Effects of Different Irrigation Water Sources Contaminated with Heavy Metals on Seed Germination and Seedling Growth of Different Field Crops

Abstract

Irrigation water quality is of critical importance for optimum crop yield of economically important field crops in the Kahramanmaraş plains. A preliminary ecotoxicological assessment is necessary before large-scale irrigation. Therefore, this study aims to evaluate the quality of irrigation water supplied from different water sources (Karasu, Erkenez, and Oklu streams on the Aksu River and Sır Dam) and the effects on the seed germination and early seedling growth of different field crops (wheat, alfalfa, ryegrass, and maize) irrigated with this water. For this, in order to evaluate the effects on seed germination and early growth parameters of forage crop seedlings, a Petri dish germination test was carried out with four replications using a completely randomized design (CRD). Before the germination assay, heavy metal concentrations including copper (Cu), iron (Fe), lead (Pb), chromium (Cr), arsenic (As), nickel (Ni), and cadmium (Cd) were analyzed in water samples obtained from different water sources. In all water samples used for the experiment, Cu concentrations exceeded the acceptable limit of 0.2 mg L⁻¹. The Cu levels found were 0.98 mg L⁻¹ in Karasu (KC), 1.627 mg L⁻¹ in Oklu (OC), 0.945 mg L⁻¹ in Erkenez (EC), and 1.218 mg L⁻¹ in Sır Dam (SD) waters. Additionally, Fe exceeded the limit only in KC, while Cd surpassed the permissible levels in EC and SD water samples. Seeds exposed to different water treatments were germinated in a climate chamber at 20 ± 1 °C. Over two weeks, daily germination and seedling growth parameters were measured. The results indicated that higher heavy metal concentrations in irrigation water led to a decline in seed germination rates and adversely impacted early seedling growth. Notably, water from Karasu Creek exhibited the most significant negative impact on all germination and growth parameters in the tested crops, especially due to Cu and Fe metal toxicity. Additionally, ryegrass seeds were most affected by these irrigation waters. This study highlights the importance of using uncontaminated quality irrigation water for optimal crop production by quantifying its impact, such as the percentage of decrease in germination or seedling growth.

1. Introduction

In Türkiye, as in many other countries, field crops are essential for both domestic consumption and export markets. Their economic, nutritional, and ecological importance makes them a cornerstone of sustainable agricultural systems [1,2]. Wheat, alfalfa, ryegrass, and corn are globally significant field crops with high nutritional value, contributing significantly to food security, livestock feed, and industrial raw materials serving as staple foods for much of the world’s population [3]. Among them, wheat and corn dominate global crop production [4]. The seeds of wheat, rye, and corn are utilized in various industries for flour, malt, bread, pasta, and cereals, while their stalks serve as livestock feed [4,5]. Alfalfa, on the other hand, is primarily used as hay for animal feeding. Wheat, a key source of protein and starch, contributes 20–30% of daily caloric intake in many societies [6]. However, these widely cultivated crops are increasingly exposed to abiotic stressors such as irregular rainfall, rising temperatures, and prolonged drought due to global climate change, leading to significant yield losses [7,8].

Germination is the critical physiological process by which a seed transitions into a seedling under favorable conditions [9]. It involves metabolic activation, culminating in the emergence of the radicle and shoot. This process comprises a cascade of biological and biochemical events, making germination and early seedling development crucial stages in crop establishment [10]. Germination begins with water absorption by the dormant seed, initiating embryonic axis elongation and radicle emergence [11]. This process involves tightly regulated morphogenetic and physiological mechanisms, including energy transfer, nutrient uptake, and biochemical changes [12,13]. The rupture of the seed coat enables root and shoot emergence, activating seed respiration [13,14]. Physically, germination progresses in two distinct phases: endosperm rupture and radicle protrusion, followed by micropylar endosperm degradation [15]. Enzymatic activity during these stages is highly sensitive to temperature, nutrient availability, and water status [16]. Therefore, abiotic factors such as oxygen content, temperature, light, pH, water availability, and water quality in the germination environment significantly affect seed physiology and seed–soil interactions [9,17]. In addition, genetic variability determines the response of seeds to external stress factors, shaping species distribution and productivity [13,17].

Water is indispensable for germination, facilitating protoplasmic hydration, oxygen dissolution, and seed coat softening to enhance permeability [13,16]. While water deficiency negatively impacts germination rates [7,18], optimal water supply enhances germination success [19]. Both water quantity and quality play pivotal roles in seed imbibition and subsequent metabolic processes [16,17,18,19]. Water activates enzymes responsible for endospermic material degradation, transport, and utilization [20]. However, water stress impairs enzymatic activity, disrupts carbohydrate metabolism, reduces cellular water potential, and alters seed hormonal balance, thereby hindering germination and seedling establishment [21].

