Photosynthetic response, antioxidase activity, and cadmium uptake and translocation in Monochoria korsakowii with cadmium exposure.

To identify the tolerance mechanisms of wetland plants exposed to heavy metal, a hydroponic experiment was used to investigate variations in photosynthetically physiological parameters and antioxidant enzyme activities in leaves of Monochoria korsakowii exposed to 0.05, 0.15, 0.30, and 0.45 mM Cd2+ for 7 d. The Cd2+ concentrations in the plant roots, stems, and leaves were also investigated. Cd2+ exposure significantly decreased the total chlorophyll content, net photosynthetic rate, intercellular carbon dioxide concentration, and stomatal conductance, while stomatal limitation value had the opposite trend (P < 0.05). During Cd2+ stress, ascorbate peroxidase activity significantly increased (P < 0.05). The translocation factor for Cd2+ was significantly lower than that of the control, and both were less than 1 (P < 0.05). Cd2+ stress damaged the photosynthetic apparatus in the leaves. During Cd2+ stress, M. korsakowii alleviated oxidative stress by increasing the activities of antioxidant enzymes, such as APX. Under 0.45 mM Cd2+ stress, increased heat dissipation was responsible for alleviating the photooxidative damage to photosynthetic organs in the leaves. Meanwhile, the majority of Cd2+ was immobilized in the roots, thus alleviating excessive Cd2+ phytotoxicity in the aboveground parts. Generally, M. korsakowii has potential application in the phytoremediation of low-cadmium-polluted water.

Pontederia sagittata and Cyperus papyrus contribution to carbon storage in floating treatment wetlands established in subtropical urban ponds.

Carbon sequestration is considered an ecosystem service of regulation provided by diverse ecosystems, including wetlands. It has been widely evaluated in the soil of natural wetlands while in constructed wetlands, there is scanty information. In Floating Treatment Wetlands (FTW) there is none. Previously, our research group reported the efficient performance of FTW in an urban polluted pond for two years. As a follow up, the aim of this work was to investigate the contribution of Cyperus papyrus and Pontederia sagittata to carbon storage (CS) in four FTW established in eutrophic urban ponds in a subtropical region. Plant growth, productivity, and CS were assessed in the aboveground biomass of C. papyrus and P. sagittata and the belowground biomass (root mix from C. papyrus and P. sagittata), throughout 26 months in 2 FTW with an area of 17.5 m2 (FTW1) and 33 m2 (FTW2) and throughout 19 months in 2 FTW with an area of 25 m2 (FTW3) and 33 m2 (FTW4), respectively. The macrophyte growth depended on various factors, such as the season, the plant species, and the location of the FTW. High relative growth rate values were found for both species (0.125 and 0.142 d-1 for P. sagittata and C. papyrus, respectively), especially during summer and early autumn. The highest values of productivity were 337 ± 125 gdw m-2d-1 for the aboveground biomass of C. papyrus in FTW2, 311 ± 96.90 gdwm-2d-1 for the aboveground of P. sagittata in FTW1, and 270 ± 107 gdw m-2d-1 for the belowground biomass in FTW2. The mean values of CS for P. sagittata found in FTW1 were 1.90 ± 0.94 kg m-2, while for C. papyrus in FTW2 they were 4.09 ± 0.73 kg m-2. The contribution of the belowground biomass to CS was also significant in FTW2 (4.58 ± 0.59 kg m-2).

Anti-enteric efficacy and mode of action of tridecanoic acid methyl ester isolated from Monochoria hastata (L.) Solms leaf.

