrespective of exposure duration. Among the treatments, the Day 6 group exhibited the highest number of unique metabolites (four), suggesting a distinct metabolic response at this stage. The control group (Day 0) showed three unique metabolites, whereas Day 3 and Day 9 each exhibited one unique metabolite, highlighting dynamic changes in stem metabolite composition in response to varying exposure durations.
The Venn diagram (Figure 5b) illustrates the distribution of leaf metabolites in S. portulacastrum under different industrial wastewater (IWW) exposure durations (0, 3, 6, and 9 days). Two metabolites were shared across all four groups, indicating their consistent presence irrespective of exposure duration. Among the treatments, the Day 3 group exhibited the highest number of unique metabolites (three), while the Day 6, Day 0 (control), and Day 9 groups each showed one unique metabolite. Notably, the Day 3 and Day 0 groups displayed the greatest overlap, suggesting higher similarity in their metabolite profiles compared to other exposure conditions. The combined Venn diagram integrates metabolites detected in both leaf and stem tissues of S. portulacastrum across all exposure durations. Four metabolites were common to all groups, indicating a stable metabolic core independent of treatment duration. The Day 6 group exhibited the highest number of unique metabolites (five), followed by the Day 3 and control (Day 0) groups with four unique metabolites each, while Day 9 showed only one unique metabolite. These findings suggest that Day 6 represents the peak of metabolic reprogramming, potentially associated with stress adaptation and activation of detoxification mechanisms in S. portulacastrum.

3.2.4. S. portulacastrum Leaves Reveal IWW-Induced Metabolomic Changes

Heat map analysis revealed dynamic metabolomic changes in S. portulacastrum leaves in response to industrial wastewater (IWW) exposure over time (Figure 6). A diverse range of metabolites was identified, including fatty acids (e.g., hexadecanoic acid, docosahexaenoic acid), hydrocarbons (e.g., 9-oxabicyclo[3.3.1], p-menthane-3,8-diol), sugars (e.g., sucrose, 4-O-methylmannose), as well as phytol and methyl stearate. At Day 1, leaf tissues exhibited strong upregulation of most metabolites, indicating a pronounced early stress response, likely associated with detoxification processes and membrane stabilization. By Day 3, although moderate upregulation persisted, a gradual decline in fatty acid and sugar levels was observed, suggesting the onset of metabolic adjustment.
In contrast, leaf samples at Day 6 showed a significant decrease in several metabolites, indicating pronounced metabolic suppression during intermediate stress exposure. However, by Day 9, the metabolite profile exhibited partial recovery, with several metabolites showing mild rebound or stabilization rather than continued decline. This pattern suggests dynamic metabolic adjustment rather than uniform depletion under prolonged stress [23].
Notably, certain hydrocarbons and aromatic compounds were more abundant at later stages, suggesting their possible involvement in sustained stress responses or adaptive metabolism. Cluster analysis grouped the treatments into two primary response phases: an early activation phase (Day 1 and Day 3) and a later adaptation/depletion phase (Day 6 and Day 9). Overall, this biphasic metabolic response highlights the ability of S. portulacastrum to rapidly activate defense mechanisms followed by a shift toward metabolic conservation and adjustment, reinforcing its potential as an effective phytoremediator in industrial wastewater environments [44].
Fatty acids such as hexadecanoic acid are commonly present in industrial effluents [45]. Their detection in plant extracts suggests that S. portulacastrum may absorb and process these compounds. Plants involved in phytoremediation can metabolize or transform pollutants as part of detoxification processes. Exposure to contaminants can also induce stress, leading to metabolic reprogramming and the synthesis of specific protective compounds [46]. Thus, S. portulacastrum may respond to industrial effluent stress by absorbing hexadecanoic acid either directly or in modified forms.
4-O-Methylmannose, a sugar derivative and plant secondary metabolite, has been reported in various plant species [47]. Although not directly involved in primary growth processes, it plays a role in defense mechanisms. It has been identified as a major compound in aqueous and methanolic stem extracts. This metabolite may function as a compatible solute, maintaining osmotic balance and protecting cells under stressful conditions [48]. Additionally, it may exhibit antioxidant properties that help mitigate oxidative stress induced by contaminants [49]. Sucrose indirectly supports phytoremediation by providing carbon and energy for plant growth and development, which are essential for pollutant uptake and accumulation. Although sucrose does not directly degrade contaminants, it enhances stress tolerance and overall plant vigor, thereby improving phytoremediation efficiency [50,51].
9,12,15-Octadecatrienoic acid (linolenic acid) plays a crucial role in plant defense and metabolism [52]. It serves as a precursor for signaling molecules such as jasmonic acid (JA), which regulate plant responses to abiotic stress and pathogen attack. It is also a key component of cell membranes and contributes to wound healing and defense mechanisms. Phytol, although a precursor of chlorophyll, tocopherols (vitamin E), and other essential plant metabolites, does not directly contribute to pollutant degradation. Instead, phytoremediation efficiency depends on plant traits such as the ability to degrade organic compounds, accumulate metals, and transform contaminants into less toxic forms.
In total, GC–MS/MS-based metabolite profiling revealed complex, organ-specific metabolic reprogramming in response to IWW exposure. The accumulation of osmoprotectants, including pinitol, sucrose, talose, and psicose, underscores the importance of compatible solutes in maintaining osmotic balance and protecting cellular structures under salt and metal stress [23,33]. Pinitol accumulation, in particular, is a well-established marker of halophytic stress tolerance and has been widely reported in S. portulacastrum and other salt-tolerant species [31,43]. In addition, stress-dependent accumulation of flavonoids and glycolipids has also been reported in S. portulacastrum [53].
The results from our study demonstrate the potential of halophytes in environmental remediation, and such studies provide further scope to devise efficient plant-based solutions for remediation of polluted aquatic ecosystems [11]. Although the observed reductions in contaminants indicate effective remediation, the absence of a no-plant control limits the ability to fully distinguish between plant-mediated and abiotic removal processes (e.g., sedimentation or precipitation). Nevertheless, the pronounced time-dependent changes in physiological attributes, antioxidant responses, and metabolite reprogramming in plants strongly support the active involvement of phytoremediation mechanisms.

