https://orcid.org/0000-0001-6960-816X
Figures
Abstract
Contaminated water used for irrigation has been reported to trigger metabolic and physiological changes in plants. This study assessed the physicochemical status, pH, total dissolved solids (TDS), electrical conductivity (EC), salinity (SAL), and metals of Nwanedi River water and its influence on the primary metabolome of disordered tomato leaves (a physiological condition) irrigated with the Nwanedi River water. The physicochemical properties of water from Nwanedi River were measured by a multi-probe field meter, metal concentration by Inductively Coupled Optical Emission Spectrometer (ICP-OES), and primary metabolite profiling of disordered leaves done using LCMS-8040 triple quadrupole mass spectrometer. The pH, EC, TDS, Cd and Pb of river water were above the stipulated standards for irrigation purposes. Levels of hypoxanthine in tomato leaves were influenced negatively by pH (r = −0.91), TDS (r = −0.93), EC (r = −0.93), and SAL (r = −0.95) as revealed by Pearson correlation. Other metabolite quantities significantly swayed by the water’s condition were histamine, thymine, 4-hydroxyproline, acetylcarnitine and carnosine. The correlations between primary metabolites in the disordered leaves and the physicochemical parameters could indicate mitigation and adaptation mechanisms of the tomato plant.
Citation: Musweswe LN, Kalu CM, Ntushelo K (2026) Physicochemical status of Nwanedi river water, and its influence on the metabolome of river-irrigated tomato leaves. PLoS One 21(3): e0342474. https://doi.org/10.1371/journal.pone.0342474
Editor: Ying Ma, Universidade de Coimbra, PORTUGAL
Received: July 24, 2025; Accepted: January 23, 2026; Published: March 13, 2026
Copyright: © 2026 Musweswe et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Tomato (Solanum lycopersicon L.) is one of the nutritious vegetables which is grown extensively and consumed as part of many home diets in salads, sandwiches, relishes, stews, and various other forms across the globe [1]. With an annual global production of approximately 189.1 million tons, tomato ranks as the second most consumed vegetable, following its close relative, potato [2]. In Africa, the annual total production of tomatoes is 21.3 million tons, with Egypt as the top producer and the only African nation in the top ten global tomato producers [2]. South Africa holds the 40th position in world tomato production and is the dominant producer in the Southern African Development Community (SADC) region. Despite favorable conditions for tomato cultivation, a significant yield gap persists within the SADC region [3]. Just like other crops, tomatoes are susceptible to various environmental factors that can lead to physical disorders and a subsequent reduction in yield and quality of the produce. The presence of contaminants in the environment, either through natural geological processes or anthropogenic activities, can significantly influence plant health and metabolism [4]. Irrigation water contributes to the exposure of contaminants experienced by plants. Multiple studies have shown that metals such as lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), and chromium (Cr) can be found in irrigation river water, exceeding permissible levels for irrigation and domestic purposes [5–7]. From a health perspective, the use of polluted water for irrigation raises health concerns and poses risks to farmers, crop handlers, and consumers [8]. Moreover, irrigation water from rivers may contribute to the quality of the plants. For aerial irrigation, the plant foliage may directly absorb metals from the irrigation water.
The accumulation of metals in different plant organs can disrupt cellular processes and lead to physiological alterations (disorders), including changes in the plant’s metabolome. To comprehend the intricate dynamics of plant physiology, researchers have turned to the study of metabolites. Metabolites encompass a diverse array of compounds, including sugars, amino acids, organic acids, lipids, and vitamins [9]. These molecules participate in essential plant biological processes, such as energy production, cellular structure maintenance, and signalling [10]. Primary metabolites, such as glucose and amino acids, play fundamental roles in plant growth and development, serving as building blocks for cellular structures and energy reservoirs [11]. Metabolites serve as crucial indicators of the physiological state of plants, offering insights into their responses to environmental stimuli, stress conditions, and overall health [12]. Hence, assessment of the relationship between the physicochemical properties of irrigation water and the plant through correlation studies is crucial.