Monochoria hastata (L.) Solms (family Pontederiaceae), an ethnomedicinal aquatic herb, is used to remedy several gastrointestinal diseases by various ethnic groups in India. The present study aimed to purify and characterize the antibacterial active ingredient against gastrointestinal (GI) diseases and its mode of action using in vitro experimental models. The active lead molecule in the ethyl acetate extract (EA-Mh) fraction has been purified and characterized through high-performance liquid chromatography (HPLC), proton nuclear magnetic resonance (1H NMR), and electrospray ionization mass spectrometry (ESI-MS) methods. The anti-enteric efficacy has been evaluated against enteropathogenic Gram-positive and Gram-negative bacteria by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), lactate dehydrogenase (LDH), and scanning electron microscopy (SEM) studies. The synergistic and antagonistic studies were done on E. coli MTCC 723 using standard antibiotics (ampicillin and kanamycin, final conc. 50 µg/ml) in a sterilized 96-well micro-plate, incubated at 37 ℃ for 24 h. The chromatographic and spectroscopic analyses revealed the presence of tridecanoic acid methyl ester (TAME) in the bioactive fraction. The compound causes significant extracellular leakage activity by disrupting cellular morphology in the Enterococcus faecalis MCC 2041 T and Salmonella enterica serovar Typhimurium MTCC 98, at a dose of 375 µg/ml and 750 µg/ml, respectively. The SEM study shows a significant rupturing of E. coli and E. faecalis cells due to TAME induced autolysis. It has synergistic activity with ampicillin. The in silico molecular docking through the AutoDock Vina 4.2 and GROMACS (ver. 5.1) Charmm27 force field results showed that the TAME had a strong binding affinity Escherichia coli DNA Gyrase B (PDB ID: 5l3j.pdb) protein and caused conformational changes. Thus, the manuscript reports the first time on the characterization of TAME from this plant with a detailed antibacterial mode of action studies.

Transcriptional, secondary metabolic, and antioxidative investigations elucidate the rapid response mechanism of Pontederia cordata to cadmium.

Pontederia cordata is previously demonstrated a cadmium (Cd) tolerant plant, and also a candidate for the phytoremediation of heavy-metal-contaminated wetlands. A hydroponic experiment was used to investigate variations in photosynthetic gas exchange parameters, antioxidative activities, chlorophyll and secondary metabolite contents, and transcriptome in leaves of the plant exposed to 0.44 mM Cd2+ for 0 h, 24 h, and 48 h. Under Cd2+ exposure for 24 h, the plant presented a favorable photosynthesis by maintaining relatively higher antioxidant activity. Cd2+ exposure for 48 h accelerated membrane peroxidation, declined photosynthetic pigment content, and increased polyphenol oxidase activity, thus interfering with photosynthesis. The phenylpropane pathway served as a chemical rather than physical defense against Cd2+ in the plant leaves. A total of 20,998, 4743, and 4413 differentially expressed genes (DEGs) were identified in the groups of 0 h vs 24 h, 0 h vs 48 h, and 24 h vs 48 h, respectively. The primary metabolic pathways of the DEGs were mainly enriched in nitrogen metabolism, starch and sucrose metabolism, fructose and mannose metabolism, as well as pentose-phosphate pathway, contributing to a stable cell structure and function. Flavonoid biosynthesis directly or indirectly played an antioxidative role against Cd2+ in the leaves. Forty-nine transcription factor (TF) families were identified, and 8 TF families were shared among the three groups. The present study provides a theoretical foundation for investigating tolerance mechanisms of wetland plants to Cd stress in terms of secondary metabolism and transcriptional regulation.

Identification and feeding characteristics of the mixotrophic flagellate Poterioochromonas malhamensis, a microalgal predator isolated from planting water of Pontederia cordata.

The microorganisms and allelochemicals in Pontederia cordata planting water may have a synergistic inhibitory effect on algae. To study this synergy, an algae-inhibiting organism was isolated and identified, and its growth and feeding characteristics were studied. The organism was identified as Poterioochromonas malhamensis yzs924 based on both its morphology and molecular barcoding employing 18S rDNA gene sequences.The growth and feeding of P. malhamensis were affected by environmental factors and the state of its prey. (1) P. malhamensis is a mixotrophic flagellate. Its heterotrophic growth was the fastest in a wheat grain medium, and its growth rate in this study reached 2.5 day-1. (2) Within a short period of time (2 days), P. malhamensis growth was slower under continuous dark conditions than under alternating light and dark conditions, but it fed on Microcystis aeruginosa more rapidly under dark conditions. (3) High pH was disadvantageous to the growth and grazing of P. malhamensis. When the pH was kept stable at 9, P. malhamensis could not grow continuously. (4) When the initial density of M. aeruginosa was 5 × 107 cells/mL or is in a period of decline, P. malhamensis could not remove all M. aeruginosa. The combined use of P. malhamensis and allelochemicals may represent a method of M. aeruginosa control, but this approach requires further research.

Phytoremediation of azoxystrobin and imidacloprid by wetland plant species Juncus effusus, Pontederia cordata and Sagittaria latifolia.