The textile industry is a major source of heavy metal contamination in Kahramanmaraş. Textile finishing plants consume significant amounts of water—approximately 95–400 L per kilogram of textile product. This water is typically drawn from rivers and discharged back after use. Beyond its high water consumption, the industry extensively uses chemicals, including dyes and auxiliary agents. As a result, industrial effluents introduce chemical and heavy metal contaminants into irrigation waters [22,23,24]. In Kahramanmaraş, textile wastewater is discharged into the Aksu River, which ultimately flows into Sır Dam. This causes toxic heavy metals to accumulate in the environment and reach hazardous levels in water resources, posing serious ecological risks [25]. This discharge, combined with domestic waste, significantly pollutes the dam water. The Aksu River and its tributaries carry heavy loads of industrial and domestic waste, yet their waters are frequently used for agricultural irrigation in the region.

The most significant effects of heavy metals on the biological cycle occur in plants [26]. The toxicity levels of plants are an especially key limiting factor for seed germination and early seedling growth [25]. Also, they have an important impact on plant growth, biomass production, flowers, fruit set, yield, and product quality [27,28]. Furthermore, heavy metals have negative effects on various physiological processes of the plant at the intracellular level such as disrupting photosynthesis, the nitrogen cycle, and binding, thus decreasing chlorophyll amounts, leading to deterioration in enzyme systems and inhibiting the uptake of useful elements [29,30]. Similarly, there are various studies on the effects of heavy metals on the development of radicle, hypocotyl, epicotyl, plumule, and seedlings in germination and early development stages of different field and horticultural crops [31,32,33,34,35]. While some heavy metals, especially Cr, Cd, Mn, Cu, Pb, and Zn, do not cause problems in plant and animal bodies at low doses, they do cause toxic effects such as metabolic disorders and growth inhibition at concentrations above the threshold values [36,37]. Although trace metals that have toxic effects on some plants have been studied for many years, there is a strong need in the literature to fully determine their phytotoxic effects [38]. For example, it has been reported that the growth of wheat (Triticum aestivum L.) is reduced by 50% at 0.5 μM Cu and 30 μM Cu concentrations [39,40]. However, there is no appropriate information about other crops.

Germination is a crucial phase in plant production, as plants cannot develop or grow without it. As the most vulnerable stage in a plant’s life cycle, germination requires optimal environmental conditions to ensure successful seedling establishment. Therefore, preliminary laboratory experiments on germination and early seedling growth are regarded as among the simplest, most accurate, convenient, and cost-effective biological monitoring methods for assessing the tolerance of different plant species and varieties to environmental changes in heavy metal concentrations [41,42].

The use of alternative water sources in agriculture can help reduce pressure on freshwater supplies, particularly in regions experiencing summer drought. Given reports of pollution from nearby factories, it is essential to assess the suitability of Aksu Stream and Sır Dam waters for agricultural irrigation, especially as drought conditions intensify. However, these water sources may contain high concentrations of cations and anions, which can lead to morphological and physiological disorders in plants, such as reduced germination, stunted root growth, and overall developmental inhibition. The effects of irrigation water on seed germination and early growth parameters vary depending on water quality, heavy metal availability, and plant species, making it crucial to evaluate these differences for sustainable agricultural production. This study aims to: i) Analyze the chemical properties of water from the dam basin and its tributaries used for irrigation; ii) Assess the impact of different water sources on the germination and early seedling development of key regional crops—wheat, alfalfa, ryegrass, and corn—due to their economic and ecological significance. The findings provide critical insights into the impact of alternative irrigation sources on seed germination and early growth, contributing to more sustainable agricultural practices.

2. Materials and Methods

2.1. Study Sites and Crop Materials

This study was carried out from 1 March to 30 July 2017 in the laboratory of the Department of Field Crops of the Faculty of Agriculture, Kahramanmaraş Sutcu Imam University. Irrigation waters containing heavy metals were collected from four different sources of the Aksu River (Erkenez Creek, Oklu Creek, and Karasu Creek) and Sır Dam Ponds located in Kahramanmaraş, Türkiye. The seeds of four field crops—wheat, clover, ryegrass, and corn—widely cultivated in the Kahramanmaraş region, particularly near the dam, were used as test plants. These crops were selected due to their extensive use by local farmers and their commercial importance. The seeds were purchased from seed production enterprises.

2.2. Preparations and Analysis of Water Samples

Images of the locations where water samples were collected are shown in Figure 1, and their geographical coordinates are provided in

Table 1. The geographical location of water sample collection points.