Among the statistical correlation techniques adopted is the Pearson correlation analysis, which helps to determine the strength of linear relationships between variables [13]. Farmers in Vhembe district cultivates more of tomato because the soil and climatic conditions favors the growth of tomato. As a result, tomato cultivation serves as a source of income and food to people in the district and the country at large. Nwanedi River is the available river in the district accessible to the farmers. Hence, it becomes a primary source of irrigation water for the farmers in the district. Although the Nwanedi River serves as a crucial source of irrigating water of tomato farms in Vhembe district, no work has been done to determine its impact on the metabolome of disordered leaves of tomatoes irrigated with this water. In this context, the study addresses the following questions: 1) Were the physicochemical parameters (pH, TDS, EC, SAL, and metal quantity) in compliance with the permissible level for irrigation purposes? 2) Can the physicochemical parameters in irrigating river water influence the metabolome of disordered tomato leaves? 3) To a lesser extent, were there variations in river water metal concentration and metabolites in disordered leaves across sample points? The objective of the current study is to assess the influence of the physicochemical status of Nwanedi River water on the primary metabolome of disordered tomato leaves irrigated with the river water. To our knowledge, this is the first study to uncover associations between irrigation water status and the primary metabolome of leaves irrigated with the water.
Materials and methods
Physicochemical properties and metals of irrigating water from five points along the Nwanedi River were determined by a multi-probe field meter and inductively coupled plasma-optical emission spectroscopy, respectively and compared to the permissible level for agricultural use. To assess the variation of metal concentration in river water, analysis of variance (ANOVA) was employed. A heatmap with clustering was used to portray the variation of primary metabolites in disordered tomato leaves from five farms adjacent to the river that receive irrigation water from the river. Physicochemical parameters of river water were then correlated with profiles of metabolites of disordered tomato leaves to determine their influence on primary metabolites in tomato leaves.
Study area and sample collection
Nwanedi River is an important catchment reservoir in the north-eastern corner of the Limpopo province in Vhembe District, Nwanedi village. Along its length, Nwanedi River is surrounded by rural communities which depend on it for various household and farming purposes, primarily for the irrigation of crops. The climatic conditions of the study area are regarded as tropical with an average annual rainfall between 400 and 1600 mm, of which about 80% occurs between October and March [14]. Average temperatures in summer reach approximately 35°C, with peak temperatures reaching a maximum about 40°C [14]. Five water samples were collected from different points along the Nwanedi River (W1-W5) downstream, and fifteen disordered tomato leaves (three per farm) from the five different farms (L1-L5) which receive irrigation water from the Nwanedi River. The disordered leaves were selected based on the following conditions: visible abnormalities that affected almost the whole leaves and the number of the occurring disordered leaves in a tomato plant (plants selected for the leave sampling must have 90% of the leaves being disordered). The specific distance and coordinates of the sampling points appear on Table 1. Sterile 400 ml containers were used for water sample collection. Tomato disorder leaves were harvested from selected plants into 3 ml tubes within the same period to ensure uniformity in the soil and climatic conditions. The collected samples were promptly transported on ice and stored at −20°C upon reaching the laboratory. Permission to sample was obtained from Limpopo Department of Agriculture and Rural Development (Nwanedi).
Estimation of physicochemical parameters in water
A multi-probe field meter (YSI TM 6 series, Sonde Marion, Germany) was used to measure electrical conductivity, salinity (SAL), total dissolved solids (TDS), and pH in the water samples. Samples (20 ml water) were digested in a 10 ml solution containing of 1M nitric acid and 50% hydrogen peroxide in a microwave digestor. The samples were then filtered through a 0.45µm pore size filter. Metal concentrations of Al, Cd, Cr, Co, Cu, Mg, Na, Ni, Pb, Ti, Sb, and V were then measured using an Inductively Coupled Optical Emission Spectrometer (Agilent Technologies 700 series ICP-OES).
