Root and shoot phenology, architecture, and organ properties: an integrated trait network among 44 herbaceous wetland species.

Integrating traits across above- and belowground organs offers comprehensive insights into plant ecology, but their various functions also increase model complexity. This study aimed to illuminate the interspecific pattern of whole-plant trait correlations through a network lens, including a detailed analysis of the root system. Using a network algorithm that allows individual traits to belong to multiple modules, we characterize interrelations among 19 traits, spanning both shoot and root phenology, architecture, morphology, and tissue properties of 44 species, mostly herbaceous monocots from Northern Ontario wetlands, grown in a common garden. The resulting trait network shows three distinct yet partially overlapping modules. Two major trait modules indicate constraints of plant size and form, and resource economics, respectively. These modules highlight the interdependence between shoot size, root architecture and porosity, and a shoot-root coordination in phenology and dry-matter content. A third module depicts leaf biomechanical adaptations specific to wetland graminoids. All three modules overlap on shoot height, suggesting multifaceted constraints of plant stature. In the network, individual-level traits showed significantly higher centrality than tissue-level traits do, demonstrating a hierarchical trait integration. The presented whole-plant, integrated network suggests that trait covariation is essentially function-driven rather than organ-specific.

Superoxide Photoproduction from Wetland Plant-Derived Dissolved Organic Matter: Implications for Biogeochemical Impacts of Plant Invasion.

Although the impacts of exotic wetland plant invasions on native biodiversity, landscape features, and carbon-nitrogen cycles are well appreciated, biogeochemical consequences posed by ecological competition, such as the heterogeneity of dissolved organic matter (DOM) from plant detritus and its impact on the formation of reactive oxygen species, are poorly understood. Thus, this study delves into O2•- photogeneration potential of DOM derived from three different parts (stem, leaf, and panicle) of invasive Spartina alterniflora (SA) and native Phragmites australis (PA). It is found that DOM from the leaves of SA and the panicles of PA has a superior ability to produce O2•-. With more stable aromatic structures and a higher proportion of sulfur-containing organic compounds, SA-derived DOM generally yields more O2•- than that derived from PA. UVA exposure enhances the leaching of diverse DOM molecules from plant detritus. Based on the reported monitoring data and our findings, the invasion of SA is estimated to approximately double the concentration of O2•- in the surrounding water bodies. This study can help to predict the underlying biogeochemical impacts from the perspective of aquatic photochemistry in future scenarios of plant invasion, seawater intrusion, wetland degradation, and elevated solar UV radiation.

A novel combination of wetland plants (Eichhornia crassipes) and biochar derived from palm kernel shells modified with melamine for the removal of paraquat from aqueous medium: a green and sustainable approach.

Herbicide contamination in aquatic systems has become a global concern due to their long- term persistence, accumulation and health risks to humans. Paraquat, a widely used and cost-effective nonselective herbicide, is frequently applied in agricultural fields for pest control. Consequently, the removal of paraquat from contaminated water is crucial. This research presents a sustainable and environmentally benign method for paraquat removal from aqueous system by integrating wetland plants (Eichhornia crassipes) with biochar derived from melamine-modified palm kernel shells. The prepared biochar was characterized by using various analytical techniques. The effectiveness of biochar in enhancing phytoremediation was evaluated through a series of experiments, showing significant paraquat removal efficiencies of 99.7, 98.3, and 82.8% at different paraquat concentrations 50, 100, and 150 mg L-1, respectively. Additionally, present study examined the impact of biochar on the growth of E. crassipes, highlighting its potential to reduce the toxic effects of paraquat even present at higher concentrations. The paraquat removal mechanism was elucidated, focusing on the synergistic role of biochar adsorption and phytoremediation capability of E. crassipes. This innovative approach is an effective, feasible, sustainable and eco-friendly technique that can contribute to the development of advanced and affordable water remediation processes for widespread application.

The novelty of this study lies in the implementation of combined approach by phytoremediation with biochar modified with melamine. This study highlighted synergistic integration of two concurrent systems. The biochar generated from waste palm kernel shells played a pivotal role in facilitating the plants' survival and resilience against the paraquat toxicity, rather than succumbing to its deleterious effects. This research delineates a robust methodology for the elimination of emerging pollutants, offering researchers a platform to make pioneering advancements in this scientific field for sustainable future.

