Mycorrhizal colonization had little effect on growth of Carex thunbergii but inhibited its nitrogen uptake under deficit water supply.

BACKGROUND AND AIMS: Plant nitrogen (N) acquisition via arbuscular mycorrhizal fungi (AMF) serves as a dominant pathway in the N nutrition of many plants, but the functional impact of AMF in acquisition of N by wetland plants has not been well quantified. Subtropical lake-wetland ecosystems are characterized by seasonal changes in the water table and low N availability in soil. Yet, it is unclear whether and how AMF alters the N acquisition pattern of plants for various forms of N and how this process is influenced by soil water conditions. METHODS: We performed a pot study with Carex thunbergii that were either colonized by AMF or not colonized and also subjected to different water conditions. We used 15N labelling to track plant N uptake. KEY RESULTS: Colonization by AMF had little effect on the biomass components of C. thunbergii but did significantly affect the plant functional traits and N acquisition in ways that were dependent on the soil water conditions. The N uptake rate of AMF-colonized plants was significantly lower than that of the non-colonized plants in conditions of low soil water. A decreased NO3- uptake rate in AMF-colonized plants reduced the N:P ratio of the plants. Although C. thunbergii predominantly took up N in the form of NO3-, higher water availability increased the proportion of N taken up as NH4+, irrespective of the inoculation status. CONCLUSIONS: These results emphasize the importance of AMF colonization in controlling the N uptake strategies of plants and can improve predictions of N budget under the changing water table conditions in this subtropical wetland ecosystem.

Antiandrogenic Effects of a Polyphenol in Carex kobomugi through Inhibition of Androgen Synthetic Pathway and Downregulation of Androgen Receptor in Prostate Cancer Cell Lines.

Prostate cancer (PC) represents the most common cancer disease in men. Since high levels of androgens increase the risk of PC, androgen deprivation therapy is the primary treatment; however this leads to castration-resistant PC (CRPC) with a poor prognosis. The progression to CRPC involves ectopic androgen production in the adrenal glands and abnormal activation of androgen signaling due to mutations and/or amplification of the androgen receptor (AR) as well as activation of androgen-independent proliferative pathways. Recent studies have shown that adrenal-derived 11-oxygenated androgens (11-ketotestosterone and 11-ketodihydrotestosterone) with potencies equivalent to those of traditional androgens (testosterone and dihydrotestosterone) are biomarkers of CRPC. Additionally, dehydrogenase/reductase SDR family member 11 (DHRS11) has been reported to be a 17ß-hydroxysteroid dehydrogenase that catalyzes the production of the 11-oxygenated and traditional androgens. This study was conducted to evaluate the pathophysiological roles of DHRS11 in PC using three LNCaP, C4-2 and 22Rv1 cell lines. DHRS11 silencing and inhibition resulted in suppression of the androgen-induced expression of AR downstream genes and decreases in the expression of nuclear AR and the proliferation marker Ki67, suggesting that DHRS11 is involved in androgen-dependent PC cell proliferation. We found that 5,7-dihydroxy-8-methyl-2-[2-(4-hydroxyphenyl)ethenyl]-4H-1-benzopyran-4-one (Kobochromone A, KC-A), an ingredient in the flowers of Carex kobomugi, is a novel potent DHRS11 inhibitor (IC50 = 0.35 µM). Additionally, KC-A itself decreased the AR expression in PC cells. Therefore, KC-A suppresses the androgen signaling in PC cells through both DHRS11 inhibition and AR downregulation. Furthermore, KC-A enhanced the anticancer activity of abiraterone, a CRPC drug, suggesting that it may be a potential candidate for the development of drugs for the prevention and treatment of CRPC.

Photosynthetic parameters of a sedge-grass marsh as a big-leaf: effect of plant species composition.