Metabolites extraction and analysis
Disordered tomato leaf samples were dried and then ground using a pestle and mortar. A 1 mL solution of 75% methanol and 25% water (v/v) was added to 10 mg of each sample. The mixture was vortexed, sonicated for 10 minutes and subsequently centrifuged at 13,000 rpm for 5 minutes. The resulting supernatant was filtered through a 0.22 μm Whatman filter membrane and then pipetted into vials. Metabolomic profiling was done using an LCMS-8040 triple quadrupole mass spectrometer (Shimadzu Corporation, Kyoto, Japan). The LCMS/MS instrument settings were configured as follows: total flow at 0.4 mL/min, injection volume of 1 μl, oven temperature ranging from 40 °C to a maximum of 85 °C, nebulizing gas flow at 3 L/min, drying gas flow at 15 L/min, and a mobile phase consisting of a 50% acetonitrile/50% water mixture. A I mL solution of 75% methanol and 25% water (v/v) was pipetted into a vial and used as a control sample. To ensure the precision of the method and instrument as well as the quality control, the following was done before the analysis of the samples: 1.) The MS resolution and sensitivity, signal-to-noise ratio or chromatographic resolution of the instrument was determined. 2.) Inter-run precision of the instrument was determined by regularly validating the above-mentioned parameters as well as recording the statistical variation during the optimal performance. This will permit an identification of suboptimal performance as a series of outliers. 3.) Runs with biological samples were checked through the control of the respective parameters, such as chromatographic resolution or the relation of total ion current of MS spectra and MS/MS spectra. Peak detection, data mining, alignment and normalization, and library searching were executed using LabSolutions Insight® multi-analyte quantitation software (Shimadzu Corporation, Kyoto, Japan). The obtained results were exported to Microsoft Excel for further analysis. Among the identified primary metabolites, 25 metabolites were the focal points because of the preliminary screening done as well as their abundance and importance in the survival and growth of tomato plant.
Data processing and statistical analysis
ANOVA (p < 0.05) and Tukey’s Honest Significant Difference (HSD) tests were employed in RStudio (version 2023.03.0 Build 386 © 2009–2023 Posit Software, PBC), to assess differences in metal concentrations among the sampling sites. Pearson correlation analysis was conducted using the “Hmisc “ package in R to identify correlations between physicochemical parameters of river water and the 25 most abundant primary metabolites in disordered tomato leaves. Because the disordered leaves and river water samples were collected within the same period to ensure uniformity in the soil and climatic condition, the Pearson correlation analysis was only focused on the physicochemical parameters of river water and the 25 most abundant primary metabolites in disordered tomato leaves. For the strong positive correlations, the correlation diagrams were presented using the EzCorrGraph app [15].The app is freely available on https://ezcorrgraph.firebaseapp.com [15]
Results
The study addressed these research questions: Were the physicochemical parameters in compliance with the permissible level for irrigation purposes? 2) Can the physicochemical parameters in irrigating river water influence the metabolome of disordered tomato leaves? 3) Were there variations in river water metal concentration and metabolites in tomato leaves across sample points? The results revealed that the physicochemical parameters in the irrigating river exceeded the recommended level for irrigation purposes. Metabolome and metal quantities also varied significantly across sampling points. Moreover, significant correlations between the physicochemical properties of irrigating river water and the primary metabolites of disordered tomato leaves suggested the influence of water quality on the metabolome of disordered tomato leaves.
Physicochemical properties of water from Nwanedi River
The pH values ranged from 8.3 to 9.82 with the maximum recorded value at sampling point W5 and minimum value at sampling point W1 (Table 2). Only W1 and W2 water samples were within Department of Water Affairs and Forestry [16] and Food Agriculture Organisation [17] acceptable level while W3, W4, and W5 surpassed the threshold for agricultural use. The EC ranged between 172.4 S/m and 1412 S/m with the maximum value recorded at W5 and the minimum value at W2. The conductivity values at all sampling points were above the permitted limits for irrigation. Notably, the EC at W5 was eight times higher than that at W2. The TDS exhibited a similar pattern to EC, ranging from 183.65 to 1209 mg/L. The level of TDS at W5 was nine times more than in W2, which had the lowest TDS level. Points W3, W4, and W5 surpassed the FAO’s recommended level of 450 mg/L of TDS for irrigation. Similarly, the SAL exhibited a comparable pattern to the TDS and EC, varying from 0.9 to 1.33 mg/L, with an average of 0.586 ± 0.52 mg/L (Table 2).
Metal concentrations in river water
The mean values of the heavy metal concentrations of river water samples with the standards are provided in Table 3. Generally, significant differences (p < 0.05) were observed across the sampling sites (river water) for most of the heavy metals. All the heavy metals present in the river water (W1-W5) were within the DWAF [16] and FAO/WHO [17,18] for irrigation use except for Cd and Pb (Table 3). Table 4 provides a summary of the figures of merit of the analysis. Calibration curve with linearity for quantification is presented in Fig 1.
