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Article

Investigation of Juncus and Iris Plant Potential—Two Native Serbian Species for Utilization in Nature-Based Solutions towards Improving the Quality of Water Contaminated with Zinc and Supporting Biodiversity

by
Amela Greksa
1,
Ivana Mihajlović
2,
Mirjana Ljubojević
1,*,
Boško Blagojević
1,
Mirjana I. Vijuk
1,
Sanja Podunavac-Kuzmanović
3,
Strahinja Kovačević
3 and
Mirna P. Štrbac
1
1
Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovića 8, 21000 Novi Sad, Serbia
2
Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia
3
Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad, Serbia
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(15), 6467; https://doi.org/10.3390/su16156467 (registering DOI)
Submission received: 15 June 2024 / Revised: 22 July 2024 / Accepted: 25 July 2024 / Published: 28 July 2024
(This article belongs to the Special Issue Biodiversity, Conservation and Sustainable Development: Research and Practices)
Browse Figures
Versions Notes

Abstract

:
The benefits of nature-based solutions to address the climate and biodiversity challenges have become widely acknowledged. In numerous ways, nature-based solutions align with the Sustainable Development Goals. Serbia, like many other countries, faces many negative impacts of climate change crises. In order to meet sustainable development goals linked to water pollution and biodiversity, we investigated the potential of two plants, namely, Iris pseudocorus L. and Juncus effusus L., and tested for zinc reduction, previously found as an emerging contaminant of urban waters in Serbia. We focused on the investigation of native Serbian plants, that are reported as highly valuable and endangered. Results confirmed that both plant species have high accumulation capacity for Zn uptake, whereas growth and resistance were higher for Juncus effusus L. plants. While the concentration of zinc in Iris plants ranged from 45.85 mg/L to 193.05 mg/L, the concentration found in Juncus plants ranged from 36.2 mg/L to 264.59 mg/L for leaves and 53.20 mg/L for roots. This study contributes to the support for achieving the Sustainable Development Goals in Serbia within biodiversity conservation and sustainable water management, by providing information of plant species that can be included in future sustainable nature-based solutions projects, like bioretention systems and constructed wetlands.

1. Introduction

In order to address a variety of global societal concerns, the 2030 Agenda for Sustainable Development established an ambitious framework of universal and indivisible goals and targets including 169 sub-targets and 17 primary Sustainable Development Goals (SDGs) that act as a worldwide benchmark for the shift to sustainability [1]. Given combined human activity and global warming, it is anticipated that global climate change will have a substantial influence on human health, food and water security, livelihoods, biodiversity, and ecological integrity, according to the most recent assessment on the status of the Intergovernmental Panel on Climate Change 2022 [2]. Short-term projections predict that global warming will reach 1.5 °C in the near future, and it will undoubtedly contribute to a number of climatic dangers and put ecosystems and people at risk. For native species investigated in hotspots, the risk of extinction increases with warming in all climate change predictions, and as for endemic species, the risk increases with warming from 1.5 °C to 3 °C over pre-industrial levels, nearly ten times larger. Given the alarming rates of biodiversity loss, urban and rural areas have a responsibility to assist in worldwide efforts that work to protect, preserve, and restore biodiversity [3]. As the understanding of these negative impacts of climate change grows, countries worldwide are implementing novel approaches known as nature-based solutions (NbSs). Nature-based solutions are defined as strategies to protect, manage, and rebuild natural environments or ecosystems that have been altered in a sustainable manner that simultaneously improve the well-being of humans and biodiversity while successfully resolving societal issues, including a wide range of ecosystem-based and social issues, including restoration, preservation, sustainable management, and the creation of “green” or natural infrastructure [4,5]. A number of applications of NbSs are applied globally and at varying scales, from the micro-scale to the macro-scale at the city level, including building windbreaks to conserve soil, safeguarding urban green spaces, maintaining and growing forested regions, and planting vegetated roofs for a variety of advantages, including enhancing biodiversity, storing carbon, and retaining runoff [6].
Nature-based solutions strategies align with the Sustainable Development Goals (SDGs) and the broader concept of sustainable development in numerous ways. Nature-based solutions support ecological services like biodiversity, urban water management, recreational and educational possibilities, phytopurification, carbon sequestration, and local climate regulation, along with biodiversity maximization [7,8]. Furthermore, significant habitats are provided by NbSs, which also strengthen biodiversity by enhancing ecological connectedness, supplying food and pollination, protecting terrestrial and semiaquatic ecosystems, and establishing a connection between the neighboring rural and urban areas [9]. By supporting biodiversity, NbSs can directly encourage a large number of environmental processes and increase ecosystem resilience and health, rich biodiversity, and activities valuable to and directly benefiting humans [10].
As an important part of NbSs, vegetation helps to address a range of climate-related challenges and vulnerabilities by offering ecosystem services. Several main issues are closely related to the selection criteria for plant species that promote sustainability. These attributes include adaptability to diverse environmental conditions, tolerance to a broad spectrum of pollutants and contaminations, superior performance across a range of climatic zones, superior performance across a range of planted mixtures and species interactions, and enhancement of biodiversity and habitats [11]. Native plants are frequently marketed for ecological restoration, gardening, and biodiversity preservation [12] and have been used extensively in sustainable practices because of their resistance to diseases and pests, as well as their capacity to store toxins in the aboveground portions of the plant, as demonstrated by several studies [13]. For example, due to their wide range of adaptations to shifting environmental conditions and species richness, grasses from family Poaceae have been documented to be employed in various NbS-like bioretention systems and constructed wetlands, including, in particular, species like Miscanthus sinensis Andersson, Phragmites australis (Cav.) Steud, Panicum virgatum Muhl., and Festuca ovina subsp. Glauca [11]. These species are globally distributed and valued for their high biomass and adaptability to varying water levels and contaminants, including heavy metals, diseases, and nutrients from wastewater [13]. Australian native plant Melaleuca ericifolia Andrews, Bot. Repos., is also widely utilized in stormwater treatment systems on a local level, because of the observed effective nutrient removal capacity uptake and sediment and pathogen removal in stormwater and wastewater [14,15]. According to Vymazal, 2013 [16], grasses like Typha spp. and Scirpus (Schoenoplectus) spp. are the most often utilized plant species in free water surface created wetlands worldwide. Because native macrophytes’ roots can withstand prolonged submersion in marsh environments, they are mostly utilized in floating islands and stormwater detention ponds, namely, Juncus acutus L., Iris pseudacorus L., Cyperus longus L., and Cyperus rotundus L., resistant to waterlogging, drought, and salt [17,18]. Iris pseudacorus L. is also among recommended plants for the phytoextraction potential of groundwater from industrial locations because of the increased resistance to the combined contaminants [18]. The native Chromolaena odorata (L.) R.M.King & H.Rob plant from Nigeria demonstrated more resistance to PAHs than the reference plant, Medicago sativa L., when the two plants were evaluated in terms of their adaptability to a site contaminated by crude oil [19]. Similarly, in assuring services related to climate change adaptation and mitigation and preserving and restoring natural ecosystems, the employment of a variety of native species in urban spaces is presented in research studies in South African urban areas, whereas Haplocarpha lyrata and Scabiosa columbaria, both native species, showed great tolerance to current urban conditions [20].
Pollution of the air, water, and soil, consistently poses a serious danger to Serbia’s biodiversity. It has been recorded that biological invasions and the spread of non-native species are most often supported by ecosystem changes or disturbances such as forest fires; the clearing of vegetation for the construction of residential areas, roads, power lines, etc.; and the alteration of watercourses [21]. Serbia’s surface waterways are at grave risk due to a variety of biological, chemical, and physical pollution sources. The growth of heavy industries, the expansion of metropolitan regions, the rise in domestic and commercial wastewaters, and inadequate equipment for their treatment cause the polluting effects of surface waters [22]. Moreover, urban stormwater runoff generated from streets is reported to have a high concentration of Zn [23]. The presence of Zn in water in concentrations higher than necessary can have a toxic effect on flora, fauna, and humans [24]. It is also documented that the transportation industry has direct impacts on habitat destruction and fragmentation, and the introduction and spread of non-native species with pollution is highlighted as a primary driver of biodiversity loss, with a negative impact on our health and the ecosystem [22].
Although sustainable practices in Serbia have been introduced in the past decade, sustainable evident-based research studies that will support further sustainable development goals are needed. For example, little is known about native plant species contributions that can be utilized for improving the quality of contaminated water, thus also supporting biodiversity. In order to fill these gaps, this work focused on accessing the ecosystem services of native vegetation to achieve two important sustainable development goals (SDGs): sustainable water management and the conservation of biodiversity by investigating the growth dynamics of two native plants, that is, plants from genus Juncus and Iris, under different Zn concentrations that can potentially be generated with polluted water. Based on scientific knowledge, plant species requirements, and their development under environmental pressure, this work aimed to recommend the future utilization of investigated plant species towards sustainable planning in Serbia.