Investigating the effect of hydraulic residence time, artificial aeration and plants presence on different constructed wetland designs treating oil industry effluent.

Constructed Wetlands (CW) have gained popularity over the last decades due to their cost-effectiveness, easy and simple operation and environmental compatibility in wastewater treatment. This ecological engineering technology appears particularly ideal for low-income regions. In this study, three widely used CW types (horizontal flow, vertical flow, and hybrid CW) were constructed and evaluated for their effectiveness in removing various pollution parameters (BOD5, COD, TSS, NH4-N, NO3-N, and TP) from an industrial effluent. Different configurations were tested such as CW type, hydraulic residence time, plants presence, and artificial aeration. Results showed that the hybrid CW configuration (i.e., vertical flow CW followed by horizontal subsurface flow CW) achieved the highest removal rates of all pollutants, i.e., more than 90% of BOD5, COD, TSS, and NH4-N. The single horizontal flow and vertical flow CW designs showed variations in the removal of NO3-N and TP (less than 30%), which were significantly improved (50% and 70%, respectively) by using the hybrid CW system. Artificial aeration significantly improves the performance of the CW system, especially for ammonia nitrogen and organic matter removal, while plants presence is also beneficial in the treatment performance. An 8-days HRT seems to be adequate for high removal rates in passive CW designs, though in aerated wetlands a lower HRT of 4 days seems sufficient. These findings suggest that the hybrid CW system could be a promising option for efficient wastewater treatment in developing regions.

Release of dissolved organic matter from wetland plants and its interaction with polycyclic aromatic hydrocarbons.

Dissolved organic matter (DOM) derived from wetland plants played a critical role in CWs pollutant migration. This study investigated the character and release pattern of DOM derived from two wetland plants, Phragmites australis and Cladophora sp., and the interaction between DOM with phenanthrene (PHE), benzo(a)pyrene (Bap), and benzo [k]fluoranthene (BkF) under different physical conditions were also studied using spectroscopic techniques. DOM release was related to plant species and withering stage. Humic acid (HA)-like fractions (C3 and C5) were dominated in P. australis (52%) and completely withered Cladophora sp. groups (55%), while protein-like fractions (C1 and C2) dominated in early withered Cladophora sp. groups (52%). Due to the cell and tissue structure difference among plants and their withering stage, DOM derived from early withered P. australis revealed a two-stage slow-fast phase, while other groups were linearly released (R2 0.87207-0.97091). A strong correlation existed between HA-like fractions and water quality index, reflecting the critical influence of plant decay in CWs operation performance. The analysis with Stern-Volmer equation indicated that plant-based DOM interacted with PAHs to form ground state complexes with possible involvement of π-π interaction, hydrogen bonding and cation bridging effect. Aromatic, molecular weight, and hydrophilicity of both DOM and PAHs affected their binding with the interaction capability in the order of BKF > Bap > PHE and C3 > C5 > C2 > C1 > C4. Besides, alkaline environment and high DO condition was highly unsuitable for the combination. Scientific management and appropriate operating condition were important in optimizing operation performance and controlling pollutant migration in CWs.

First report of Puccinia recondita rust on native jewelweed (Impatiens capensis) in Pennsylvania.

Jewelweed (Impatiens spp., Balsaminaceae) is a common native annual plant within Pennsylvania wetland ecosystems, many of which are under threat from invasive non-native plants, and is an important wetland indicator plant (code FACW; facultative wetland). In May 2014, rust disease symptoms on native jewelweed (Impatiens capensis Meerb.) were observed within a small (0.1 ha) wet area in York County, southeastern Pennsylvania (39.9080648oN, -77.2472024oW). Rust symptoms were noted on most jewelweed plants within the wet area. Foliar symptoms included chlorosis and premature defoliation; infected stems were distorted. Infected leaves and stems contained orange, erumpent aecia with white fragmented peridia (Fig. 1). Symptomatic leaves and stem sections were collected from five infected plants within one small (5 X 5 m) plot in the center of the wet area and taken to the laboratory for microscopic observations and morphological measurements. Mean aecia diameter was 299.2 ± 55.0 µm (n = 60). Aeciospores were single-celled, orange, and generally globose (Fig. 2) with a mean diameter of 24.4 ± 1.4 µm, (n = 60). Disease symptomology and aecia morphology were consistent with Puccinia recondita Dietel & Holw. DNA extraction (from infected stem material), polymerase chain reactions, and DNA sequencing of the 28S region of the nuclear ribosomal DNA repeat was conducted following protocols in Aime (2006) and Aime et al. (2018). The sequence shares 99.34% identity (903 / 909 bp) with P. recondita (BPI 910319) collected in California (KY798399). A voucher specimen has been deposited in the Arthur Fungarium at Purdue University (PUR N24229) with corresponding 28S sequence (GenBank accession OR648406). P. recondita has been reported on native I. capensis in Indiana (Koslow and Clay 2010) and North Carolina (Grand 1985), but not in Pennsylvania to the best of our knowledge (Farr and Rossman 2022). If this rust disease becomes severe on native jewelweeds in Pennsylvania, it may adversely affect our ability to accurately classify native wetlands in the state. In addition, P. recondita is a heteroecious rust that is a major pathogen of grain crops of economic importance (i.e., wheat, barley, oats), which are grown in southeastern Pennsylvania near the infested area. Further research is warranted to understand if native, annual jewelweed can serve as a secondary or alternate host to cause rust disease in major cereal crops.