Azoxystrobin (strobilurin fungicide) and imidacloprid (neonicotinoid insecticide) have been detected in surface waters near treated agricultural, urban, and mixed landscapes. The hazards of pesticide runoff can be prevented through best management practices, including the establishment of diverse wetland plant barriers that can phytoremediate the chemicals in which they come into contact with. In this study, the wetland plant species softrush (Juncus effusus), pickerelweed (Pontederia cordata), and arrowhead (Sagittaria latifolia) were planted in sandy soil containers that were then placed in azoxystrobin or imidacloprid treated water. Every week for 2 months, water samples were collected for pesticide residue analysis using high-performance liquid chromatography (HPLC). At 14, 28, and 56 days after initiation, plants were destructively harvested and analyzed for pesticide residue in soil, above-ground vegetation, and below-ground vegetation. Results from this study report P. cordata reduced greater azoxystrobin (51.7% reduction compared to treated non-planted containers) compared to J. effusus and S. latifolia (24.9% and 28.7% reduction from non-planted containers) at 56 days. However, S. latifolia reduced greater imidacloprid (79.3% reduction compared to non-planted containers) compared to J. effusus and P. cordata (36.0% and 37.1% reduction from non-planted containers) at 56 days.Novelty statement: While research has found that wetland plants can absorb and remediate synthetic chemicals, this practice is only sustainable if used with native plants that require low maintenance and are tolerant to the applied substances. Various previous studies observe plants that are fast-growing, tolerant to environmental conditions, require low-maintenance, and are hardy. However, these plant species are not always suitable for any location and are often considered invasive and/or weed-like. The present research initiates a list of plant species which can be used within the southeastern United States and similar areas to phytoremediate commonly used pesticides azoxystrobin and imidacloprid and prevent off-target movement into sensitive water systems.

A Report on Multi-Target Anti-Inflammatory Properties of Phytoconstituents from Monochoria hastata (Family: Pontederiaceae).

This study aims to investigate the potential analgesic properties of the crude extract of Monochoria hastata (MH) leaves using in vivo experiments and in silico analysis. The extract, in a dose-dependent manner, exhibited a moderate analgesic property (~54% pain inhibition in acetic acid-induced writhing test), which is significant (** p < 0.001) as compared to the control group. The complex inflammatory mechanism involves diverse pathways and they are inter-connected. Therefore, multiple inflammatory modulator proteins were selected as the target for in silico analysis. Computational analysis suggests that all the selected targets had different degrees of interaction with the phytochemicals from the extract. Rutin (RU), protocatechuic acid (PA), vanillic acid (VA), and ferulic acid (FA) could regulate multiple targets with a robust efficiency. None of the compounds showed selectivity to Cyclooxygenase-2 (COX-2). However, regulation of COX and lipoxygenase (LOX) cascade by PA can reduce non-steroidal analgesic drugs (NSAIDs)-related side effects, including asthma. RU showed robust regulation of cytokine-mediated pathways like RAS/MAPK and PI3K/NF-kB by inhibition of EGFR and IKBα (IKK), which may prevent multi-organ failure due to cytokine storm in several microbial infections, for example, SARS-CoV-2. Further investigation, using in vivo and in vitro experiments, can be conducted to develop multi-target anti-inflammatory drugs using the isolated compounds from the extract.

Reduced pests, improved grain quality and greater total income: benefits of intercropping rice with Pontederia cordata.

BACKGROUND: Intercropping, which is growing two or more different crops in the same field simultaneously, is an effective traditional agricultural practice for productivity, resource utilization, and pest control. However, study on intercropping in paddy fields is limited. So in this study, field experiments of 2 years/four seasons (early and late seasons in 2016 and 2017) were conducted to examine the effects of rice-Pontederia cordata intercropping on rice plant growth, pest control, yield, income, and grain quality. RESULTS: We found rice-P. cordata intercropping significantly decreased the occurrence of rice diseases and pests, with a 22.0-45.9% reduction in sheath blight and a 33.8-34.4% reduction in leaf folders. The mean land equivalent ratio (LER) (1.09) result indicates that intercropping rice and P. cordata generated positive yield effects. In addition, due to the economic profit from the replacement stripe of P. cordata in the rice paddy field, intercropping rice with P. cordata could greatly enhance farmer income. The average total income of rice intercropped with P. cordata was 2.5-fold higher than that of rice monoculture. Furthermore, intercropping significantly improved grain quality compared with the rice monoculture. It significantly increased the milled rice rate and whole milled rice rate by 11.2% and 12.8%, respectively, but decreased the chalky rice rate by 30.9-39.8% and chalkiness degree by 32.2%. CONCLUSIONS: We suggest that rice-P. cordata intercropping provides an environmentally effective way to control rice diseases and pests, results in higher overall productivity and total income, and improves grain quality. © 2021 Society of Chemical Industry.