3.2.5. Phytotoxicity of Phytoremediated IWW

Industrial effluents are discharged into the environment in many developing nations; it has hence become essential to develop advanced techniques of remediation such as photocatalytic technology, which has shown eco-friendly, cost-effective and energy-efficient solutions [34]. However, it is crucial to investigate the toxic effects of both treated and untreated effluents on plants [54,55]. Generally, the toxicity of the treated wastewater or effluents is assessed using plant systems to determine the magnitude and reusability of industrial effluents [56]. These plant-based bioassays are simple, requiring a small amount of sample and seeds [57]. In this study, the untreated IWW containing different pollutants showed a toxic effect in terms of decreased germination of V. radiata seeds, with decreased germination percentage, root, and shoot lengths, as compared to the seeds grown in treated water (Table 2). Untreated IWW significantly inhibited germination (15%), indicating a strong phytotoxic effect (Figure 7A). However, these effects were reduced upon exposure of IWW to the halophyte S. portulavastrum (Figure 7B,C). The germination rate increased to 65%, 80%, and 95% after 3, 6, and 9 days of IWW exposure, respectively, suggesting that effective phytoremediation of wastewater can significantly reduce negative effects and promote plant growth. In previous studies, S. portulacastrum has been employed for phytoremediation of textile dyes, and the treated samples were shown to be non-toxic through phytotoxicity using Vigna sp. [58,59].
Phytotoxicity assay with V. radiata revealed direct evidence of toxicity reduction following phytoremediation. Untreated IWW significantly reduced germination and seedling growth, indicating its toxicity. In contrast, the steady improvement in germination percentage, root and shoot length, and survival rate with increasing exposure period reveals that S. portulacastrum successfully detoxifies wastewater. Non-germination is considered the most severe kind of phytotoxic stress since it entirely impairs plant establishment [60]. The significant recovery observed by day 9 (95% germination) suggests that phytoremediation not only reduced chemical toxicity but also restored biological compatibility, hence supporting the potential reuse of treated wastewater for agricultural applications. These results are consistent with previous research in which S. portulacastrum-treated wastewater had little phytotoxic effect. The results suggest the potential application of halophytes in the remediation of wastewaters [61] for achieving sustainable, environmental security.