Beyond a 'just add water' perspective: environmental water management for vegetation outcomes.

Practitioners of environmental water management (EWM) operate within complex social-ecological systems. We sought to better understand this complexity by investigating the management of environmental water for vegetation outcomes. We conducted an online survey to determine practitioners' perspectives on EWM for non-woody vegetation (NWV) in the Murray-Darling Basin, Australia with regards to: i) desirable outcomes and benefits; ii) influencing factors and risks; iii) challenges of monitoring and evaluation, and iv) improving outcomes. Survey participants indicated that EWM aims to achieve outcomes by improving or maintaining vegetation attributes and the functions and values these provide. Our study reveals that EWM practitioners perceive NWV management in a holistic and highly interconnected way. Numerous influencing factors as well as risks and challenges to achieving outcomes were identified by participants, including many unrelated to water. Survey responses highlighted six areas to improve EWM for NWV outcomes: (1) flow regimes, (2) vegetation attributes, (3) non-flow drivers, (4) management-governance considerations, (5) functions and values, and (6) monitoring, evaluation and research. These suggest a need for more than 'just water' when it comes to the restoration and management of NWV. Our findings indicate more integrated land-water governance and management is urgently required to address the impacts of non-flow drivers such as pest species, land-use change and climate change. The results also indicate that inherent complexity in EWM for ecological outcomes has been poorly addressed, with a need to tackle social-ecological constraints to improve EWM outcomes.

Phytotoxic Effects of Tetracycline and its Removal Using Canna indica in a Hydroponic System.

Wetland plants are gaining interest as potential agents for removing emerging contaminants. However, there have been limited studies examining the ability of these plant species to remove antibiotics and their tolerance to stress. This study aimed to investigate the potential of Canna indica, an indigenous wetland plant species in India, for tetracycline-induced oxidative stress, antioxidant activity, and removal of antibiotics from nutrient media and domestic wastewater. Canna indica exhibited a removal rate of approximately 91.05 ± 0.18% for tetracycline in antibiotic containing nutrient media and 87.97 ± 0.39% in domestic wastewater. Notably, the exposure to the drug during the 30 d reaction period led to the accumulation of reactive oxygen species in the plant tissues. Consequently, there was a decline in chlorophyll content, alongside an increase in antioxidant activity, membrane permeability, and K + ion leakage. These findings emphasize the importance of monitoring tolerance levels induced by antibiotics in plant species. Thus, monitoring the antibiotic-induced-tolerance levels in plant species is crucial for maintaining plant health and effectively managing abiotic stress, ensuring efficient recovery and facilitating an effective wetland treatment system.

Chloride removal capacity and salinity tolerance in wetland plants.