A comparison of the mechanisms and performances of Acorus calamus, Pontederia cordata and Alisma plantagoaquatica in removing nitrogen from farmland wastewater.

This study examined the performances of Acorus calamus, Pontederia cordata, and Alisma plantagoaquatica in removing nitrogen (N) from farmland wastewater. P. cordata showed the fastest rate of N removal, followed by A. plantagoaquatica, whereas that of A. calamus was slowest. P. cordata and A. plantagoaquatica achieving a greater rate of TN reduction in soil than that by A. calamus. A. plantagoaquatica demonstrated the highest N adsorption capacity, 32.6% and 392.1% higher than that of P. cordata and A. calamus, respectively. The higher potential nitrification and denitrification rate, and abundance of functional genes in the P. cordata microcosm resulted in a stronger process of nitrification-denitrification, which accounted for 65.99% of TN loss. Plant uptake and nitrification-denitrification were responsible for 50.06% and 49.94% of TN removed within the A. plantagoaquatica. Nitrification-denitrification accounted for 86.35% of TN loss in A. calamus. These findings helped to insight into N removal mechanisms in different plants.

Pontederia cordata, an ornamental aquatic macrophyte with great potential in phytoremediation of heavy-metal-contaminated wetlands.

Pontederia cordata can tolerate heavy metal toxicity and possesses great potential for phytoremediation of heavy-metal-contaminated wetlands, yet how it copes with heavy metal stress has still not been determined. Hydroponic experiments were used to assess the effects of various levels of Cd2+ on the photosynthesis and activity of redox-regulatory systems in the plant leaves, and we also sought to elucidate the tolerance mechanism of the plant to Cd2+ by investigating Cd2+ enrichment characteristics and chemical forms. The plant can manage a low cadmium concentration (≤0.04 mM) with relatively stable biomass and photosynthetic performance. Cd2+ at the highest concentration (0.44 mM) decreased superoxide dismutase and peroxidase activities by 37.17% and 93.29%, respectively. Similar trends were demonstrated in the contents of ascorbic acid, carotenoids, lutein, glutathione, and non-protein thiol, as well as phytochelation in the leaves, exacerbating membrane peroxidation despite the significantly increased catalase activity observed. Moreover, the highest Cd2+ concentration disturbed the biosynthesis of chlorophyll precursors in the leaves, reduced chlorophyll a and b, as well as total chlorophyll contents by 60.47%, 67.47%, and 68.12%, respectively, which inhibited photosynthesis, leading to a decline in biomass. Compared with maximum quantum efficiency (Fv/Fm) and the potential activity (Fv/Fo) of photosystem II, the performance index for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors (PIabs), and of PSI end acceptors (PItotal), can indicate Cd2+ toxicity to the photosynthetic apparatus in the leaves. 49.95%-76.90% of the Cd2+ was sequestered in the plant roots, restraining translocation from roots to shoots, which is considered a tolerance mechanism, probably resulting from disturbed transpiration in leaves and increased Cd2+ content with low activity. Pontederia cordata is a candidate plant for phytoremediation of heavy-metal -contaminated wetlands.

Cadmium phytotoxicity, related physiological changes in Pontederia cordata: antioxidative, osmoregulatory substances, phytochelatins, photosynthesis, and chlorophyll fluorescence.