	Karasu Creek	Erkenez Creek	Oklu Creek	Sır Dam
Latitude	37°31′3.45″ K	37°32′25.56″ K	37°33′49.39″ K	37°34′30.35″ K
Longitude	36°56′0.85″ D	36°55′13.30″ D	36°54′42.67″ D	36°48′6.19″ D

. Water samples were collected as per the standard method of sampling techniques [43]. Creek water samples were taken from the middle part of the stream which was flowing fastest and not stagnant, at early morning irrigation time. The mixture was prepared by taking water from the Sır Dam from three different depths: the deepest part of the dam, the middle part, and the surface. The tap water used as a control was collected after the faucet was allowed to run for 30–60 seconds. The water samples were taken in 1 L plastic bottles, filtered, and solid impurities were removed. These water samples were used for the irrigation of crop seeds. The concentration of some pollutant heavy metals Cu, Fe, Ni, Pb, Cr, As, and Cd in the initial water samples was determined by Inductively Coupled Plasma Optical Emission Spectroscopy (Perkin Elmer ICP-OES-6000, Agilent, Santa Clara, CA, USA) at ÜSKİM (University, Industry, Public Cooperation Development, Application and Research Center).

The pollution level of the water samples used for irrigation was assessed considering the maximum permissible limits, summarized in

Table 2. Maximum permissible limits of heavy metals in irrigation waters [44].

Elements	Maximum Possible Amount per Unit (kg ha−1)	Allowable Maximum Concentrations
		Boundary Values in Cases of Continuous Irrigation for All Kinds of Soil (mg L−1)	When Watering Less than 24 Years in Clay Soils with a pH Value Between 6.0–8.5 (mg L−1)
Arsenic (As)	90	0.1	2.0
Cadmium (Cd)	09	0.01	0.05
Chrome (Cr)	09	0.1	1.0
Copper (Cu)	190	0.2	5.0
Iron (Fe)	4600	5.0	20.0
Lead (Pb)	4600	5.0	10.0
Nickel (Ni)	920	0.2	2.0

. Heavy metal concentrations below or equal to these values in the irrigation waters do not pose any toxic effects for up to 24 years on clayey soils with a pH of 6.0–8.5.

2.3. Experimental Procedure and Measurement

The seeds were germinated in water samples obtained from four different sources (Table 1) in comparison to tap water (control). Before sowing, the seeds were kept in a 5% NaClO (sodium hypochlorite) solution for 5 m and sterilized and rinsed with tap water [42]. After lining the Petri dishes with filter paper (Cytiva Whatman 589/1 Circles—90 mm), 25 seeds were sown using 20 mL of irrigation water sample in each Petri dish according to the assigned treatments in a completely randomized design (CRD) with four replicates. The seeds were germinated in a room-temperature climate of 20 ± 1 °C. The seed germination was monitored daily for 14 days. Germination rate, root length, plumage length, seedling length, seedling age, weight, seedling dry weight, and seedling vigor index values were measured daily. Germination percentage was calculated as the ratio between the number of germinated seeds and the total number of seeds. Seedling length, radicle, and plumule were separated and measured with a ruler. The fresh and dry biomass was determined gravimetrically by weighing before and after drying (at 80 °C for 24 h) [45]. The vigor index was calculated by multiplying the seedling length by the germination percentage, as shown in Equation (1).

Vigor index (VI) = Seedling length × Germination percentage

(1)

2.4. Statistical Analysis

All obtained experimental results were statistically analyzed using the SAS Statistical Program Version 9.1 [46]. An LSD test was used to reveal the differences between the averages of different crops, different irrigation waters, and their interactions [47].

3. Results

In this study, heavy metal concentrations in all irrigation water samples were measured and compared with the maximum allowable limits (Table 2 and

Table 3. Heavy metal concentrations in irrigation waters used in this study.

	AMC	KC	OC	EC	SD
Cu (mg L−1)	0.2	0.98	1.627	0.945	1.218
Fe (mg L−1)	5.0	18.69	0.555	2.395	8.89
Pb (mg L−1)	5.0	0.00015	0.00056	4.5	0.013
Cr (mg L−1)	5.0	0.097	0.00038	0.02	0.00013
As (mg L−1)	1.0	0.206	0.171	0.165	0.132
Ni (mg L−1)	0.5	0.00328	0.04	0.00067	0.00067
Cd (mg L−1)	0.005	0.00068	0.00069	0.099	0.115

Notes: AMC: Allowable Maximum Concentration; KC: Karasu Creek; OC: Oklu Creek; EC: Erkenez Creek; SD: Sır Dam; Red colors show higher concentrations.

). The results show that Cu levels in Karasu Creek irrigation water are approximately 5 times higher than the permissible limit, while Fe levels are 3.7 times higher (Table 2). Similarly, Cu concentrations were found to be 8 times higher in Oklu Creek, 5 times higher in Erkenez Creek, and 6 times higher in Sır Dam compared to the permissible limits. In Sır Dam water samples, high concentrations of Fe were also obtained, but these values were only 1–2 times higher than the maximum permissible limit. Cd concentrations were extremely high in Erkenez Creek and Sır Dam, 20 times and 23 times above the permissible limit, respectively (Table 3).