2. Materials and Methods

2.1. Plant Species Description

For the purpose of the investigation, two native Serbian plant species were used, namely, Juncus effusus L. (soft rush) and Iris pseudacorus L (yellow flag) (Table 1). Juncus effusus L. is a perennial in the rush family Juncaceae. It is a macrophyte with a broad, nearly global distribution and a wide ecological tolerance, which is evidenced by a high resistance to several toxic metal(loid)s [25]. It grows best in the temperate biome, mainly found in wetland margins, marshes, fields, and meadows, and it is characterized by a horizontal subterranean stem called a rhizome, from which roots sprout, developing dense sterile and blooming shoots from rhizome buds while the rhizome descends 1.5–3 cm below the surface to grow horizontally [26]. Likewise, Iris pseudacorus L. (fam. Iridaceae) is a 40–150 cm tall, glabrous perennial. The roots are often 10–20 cm long but can reach 30 cm, the rhizome has a diameter of 1–4 cm, and it grows in marshes, lake or riverbank shorelines, and wetland margins that can be used for both urban landscaping and wastewater remediation [27]. This plant tolerates polluted environments; is useful for water treatment purposes; grows best in very wet conditions; is also common in CWs, where it tolerates submersion, low pH, and anoxic soils; and it also displays a high rate of biomass production [28,29]. Iris pseudocorus L. is also a nitrophile because it can survive in soils with low oxygen levels [30].
According to the Rulebook on the Proclamation and Protection of Strictly Protected and Protected Wild Species of Plants, Animals and Mushrooms [31], Iris pseudacorus L. is listed as a highly valuable and commercial species and is subjected to the provisions of the regulation on placing under control the use and circulation of wild flora and fauna, whereas the collection of Iris species from natural habitats in quantities and in ways that would threaten their survival in the future is prohibited in order to ensure their sustainable use. The distribution of Iris pseudacorus L. in Serbia includes Willow (Salix), alder (Alnus), and birch (Betula) riverine forests; riverine willow (Salix) forests; white willow (Salix alba) woods in Central Europe; and marsh forests with narrow-leaf ash (Fraxinus) [32]. Some Juncus species are allocated as pioneer and ephemeral vegetation that can be found on moist salt flats, wet habitats, and along the canals and the banks of the Danube River [33]. Among them, Juncus efussus L. is listed as an endangered species in Serbia that should be preserved.