Deicing with sodium chloride maintains safe roads in the winter, but results in stormwater runoff with high chloride (Cl-) content that causes various downstream problems. Chloride-rich water risks contaminating groundwater, shortening the lifespan of concrete and metal constructions, and being toxic to aquatic organisms. Current stormwater treatment methods are unable to remove Cl-, but wetland plants with high chloride uptake capacity have potential to decrease Cl- concentrations in water. The aim was to identify suitable plant species for removing Cl- from water for future studies on phytodesalination of water, by comparing 34 wetland plant species native to Sweden in a short-term screening. Additionally, Carex pseudocyperus, C. riparia, and Phalaris arundinacea was further compared as to their salinity tolerance and tissue Cl- concentration properties. Results show that Cl- removal capacity, tissue accumulation, and tolerance varied between the investigated species. Removal capacity correlated with biomass, dry:fresh biomass ratio, water uptake, and transpiration. The three tested species tolerated Cl- levels of up to 50-350 mg Cl- L-1 and accumulated up to 10 mg Cl- g-1 biomass. Carex riparia was the most Cl-tolerant species, able to maintain growth and transpiration at 500 mg Cl- L-1 during 4 weeks of exposure and with a medium removal capacity. Due to a large shoot:plant biomass ratio and high transpiration, C. riparia also had high shoot accumulation of Cl-, which may facilitate harvesting. Phalaris arundinacea had the highest removal capacity of the investigated species, but displayed decreased growth above 50 mg Cl- L-1. From this study we estimate that wetland plants can remove up to 7 kg Cl- m-2 from water if grown hydroponically, and conclude that C. riparia and P. arundinacea, which have high tolerance, large biomass, and high accumulation, are suitable candidates for further phytodesalination studies.

Antioxidant response in arbuscular mycorrhizal fungi inoculated wetland plant under Cr stress.

Arbuscular mycorrhizal fungi (AMF) provide a positive effect on antioxidant mechanisms in terrestrial plants under heavy metal stress. This study investigated the effects of AMF on wetland plant (Iris wilsonii) growth and antioxidant response under Cr stress at different water depths. Results showed that AMF inoculated I. wilsonii had higher antioxidant response than non-inoculated controls, with shoot superoxide dismutase (SOD), root SOD, shoot peroxidase (POD), and root POD contents increased by 4.7-39.6%, 7.5-29.5%, 11.2-68.6%, 16.8-50.3%, respectively. Meanwhile, shoot (root) proline, malondialdehyde (MDA) and superoxide anion (O2.-) contents in the AMF inoculated I. wilsonii were 10.2-44.3% (2.8-37.2%), 11.5-35.4% (16.9-28.2), and 14.9-30.5% (-0.9-26.3%) lower than those in the non-inoculated controls, respectively. Besides, AMF improved the growth of I. wilsonii with biomass, height, chlorophyll, K, and P contents in the shoots increased by 10.5-32.5%, 17.4-44.9%, 4.7-37.7%, 12.0-30.7%, 13.5-20.6%, respectively. Moreover, the I. wilsonii tolerance to Cr stress was also enhanced under the water depth of 6-3 cm. Therefore, AMF play an important role in wetland plant growth and antioxidant response under Cr stress, and it can improve wetland plants' tolerance to Cr stress at fluctuating water depth.

Effects of a spatially heterogeneous nutrient distribution on the growth of clonal wetland plants.

BACKGROUND: Clonal plants are important in maintaining wetland ecosystems. The main growth types of clonal plants are the guerrilla and phalanx types. However, little is known about the effects of these different clonal growth types on plant plasticity in response to heterogeneous resource distribution. We compared the growth performance of clonal wetland plants exhibiting the two growth forms (guerrilla growth form: Scirpus yagara, Typha orientalis, Phragmites australis and Sparganium stoloniferum; phalanx growth form: Acorus calamus, Schoenoplectus tabernaemontani and Butomus umbellatus) grown in soil substrates that were either homogeneous or heterogeneous but had the same total amount of nutrients. RESULTS: We found that the morphological traits (plant height, ramet number, spacer diameter and length) and biomass accumulation of the guerrilla clonal plants (T. orientalis) were significantly enhanced by heterogeneity, but those of the phalanx clonal plants (A. calamus, S. tabernaemontani and B. umbellatus) were not. The results showed that the benefits of environmental heterogeneity to clonal plants may be correlated with the type of clonal structure. CONCLUSIONS: Guerrilla clonal plants, which have a dispersed, flexible linear structure, are better suited to habitats with heterogeneous resources. Phalanx clonal plants, which form compact structures, are better suited to habitats with homogeneous resources. Thus, wetland clonal species with the guerrilla clonal structure benefit more from soil nutrient heterogeneity.

Tolerant mechanisms to O2 deficiency under submergence conditions in plants.