Based on these results, it can be stated that the analyzed water samples have a high content of Cu, Fe, and Cd and, therefore, their use as irrigation water can affect crop growth.

In order to determine how plant growth is influenced by irrigation water with high levels of such heavy metals, some important parameters were determined in each case. The mean values of all the parameters are shown in

Table 4. The Average GR, RL, PL, SL, SFW, SDW, and VI Values for Species and Irrigation Water.

		GR (%)	RL (cm)	PL (cm)	SL (cm)	SFW (g)	SDW (g)	VI
		**	**	**	**	**	**	**
Species	Wheat	98 a	16.96 a	11.63 a	28.58 a	1.68 b	0.34 c	2812 a
	Alfalfa	96 a	9.38 c	7.25 b	16.64 b	1.46 b	0.47 b	1598 b
	Ryegrass	78 b	9.31 c	6.97 b	16.28 b	0.28 c	0.04 d	1352 c
	Corn	72 b	11.36 b	6.63 b	17.99 b	4.66 a	0.62 a	1322 c
	LSD	6.97	1.76	0.88	2.17	0.68	0.09	232.60
		**	**	**	**	ns	**	**
Irrigation waters	Control	95 a	11.50 a	8.16 a	19.66 a	2.17	0.42 ab	1874 a
	Erkenez Creek	87 a	12.11 a	8.55 a	20.67 a	2.02	0.50 a	1841 a
	Oklu Creek	89 a	13.14 a	8.55 a	21.69 a	2.45	0.34 bc	1967 a
	Karasu Creek	71 b	8.46 b	6.60 b	15.06 b	1.61	0.27 c	1177 b
	Sır Dam	87 a	13.55 a	8.73 a	22.28 a	1.84	0.31 bc	1997 a
	LSD	7.98	1.97	0.98	2.43	0.76	0.11	260.10
	Mean	86	11.75	8.12	19.87	2.02	0.37	1771
	CV %	12.77	23.64	17.04	17.24	53.28	41.27	20.74

Notes: ** Significant at p < 0.01; ns: not significant; GR: Germination Rate; RL: Radicle length; PL: Plumule Length; SFW: Seedling Fresh Weight; SDW: Seedling Dry Weight; VI: Vigor Index (Different letters stand for statistically significant differences at p < 0.05 (Fisher LSD test)). Bold colors show higher values.

. The obtained results of statistical analysis indicate that all considered parameters were significantly affected by the irrigation of plants with water with a high content of heavy metals.

3.1. Germination Rate (%)

In terms of germination rate, cultivar, irrigation water, and cultivar × irrigation water interaction were statistically significant (Table 4 and Figure 2). The highest germination rate was seen in wheat with 98.20%, followed by clover with 96%. The lowest germination rate was seen in corn at 72%. The highest germination rate in terms of irrigation water was obtained from the control application at 95.25%, and the lowest germination rate was obtained from KC water at 71.75%. The highest germination rate in terms of cultivar × irrigation water interaction was seen in alfalfa irrigated with OC water at 100%, followed by wheat irrigated with SD and OC water at 99%. The lowest germination rate was 44% for Italian ryegrass irrigated with KC water (Figure 2).

3.2. Radicle Length (cm)

In terms of radicle length, the effects of cultivar, irrigation water, and the interaction between cultivar and irrigation water were statistically significant (Table 4 and Figure 3). The highest radicle length was observed in wheat, with 16.95 cm, followed by corn at 11.31 cm. The lowest radicle length was recorded in ryegrass, at 9.31 cm. Regarding irrigation water, the highest radicle length (13.54 cm) was observed with SD irrigation water application, while the lowest (8.46 cm) was associated with KC water. For the cultivar × irrigation water interaction, wheat irrigated with OC water showed the highest radicle length at 20.19 cm, followed by wheat irrigated with SD water at 19.46 cm. The lowest radicle length (8.41 cm) was recorded in alfalfa irrigated with OC water (Figure 3).

Statistically, the lowest radicle lengths were detected in all different plant species irrigated with KC water.

3.3. Plumule Length (cm)

Data regarding plumule length, cultivar, and irrigation water were statistically significant; cultivar × irrigation water interaction was non-significant (Table 4 and

Table 5. The Average GR, RL, PL, SL, SFW, SDW, and VI Values for Interactions between Species and Irrigation Water.