2.2. Experimental Setup

The plants for the experiment were obtained from a local nursery and they were around 12 to 24 months old. A total of 40 plants were selected, that is, 20 plants per species. Before setting up the experiment, the plants were removed from the pots, cleaned of soil, and their roots were washed several times with distilled water, after which the plants were left to dry. Morphometric characteristics such as weight and height were measured for each plant, after which the plants were placed in 720 mL glass jars with distilled water and Hoagland nutrient solution containing Ca(NO3)2 × 4H2O, 1250 mg L−1; KNO3, 410 mg L−1; NH4H2PO4, 280 mg L−1; MgCl2 × 6H2O, 624 mg L−1; FeSO4 × 7H2O, 60 mg L−1; EDTA-Na2, 80 mg L−1; H3BO3, 6 mg L−1; MnCl2 × 4H2O, 4 mg L−1; ZnSO4 × 7H2O, 0.04 mg L−1; and CuSO4 × 5H2O, 0.04 mg L−1 [36]. Weight was measured with the digital weighing balance instrument Adam Dune DCT 2000, while the height of plants was measured with a ruler. Four plants of each species were placed in jars containing only Hoagland nutrients without Zn concentration (herein referred as control jars), while the other plants were placed in jars containing different Zn concentrations. There were four plants per species for each concentration. The maximum permitted concentration of zinc is 0.5 mg/L for class I, 1 mg/L for class II, 2 mg/L for class III, 5 mg/L for class IV, and ˃5 mg/L for class V, under the Serbian regulations [37]. In order to match concentrations that were both lower and higher than the maximum permitted concentration for class III, we changed these values. The final Zn concentrations were as follows:
(a)
Untreated control (plants were only in a Hoagland nutrient solution)—treatment T1.
(b)
Plants in a Hoagland nutrient solution containing 0.5 mg/L of Zn in each jar—treatment T2.
(c)
Plants in Hoagland nutrient solution containing 1 mg/L of Zn in each jar—treatment T3.
(d)
Plants in Hoagland nutrient solution containing 2 mg/L of Zn in each jar—treatment T4.
(e)
Plants in Hoagland nutrient solution containing 4 mg/L of Zn in each jar—treatment T5.
During the experiment, plants were placed in a simple, constructed growth chamber (Figure 1), containing an LED bar and reflective Mylar film described in Žunić et al. [38]. A hydroponic LED light bar with a 12:12 (day–night) photoperiod and light intensity of 200 μmol photons m−2 s−1 was used with dominant wavelengths (blue and red spectrum) at 460 nm and 630 nm, respectively. This spectrum delivers a uniform dispersion of the necessary wavelengths for propagation, as it accelerates plant cell multiplication. Inside the growing chamber, the temperature was maintained at around 26 ± 2 °C.
The plant roots naturally interact with the soil microbiome, which could improve water quality through various processes such as nutrient cycling, the degradation of organic matter, or the inhibition of algal growth. However, in this study, distilled water was used as medium for plants’ growth, therefore, microbial communities were not formed.
Plants were in the growth chamber for 4 weeks, from November to December, and their general condition was regularly tested—changes in the color of the leaves, root damages, changes in plant growth, etc. Water volume in jars was kept at the same level by adding distilled water to the jars with a noticeable amount of evaporated water. During the experiment setup, jars were filled two times with new Hoagland’s solution and the mentioned Zn concentrations, respectively, on the 14th and 28th days after experiment setup. With each addition of the new water solution and Zn, the pH and EC values of water samples were measured by a pH meter (EcoScan 6; Eutech Instruments, Nijkerk, The Netherlands) and an EC meter (Testo 206 pH2; Testo, Eriskirch, Germany), and also, the growth of plants in jars was recorded. The pH and average conductivity were measured in order to analyze whether changes in the EC and pH of water might be caused by the increasement in the Zn concentrations in solution or impact the removal of Zn. In Table 2, the sample labels of analyzed plants are explained.

2.3. Plant Preparation for Zn Analysis

At the end of the experiment, all plants were taken out of the jars and left to dry naturally at room temperature for 20 days using filter paper. After drying, plants’ weights were recorded before they were divided into root and shoot portions and prepared for Zn analysis. Dried plant samples (1 g) were grounded in a blender to a powdery fraction and digested with a mixture of nitric (HNO3) and perchloric acid (HClO4) for the determination of Zn (nitric -perchloric acid wet digestion in an open vessel) [39]. The measurements were performed by an atomic absorption spectrophotometer (Shimadzu 6300, Tokyo, Japan), using the flame technique. The flame atomic absorption technique identifies elements by measuring the absorption of specific wavelengths of light. A liquid sample containing the ions of the selected metal is first atomized by a nebulizer into tiny droplets, which enter a flame (air-acetylene) where they are further broken down into free atoms. As the atomized atoms pass through the flame, they absorb light at characteristic wavelengths that are unique to each element and obtained by using a specific hollow cathode lamp. For zinc, the characteristic wavelength is 213.9 nm. The amount of absorption is directly proportional to the concentration of the element in the sample. A total of 60 plant material samples were tested. Control jars for both Juncus and Iris plants were analyzed as one common sample (marked as J1R,L-J4R,L and IR1R,L-IR4R,L). Accuracy was evaluated with the certified reference material LGC6175 (LGC, London, United Kingdom). Calibration curves for the determination of Zn were processed with different dilutions of the standard stock solutions at a conc. of 1000 mg/L (J.T: Baker, The Netherlands). The linear regression lines were obtained with R ≥ 0.95.

2.4. Data Analysis

The chemometric analysis included the application of the Wilcoxon Matched Pairs Test (WMPT), as a non-parametric statistical test. It is considered an alternative to the t-test for dependent samples. Also, principal component analysis (PCA) was applied as a chemometric pattern recognition technique. The WMPT and PCA were carried out by using the statistics v.14.0.0.15 program [40]. The chemometric analysis was carried out with the natural (non-standardized) data, considering the fact that all the processed data were compared and on the same scale.
To illustrate the characteristics of metal translocation from roots to shoots, the mobilization ratio (Equation (1)) or translocation factor (TF) for zinc in plants was computed. The translocation factor (TF) defines the link between the chemical composition of the leaves and their root content, which provides information on plant efficiency while transporting metals from roots to leaves [13], thus contributing to phytoextraction.
TF = Metal concentration in shoots/Metal concentration in roots

3. Results

3.1. Plant Growth Dynamics and Responses to Different Zn Concentrations

Vegetative growth and biomass were the parameters measured to evaluate the plant’s tolerance to varying Zn concentrations. These parameters were recorded at the beginning, during, and at the end of the experiment. Leaf growth measurements of Juncus efussus L. and Iris pseudacorus L. were made by measuring the length of the leaves with a ruler from the top to the bottom of leaves. Root measurements were conducted at the end of the experiment when plants were left to dry from the initial point of growth to the endpoint of the roots. Juncus effusus L. plants showed significant plant growth under both low and high Zn concentrations. Leaf biomass was significantly greater and plants were more robust, actively growing and without any damage. It was also noticed that the root system in the water solution was developing new adventive roots soon after the beginning of the experiment (after 6 days). Moreover, Juncus roots demonstrated a high uptake capacity of water, which was noted based on water infiltrating from the top of the jars containing Juncus plants. On the contrary, Iris pseudacorus L. plants were affected by Zn treatments, in both leaves and roots. The leaves became dry and yellow and the roots had brown spots, mucus appeared on the surface of the jar 7 days after placing the plants in the jars, and there was observable algal growth in all treatments. At the end of the experiment, the decrease in the leaf biomass was noted, so the leaves were not used for the analysis of Zn. However, the presence of new, developing roots was also noted during the experiment. Relative to the initial weight, plants of Juncus effusus L. gained weight from 8.96% to 62.78% with an average biomass increase amounting to 32.01% (Table 3). For some Iris pseudacorus L. plants, there were reductions in plant weight, ranging from 2.98 to 23.15% compared to the initial one, due to the loss of leaf mass. Compared with the control treatments, Juncus plants that were grown in solution with the increased content of Zn grew by up to 53.82% on average, that is, the highest obtained biomass calculated for a plant that grew in nutrient solution with Zn concentrations of 4 mg/L (plant marked as J17).