Wetland plants can tolerate long-term strict hypoxia and anoxic conditions and the subsequent re-oxidative stress compared to terrestrial plants. During O2 deficiency, both wetland and terrestrial plants use NAD(P)+ and ATP that are produced during ethanol fermentation, sucrose degradation, and major amino acid metabolisms. The oxidation of NADH by non-phosphorylating pathways in the mitochondrial respiratory chain is common in both terrestrial and wetland plants. As the wetland plants enhance and combine these traits especially in their roots, they can survive under long-term hypoxic and anoxic stresses. Wetland plants show two contrasting strategies, low O2 escape and low O2 quiescence strategies (LOES and LOQS, respectively). Differences between two strategies are ascribed to the different signaling networks related to phytohormones. During O2 deficiency, LOES-type plants show several unique traits such as shoot elongation, aerenchyma formation and leaf acclimation, whereas the LOQS-type plants cease their growth and save carbohydrate reserves. Many wetland plants utilize NH4+ as the nitrogen (N) source without NH4+-dependent respiratory increase, leading to efficient respiratory O2 consumption in roots. In contrast, some wetland plants with high O2 supply system efficiently use NO3- from the soil where nitrification occurs. The differences in the N utilization strategies relate to the different systems of anaerobic ATP production, the NO2--driven ATP production and fermentation. The different N utilization strategies are functionally related to the hypoxia or anoxia tolerance in the wetland plants.

Seed germination and early seedling growth of six wetland plant species in saline-alkaline environment.

This study focused on the effect of saline and alkaline stress on six typical wetland plant species during seed germination and early seedling growth stages. Based on the indicators of germination, seedling growth and ionic absorption in seedlings, relatively saline and alkaline tolerant plant species were selected and tolerance mechanism was discussed. Results showed that the existence of saline and alkaline stress inhibited the capacity of germination and early seedling growth of most tested plant species to varying degrees, therein effects of saline-alkaline stress were greater than saline stress. Based on the results of principal component analysis (PCA), germination percentage, K+ content, plant height, Na+ content and Na+/K+ ratios can be selected as representative indicators for saline and alkaline tolerance evaluation during seed germination and early seedling growth stages. Among tested species, Juncus effusus and Vetiveria zizanioides exhibited relatively higher saline and alkaline tolerant capacity during their seed germination and early seedling growth. Additionally, both species increase K+ accumulation and retain lower Na+/K+ ratios, which might be their tolerance mechanisms at ion level. In conclusion, V. zizaniodes and J. effusus were recommended as potential plant species for restoring degraded saline-alkaline wetlands and/or establishing constructed wetlands for treating saline wastewater.

Plant traits related to the heavy metal removal capacities of wetland plants.

Plants are the crucial component of floating treatment wetlands (FTWs). However, heavy metal removal capacity varies between plant species, and the relationships between plant traits and differences in removal capacity remain unclear. This study sought to determine: (1) the relationships between plant traits and removal of Cd, Cu, Pb, and Zn from water, and (2) the relationships between the removal patterns of these metals. Plants of 34 wetland plant species were exposed to heavy metal concentrations common in stormwater for five days, and 20 traits were measured on each plant. Results indicate that the most important plant traits for heavy metal removal from water are transpiration and high total biomass, especially large amounts of fine roots and leaves. The same traits were generally related to removal both initially and after longer exposure, with stronger correlations found after longer exposure. Plant removal of one metal was likely correlated with removal of the other metals, and the plant removal capacity after 30 min of exposure was correlated with the removal capacity five days later. The present results can be used in selecting plants for enhanced heavy metal removal by FTWs and in identifying additional useful plant species, allowing adaptation to local conditions.

The PM removal process of wetland plant leaves with different rainfall intensities and duration.