		GR (%)	RL (cm)	PL (cm)	SL (cm)	SFW (g)	SDW (g)	VI
		**	*	ns	ns	ns	**	*
Wheat	Control	98 ab	15.99 c	11.03	27.01	1.51	0.34 de	2643 c
	Erkenez Creek	98 ab	17.93 b	11.63	29.56	1.62	0.36 de	2899 b
	Oklu Creek	99 a	20.19 a	12.83	33.02	2.04	0.32 e	3266 a
	Karasu Creek	97 abc	11.22 efg	10.76	21.98	1.55	0.34 de	2143 d
	Sır Dam	99 a	19.46 a	11.88	31.34	1.67	0.35 de	3107 a
Alfalfa	Control	98 ab	8.69 i	7.00	15.68	1.37	0.65 bc	1538 f
	Erkenez Creek	96 abc	9.23 i	8.06	17.31	1.83	1.04 a	1659 ef
	Oklu Creek	100 a	8.42 i	6.57	14.98	1.34	0.23 ef	1498 fg
	Karasu Creek	88 bcd	8.73 i	6.18	14.91	1.09	0.17 ef	1306 gh
	Sır Dam	98 ab	11.83 ef	8.48	20.30	1.67	0.27 e	1988 d
Italian Ryegrass	Control	93 abcd	8.86 i	7.65	16.51	0.33	0.04 f	1536 f
	Erkenez Creek	87 cd	11.56 ef	7.39	18.95	0.26	0.04 f	1653 ef
	Oklu Creek	85 d	9.91 ghi	7.40	17.31	0.36	0.05 f	1467 fg
	Karasu Creek	44 g	4.25 j	4.70	8.95	0.21	0.03 f	429 j
	Sır Dam	85 d	11.98 ef	7.69	19.67	0.23	0.04 f	1672 ef
Corn	Control	92 abcd	12.48 e	6.97	19.45	5.48	0.65 bc	1778 e
	Erkenez Creek	68 e	9.71 hi	7.14	16.85	4.36	0.59 bc	1149 h
	Oklu Creek	74 e	14.03 d	7.41	21.44	6.08	0.76 b	1636 ef
	Karasu Creek	58 f	9.65 hi	4.77	14.41	3.58	0.53 cd	827 i
	Sır Dam	68 e	10.93 fgh	6.87	17.80	3.78	0.58 bc	1218 h
	LSD	9.09	1.37	0.46	1.60	0.38	0.18	186.90
	Mean	86	11.75	8.12	19.87	2.02	0.37	1771
	CV %	12.77	23.64	17.04	17.24	53.28	41.27	20.74

Notes: ** Significant at p < 0.01; * Significant at p < 0.05 ns: not significant; GR: Germination Rate; RL: Radicle length; PL: Plumule Length; SFW: Seedling Fresh Weight; SDW: Seedling Dry Weight; VI: Vigor Index (Different letters stand for statistically significant differences at p < 0.05 (Fisher LSD test)).

). The highest plumule length was seen in wheat at 11.63 cm, followed by alfalfa at 7.25 cm. The lowest plumule length was seen in ryegrass at 6.63 cm. The highest and lowest plumule length values were found to be consistent with the radicle length values. In terms of irrigation water, the highest plumule length value was observed with SD irrigation water application at 8.73 cm, and the lowest plumule length of 6.60 cm was observed with KC water. The highest plumule length was seen in wheat irrigated with OC water, at 12.83 cm. The lowest plumule length was observed in ryegrass irrigated with KC water, at 4.70 cm (Table 4).

3.4. Seedling Length (cm)

Seedling length was significantly affected by cultivar and irrigation water, while their interaction was non-significant (Table 4 and Table 5). Wheat exhibited the highest seedling length (28.58 cm), followed by corn (17.99 cm). The lowest seedling length was seen in Italian ryegrass, 16.28 cm. Among irrigation water sources, the highest seedling length was recorded with SD water (22.28 cm), while the lowest was observed with KC water (15.06 cm). The highest seedling length in terms of cultivar × irrigation water interaction was observed in wheat irrigated with OC water, at 33.02 cm, followed by wheat irrigated with SD water, at 31.34 cm. The lowest seedling length was observed in Italian ryegrass irrigated with KC water, at 8.94 cm (Table 4).

3.5. Seedling Fresh Weight (g)

Regarding seedling fresh weight, only differences between cultivar means were statistically significant (Table 4). Corn had the highest seedling fresh weight (4.65 g), followed by wheat (1.67 g). The lowest seedling fresh weight was observed in Italian ryegrass at 0.27 g. In terms of irrigation water, the highest seedling fresh weight value resulted from OC irrigation water application with 2.45 g, and the lowest seedling fresh weight resulted from KC water with 1.60 g. In terms of variety × irrigation water interaction, the highest seedling fresh weight was seen in corn irrigated with OC water at 6.07 g, followed by control application in corn at 5.48 g. The lowest seedling fresh weight was observed in Italian ryegrass irrigated with KC water, at 0.21 g (Table 4).