Metabolomic profile of disordered tomato leaves
Table 5 provides a summary of total ion chromatogram of the leaves extract indicating the retention time and mass to charge ratio which is used in the accurate prediction of the identified metabolites when compared to the known metabolites in the database built in the system software. The metabolites of disordered tomato leaves varied across sampling points (Fig 2). The dendrogram on heat map clustered sampling point (farms) L2 and L4 based on the similarity level of the following metabolites: 4-hydroxyproline, niacinamide, norepinephrine, nicotinic acid, carnosine, acetylcarnitine, choline, acetylcholine, symmetric dimethylarginine, dimethylglycine, FMN, thymine, dopa, dopamine, tyrosine, carnitine, valine, 5-glutamylcysteine, guanosine3’,5’-cyclic monophosphate and guanosine monophosphate metabolites. Similarly, L1 and L5 clustered together with 4-hydroxyproline, niacinamide, norepinephrine, nicotinic acid, carnosine, dimethylglycine, histamine, FMN, thymine, dopa, 5-glutamylcysteine, guanosine3’,5’-cyclic monophosphate and guanosine monophosphate in common for the two sampling points. Additionally, L3 was more clustered with L2-L4 than L1-L5 clusters. High levels of 4-hydroxyproline, niacinamide, acetylcarnitine, creatinine, carnosine, nicotinic acid, and norepinephrine were observed across all farms.
The dendrogram illustrates complete-linkage agglomerative clustering based on Euclidean distance. The colour spectrum represents the relative abundance levels, transitioning from low (green) to high (reddish).
Relationship of primary metabolites of tomato leaves with physicochemical properties of water
Pearson correlation analysis revealed significant (p < 0.05) negative associations of Hypoxanthine with pH (r = −0.91; p < 0.05), TDS (r = −0.93; p < 0.05), EC (r = −0.93; p < 0.05), and SAL (r = −0.95; p < 0.05) (Table 6).
The synthesis of histamine is influenced by TDS and EC. TDS, EC, pH, and SAL are major physicochemical parameters that play key roles in the synthesis of thymine, 4-hydroxyproline, and acetylcarnitine. Carnosine is mainly influenced by SAL (Fig 3).
The nodes displayed correlated characteristics, and the numerical value between two parameters represents their correlation coefficient.
Discussion
Due to the scarcity of irrigation water in many regions of South Africa, farmers have increasingly relied on river water to irrigate crops. Given that Nwanedi River play a vital role in supporting farmers with irrigation water, it was necessary to ascertain the physicochemical quality of the water and its impact on the metabolome of tomato leaves. The study showed that the irrigation water from the Nwanedi is unsuitable for irrigation purposes, and influences metabolites in the tomato leaves.
Physicochemical parameters such as TDS, pH, EC, and SAL are vital for evaluating water quality, offering valuable insights into water composition and suitability for purposes like drinking, agriculture, or industry [19]. The physicochemical parameters (pH, TDS, EC, and SAL) of the five points in the Nwanedi River showed variations (Table 2). This was surprising considering the flow of the water, which should likely cause uniformity of conditions. This could imply that every point in the river does not have uniform physicochemical properties probably due to different environmental as well as biological activities occurring at the different points of the water. Furthermore, the agricultural activities prevalent in the study area could account for the variations. The study conducted by Obire et al. [20] revealed that the discharge of fertiliser waste from a neighbouring fertiliser industry caused an increase in the pH, EC, and TDS levels in Okrika creek, in comparison to the unaffected Ikpukulubie stream (control). TDS is comprised of dissolved ions and salts which directly affect EC of the water [21]. Hence, with an increase in TDS concentration, EC also rises [22]. Studies have shown the relationship between EC, TDS, and SAL; as TDS increases, EC and SAL also increase due to increased dissolved salts and ions [23]. Additionally, both EC and TDS impact water pH [23]. The TDS in water can result in either high or low pH values, depending on the substances present in the water; thus, the relationship between TDS and pH is not necessarily linear [22]. Water with a high concentration of alkaline minerals, such as calcium carbonate, tends to be basic, whereas water dominated by acidic components, such as metal ions, tends to be acidic [22]. In this present study, the pH of W3, W4, and W5 were above the DWAF [16]and FAO [17]permissible limit for irrigation (Table 2). Similarly, the EC for all the water sampling points were above the limits. The TDS for W3, W4, and W5 were above the limits. This showed the relationship between TDS, EC, and pH for the samplings. Netshifhefhe. [24] reported that pH and TDS of Nwanedi River were within the stipulated standard whereas the EC was above the stipulated standard. Similarly, in this study, EC was above the stipulated standard. The variations in the TDS and pH of the various sampling points recorded in this present study and the work done by Netshifhefhe [24] could be attributed to increased anthropogenic activities in the current year. This poses a serious concern as most of these parameters were not within the stipulated standards, making the water unsafe for irrigation purposes.