3.2. Accumulation of Zn in Plants

Concentrations of Zn in Iris and Juncus plants in different treatments are presented in Table 4. As it can be noted, the maximum measured Zn concentration was found in Juncus effusus L. plant roots (plant marked as J19r), amounting to 264.59 (mg/L). Similar high concentrations were also detected in Juncus plants marked as J16r, J18r, and J19r. These Juncus plants were maintained in jars that were filled with solution amended with the highest Zn concentration, 4 mg/L of Zn per water solution in the jar (T5). The average Zn concentration in Juncus plants was 76.12 mg/L for leaves and double that for roots, which is 144.78 mg/L, while the average Zn concentration for Iris roots was 134.53 mg/L. The lowest concentration of Zn was detected in control plants (for Juncus leaves J1L-J4L) and the roots of Juncus plant J7r. For Iris pseudacorus L. roots, the plant marked as IR7 was detected as having the smallest Zn concentration (45.85 mg/L). The average accumulated Zn in Iris plants was 191.27 mg/L. In general, the concentration of Zn in the rhizome and root tissues increased with increasing Zn concentrations in the growth media. As for the control jars, total Zn ranged from 36.2 mg/L for Juncus leaves to 110 mg/L for Iris roots.
Starting from the lowest to the highest, the concentration of Zn in plants was in the following order:
Juncus effusus L. leaves < Juncus effusus L. roots < Iris pseudacorus L. roots.

3.3. Translocation Factor (TF)

Due to the decreased leaf biomass of Iris pseudacorus L. at the end of the experiment, the translocation factor (TF) was calculated only for Juncus effusus L. The levels of the translocation factor were TF < 1.0, ranging from 0.33 to 0.99 (Figure 2). The average calculated TF value was 0.60. This finding suggests that Zn can be easily accumulated by Juncus plants, transported to their aboveground parts, and that Juncus effusus L. meets the requirements for the phytostabilization of urban ecosystem soil contamination with HMs [41,42].

3.4. Physicochemical Properties of Water Solutions in Jars

The pH of the nutrient solution was in the range from acidic to alkaline, ranging from 3.4 to 7.18 for Iris plants, with an average value of 6.35 during the first measurement (after 8 days of the experiment), from 7.63 to 9.12 with an average value of 8.22 for the second measurement (after 20 days of the experiment), and from 6.6 to 8.6 with an average value of 7.65 (at the end of experiment). The lowest value of pH was measured in the Iris plant marked as IR18, placed in a jar with a water solution with the highest Zn concentration. The values of pH for Juncus plants were in the range from 6.5 to 7.15 after the first measurement, from 6.57 to 8.05 for the second measurement, and from 6.77 to 7.5 for the third measurement. Much greater variability in pH values was noted for Iris plants, where the values of pH ranged from 3.11 to 9.12. The electric conductivity (EC) of water varied from 870 to 1929 µS/m−1 for Iris pseudacorus L. and from 744 to 1960 for Juncus effusus L. The maximum EC of the water solution amounting to 1960 µS/cm−1 was noted for plants under the highest treatment of Zn, which was 4 mg/L (T5). This value was measured at the end of the experiment. The lowest EC values were also noted for Juncus plants that were in water solutions with the highest treatment of Zn during the third measurement, obtained after three weeks from the beginning of the experiment.
The changes in the average conductivity and pH during the experiments measured at defined sampling terms are presented in Figure 3.

3.5. Results of Chemometric Analysis

The results of the Wilcoxon Matched Pairs Test (WMPT) are presented in Table 5. The data indicate that in terms of Zn concentration, there is a significant difference between the samples of Juncus effusus L. leaves and Juncus effusus L. roots as well as between the samples of Juncus effusus L. leaves and Iris pseudacorus L. roots. These tests are significant at p < 0.05. However, there is no significant difference between the samples of Juncus effusus L. roots and Iris pseudacorus L. roots.
In Figure 4, there is a box–whisker plot of the concentration of Zn determined in twenty samples of each plant. The box–whisker plot presents the mean value, deviation (SD) limit, and 1.96 SD limit (the whisker).
As it can be seen, the lowest mean and standard deviation are observed in Juncus effusus L. leaves. Higher Zn concentrations are present in Juncus effusus L. roots and Iris pseudacorus L. roots. The high concentration and standard deviation range are noticed for Juncus effusus L. roots.
The PCA was carried out on the data that include the conductivity and pH values, separately. The results of the PCA of the conductivity data are given in Table 6. The graphical representation of the results is given in Figure 5. The 4-PC model was obtained so that the first 2 PCs cover 76.6% of the total variance. These PCs have Eigenvalues higher than 1, therefore, the 2-PC model was taken into consideration.
In Figure 5, there are score and loading plots of the 2-PC model. The score plot indicates that the Iris pseudacorus L. samples (IR) and Juncus effusus L. samples (J) are clearly separated by the PC2 = 0 line. The J samples are described by the positive PC2 values, while the IR samples have negative PC2 values. The loading plot indicates that this distribution is mostly induced by ST1 and ST4 measurements (the first and last days of measurements). Along the PC1 axis, there is no separation of the samples. Therefore, the IR and J samples mostly differ on the first and the last day of the measurements.
The PCA based on pH values resulted in the 4-PC model, in which the first two PCs cover 83.27% of total variance and have Eigenvalues higher than 1 (Table 7).
The score plot, presented in Figure 6, indicates the significant separation of the J sample along PC2 axis. All the J samples have positive PC2 values, including two outliers from IR samples (IR18 and IR19). This separation is achieved based on ST2 and ST3 measurements, since those two variables have the highest influence on the distribution along the PC2 axis, as it can be seen on the loading plot in Figure 6. Therefore, pH could be a discriminating factor for the IR and J samples measured at ST2 and ST3. The IR and J samples cannot be separated along the PC1 axis, except the IR17, IR18, and IR19 samples that could be considered to be the outliers since they are placed further from the rest of the samples (the lowest pH).