The study estimates the parameters of the photosynthesis-irradiance relationship (PN/I) of a sedge-grass marsh (Czech Republic, Europe), represented as an active "green" surface-a hypothetical "big-leaf". Photosynthetic parameters of the "big-leaf" are based on in situ measurements of the leaf PN/I curves of the dominant plant species. The non-rectangular hyperbola was selected as the best model for fitting the PN/I relationships. The plant species had different parameters of this relationship. The highest light-saturated rate of photosynthesis (Asat) was recorded for Glyceria maxima and Acorus calamus followed by Carex acuta and Phalaris arundinacea. The lowest Asat was recorded for Calamagrostis canescens. The parameters of the PN/I relationship were calculated also for different growth periods. The highest Asat was calculated for the spring period followed by the summer and autumn periods. The effect of the species composition of the local plant community on the photosynthetic parameters of the "big-leaf" was addressed by introducing both real (recorded) and hypothetical species compositions corresponding to "wet" and "dry" hydrological conditions. We can conclude that the species composition (or diversity) is essential for reaching a high Asat of the "big-leaf "representing the sedge-grass marsh in different growth periods.

CrUGT87A1, a UDP-sugar glycosyltransferases (UGTs) gene from Carex rigescens, increases salt tolerance by accumulating flavonoids for antioxidation in Arabidopsis thaliana.

Salt stress is a serious abiotic stressor impeding plant growth and crop production around the world. Plant glycosyltransferases are thought to serve important roles in dealing with stress conditions, however, the functional role of how UGTs cope with salt stress is not well understood. Carex rigescens (Franch.) V. Krecz, is a widely distributed species of turfgrass with strong salinity tolerance found in northern China. To investigate how the glycosyltransferase gene, CrUGT87A1, functions in C. rigescens, we performed analyses of cloning, transcriptional expression, subcellular localization, and overexpression. The full-length sequence of CrUGT87A1 is 1455 bp with a 1338 bp length ORF, which encodes 445 amino acids, while CrUGT87A1 was found to be a nuclear and plasmalemma-localized protein. We found that the transcriptional expression of CrUGT87A1 was up-regulated under ABA, heat, salt, and drought treatments in leaf tissues. CrUGT87A1 overexpression in Arabidopsis plants had a significantly higher germination rate, better growth and physiology, and a higher expression levels of transcripts related to salt stress-related genes under high-salinity conditions, suggesting that CrUGT87A1 is involved in salt tolerance. The transcriptional expression of genes related to flavonoid-synthesis related and the flavonoid content reflected higher accumulations of flavonoids in transgenic plants. Our study demonstrated that CrUGT87A1 could play an important role in resisting salt stress due to increased flavonoid accumulation, which can promote antioxidation when dealing with high-salinity conditions. This study advances our collective understanding of the functional role of UGTs and can be used to improve the salt tolerance and breeding of crops and plants.

PacBio single-molecule long-read sequencing shed new light on the complexity of the Carex breviculmis transcriptome.

BACKGROUND: Carex L., a grass genus commonly known as sedges, is distributed worldwide and contributes constructively to turf management, forage production, and ecological conservation. The development of next-generation sequencing (NGS) technologies has considerably improved our understanding of transcriptome complexity of Carex L. and provided a valuable genetic reference. However, the current transcriptome is not satisfactory mainly because of the enormous difficulty in obtaining full-length transcripts. RESULTS: In this study, we employed PacBio single-molecule long-read sequencing (SMRT) technology for whole-transcriptome profiling in Carex breviculmis. We generated 60,353 high-confidence non-redundant transcripts with an average length of 2302-bp. A total of 3588 alternative splicing events, and 1273 long non-coding RNAs were identified. Furthermore, 40,347 complete coding sequences were predicted, providing an informative reference transcriptome. In addition, the transcriptional regulation mechanism of C. breviculmis in response to shade stress was further explored by mapping the NGS data to the reference transcriptome constructed by SMRT sequencing. CONCLUSIONS: This study provided a full-length reference transcriptome of C. breviculmis using the SMRT sequencing method for the first time. The transcriptome atlas obtained will not only facilitate future functional genomics studies but also pave the way for further selective and genic engineering breeding projects for C. breviculmis.

Overexpression of CrCOMT from Carex rigescens increases salt stress and modulates melatonin synthesis in Arabidopsis thaliana.