Netshifhefhe. [24] observed that Cr and Pb in the water samples from Nwanedi River were below detectable limits. Unlike the present study, where Cr and Pb were above the stipulated standards (Table 3). This could be linked to increased anthropogenic activities within the area. Given that the river serves as a source of water for irrigation, using water from the Nwanedi River for this purpose may affect crops due to the potential absorption of metals by plants [25].This increase in the metals could be a factor to the disorder observed in the tomato leaves used in this study. Ahmed et al. [26] observed significant reductions in plant growth parameters and impaired photosynthetic activity in tomato plants irrigated by heavy metal (Pb, Cd, Cr, Cu, Ni, Fe, Mn, Zn, and Co) contaminated water. Irrigating tomatoes with metals contaminated water may increase the metals in the fruit beyond permissible limits [27] and altered the nutrient composition in tomato fruits [28]. Metals present at environmentally relevant concentrations can induce notable metabolic changes in plants, leading to shifts in carbohydrates, amino acids, organic acids, and other biomolecules in cells [29].
In addition, Haddou et al. [30] observed changes in the abundance of the metabolites in plants irrigated with river water. Mohammed and Abdulqader [31] highlighted that variations in the primary metabolites in plants under river irrigation water could be linked to the changes in the quality of the water and soil quality. This could account for the variations in the abundance of the primary metabolites in the disordered tomato leaves irrigated with the water from Nwanedi River as indicated in the heatmaps (Fig 2). Notably, disordered tomato leaf samples had a high level of metabolites such as amino acids (creatinine, carnosine), vitamins (niacinamide, nicotinic acid), and other known metabolites (norepinephrine). The abovementioned primary metabolites are involved in aiding plants to cope with stress in one way or another [32]. Studies have reported high levels of amino acids like 4-hydroxyproline (proline derivative) in plants subjected to saline stress, suggesting their role in stress response. Carnosine, a dipeptide primarily made up of β-alanine and L-histidine, possesses antioxidative properties which enhance enzymatic activity and non-enzymatic antioxidants, thereby mitigating oxidative damage in plants by scavenging reactive oxygen species (ROS) generated under abiotic stress conditions [33,34]. High levels of niacinamide and nicotinic acid have been reported in plants undergoing oxidative stress, thus aiding in enhancing salt tolerance in various crops [35,36]. Norepinephrine, belonging to the catecholamine family, functions as a hormone and neurotransmitter in plants [37]. This could account for the abundance of these metabolites in the leaves of the tomato in an attempt to survive, and also indicates that the water from the Nwanedi River could contain some elements that cause stress to the plants, leading to the decay of the leaves. A positive correlation between plant primary metabolites and water physicochemical parameters could indicate the mitigation activities of the plant to stress, whereas a negative correlation could indicate the adjustment of metabolic pathways by the plant to ensure their survival [38]. Studies have reported that Water pH, TDS, EC, and SAL may alter primary metabolites in plants [30,39]. In the current study, Pearson correlation analysis revealed a significant (p < 0.05) negative correlation of hypoxanthine (Purine) with pH, TDS, EC, and SAL (Table 4). These correlations suggest that elevated water pH, TDS, EC, and SAL levels lead to decreased hypoxanthine content in tomato leaves. Several studies have acknowledged the role of purine in nitrogen recycling and remobilization as well as their role in the survival of plant in stress conditions via various metabolic pathways involving enzymes such as xanthine dehydrogenase [40–49]. Findings of this study demonstrated that the pH levels in the river water remained consistently high, measuring above 8, and were found to have a detrimental impact on hypoxanthine concentration. In addition, tomato plant leaves (L4 and L5) irrigated with water from river points with high pH (W4 and W5) exhibited very low hypoxanthine levels. Munyai et al. [49] also observed that Potato cultivars (Marykies and Royal) irrigated with acidic mine water had lower hypoxanthine levels compared to those irrigated with tap water. In the study of Kalu et al. [48], plants sampled from a riverbank with a pH level of 7.81 ± 0.2 and from the tail of an acid dam with a pH of 5.01 ± 0.27 showed low hypoxanthine concentrations, in contrast to plants from the tail of an acid mine dam with a pH of 6.50 ± 0.6. The results of this study, incongruent with Kalu et al. [48] and Munyai et al. [49] suggest that high and low pH levels can reduce hypoxanthine concentrations, while moderate pH levels may promote hypoxanthine production.