4. Discussion

The results of the analysis indicated that average concentrations of Zn were higher in the roots of Iris pseudacorus L. plants than in the roots of Juncus effusus L., suggesting that Iris pseudacorus L. can accumulate higher concentrations of Zn than Juncus effusus L. However, the overall results showed that both species significantly accumulated dissolved Zn. Zinc concentrations were similarly distributed in root tissues of Juncus and Iris plants, suggesting that the Zn distribution in plant parts usually follows the pattern roots > foliage > branch > trunk, reported in a study conducted by [43], and the concentration sequence of the HMs is mostly as follows: rhizosphere soils > roots > shoots [44]. The biologically active, high surface area formed by plant roots that are rapidly growing can be extremely active in absorbing pollutants from water [45]. These features make Juncus plant an ideal plant for rhizofiltration as a mechanism to remove pollutants from water, where most of the pollutants are retained in the root system. Metals that are commonly present in roots are the main target of the rhizofiltration technique, including Zn. In the indigenous zinc smelting area in the northwest region of Guizhou Province, China, Pen et al. [46] pointed out that Juncus effusus L. could be used for phytostabilization or as a pioneer plant for the phytoremediation of potentially toxic HMs. In deciding whether an accumulator can be used for phytoextraction or phytostabilization purposes, the heavy-metal accumulation in roots or aboveground shoots is a major factor [47].
The phytoremediation potential of the plants is generally evaluated by determining the bioconcentration factor (BCF) [48]. Bioconcentration values > 2 are considered to be higher values. Plants can be used as phytostabilizers if they have bioconcentration factors > 1. According to Takarina and Pin [49] and Sharma et al. [13], plants with BCF > 1 and TF < 1 are reported to demonstrate the possibility of phytostabilization. A BCF value higher than 1 indicates that the plant is a hyperaccumulator of the special pollutant. Based on studies conducted so far, Juncus plants demonstrated very high BCF values. A study conducted by Ladislas et al. [50] showed very high concentrations of Zn in Juncus plants collected from a detention pond receiving highway runoff that was also confirmed to have a very high bioconcentration factor (BCF = 4.8) by Juncus sp. Our study also revealed that based on the calculated TF values, Juncus can be used for remediation. All calculated values for TF for Juncus plants were high, whereas the highest values were obtained for plants that were grown in higher Zn concentrations, for example, T5 (4 mg/L of Zn).
Our study did not examine the concentration of Zn in Iris pseudacorus L. leaves, but as previously reported by several authors [51,52,53,54,55], the roots/rhizomes were the primary organs for HM accumulation and concentrations in wetland plants like Iris pseudacorus L. compared to stems, leaves, and flowers, so we hypothesized that the concentration of Zn would be much lower in Iris leaves than in roots, if they were included in the analysis. According to Hamzah Saleem et al. [24], the majority of Zn in plants is found in its roots, whereas a small percentage is transported to the leaves and stems and even small lateral roots can retain more Zn than other vegetation components. Moreover, roots are relatively sensitive to oxygen deprivation, and the survival capacity of most tolerant species resides in the shoots or rhizomes [51]. However, as reported by Gupta et al. [56], Zn is among the easily biologically available metals in plants, and soluble forms of Zn are readily available to plants.
According to Balafrej et al. [57], Zn toxicity increases with its bioavailability. The most obvious symptoms of Zn toxicity reported in plants are the inhibition of growth; the chlorosis of young leaves, mainly in new leaves; depressed plant growth; curled leaf tips; reduced photosynthetic rate; nutrient imbalance; and membrane degradation [24,57,58]. Morphological and growth indicators including root length and shoot height are the most common indicators to describe plant tolerance [47]. In this study, Juncus effusus L. plants did not show any visible Zn toxicity symptoms since all plants survived, even at the high Zn concentrations (Figure 7). All plants had a high biomass; on average, they grew from 18–44 mm after 40 days of the experiment. A significant increase in the weight of Juncus plants was also noted. Relative to the initial weight, at the end of the experiment, average plant weight increased from 7.79 to 62.78%. Based on the root growth of Juncus effusus L. in the present study, it can be concluded that from the aspect of root development, Zn had also a positive effect on Juncus effusus L. roots. For Iris plants, the increasement in weight varied from 3.07% to 57.14%. It was noted that the highest recorded percentage of plant weight of both Iris and Juncus plants was calculated for the plants that were grown in jars with the Zn concentration of 4 mg/L (plants marked as J17 and IR17).
Similar responses of the Juncus and Iris plants to different Zn exposure levels were also reported by several authors. For the populations of Juncus, Juncus effuses L., and Juncus articulatus L., studies reported the tolerance of concentrations of Zn of up to 100 μmol L−1, but growth was inhibited at the higher treatment levels [59]. On the contrary, Mateos-Naranjo et al. [60] showed that Zn excess (concentrations up to 100 mmol−1) did not cause toxicity symptoms such as chlorosis, necrosis, or affected photosynthesis, suggesting that Juncus acutus L. is a hypertolerant species to Zn. The growth of Juncus effusus L. was in very good condition due to the high number of new shoots in an experimental hydroponic study [61]. In the present study, there were notable morphological changes through biomass reductions after 7 days of treatment at all Zn concentrations for the Iris plants (Figure 8). These findings are similar to the results obtained by Gariepy [62] for species Acorus calamus L., which is comparable to species Iris pseudacorus L. with respect to its morphology and lifestyle. After 30 days of growth in nutrient solution, the plants showed a yellowing of leaves in all treatments, which could have been due to nutrient overloading or natural senescence patterns. Furthermore, this could also be explained with a natural cycle in which leaves would grow, become yellow, and then the plant would produce new shoots to replace the old ones, which was also observed in Acorus plants in the mentioned study [62], because our experiment was set in the fall (November–December). The outer leaves of Iris pseudacorus L. showed damage after 1–2 weeks under anoxia, with the tips turning soft and brown, and after 28 d, the total soluble carbohydrate (TSC) content of leaves reduced by 60%, which was 45% higher than for the species Acorus calamus L. [51].
On the contrary, Caldelas et al. [28] reported a high rate of survival and continued growth of Iris pseudacorus L. plants in nutritive solution with ZnCl2, along with remarkable accumulation of Zn in roots and leaves. For other HMs, like cadmium (Cd), Iris pseudacorus L. was shown to be tolerant with medium (2 mg/L) and high (4 mg/L) Cd dose treatment [55]. Similar results were obtained by Branković et al. [53] in a floating wetland. Phragmites australis and Iris pseudacorus L. displayed 100% survival with no toxicity symptoms such as withering, necrosis, or chlorosis according to visual observations throughout the growth period. Iris pseudacorus L. was also associated with high efficiency in the removal of silver nanoparticles (approximately 96%) in a vertical flow wetland system and the reduction in COD compounds (83%), total N (61%), ammonia (42%), and total P (70%) [63].
The water quality changes and plant growth can be affected by the pH of the water [64]. It has been reported that increased mobility of Zn and Mn is most effective with pH = 6 [65]. It has also been reported that Zn is more bioavailable at an acid pH than at an alkaline pH [66]. Thus, the pH value decreases due to the release of organic acids and H+, which facilitates Zn solubilization and uptake by plants. Our study revealed that the highest variation in the pH values of the solution for Iris pseudacorus L. was noted after the second treatment with Zn, namely, 10 days after replacing the nutrient solution + Zn with a new solution and the same Zn concentrations. For example, the pH of Iris pseudacorus L. plants grown in the T5 Zn treatment (4 mg/L) increased from 3.4 to 8.05 and from 3.69 to 8.6. Until the end of the experiment, the pH of water decreased the most from the beginning of the experiment for plants under all treatments. For the species Juncus effuses L., the same trend of the pH changes was noted. In general, the average pH values of water for Iris plants were higher than for the Juncus plants. These results are similar to those published by Wu et al. [61]. The pH of the experimental water increased from 4 to more than 7 after 20 days of growing the plants in water, which means that the water changed from acidic to weakly alkaline, and the pH of the water was stabilized at 7–8 in the later stages of the conducted experiment [61]. The increasement in the pH of the water solution might be caused by the presence of the amino functional groups in the roots of aquatic plants like Acorus calamus L. and Juncus effusus L., which can form complexes with the heavy metal ions of Cu, resulting in an increase in the pH of the solution [67].
The rapid increase in algal biomass was linked with an increase in pH for all treatments, affecting EC and increasing the pH of the water solution. Like in our study, there was also observable algal growth in all hydroponically grown Iris plant treatments with no apparent preference for any specific Zn concentration [62,68]. The high variability in pH and EC can be explained by the nutrient uptake of the plants [69]. It was reported that Iris and Phragmites plants reduced the ions in the water column to the greatest degree, possibly due to enhanced direct nutrient uptake. Furthermore, nutrient solution at a constant EC can increase the EC in the root environment in nutrient solution [70].
The electrical conductivity (EC) is an index of salt concentration and an indicator of its salt content, ionic content, and impurity content [71]. A higher EC means higher salt concentration, while a lower EC means a lower salt concentration. The mean nutrient solution EC in our study ranged between 1087 µS/cm−1 and 1569 µS/cm−1 for Juncus plants and between 1121 µS/cm−1 and 1218 µS/cm−1 for Iris plants. The lowest single values of EC were recorded for Juncus plants, with the lowest value of 744 µS/cm−1 obtained from Juncus plants grown in the T5 Zn treatment (4 mg/L), while the lowest average EC values were measured for Iris plants, both during the third measurement. Very high EC values were also noted at the end of the experiment, for plants under the T5 treatment, both for Iris and Juncus plants. Changes in the conductivity of water might be caused with the increasement in the Zn concentrations in solution, also accumulated in plants.