KEY MESSAGE: CrCOMT, a COMT gene in Carex rigescens, was verified to enhance salt stress tolerance in transgenic Arabidopsis. High salinity severely restricts plant growth and development while melatonin can alleviate salt damage. Caffeic acid O-methyltransferase (COMT) plays an important role in regulating plant growth, development, and stress responses. COMT could also participate in melatonin biosynthesis. The objective of this study was to identify CrCOMT from Carex rigescens (Franch.) V. Krecz, a stress-tolerant grass species with a widespread distribution in north China, and to determine its physiological functions and regulatory mechanisms that impart tolerance to salt stress. The results showed that the transcription of CrCOMT exhibited different expression patterns under salt, drought, and ABA treatments. Transgenic Arabidopsis with the overexpression of CrCOMT exhibited improved growth and physiological performance under salt stress, such as higher lateral root numbers, proline level, and chlorophyll content, than in the wild type (WT). Overexpression of CrCOMT also increased dehydration tolerance in Arabidopsis. The transcription of salt response genes was more highly activated in transgenic plants than in the WT under salt stress conditions. In addition, the melatonin content in transgenic plants was higher than that in the WT after stress treatment. Taken together, our results indicated that CrCOMT may positively regulate stress responses and melatonin synthesis under salt stress.

Growth, physiology, and transcriptional analysis of Two contrasting Carex rigescens genotypes under Salt stress reveals salt-tolerance mechanisms.

Salt stress is a major abiotic stress threatening plant growth and development throughout the world. In this study, we investigated the salt stress adaptation mechanism of Carex rigescens (Franch.) V. Krecz, a stress-tolerant turfgrass species with a wide distribution in northern China. Specifically, we analyzed the growth, physiology, and transcript expression patterns of two C. rigescens genotypes (Huanghua and Lvping No.1) exposed to salt stress. Results show that Huanghua demonstrated better growth performance, and higher turf quality (TQ), photochemical efficiency (Fv/Fm), relative water content (RWC), proline content, and lower relative electrolyte leakage (REL) during seven days of salt treatment compared to Lvping No.1, suggesting that Huanghua is more salt tolerant. Significant differences in reactive oxygen species (ROS), Malondialdehyde (MDA), melatonin, non-enzymatic antioxidants, lignin, and flavonoid content, as well as in antioxidant activity between Huanghua and Lvping No.1 after salt stress indicate the diverse regulation involved in salt stress adaptation in C. rigescens. These results, combined with those of the transcript expression pattern of involved genes, suggest that Huanghua is more active and efficient in ROS scavenging, Ca2+ binding, and its phytohormone response than Lvping No.1. Meanwhile, Lvping No.1 showed relatively higher phenylpropanoid synthesis, using flavonoid and lignin as supplements for the inadequate ROS-scavenging capacity and the development of vascular tissues, respectively. These performances illustrate the differences between the two genotypes in multifaceted and sophisticated actions contributing to the tolerance mechanism of salt stress in C. rigescens. In addition, the significantly higher content of melatonin and the rapid induction of Caffeic acid O-methyltransferase (COMT) highlight the role of melatonin in the salt stress response in Huanghua. The results of our study expand existing knowledge of the complexity of the salt stress response involving the antioxidant system, Ca2+ signaling, phytohormone response signaling, and phenylpropanoid pathways. It also provides a basis for further study of the underlying mechanism of salt tolerance in C. rigescens and other plant species.

Calling from distance: attraction of soil bacteria by plant root volatiles.

Plants release a wide set of secondary metabolites including volatile organic compounds (VOCs). Many of those compounds are considered to function as defense against herbivory, pests, and pathogens. However, little knowledge exists about the role of belowground plant VOCs for attracting beneficial soil microorganisms. We developed an olfactometer system to test the attraction of soil bacteria by VOCs emitted by Carex arenaria roots. Moreover, we tested whether infection of C. arenaria with the fungal pathogen Fusarium culmorum modifies the VOCs profile and bacterial attraction. The results revealed that migration of distant bacteria in soil towards roots can be stimulated by plant VOCs. Upon fungal infection, the blend of root VOCs changed and specific bacteria with antifungal properties were attracted. Tests with various pure VOCs indicated that those compounds can diffuse over long distance but with different diffusion abilities. Overall, this work highlights the importance of plant VOCs in belowground long-distance plant-microbe interactions.

How functional is a trait? Phosphorus mobilization through root exudates differs little between Carex species with and without specialized dauciform roots.