Today, particulate-matter (PM) pollution has become one of the most severe air-pollution problems. As the most commonly used method in daily life, phytoremediation can use plant organs (such as leaves) as biological filters for pollutants to repair the atmosphere. At the same time, rainfall can remove PM from plant-leaf surfaces and enable them to adsorb PM again. By simulating natural rainfall, the rainfall characteristics are quantified as rainfall intensity and rainfall duration, and we use the washout-weighing method to obtain the amount of PM removed from the leaf surface. Then, use a scanner to scan the leaves after rain to get their images, and use Image J software to process the images to obtain leaf area. Finally, the amount of PM removed by rain per unit leaf area can be calculated. It will be used to explore the impact of different rainfall intensity and duration on the removal of PM from the leaf surface of wetland plants. The results showed that under three rainfall intensities used in this experiment, the removal of PM from plant-leaf surfaces all increased with an increase in rainfall duration. When the particle size is 10-100-µm, and the rainfall intensity is 30 mm/h, the removal amount of plant particles tested in this experiment is the largest. With increased rainfall duration, the removal of PM from plant-leaf surfaces increased sharply at first, then slowly, and finally tended to be stable. The removal efficiency of PM on the blade surface is most apparent at the early stage of rainfall, and then gradually weakens. Among the four wetland plants tested in this experiment, in the range of 10-100-µm, the number of PM on the leaf surface of Scirpus validus is the largest, and the optimum rainfall intensity is 30 mm/h; in the range of 2.5-10-µm, the number of PM on the leaf surface of Typha orientalis is the largest, and the optimal rainfall intensity is 30 mm/h; in the range of 0.45-2.5-µm, the number of PM on the leaf surface of Iris wilsonii is the largest, and the optimal rainfall intensity is 15 mm/h. Wetland species with high particle accumulation capacity can provide references for vegetation restoration of degraded wetland plants and plant cultivation in constructed wetlands. At the same time, the best rainfall intensity and duration for removing particulate matter on the surface of plant leaves were obtained through experiments, which provided a reference for the design of automatic plant irrigation systems and dust removers in different scenarios.

Toxic effect of perfluorooctane sulfonate on plants in vertical-flow constructed wetlands.

Per-and polyfluoroalkyl substances (PFASs) can be taken up and bioaccumulated in plants, but the toxic mechanisms of PFASs on wetland plants are still unclear. In present study, the toxic influences of perfluorooctane sulfonate (PFOS) on Eichhornia crassipes (E. crassipes) and Cyperus alternifolius (C. alternifolius) in a vertical-subsurface-flow constructed wetland were evaluated. The results showed that E. crassipes was more tolerant to PFOS stress than C. alternifolius, and the growth and chlorophyll synthesis of the two plants were promoted by low concentration (<0.1 mg/L) of PFOS, and the chlorophyll synthesis was inhibited by high concentration (10 mg/L) of PFOS but the growth did not change obviously. The catalase activity and malondialdehyde content in the leaves of the two plants increased, peroxidase activity decreased under exposure to high concentrations of PFOS, and superoxide dismutase activity did not change. Under PFOS stress, the membrane of plant leaves and the cell structure of the two wetland plants were destroyed, and the mitochondrial contour of root cells became incomplete. Tanscriptomic analysis showed that the expression levels of genes related to cell wall formation, the cell apoptosis pathway, material synthesis, and metabolism in the plants were changed by PFOS. Analysis in fluorogenic quantitative real time polymerase chain reaction (RT-qPCR) also confirmed that the photosynthesis system of E. crassipes was inhibited, while that of C. alternifolius was promoted.

Relationship between electrogenic performance and physiological change of four wetland plants in constructed wetland-microbial fuel cells during non-growing seasons.

To find suitable wetland plants for constructed wetland-microbial fuel cells (CW-MFCs), four commonly used wetland plants, including Canna indica, Cyperus alternifolius L., Acorus calamus, and Arundo donax, were investigated for their electrogenic performance and physiological changes during non-growing seasons. The maximum power output of 12.82mW/m2 was achieved in the A. donax CW-MFC only when root exudates were being released. The results also showed that use of an additional carbon source could remarkably improve the performance of electricity generation in the C. indica and A. donax CW-MFCs at relatively low temperatures (2-15°C). However, A. calamus withered before the end of the experiment, whereas the other three plants survived the winter safely, although their relative growth rate values and the maximum quantum yield of PSII (Fv/Fm) significantly declined, and free proline and malondialdehyde significantly accumulated in their leaves. On the basis of correlation analysis, temperature had a greater effect on plant physiology than voltage. The results offer a valuable reference for plant selection for CW-MFCs.

Constructed wetlands and hyperaccumulators for the removal of heavy metal and metalloids: A review.