5. Potential and Challenges for the Utilization of Juncus and Iris Plants towards Supporting Water Quality and Biodiversity SDGs in Serbia

Within the SDGs, enhancing water quality by 2030 through lowering pollution and reducing the amount of untreated wastewater is highlighted under SDG 6—“Ensure availability and sustainable management of water and sanitation for all” [1]. According to the data from the degree of integrated water resource management (IWRM) in Serbia, the estimated indicator of achieving the water quality SDG expanded by 36% from the period of 2017 to 2020 [72], but this value is still in the medium-low category compared with other countries. Native plants contribute to environmental sustainability in two ways: they conserve water and create ecologically varied habitats [12]. The term biodiversity refers to the diversity of living things found in all kinds of environments, including terrestrial, marine, and other aquatic ecosystems, as well as the ecological complexes that support them. This diversity includes differences within and between species as well as ecosystems [73]. The Global Strategy for Plant Conservation (GSDG) aims to stop the ongoing loss of plant species diversity and to globally save plant species listed in the Convention on Biological Diversity. Plant species found in Serbia comprise 43.3% of all species found in Europe, while about 39% of Europe’s vascular plant species are also found in Serbia. Because of its location, Serbia is home to a large number of endemic species (local endemics: 1.5% or 59 species; and Balkan endemics: 8.06% or 287 species) [21]. However, despite Serbia’s abundance in biodiversity, the key human activities that have an impact on biodiversity loss are mining, energy, transportation, tourism, industrial growth, urbanization, forest exploitation, hunting, fishing, agriculture, and forestry. Knowing that this activities will continue to develop, followed by ongoing climate change, conserving biodiversity and creating resilience should be one of the prioritized goals.
Based on much research data, the reported ecosystem services provided by both analyzed species in this study are countless, along with proven resilience to a range of environmental circumstances, so it can be concluded that the analyzed species have a range of implementation scales, both in urban and suburban areas, because many studies revealed the resilience of Juncus and Iris plants. In research conducted by Laukli et al. [74] with the aim to test plants’ performances subjected to a variety of combined stresses, such as intermittent flooding, de-icing salts, and road dust, Iris pseudacorus L. was shown to be among species/cultivars that were well developed and had a high survival percentage. Similar to Iris plants, the genus Juncus has also demonstrated resistance to salinity, drought, and flooding; hence, it is advised that they be included in NbSs in a variety of geographic areas. A recent research study demonstrated that Juncus effusus L. has shown to be resilient to a variety of climatic conditions, including higher speeds and frequent flooding. This resulted in vast amounts of biomass, quick growth, and a very advantageous plant structure [75]. Species from the Iris genus are commonly grown ornamentals, making them an easy choice for phytoremediation in landscaping design, as they are recognized by their characteristic springtime blooms [76]. Furthermore, Juncus species have been used to remediate marshes, sediments, and soils of various heavy metals. Mine drainage and other industrial and domestic wastes are effectively treated by Juncus plants [77]. Possessing a strong capacity to remove nutrients, total nitrogen (TN), total phosphorus (TP), and potassium (K), the plants from genus Juncus are the most commonly reported for nutrient removal capability in bioretention systems [78,79]. Additionally, it has been shown that Iris pseudacorus L. can withstand extended durations of oxygen deprivation brought on by insufficient soil drainage, protracted floods, total submersion, or ice encasement [51]. Iris pseudocorus L. plants are useful for enhancing nutrient removal in stormwater bioretention cells [80]. Moreover, by attracting beneficial pollinators, like bumblebees and solitary bees, Iris plants can create a rich and diverse community of species [81].