Root structures secreting carboxylates and phosphatases are thought to enhance a plant's phosphorus (P) acquisition. But do closely related species with and without such structures really differ in root exudation, P mobilization, or ecological niche? We investigated this by comparing 23 European Carex species with and without 'dauciform roots' (DRs). Plants grown in pots with sand were screened for DR formation, phosphatase activities, carboxylate exudation, and utilization of various organic and inorganic P compounds. Ecological niches were compared using ecological indicator values and nutrient concentrations of plant shoots in natural habitats. Species of subgenus Carex formed DRs, while species of subgenus Vignea did not. Species with DRs had higher root diesterase activity than species without DRs, exuded more citrate but less oxalate and less total carboxylates, and allocated less biomass to roots. Species with and without DRs showed similar growth responses to different forms of P and different amounts of P supplied; their natural habitats do not differ in soil fertility or degree of P limitation. Despite some differences in physiological function, DRs did not influence the P acquisition and nutritional niche of European Carex species, suggesting that species with and without DRs do not exhibit distinct P-acquisition strategies.

Research on Root Responses to Pb and Zn Combined Stress of Carex putuoshan.

Pb hyper-accumulated Carex putuoshan was taken as experimental material and subjected to combined stress of Pb and Zn. The differential expression of proteins in their roots were analyzed by Proteomic Approach. The protein that was directly involved in the cellular defense under the Pb and Zn combined stress was separated, and expression of those genes was analyzed with Carex Evergold as control. The results were obtained by MALDI-TOF/MS analysis. After applying Pb and Zn combined stress, the expression of 9 protein spots (including 7 different proteins, 2 identical proteins, 1 unknown protein) in Carex putuoshan root was found to be significantly up-regulated. Five proteins were obtained from the 9 proteins related to carbohydrate metabolism, including malate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, frutose-1,6-bisphosphate aldolase, enolase, and 6- phosphogluconate dehydrogenase. Two proteins were related to protein biosynthesis, including isoflavone reductase and phytochelatin synthase (PCS). From these proteins, the most important protein is PCS, which is a key enzyme in the synthesis of phytochelatins (PCs) and plays an important role in chelation. It is directly involved in cellular defense under Pb and Zn stress. After Pb and Zn combined stress, the CpPCS in Carex putuoshan was cloned. The full length of cDNA is 1461 bps, and it encodes 486 amino acids with molecular weight of 53.86 kD and pI value of 6.12. Two typical phytochelatin synthase subfamily domains constitute CpPCS protein, which includes three adjacent Cys-Cys elements in the C-terminal region. Phylogenetic analysis of PCS proteins from different species showed that it had the closest relationship with the Oryza sativa and Triticum aestivum. Real-time quantitative PCR analysis indicated that CpPCS and CePCS (Carex Evergold) genes were expressed in the root. The CpPCS and CePCS genes were up-regulated by Pb and Zn treatments. The expression of CpPCS was higher than that of CePCS under the same condition. The study found that CpPCS expression was increased by Pb and Zn stress in the Carex putuoshan enrichment process of Pb, which lead to high expression of PCS protein. CpPCS improved the accumulation ability and resistance of Carex putuoshan to heavy metals with the expression level of glucose metabolism related proteins increasing after Pb and Zn stress.

The effect of iron plaque on lead translocation in soil-Carex cinerascens kukenth. system.

A pot experiment was conducted to investigate the effect of iron plaque on Pb uptake by and translocation in Carex cinerascens Kukenth. grown under open-air conditions. Using Scanning Electron Microscopy and Energy Dispersive X-Ray Spectrometry, iron plaque was present as an amorphous coating on root surfaces with uneven distribution. The amount of iron plaque increased significantly with increasing Fe additions regardless of Pb additions. The presence of iron plaque on the root surface of Carex cinerascens Kukenth. increased the concentrations of Pb adsorbed by iron plaque. The Pb percentage in whole roots increased by 14.52% at 500 mg kg(-1) Fe treatment than at 0 mg kg(-1) Fe, and the distribution coefficient (DC) of Pb and translocation factor (TF) root increased with Fe additions, but translocation factor (TF) shoot decreased with Fe additions. The results suggested that iron plaque could promote the translocation of Pb from soil to roots to some extent, and it played a role to reduce heavy metals pollution of Poyang Lake wetland.

Plasticity of nitrogen allocation in the leaves of the invasive wetland grass, Phalaris arundinacea and co-occurring Carex species determines the photosynthetic sensitivity to nitrogen availability.