4. Conclusions

Overall, the findings demonstrate that S. portulacastrum is an efficient phytoremediator capable of significantly reducing organic load, inorganic ions, heavy metals, and phytotoxicity in industrial effluents. Physicochemical analyses, including COD, BOD, TDS, TSS, ammonia, phosphate, and nitrate, along with biochemical profiling of photosynthetic pigments, phenolic and flavonoid contents, and time-dependent metabolic responses, provide a comprehensive understanding of its remediation potential. However, the present study is limited to evaluating contaminant removal from the aqueous phase, as tissue-level accumulation (root vs. shoot), translocation factor, and mass balance analyses were not assessed. Therefore, while substantial reductions in metal concentrations were observed, these findings should not be interpreted as evidence of confirmed hyper-accumulation or internal metal partitioning within plant tissues. Despite these limitations, the observed physiological and metabolic responses strongly support the active role of plant-mediated processes in remediation. The study highlights the resilience of halophytic species and underscores their suitability for sustainable wastewater treatment applications, particularly in hydroponic systems and constructed wetlands. Future investigations integrating tissue-specific metal accumulation and mass balance approaches will further strengthen the mechanistic understanding and practical applicability of this phytoremediation strategy.

Author Contributions

Conceptualization, T.T. and R.P.; methodology, T.T. and S.C.P.; investigation, T.T. and S.C.P.; writing—original draft preparation, T.T.; writing—review and editing, S.P. and G.C.N. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original data presented in this study are available from the authors.

Acknowledgments

The authors would like to thank A.W. Santosh Kumar, Hon’ble Vice Chancellor, Amity University Maharashtra, Mumbai, for the support and encouragement and for providing facilities for carrying out the research.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
IWWIndustrial Wastewater
CODChemical Oxygen Demand
BODBiological Oxygen Demand
TSTotal Solids
TSSTotal Suspended Solids
TDSTotal Dissolved Solids
ICP-OESInductively Coupled Plasma–Optical Emission Spectrometry
DMSODimethyl Sulfoxide
TPCTotal Phenolic Content
TFCTotal Flavonoid Content
DNSADinitro Salicylic Acid