Moreover, Munyai et al. [49] also reported that potato plants irrigated with acid mine drainage treated with 2 g of quicklime (which raises the pH) had higher concentrations of histamine, 4-hydroxyproline, and acetylcarnitine compared to those treated with untreated AMD. This suggests that an increase in pH enhances the synthesis of these metabolites. A similar trend is observed in the present study, where a positive correlation was found between the primary metabolites in disordered tomato leaves and the physicochemical parameters of the irrigation water, indicating the pivotal role these environmental factors play in plant metabolism. As presented in Fig 3, histamine is positively influenced by TDS and EC, while carnosine was primarily associated with salinity (SAL). Furthermore, TDS, EC, pH, and SAL were identified as key physicochemical factors driving the synthesis of thymine, 4-hydroxyproline, and acetylcarnitine.
Thymine (vitamin B1), besides its role as a coenzyme in metabolic pathways such as carbon assimilation and respiration, has also been reported to aid plants’ responses to biotic and abiotic stress [50]. Studies have shown that under saline conditions, plants turn to increase the accumulation of thymine [51]. Li et al. [52] treated cotton plants with 100 mL (per plant) and observed an upregulation of genes responsible for thiamine biosynthesis, along with an increase of thymine level in roots. Moreover, exogenous application of thymine has been shown to improve salinity resistance in crops peas [53], beans [54], rice [55], and wheat [56]. Similarly, positive correlation between thymine and SAL suggests that tomato plants may upregulate thymine production as a strategy to mitigate salinity-induced stress. This study provided evidence that irrigation water from the Nwanedi River directly influence the metabolome of irrigated tomato crops, thus the wellbeing of the crop. Additionally, metabolites responsible for the survival of tomato plant, as influence by physicochemical parameter of water were identified. As the irrigation water from the river is necessary to ensure the cultivation of tomato in the district, maintaining a good status for the physicochemical parameter of the river is pertinent. This is due to the long-term impact it will have on the growth, survival, and nutritional component of the tomato as impacted by the interactions between the physicochemical parameters of the water and the metabolite perturbation of the tomato plant. This calls for adequate attention to be given to any environmental and industrial activities that could lead to the pollution of Nwanedi River.
Conclusion
Water quality, particularly its physicochemical properties, plays a crucial role in shaping the plant metabolome. Stress induced by factors such as salinity, pH, TDS, and EC can lead to downregulation of certain metabolites while promoting the synthesis of others to support survival. This study provides baseline information on the primary metabolites’ perturbation of the disordered leaves under high physicochemical parameters of irrigation water, either to mitigate the impact of the harsh environment or to adapt to the environment to ensure their survival. The occurrence of the physicochemical parameters of water from the Nwanedi River above the Department of Water Affairs and Forestry and the Food and Agriculture Organisation acceptable level underscores the need for appropriate policies to ensure good physicochemical status of irrigation water from the river, as well as agricultural and industrial policies that will minimize or prevent the pollution of the river through discharge from the two sectors. Among the limitations of this study are the single-season sampling and confounding factors (particularly soil properties), which were not measurable due to the scope of the research and the sample size used to test correlation. Further study is recommended to uncover the seasonal impacts on the physicochemical parameters of the Nwanedi River, as well as the corresponding influence on the metabolite perturbation of the tomato plant in the district. In addition, further study is encouraged to increase the sampling size used for correlation analysis and take into consideration the confounding factors, such as the soil properties, to deepen the knowledge on their impacts on the metabolite perturbation of the tomato plant irrigated with water from Nwanedi River. Furthermore, studies are recommended to deepen our understanding of the genes involved in their adaptation through transcriptomic studies. This will provide further insight into the complex interactions between the plants, environmental factors and abiotic components in agroecosystems, ultimately informing sustainable management practices and policies for environmental conservation and human health protection in view of the consumption of food grown with river water as an irrigation water.
Acknowledgments
Department of Agriculture and Animal Health, Science Campus, University of South Africa, is duly acknowledged.
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