Phalaris arundinacea displaces the slower-growing, native sedge, Carex stricta, where nitrogen availability is high. Our aim was to address whether morphological and physiological traits associated with carbon gain for P. arundinacea and C. stricta responded to nitrogen supply differently and if the species exhibited different degrees of plasticity in these traits. The plants were grown in gravel and provided modified Hoagland's solution containing four nitrogen concentrations from 0.15 to 15 mM for 6 to 7 weeks. Supplied nitrogen affected the leaf nitrogen content to the same degree for both species. Increasing supplied nitrogen strongly increased CO2 assimilation (A), photosynthetic nitrogen use efficiency (PNUE), and respiration for P. arundinacea but had only a small effect on these parameters for C. stricta. Relative to growth at 15 mM nitrogen, growth at 0.15 mM for young leaves decreased carboxylation capacity and efficiency and the capacity for electron transport for P. arundinacea and a larger, stouter Carex species, Carex lacustris, by 53 to 70% but only 20 to 24% for C. stricta. Leaf nitrogen decreased approximately 50% for all species, but vacuolar nitrate did not decrease for P. arundinacea and C. stricta, suggesting that it does not serve as a nitrogen reserve for use during nitrogen deprivation in these species. After 4 months of nitrogen deprivation, P. arundinacea doubled A in 12 days after being supplied 15 mM nitrogen, whereas A for C. stricta increased only 22%. We propose that one factor linking P. arundinacea abundance to nitrogen availability involves this species' plastic response of carbon gain to nitrogen supply. C. stricta appears to be adapted to tolerate low nitrogen availability but cannot respond as rapidly and extensively as P. arundinacea when nitrogen supply is high.

Natural attenuation potential of tricholoroethene in wetland plant roots: role of native ammonium-oxidizing microorganisms.

Bench-scale microcosms with wetland plant roots were investigated to characterize the microbial contributions to contaminant degradation of trichloroethene (TCE) with ammonium. The batch system microcosms consisted of a known mass of wetland plant roots in aerobic growth media where the roots provided both an inoculum of root-associated ammonium-oxidizing microorganisms and a microbial habitat. Aqueous growth media, ammonium, and TCE were replaced weekly in batch microcosms while retaining roots and root-associated biomass. Molecular biology results indicated that ammonium-oxidizing bacteria (AOB) were enriched from wetland plant roots while analysis of contaminant and oxygen concentrations showed that those microorganisms can degrade TCE by aerobic cometabolism. Cometabolism of TCE, at 29 and 46 µg L(-1), was sustainable over the course of 9 weeks, with 20-30 mg L(-1) ammonium-N. However, at 69 µg L(-1) of TCE, ammonium oxidation and TCE cometabolism were completely deactivated in two weeks. This indicated that between 46 and 69 µg L(-1) TCE with 30 mg L(-1) ammonium-N there is a threshold [TCE] below which sustainable cometabolism can be maintained with ammonium as the primary substrate. However, cometabolism-induced microbial deactivation of ammonium oxidation and TCE degradation at 69 µg L(-1) TCE did not result in a lower abundance of the amoA gene in the microcosms, suggesting that the capacity to recover from TCE inhibition was still intact, given time and removal of stress. Our study indicates that microorganisms associated with wetland plant roots can assist in the natural attenuation of TCE in contaminated aquatic environments, such as urban or treatment wetlands, and wetlands impacted by industrial solvents.

Do peat amendments to oil sands wet sediments affect Carex aquatilis biomass for reclamation success?

The oil sands industries of Alberta (Canada) have reclamation objectives to return the mined landscape to equivalent pre-disturbance land capability. Industrial operators are charged with reclaiming a vast landscape of newly exposed sediments on saline-sodic marine-shales sediments. Incorporated in these sediments are by-products resulting from bitumen extraction (consolidated tailings (CT), tailings-sand (TS), and oil sands processed water (OSPW)). A sedge community dominated by Carex aquatilis was identified as a desirable and representative late-succession community for wet-meadow zones of oil sands-created marshes. However, the physical and chemical conditions, including high salinity and low nutrient content of CT and TS sediments suppress plant growth and performance. We experimentally tested the response of C. aquatilis to amendments with peat-mineral-mix (PM) on oil sand sediments (CT and TS). In a two factorial design experiment, we also tested the effects of OSPW on C. aquatilis. We assessed survival, below- and aboveground biomass, and physiology (chlorophyll a fluorescence). We demonstrated that PM amendments to oil sands sediments significantly increased C. aquatilis survival as well as below and aboveground biomass. The use of OSPW significantly reduced C. aquatilis belowground biomass and affected its physiological performance. Due to its tolerance and performance, we verified that C. aquatilis was a good candidate for use in reclaiming the wet-meadow zones of oil sands-created marshes. Ultimately, amending CT and TS with PM expedited the reclamation of the wetland to a C. aquatilis-community which was similar in gross structure to undisturbed wetlands of the region.