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Figure 1. Growth of S. portulacastrum plants in IWW after (A) 3rd Day, (B) 6th Day, (C) 9th Day of exposure.
Figure 1. Growth of S. portulacastrum plants in IWW after (A) 3rd Day, (B) 6th Day, (C) 9th Day of exposure.
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Figure 2. (A) Ammonia, Phosphate and Nitrate concentrations (mg/L) in treated and untreated IWW after 3, 6, and 9 days of exposure. (B). Levels of COD and BOD (mg/L) in untreated IWW (Day 0) and treated IWW after 3, 6, and 9 days of exposure.
Figure 2. (A) Ammonia, Phosphate and Nitrate concentrations (mg/L) in treated and untreated IWW after 3, 6, and 9 days of exposure. (B). Levels of COD and BOD (mg/L) in untreated IWW (Day 0) and treated IWW after 3, 6, and 9 days of exposure.
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Figure 3. Chlorophyll content in S. portulacastrum under IWW stress at different treatment durations (0 Day, 3rd day, 6th day and 9th day). Data are presented as mean ± standard error (SE) of three independent replicates. Asterisks (*) indicate statistically significant differences compared with the control (Day 0) (p < 0.05).
Figure 3. Chlorophyll content in S. portulacastrum under IWW stress at different treatment durations (0 Day, 3rd day, 6th day and 9th day). Data are presented as mean ± standard error (SE) of three independent replicates. Asterisks (*) indicate statistically significant differences compared with the control (Day 0) (p < 0.05).
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Figure 4. (A) Total Phenolic Content, (B) Total Flavonoid Content in S. portulacastrum plants under exposure to IWW (0 Day, 3rd day, 6th day and 9th day). Data are presented as mean ± standard error (SE) of three independent replicates. Asterisks (*) indicate statistically significant differences compared with the control (Day 0) (p < 0.05).
Figure 4. (A) Total Phenolic Content, (B) Total Flavonoid Content in S. portulacastrum plants under exposure to IWW (0 Day, 3rd day, 6th day and 9th day). Data are presented as mean ± standard error (SE) of three independent replicates. Asterisks (*) indicate statistically significant differences compared with the control (Day 0) (p < 0.05).
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Figure 5. IWW induced organ-specific metabolites in a time-dependent manner. (a) Venn diagram of stem metabolites; (b) Venn diagram of leaf metabolites; (c) Venn diagram of all metabolites present in the plant as per exposure time (0, 3, 6 and 9 days).
Figure 5. IWW induced organ-specific metabolites in a time-dependent manner. (a) Venn diagram of stem metabolites; (b) Venn diagram of leaf metabolites; (c) Venn diagram of all metabolites present in the plant as per exposure time (0, 3, 6 and 9 days).
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Figure 6. Heat map analysis of all the metabolites in S. portulacastrum leaves.
Figure 6. Heat map analysis of all the metabolites in S. portulacastrum leaves.
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Figure 7. Phytotoxicity of IWW using seed germination in mung bean. D3, D6, and D9 indicate days after IWW exposure, and IWW without exposure to S. portulacastrum. (A)—Day 1 of seed germination, (B)—Day 4 of seed germination, and (C) Day 7 of seed germination.
Figure 7. Phytotoxicity of IWW using seed germination in mung bean. D3, D6, and D9 indicate days after IWW exposure, and IWW without exposure to S. portulacastrum. (A)—Day 1 of seed germination, (B)—Day 4 of seed germination, and (C) Day 7 of seed germination.
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Table 1. Estimation of heavy metals and other elements in treated and untreated IWW.
Table 1. Estimation of heavy metals and other elements in treated and untreated IWW.
Heavy MetalsAlCrCuFeKMgMnNiPdZnNa
(mg/L)
Untreated IWW0.330.110.019.6786.0640.241.90.050.040.28725.28
IWW Treated for 09 days0.020.030.010.437.818.680.24000336.6
F-value679.272NA2221.4473,716.755,876.976.4513.478.9137.222,583,442
p-value1.29 × 10−51.06 × 10−3NA1.21 × 10−61.10 × 10−91.92 × 10−99.43 × 10−42.14 × 10−24.06 × 10−23.04 × 10−48.99 × 10−13
Significance*** (p < 0.001)** (p < 0.01)NS*** (p < 0.001)*** (p < 0.001)*** (p < 0.001)*** (p < 0.001)* (p < 0.05)* (p < 0.05)*** (p < 0.001)*** (p < 0.001)
* p < 0.05; ** p < 0.01; *** p < 0.001; NS = not significant; NA (not applicable) indicates that statistical analysis (F-value and p-value) could not be performed due to zero variance among replicates (identical values across treatments).
Table 2. Phytotoxicity assessment of IWW on seed germination and seedling growth of Vigna radiata.
Table 2. Phytotoxicity assessment of IWW on seed germination and seedling growth of Vigna radiata.
IWW Exposure (Days)
Seed
germination parameters		0 369
Root length (cm)0.53 ± 0.051.87 ± 0.122.96 ± 0.154.93 ± 0.20
Shoot length (cm)3.10 ± 0.103.8 ± 0.155.10 ± 0.203.9 ± 0.18
Survival%0 ± 045 ± 370 ± 485 ± 3
Germination %15 ± 265 ± 480 ± 395 ± 2
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Taskeen, T.; Patil, S.C.; Patil, R.; Nikalje, G.C.; Penna, S. Evaluation of Sesuvium portulacastrum (L.) L. as a Halophytic Candidate for the Phytoremediation of Industrial Wastewater. Sustainability 2026, 18, 5439. https://doi.org/10.3390/su18115439

AMA Style

Taskeen T, Patil SC, Patil R, Nikalje GC, Penna S. Evaluation of Sesuvium portulacastrum (L.) L. as a Halophytic Candidate for the Phytoremediation of Industrial Wastewater. Sustainability. 2026; 18(11):5439. https://doi.org/10.3390/su18115439

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Taskeen, Tamanna, Sanket Chandrakant Patil, Ravishanker Patil, Ganesh Chandrakant Nikalje, and Suprasanna Penna. 2026. "Evaluation of Sesuvium portulacastrum (L.) L. as a Halophytic Candidate for the Phytoremediation of Industrial Wastewater" Sustainability 18, no. 11: 5439. https://doi.org/10.3390/su18115439

APA Style

Taskeen, T., Patil, S. C., Patil, R., Nikalje, G. C., & Penna, S. (2026). Evaluation of Sesuvium portulacastrum (L.) L. as a Halophytic Candidate for the Phytoremediation of Industrial Wastewater. Sustainability, 18(11), 5439. https://doi.org/10.3390/su18115439

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