3.6. Seedling Dry Weight (g)

The cultivar, irrigation water, and cultivar × irrigation water interactions were all statistically significant factors for seedling dry weight (Table 4 and Figure 4). The highest seedling dry weight was observed in corn at 0.62 g, followed by alfalfa at 0.47 g. The lowest seedling dry weight was observed in Italian ryegrass at 0.03 g. In terms of irrigation water, the highest seedling dry weight value was found to be 0.50 g from EC irrigation water, and the lowest seedling dry weight was reported from KC water at 0.26 g. The highest seedling dry weight in terms of cultivar × irrigation water interaction was observed in alfalfa irrigated with EC water at 1.03 g, followed by OC water at 0.75 g. The lowest seedling dry weight value, between 0.03–0.05 g, was observed in all applications in Italian ryegrass (Figure 4).

3.7. Vigor Index

In terms of the vigor index, the effects of variety, irrigation water, and the interaction between variety and irrigation water were found to be statistically significant (Table 4, Figure 5). The highest vigor index was recorded in wheat (2812), followed by alfalfa (1598), while corn exhibited the lowest vigor index (1322). Regarding irrigation water, the highest vigor index (1997) was observed with the SD irrigation water application, whereas the lowest vigor index (1177) was associated with KC water. For the variety × irrigation water interaction, the highest vigor index was obtained in wheat irrigated with OC water (3266), followed by wheat irrigated with SD water (3107). In contrast, the lowest vigor index (429) was recorded in Italian ryegrass irrigated with KC water (Figure 5).

4. Discussion

Germination and the early plant growth stage are of critical importance in plant breeding [48]. Especially for field crops, germination success is essential for the abundant production of high-yield and high-quality plants [48,49]. Along with quality seeds, quality water supply, and irrigation frequency are also very important [50]. The decrease in water potential during germination periods can negatively affect seed germination and cause osmotic stress. Since the Mediterranean region is one of the more sensitive regions exposed to global climate change [51], irregularity in rainfall occurrence and amount causes water scarcity and encourages the use of alternative irrigation water sources. However, it should not be forgotten that the use of alternative irrigation waters containing heavy metals or having salinity problems is an important factor affecting germination and plant growth parameters [52]. In order for a plant to survive and continue its generation, the environment in which it grows must be free from heavy metal stress [53]. Similarly, some researchers have reported that heavy metal toxicity significantly reduces the germination rate and seedling growth of different plants [31,54]. In contrast, it has been stated that the germination and early seedling growth parameters of Leucaena are not affected by water quality [55], and winter wheat and spring maize plants can develop resistance after the early growth stage [56]. Although most plants have phytotoxic tolerance to some heavy metals, other heavy metals can cause serious negative effects on that plant. For instance, Talebi et al. [57] reported in a study that triticale germination percentage and rate were significantly affected by heavy metals, especially Cd. The data from our study reveals that wheat was the most resistant plant to heavy metals in irrigation water, exhibiting the highest germination rate. In particular, the heavy iron content of KC irrigation water reaches very dangerous levels, because this metal is present far above the permitted limits. For this reason, it has been observed that there is a significant decrease in the germination percentage of seeds due to the heavy metal concentration in irrigation waters. This may be due to the toxic effects of concentrated ions on the germination process [58].

The observed decrease in seed germination percentage due to the presence of heavy metals is consistent with the findings of other researchers. For example, Rahman Khan and Mahmud Khan [59] observed a decrease in seed germination in chickpeas treated with 50, 100, 200, and 400 ppm nickel and cobalt compared to the control. Similarly, Singh et al. [60] observed a decrease in germination percentage in wheat treated with copper at 5, 25, 50, and 100 ppm. Peralta-Videa [61] reported that alfalfa seed germination and seedling growth were adversely affected by heavy metals (Cd, Cr, Cu, and Ni). Azmat et al. [62] also reported that Lens culinaris seed germination was inhibited by Pb. Similarly, Talebi et al. [57] determined that Cu²⁺ and Cd concentrations applied at 1000 mg/L⁻¹ were the most significant inhibitory factors for the germination and seedling growth of triticale seeds. Tsamo et al. [31] reported that there was a significant decrease in the germination rates of corn and bean seeds irrigated with increased Cu²⁺ element and that there was no germination in beans in 600 μmol/L Cu²⁺ solution. In this study, the Cu²⁺ concentration in all irrigation waters, Fe concentration in KC and SD waters, and Cd concentration in EC and SD waters were above the permissible amounts for the germination of seeds of different crops and early seedling development. High concentrations of Fe, Cu, and Cd can cause a wide range of phytotoxic symptoms such as reduced germination rate, chlorosis, root rot, and growth inhibition, as well as a wide range of morphological and physiological disorders [53,63,64,65]. Similarly, the presence of Co, Cu, and Zn in cucumber and wheat [32]; Zn in Nigella sativa and Triticum aestivum [33]; and Co in wheat, alfalfa, and tomato [34] resulted in reduced germination rates.