Water pollutions of heavy metal and metalloids (HMMs), typically including As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn, are becoming a severe environmental problem to be controlled. Constructed wetlands (CWs) have been intensively investigated and applied for the removal of HMMs. By analyzing a mass of data from the existing literatures, this review found that the HMM removals in CWs varied from 12.35 % to 91.01 %, depending upon the HMM species and CW conditions. Nonetheless, 88.50 % of the influent HMMs were eventually immobilized in the CW sediments, while the common wetland plants are inefficient (i.e., accounting for 4.64 %) to uptake and accumulate the HMMs. It was also found that the concentrations of certain HMMs in the CW sediments have already exceeded up to 100 % of various environmental standards, indicating the urgency of introducing HMM hyperaccumulators in the systems. Through comparison, both the aboveground and belowground HMM accumulating capacities of reported hyperaccumulators were higher by magnitudes than common wetland plants. Following this, the efficacies and mechanisms of candidate hyperaccumulators were provided for the various scenarios of HMM control in CWs. Further, the selection principals, culture methods, and harvest strategies of hyperaccumulator in CWs were discussed. Finally, several perspectives were suggested for the future research. Overall, this review provided guiding information for the utilization of hyperaccumulators in CWs, which can improve the efficiency and sustainability of HMM removal in the CW systems.

Unraveling phytoremediation mechanisms of the common reed (Phragmites australis) suspension cells towards ciprofloxacin: Xenobiotic transformation and metabolic reprogramming.

Phytoremediation is an effective solution to treat pollution with antibiotic compounds in aquatic environments; however, the underlying mechanisms for plants to cope with antibiotic pollutants are obscure. Here we used cell suspension culture to investigate the distribution and transformation of ciprofloxacin (CIP) in common reed (Phragmites australis) plants, as well as the accompanying phenotypic and metabolic responses of plants. By means of radioactive isotope labelling, we found that in total 68 % of CIP was transformed via intracellular Phase I transformation (reduction and methylation), Phase Ⅱ conjugation (glycosylation), and Phase Ⅲ compartmentalization (cell-bound residue formation mainly in cell walls, 23 %). The reduction and glycosylation products were secreted by the cells. To mitigate stress induced by CIP and its transformation products, the cells activated the defense system by up-regulating both intra- and extra-cellular antioxidant metabolites (e.g., catechin, l-cystine, and dehydroascorbic acid), anti-C/N metabolism disorder metabolites (e.g., succinic acid), secreting signaling (e.g., nicotinic acid), and anti-stress (e.g., allantoin) metabolites. Notably, the metabolic reprogramming could be involved in the CIP transformation process (e.g., glycosylation). Our findings reveal the strategy of wetland plants to cope with the stress from CIP by transforming the xenobiotic compound and reprogramming metabolism, and provide novel insights into the fate of antibiotics and plant defense mechanisms during phytoremediation.

The uptake, transportation, and chemical speciation of Sb(III) and Sb(V) by wetland plants Arundinoideae (Phragmites australis) and Potamogetonaceae (Potamogeton crispus).

Antimony (Sb) is increasingly released and poses a risk to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, but the current knowledge regarding the effects of Sb(III) and antimonate (Sb(V)) exposure is limited to wetland plants, especially the Sb speciation in plants. In this study, Phragmites australis and Potamogeton crispus were exposed to 10 and 30 mg/L Sb(III) or Sb(V) for 20 days. The total concentration, subcellular distribution, and concentration in the iron plaque of Sb were determined. The Sb speciation in plants was analyzed by HPLC-ICP-MS. It illustrated that Sb(III) exposure led to more Sb accumulation in plants than Sb(V) treatments, with the highest Sb concentration of 405.35 and 3218 mg/kg in Phragmites australis and Potamogeton crispus, respectively. In the subcellular distribution of Sb, accumulation of Sb mainly occurred in cell walls and cell cytosol. In Phragmites australis, the transport factor in the Sb(V) treatments was about 3 times higher than the Sb(III) treatments, however, it was lower in the Sb(V) treatments than Sb(III) treatments for Potamogeton crispus. Sb(V) was detected in the plants of Sb(III) treatments with different Sb(V)-total Sb vitro (Phragmites australis: 34 % and, Potamogeton crispus: 15 %), moreover, Sb(V) was also detected in the nutrient solution of Sb(III) treatments. Antimony exposure caused a reduction of the iron plaque formation, at the same time, the root aerenchyma formation was disrupted, and this phenomenon is more pronounced in the Sb(III) treatments. Moreover, the iron plaque has a higher sorption potential to Sb under Sb(III) exposure than that under Sb(V) exposure. The results can fill the gap for antinomy speciation in wetland plants and expand the current knowledge regarding the Sb translocation in wetland systems.