6. Conclusions

The aim of this research was to investigate the resilience of two native perennial Serbian plants, Juncus effusus L. and Iris pseudocorus L., to one of the emergent heavy metals, Zn, previously found in urban waters. The overall results have demonstrated that both plant species can be effective at reducing Zn loadings to the environment. Although, growth and resistance were shown to be higher for Juncus effusus L. plants. We mainly focused on the usage of vegetation in NbSs towards enhancing biodiversity and achieving water quality, as part of the SDGs, aiming to fill the gaps about the potential of particular species in order to encourage their usage in future sustainable practices such as constructed wetlands, bioretention systems, etc. Therefore, this study contributes to supporting sustainable water management and Serbia’s Sustainable Development Goals in biodiversity conservation that are highlighted within “The Biodiversity Strategy and Action Plan (BSAP) of Serbia” [21]. Some of the main tasks highlighted in this plan are helping endangered Serbian species, ecological groups, and their natural environments; preserving genetic diversity and capacity for evolution; and restoring biological variety in damaged environments. By providing information about some of the endangered species and their potential for utilization in various NbS projects, this study was an initial step for further field and laboratory research.

Author Contributions

All authors contributed to the study conception and design. Conceptualization: A.G.; methodology: setting up the experiment, laboratory analysis, and investigation were performed by A.G. and I.M.; chemical analysis was performed by M.I.V. and M.P.Š.; data analysis was performed by M.L., B.B., S.P.-K. and S.K. The first draft of the manuscript was written by A.G. and all authors commented on previous versions of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research work was financially supported by the Provincial Secretariat for Higher Education and Scientific Research Autonomous Province of Vojvodina, Republic of Serbia, as a part of research project of the author A. G. entitled “Investigation of the potential for the application of bioretention systems in the territory of the city of Novi Sad in order to collect and treat stormwater runoff” (No. 142-451-2968/2022-04). The other authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All relevant data are already contained within the article.