The lowest radicle length measured from the early seedling development parameters of the seeds was obtained from KC water. It is thought that the heavy metal content of KC water slows down the radicle development in parallel with the negative effect on the germination rate. Similarly, there is a direct relationship between the concentration of heavy metals used in irrigation and radicle length, because radicle length decreases as the heavy metal concentration increases [57,66]. The heightened sensitivity of root length to heavy metals can be attributed to the plant root being the initial point of contact with toxic substances in the growth medium. Some studies have indicated that Cd application has negative effects on Triticum aestivum, Zea mays, Sorghum bicolor, and Cucumis sativus plants, especially on the root part, the root being the most sensitive part of the plant [67,68]. Also, some researchers found that Al destroyed roots in wheat [69]; Hg, Cd, Co, Cu, Pb, and Zn in cucumber and wheat resulted in smaller root lengths, shorter root age, and lesser dry weight [32]; Co inhibited root growth in wheat, clover, and tomatillo [34]; Cd decreased the root growth and root tolerance index in maize [35]. Furthermore, some researchers have suggested that the inhibition of root elongation by heavy metals may result from interference with cell division, including the induction of chromosomal aberrations and abnormal mitosis [70], which could adversely affect seedling growth.

It is observed that Karasu Creek irrigation water, which contains high concentrations of Cu and Fe heavy metals, slows down plumule growth in parallel with its negative effect on germination rate and radicle length. Talebi et al. [57] the highest plumule length of triticale was determined in the control application and the shortest plumule length was determined in the highest (1000 ppm) heavy metal concentration. At higher concentrations, it was thought that the presence of inhibitory chemicals could completely stop seedling growth [71]. Maity et al. [72] found that the lowest values of growth parameters of Cicer arietium were a result of the use of industrial wastewater. The increase in heavy metal concentration in wastewater can cause inhibition of enzyme activity by reducing enzyme dehydrogenase activity, which is considered to be one of the biochemical changes that negatively affect seedling biomass. Cd absorbed by plants accumulates in different parts of the plant, causing growth inhibition and reducing root and shoot growth by inhibiting cell division and cell growth or both [73,74,75]. He et al. [76] reported that Cd inhibited plumule and radicle growth in rice.

In this study, it was observed that the highest and lowest seedling length values were compatible with radicle and plumule length values. According to seedling length, wheat was the most resistant to heavy metal-containing irrigation water. Seedling development was found to slow in parallel with the negative effects of heavy metals—particularly Cu and Fe—present in Karasu Creek irrigation water. Similarly, Maity et al. [72] stated that industrial wastewater negatively affected the seedling length of Cicer arietium. Athar and Ahmad [77] noticed that the toxic effects of certain heavy metals on the seedling length and grain yield of wheat (Triticum aestivum L.) caused significant decreases in both parameters, and that Cd was the most toxic metal, followed by Cu, Ni, Zn, Pb, and Cr.

KC irrigation water had negative effects on germination and seedling growth, impacting the mass formation of the plant. This could be due to the higher Fe concentration in KC irrigation water, well above the allowable limits. Similarly, Talebi et al. [57] reported that the presence of heavy metals significantly reduced the fresh and dry weight of triticale seedlings compared to the control. The ability of heavy metals to reduce the fresh and dry weight of triticale was as follows: Cd > Cu > Pb. Zeng et al. [78] reported that Pb caused a decrease in rice biomass. The decrease in biomass was also attributed to the inhibition of chlorophyll synthesis and photosynthesis by heavy metals [60,79]. These researchers observed a significant reducing effect on wheat (Triticum aestivum L.) fresh weight, and dry weight with increasing Cu²⁺ concentrations. Tsamo et al. [31] found that the fresh and dry weight of plants with high heavy metal concentrations was very low compared to control experiments. Similarly, Athar and Ahmad [77] reported that exposure of wheat plants to heavy metals resulted in a decrease in the dry weight content and grain yield of the plants and a significant decrease in the protein content in plant tissues and grains. This suggests that heavy metals negatively impact the growth and yield of wheat plants, corroborating previously reported phytotoxic effects of these metal ions [77]. In another study, it was determined that the aboveground biomass of maize and bean seedlings irrigated with different Cu²⁺ concentrations was shorter than the control [31]. The decrease in fresh and dry weight of plants may also be due to the concentration of heavy metals in water, protein degradation of amino acid metabolism at high concentrations [31], and a decrease in carotenoid and chlorophyll content [80].