Temporary storage or permanent removal? The division of nitrogen between biotic assimilation and denitrification in stormwater biofiltration systems.

The long-term efficacy of stormwater treatment systems requires continuous pollutant removal without substantial re-release. Hence, the division of incoming pollutants between temporary and permanent removal pathways is fundamental. This is pertinent to nitrogen, a critical water body pollutant, which on a broad level may be assimilated by plants or microbes and temporarily stored, or transformed by bacteria to gaseous forms and permanently lost via denitrification. Biofiltration systems have demonstrated effective removal of nitrogen from urban stormwater runoff, but to date studies have been limited to a 'black-box' approach. The lack of understanding on internal nitrogen processes constrains future design and threatens the reliability of long-term system performance. While nitrogen processes have been thoroughly studied in other environments, including wastewater treatment wetlands, biofiltration systems differ fundamentally in design and the composition and hydrology of stormwater inflows, with intermittent inundation and prolonged dry periods. Two mesocosm experiments were conducted to investigate biofilter nitrogen processes using the stable isotope tracer 15NO3(-) (nitrate) over the course of one inflow event. The immediate partitioning of 15NO3(-) between biotic assimilation and denitrification were investigated for a range of different inflow concentrations and plant species. Assimilation was the primary fate for NO3(-) under typical stormwater concentrations (∼1-2 mg N/L), contributing an average 89-99% of 15NO3(-) processing in biofilter columns containing the most effective plant species, while only 0-3% was denitrified and 0-8% remained in the pore water. Denitrification played a greater role for columns containing less effective species, processing up to 8% of 15NO3(-), and increased further with nitrate loading. This study uniquely applied isotope tracing to biofiltration systems and revealed the dominance of assimilation in stormwater biofilters. The findings raise important questions about nitrogen release upon plant senescence, seasonally and in the long term, which have implications on the management and design of biofiltration systems.

Temperature, plant species and residence time effects on nitrogen removal in model treatment wetlands.

Total nitrogen (TN) removal in treatment wetlands (TWs) is challenging due to nitrogen cycle complexity and the variation of influent nitrogen species. Plant species, season, temperature and hydraulic loading most likely influence root zone oxygenation and appurtenant nitrogen removal, especially for ammonium-rich wastewater. Nitrogen data were collected from two experiments utilizing batch-loaded (3-, 6-, 9- and 20-day residence times), sub-surface TWs monitored for at least one year during which temperature was varied between 4 and 24 °C. Synthetic wastewater containing 17 mg/l N as NH4 and 27 mg/l amino-N, 450 mg/l chemical oxygen demand (COD), and 13 mg/l SO4-S was applied to four replicates of Carex utriculata, Schoenoplectus acutus and Typha latifolia and unplanted controls. Plant presence and species had a greater effect on TN removal than temperature or residence time. Planted columns achieved approximately twice the nitrogen removal of unplanted controls (40-95% versus 20-50% removal) regardless of season and temperature. TWs planted with Carex outperformed both Typha and Schoenoplectus and demonstrated less temperature dependency. TN removal with Carex was excellent at all temperatures and residence times; Schoenoplectus and Typha TN removal improved at longer residence times. Reductions in TN were not accompanied by increases in NO3, which was consistently below 1 mg/l N.

Stormwater nitrogen removal performance of a floating treatment wetland.