Acknowledgments

The authors would like to thank Timea Hajnal-Jafari, Simonida Đurić, and Dragana Stamenov from the University of Novi Sad, Faculty of Agriculture, Department of Field and Vegetable Crops, Laboratory for Soil Microbiology, for technical assistance during performing laboratory analyses.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Experimental jars with Juncus effusus L. and Iris pseudacorus L. grown hydroponically in a constructed growth chamber: (a) jars with Juncus plants; (b) jars with Iris plants.
Figure 1. Experimental jars with Juncus effusus L. and Iris pseudacorus L. grown hydroponically in a constructed growth chamber: (a) jars with Juncus plants; (b) jars with Iris plants.
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Figure 2. Translocation factor (TF) for Juncus plants.
Figure 2. Translocation factor (TF) for Juncus plants.
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Figure 3. The change in the average conductivity and pH during the experiments measured at defined sampling terms: (a,b) for Iris pseudacorus L. and (c,d) for Juncus effusus L. Average conductivity and average pH were calculated based on four samples in the experimental set.
Figure 3. The change in the average conductivity and pH during the experiments measured at defined sampling terms: (a,b) for Iris pseudacorus L. and (c,d) for Juncus effusus L. Average conductivity and average pH were calculated based on four samples in the experimental set.
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Figure 4. Box–whisker plot of the Zn concentrations in the samples of Juncus effusus L. leaves and roots and Iris pseudacorus L. roots. Each box–whisker graph refers to twenty measurements (including control measurements) of the specified plant samples.
Figure 4. Box–whisker plot of the Zn concentrations in the samples of Juncus effusus L. leaves and roots and Iris pseudacorus L. roots. Each box–whisker graph refers to twenty measurements (including control measurements) of the specified plant samples.
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Figure 5. Score (a) and loading (b) plots based on the conductivity data (IR—Iris pseudacorus samples; J—Juncus effusus samples; ST—sampling term).
Figure 5. Score (a) and loading (b) plots based on the conductivity data (IR—Iris pseudacorus samples; J—Juncus effusus samples; ST—sampling term).
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Figure 6. Score (a) and loading (b) plots based on the pH data (IR—Iris pseudacorus samples; J—Juncus effusus samples; ST—sampling term).
Figure 6. Score (a) and loading (b) plots based on the pH data (IR—Iris pseudacorus samples; J—Juncus effusus samples; ST—sampling term).
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Figure 7. During the experiment, the growth responses of Juncus effusus L. plants were as follows: (a) an increase in biomass; (b) water infiltration through roots; and (c) the production of new, adventive roots.
Figure 7. During the experiment, the growth responses of Juncus effusus L. plants were as follows: (a) an increase in biomass; (b) water infiltration through roots; and (c) the production of new, adventive roots.
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Figure 8. The Iris pseudacorus L. plants exhibited the following growth responses during the experiment: (a) a decrease in leaf biomass; (b) brown spots on the rhizomes/roots with the new adventive root formation; and (c) algal growth in all jars with varying Zn concentrations.
Figure 8. The Iris pseudacorus L. plants exhibited the following growth responses during the experiment: (a) a decrease in leaf biomass; (b) brown spots on the rhizomes/roots with the new adventive root formation; and (c) algal growth in all jars with varying Zn concentrations.
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Table 1. Juncus and Iris plant features [31,32,33,34,35].
Table 1. Juncus and Iris plant features [31,32,33,34,35].
Plant NameFamilyDistribution/
Origin in Serbia		Vegetation TypeHabitatGrowth and Planting RequirementsPhenology/
Flowering Time
Juncus effusus L. (M, E) 1JuncaceaeNative aGrassesAquatic,
Terrestrial
wetlands		Tolerant to shade and partial shade; tolerant to acid soils; tolerant to a range of temperatures; prefers moist-to-wet soil conditionsEarly spring through summer; long flowering time
Iris pseudocorus L. (O, M) 1IridaceaeNative aPerennialAquatic
Wetlands		Works best in acidic, moist-to-wet, humus-rich soils; full sun or partial shade; prefers moist-to-wet soil conditionsApril to mid-May; short flowering time
1 (M)—also used in medicine, (E)—environmental uses; (O)—also important as an ornamental species. a -naturally found and adapted within the study region
Table 2. Determination of plant samples during analysis.
Table 2. Determination of plant samples during analysis.
Iris pseudacorus L. *Juncus effusus L.
Sample Determination
(Roots)		Sample Determination (Leaves)Sample Determination
(Roots)		Zn Concentration
IR1JL1JR1Control
IR2JL2JR2Control
IR3JL3JR3Control
IR4JL4JR4Control
IR5JL5JR50.5 mg/L
IR6JL6JR60.5 mg/L
IR7JL7JR70.5 mg/L
IR8JL8JR80.5 mg/L
IR9JL9JR91 mg/L
IR10JL10JR101 mg/L
IR11JL11JR111 mg/L
IR12JL12JR121 mg/L
IR13JL13JR132 mg/L
IR14JL14JR142 mg/L
IR15JL15JR152 mg/L
IR16JL16JR162 mg/L
IR17JL17JR174 mg/L
IR18JL18JR184 mg/L
IR19JL19JR194 mg/L
IR20JL20JR204 mg/L
* Only roots.
Table 3. The summary statistics (ranges, means, and standard deviations) differences between the observed morphometric parameters among Juncus and Iris plants before and at the end of the experiment.
Table 3. The summary statistics (ranges, means, and standard deviations) differences between the observed morphometric parameters among Juncus and Iris plants before and at the end of the experiment.
Juncus effusus L.Iris pseudacorus L.
ValueWeight (g)Height (cm) aWeight (g) bHeight (cm) bWeight (g)Height (cm) aWeight (g) bHeight (cm) b
Min254039.3594.79.57.80
Max103.68312010474.63.696.56
Mean ± SD65.95 ± 22.2155.65 ± 8.6083.98 ± 22.0380.65 ± 13.3524.40 ± 19.1318.88 ± 9.1832.43 ± 23.910.75 ± 1.76
a—before the experiment; b—after the experiment.
Table 4. Concentration of Zn in Iris and Juncus plants in different treatments (T1–T5).
Table 4. Concentration of Zn in Iris and Juncus plants in different treatments (T1–T5).
Zn Treatments in Jars (mg/L)Zn Concentration in Juncus efussus L. Leaves (mg/L)Zn Concentration in Juncus efussus L. Roots (mg/L)Zn Concentration in Iris pseudacorus L. Roots (mg/L)
Control jars (T1)36.2110.93191.27
T2 (0.5 mg/L)49.95108.65112
59.7660.20102.5
48.6353.2045.85
77.3689.60103.57
T3 (1 mg/L)56.3781.21102.07
55.94113.4851.57
57.58150.92177.82
59.12134.1187.41
T4 (2 mg/L)111.42196.53150.73
68.18156.71186.96
59.96121.65154.66
111.83205.49186.47
T5 (4 mg/L)68.26118.07147.11
92.83262.98167.4
113.17264.59193.05
167.5232.93126.59
Average76.12144.78191.27
Table 5. The results of the WMPT.
Table 5. The results of the WMPT.
Zn Concentration in:Wilcoxon Matched Pairs Test—Marked Tests * Are Significant at p < 0.05
Valid NTZp-Value
Juncus effusus L. leaves
and
Juncus effusus L. roots *		1703.620.00029
Juncus effusus L. leaves
and
Iris pseudacorus L. roots *		1793.200.00140
Juncus effusus L. roots
and
Iris pseudacorus L. roots		17640.590.55403
(T)—t score for paired (Wilcoxon(t) test). (Z)—z value for the selected confidence interval (Wilcoxon(z) test). * Significance of marked tests between different samples
Table 6. The PCA model based on the conductivity data of the samples.
Table 6. The PCA model based on the conductivity data of the samples.
PCEigenvalue% of Total VarianceCumulative EigenvalueCumulative %
11.6741.681.6741.68
21.4034.913.0676.60
30.7017.413.7694.00
40.246.004.00100.00
Table 7. The PCA model based on the pH data of the samples.
Table 7. The PCA model based on the pH data of the samples.
PCEigenvalue% of Total VarianceCumulative EigenvalueCumulative %
11.8245.531.8245.53
21.5137.743.3383.27
30.5313.333.8696.59
40.143.414.00100.00
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Greksa, A.; Mihajlović, I.; Ljubojević, M.; Blagojević, B.; Vijuk, M.I.; Podunavac-Kuzmanović, S.; Kovačević, S.; Štrbac, M.P. Investigation of Juncus and Iris Plant Potential—Two Native Serbian Species for Utilization in Nature-Based Solutions towards Improving the Quality of Water Contaminated with Zinc and Supporting Biodiversity. Sustainability 2024, 16, 6467. https://doi.org/10.3390/su16156467

AMA Style

Greksa A, Mihajlović I, Ljubojević M, Blagojević B, Vijuk MI, Podunavac-Kuzmanović S, Kovačević S, Štrbac MP. Investigation of Juncus and Iris Plant Potential—Two Native Serbian Species for Utilization in Nature-Based Solutions towards Improving the Quality of Water Contaminated with Zinc and Supporting Biodiversity. Sustainability. 2024; 16(15):6467. https://doi.org/10.3390/su16156467

Chicago/Turabian Style

Greksa, Amela, Ivana Mihajlović, Mirjana Ljubojević, Boško Blagojević, Mirjana I. Vijuk, Sanja Podunavac-Kuzmanović, Strahinja Kovačević, and Mirna P. Štrbac. 2024. "Investigation of Juncus and Iris Plant Potential—Two Native Serbian Species for Utilization in Nature-Based Solutions towards Improving the Quality of Water Contaminated with Zinc and Supporting Biodiversity" Sustainability 16, no. 15: 6467. https://doi.org/10.3390/su16156467

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