There was a direct relationship between heavy metal concentration and a decrease in the vigor index; the vigor index decreased as the heavy metal concentration level increased. Similar results were also observed by Channappagoudar [81] and Talebi et al. [57]. Also, Shaikh et al. [82] studied the phytotoxic effects of different concentrations of Cr, Cd, Mn, and Zn on seed germination, root, shoot, seedling growth, seedling vigor index and tolerance index of wheat and found that heavy metals adversely affected the normal growth of plants by reducing seed germination, root and shoot length compared to control. It was determined that the highest vigor index value in terms of irrigation waters was obtained from SD water application, and the lowest vigor index from KC water. The negative effects of KC irrigation water on germination rate and seedling growth also decreased the vigor index values of the plant. This is due to the presence of iron heavy metal in KC irrigation water well above the allowable limits.

Heavy metals such as Fe, Cu, Zn, and Mn are essential for plant growth at appropriate concentrations, but some are harmful to plants when exceeded above acceptable levels [31,83]. These include Cd, Hg, Pb, and As [84]. For example, high concentrations of Pb and Cu also cause oxidative stress in plants [85], which leads to the destruction of macromolecules and the disruption of metabolic pathways [86]. Vassilev et al. [87] showed in their study how copper toxicity affects the growth of barley plants. This toxicity caused leaf chlorosis by degrading photosynthetic elements. In our study, the Cu element was found to be a phytotoxic metal for plants in all water samples, Fe element in KC and SD waters, and Cd element in EC and SD waters. Athar and Ahmad [77] found that Cd was the most toxic metal for free-living nitrogen-fixing bacteria and wheat plants, causing significant decreases in the dry weight of shoot, root, and grain yield after Cu, Ni, and Zn, respectively. Kalyanaraman and Sivagurunathan [88] reported that Cd and Cu had higher phytotoxicity than other elements. Similarly, Tsamo et al. [31] reported that heavy metals Zn and Cu significantly affected other plant growth parameters such as germination, shoot length, leaf area index, and shoot circumference of bean plants and Pb of maize. However, the presence of more than one heavy metal concentration in the environment may also cause antagonistic effects [77]. For example, it has been reported that Cd antagonized the inhibitory effect of Zn on the total amount of mineralized carbon [89]. It has been reported that the decrease in seed germination and plant growth parameters is a reflection of the increase in industrial pollution [90].

5. Limitations of the Study

The Aksu River is home to numerous textile factories, and a more comprehensive study would require analyzing the wastewater from each factory to identify the primary pollutants and implement necessary precautions. This research needs to be conducted in larger areas in different regions and larger water resources. Certain heavy metals (Cu, Fe, Pb, Cr, As, Ni, Cd) were analyzed in this study. However, the effects of other potentially toxic elements (e.g., Zn, Mn) should also be examined. The study was conducted in a controlled laboratory environment. Under field conditions, the mixing of irrigation water with the soil and its long-term effects could not be evaluated. Only four different field crops (wheat, alfalfa, meadow grass, and corn) were used. Studies with more plant species may be useful to determine the tolerance of different species to heavy metals. It would be useful to examine the accumulation rates of heavy metals not only in irrigation water but also in soil and plants. In addition, the long-term effects of heavy metals in irrigation water on plant growth and development, yield, and soil vitality should be investigated. Biological or chemical treatment methods should be tested and their effects should be examined to eliminate the negative effects of heavy metals. Species resistant to heavy metal toxic effects should be studied.

6. Conclusions

The effect of environmental stress factors on plants is generally determined by the responses of the organelles whose morphological and functional integrity are affected. In this study, the effects of polluted irrigation waters on germination and early seedling growth performances of some field crop species were investigated. All irrigation waters containing heavy metals significantly reduced the germination and seedling growth of wheat, alfalfa, ryegrass, and maize seeds. In particular, Karasu Creek irrigation water had the most negative impact on germination and early development of all plant seeds. In addition, corn and Italian ryegrass seeds exhibited poorer germination compared to wheat and alfalfa seeds under heavy metal pollution. According to the results obtained from this study, reduced germination and delayed growth will be observed in plants grown in soils in irrigation processes with water contaminated with heavy metals. The most important reason for this is that high concentrations of heavy metals alter the physiological and biochemical activities of seeds. This study highlights the risk to the yield and availability of wheat, alfalfa, ryegrass, and maize in the studied regions if agricultural areas are not protected from various soil pollutants, particularly those resulting from industrial activities near farmlands. To mitigate these issues, wastewater treatment systems in factories near streams must remain continuously operational, and strict legal measures should be enforced. Additionally, irrigation water from the Aksu River and Sır Dam should be filtered and treated to remove heavy metals before use. The findings of this study will aid farmers and city officials in educating the public on the impact of environmental pollution on food security, livelihoods, and overall health.