The nitrogen (N) removal efficiency and effluent quality of two parallel stormwater retention ponds, one retrofitted with a floating treatment wetland (FTW) and one without any vegetation, was compared in a field trial. This study shows that inclusion of FTWs in stormwater retention ponds has potential to moderately improve N removal. Median FTW outlet event mean concentrations (EMCs) were lower than median inlet and control pond outlet EMCs for all species of N, except for NH(4)-N. Performance was statistically better from late spring to end autumn due to higher organic nitrogen (ON) removal and denitrification in presence of the FTW. Low dissolved oxygen (DO), higher temperature and increased organic matter (OM) and microbial activity below the FTW, likely facilitated the higher denitrification rates observed over this period. Greater sediment N accumulation in the FTW pond also contributed to its higher overall N removal. Higher OM availability in the FTW pond due to release of root exudates and supply of detritus from plant die-back may have contributed to floc formation in the water column, increasing particulate ON settlement. Enhanced ON mineralisation may also be responsible but was probably limited in summer due to the low DO induced by the FTW. Direct uptake by the plants appears to be of less importance.

The ecological response of Carex lasiocarpa community in the Riparian Wetlands to the environmental gradient of water depth in Sanjiang Plain, Northeast China.

The response of Carex lasiocarpa in riparian wetlands in Sanjiang Plain to the environmental gradient of water depth was analyzed by using the Gaussian Model based on the biomass and average height data, and the ecological water-depth amplitude of Carex lasiocarpa was derived. The results indicated that the optimum ecological water-depth amplitude of Carex lasiocarpa based on biomass was [13.45 cm, 29.78 cm], while the optimum ecological water-depth amplitude of Carex lasiocarpa based on average height was [2.31 cm, 40.11 cm]. The intersection of the ecological water-depth amplitudes based on biomass and height confirmed that the optimum ecological water-depth amplitude of Carex lasiocarpa was [13.45 cm, 29.78 cm] and the optimist growing water-depth of Carex lasiocarpa was 21.4 cm. The TWINSPAN, a polythetic and divisive classification tool, was used to classify the wetland ecological series into 6 associations. Result of TWINSPAN matrix classification reflected an obvious environmental gradient in these associations: water-depth gradient. The relation of biodiversity of Carex lasiocarpa community and water depth was determined by calculating the diversity index of each association.

Irrigation of three wetland species and a hyperaccumlating fern with arsenic-laden solutions: observations of growth, arsenic uptake, nutrient status, and chlorophyll content.

Engineered wetlands can be an integral part of a treatment strategy for remediating arsenic-contaminated wastewater, wherein, As is removed by adsorption to soil particles, chemical transformation, precipitation, or accumulation by plants. The remediation process could be optimized by choosing plant species that take up As throughout the seasonal growing period. This report details experiments that utilize wetland plant species native to Ohio (Carex stricta, Pycnanthemum virginianum, and Spartina pectinata) that exhibit seasonally related maximal growth rates, plus one hyperaccumulating fern (Pteris vittata) that was used to compare arsenic tolerance. All plants were irrigated with control or As-laden nutrient solutions (either 0, 1.5, or 25 mg As L(-1)) for 52 d. Biomass, nutrient content, and chlorophyll content were compared between plants treated and control plants (n = 5). At the higher concentration of arsenic (25 mg L(-1)), plant biomass, leaf area, and total chlorophyll were all lower than values in control plants. A tolerance index, based on total plant biomass at the end of the experiment, indicated C. stricta (0.99) and S. pectinata (0.84) were more tolerant than the other plant species when irrigated with 1.5 mg As L(-1). These plant species can be considered as candidates for engineered wetlands.

Evaluating Escherichia coli removal performance in stormwater biofilters: a laboratory-scale study.

Biofilters are common, low energy technologies used for the treatment of urban stormwater. While they have shown promising results for the removal of stormwater microorganisms, certain factors affect their performance. Hence, this study investigated the effects of particle-microbial interaction, inflow concentration, antecedent microbial levels and plant species on microbial removal capacity. A biofilter column study was set up to evaluate removal performance and a sequential filtration procedure was used to estimate microbial partitioning. The columns were dosed with different concentrations of free phase Escherichia coli only and E. coli mixed with stormwater sediment. Results indicate that the microbial removal is significantly affected by inflow concentration and antecedent microbial levels. Leaching was only observed when a relatively low inflow concentration event occurred within a short period after a very high inflow concentration event. Finally, Lomandra longifolia showed better removal compared with Carex appressa.