Pontederia cordata is a heavy metal accumulator, while the heavy metal tolerance mechanisms of this plant are not well understood. Hydroponic experiments were used to assess the effects of Cd2+ on antioxidative activities, osmoregulatory substances and photosynthesis in leaves. Exposure of 5 mg L-1 Cd2+ for 7 days, the photosynthetic apparatus functioned normally and sustained a relatively high photosynthetic rate, and good growth was observed. Under 50 and 75 mg L-1 Cd2+, accelerated lipid peroxidation and increased peroxidase activity (POD; E.C.1.11.1.7) were detected, while no significant differences were observed in superoxide dismutase (SOD; E.C.1.15.1.1) and catalase (CAT; E.C.1.11.1.6) activities, as well as in lutein, ascorbic acid, and glutathione contains of leaves. Proline content increased, while soluble sugar and soluble protein contents decreased under 75 mg L-1 Cd2+. Cd2+ at different concentrations induced a reduction in carotenoid, total carotenoid, and ascorbic acid-dehydroascorbate contents. A significant increase in phytochelatin content was induced by 75 mg L-1. Chlorophyll content decreased under Cd stress and disturbed photosynthesis, causing dramatic reductions in photosynthetic parameters. Stomatal closure was responsible for a reduced photosynthetic rate under Cd2+ exposure. Cd2+ concentrations of no less than 25 mg L-1 disorganized the photosynthetic apparatus, induced the partial closure, and decreased activity of the photosystem II (PS II) reaction center, thus disturbing light conversion and utilization, thereby decreasing the photosynthetic efficiency in PS II.

Architectural constraints, male fertility variation and biased floral morph ratios in tristylous populations.

Tristyly is a genetic polymorphism in which populations are comprised of three floral morphs (mating types) differing reciprocally in sex-organ height. Intermorph (disassortative) mating governed by a trimorphic incompatibility system should result in 1:1:1 morph ratios at equilibrium, but both deterministic and stochastic processes can cause skewed morph ratios in tristylous populations. Here, we investigate mechanisms causing morph-ratio bias in Pontederia parviflora, an emergent aquatic native to tropical America. We compared reproductive traits among morphs and surveyed 71 populations to determine patterns of morph-ratio bias. We then used simulation models of morph-frequency dynamics to test the hypothesis that morph-specific differences in pollen production and their influence on male fertility can explain patterns of morph-ratio bias. Ninety-seven percent of populations that we sampled were tristylous, but with a significant excess of the short-styled morph and a deficiency of the long-styled morph. Atypically for a tristylous species, mid-level anthers of the short-styled morph produced over twice as much pollen compared with the corresponding anthers of the long-styled morph. Our computer models incorporating this difference in male fertility resulted in morph ratios not significantly different from the average frequencies from our survey suggesting that the short-styled morph is more successful than the long-styled morph in siring ovules of the mid-styled morph. We propose that the difference in male fertility between morphs may be a non-adaptive consequence of a developmental constraint caused by the architecture of tristyly in Pontederiaceae.

Effects of aqueous extracts from the rhizome of Pontederia cordata on the growth and interspecific competition of two algal species.

Single and co-culture systems of Microcystis aeruginosa and Scenedesmus obliquus were prepared with different initial algal densities and treated with different concentrations of aqueous extracts from the rhizome of Pontederia cordata to study its inhibitory effect on algal growth and the competitive relationship between these two algal species. The results showed that aqueous extracts could inhibit the growth of M. aeruginosa and S. obliquus, and the inhibition rate of aqueous extracts on the growth of M. aeruginosa was always higher than that of S. obliquus. A Lotka-Volterra competition model revealed that these two algal species can co-exist without the addition of aqueous extracts, and S. obliquus exhibited a stronger ability to compete than that of M. aeruginosa. Meanwhile, the dominant algal species changed with the addition of aqueous extracts regardless of the initial ratios of the two algae. The species ratio of mixed cultures had a strong effect on the interspecific interaction between the two algae. The higher proportion of S. obliquus in the initial proportion of two algae, the stronger competitive ability of S. obliquus when compared with that of M. aeruginosa.

Impact of Three Species of Aquatic Plants on Anopheles quadrimaculatus and its Effect on the Efficacy of Boric Acid Sugar Baits.

The purpose of this study was to investigate the sugar-feeding behavior of Anopheles quadrimaculatus by measuring the impact of different aquatic plants on its survival. At the same time, the potential use of boric acid in toxic sugar bait (TSB) applications to the leaves of these plants was also evaluated. Mean survival rates of mosquitoes after 120 h feeding on 3 common aquatic plant species-Thalia geniculata, Pontederia cordata, and Limnobium spongia-were 10.55%, 1.86%, and 6.21%, respectively. No significant difference in mortality between mosquitoes feeding on separate plant species was detected (P = 0.05). The TSB efficacy was evaluated by leaf dip bioassay to compare 24-h mortality of mosquitoes feeding on leaves treated with TSB formulation (1% boric acid, 10% sucrose) and leaves dipped in 10% sucrose. Mortality was significantly higher for TSB-treated leaves for T. geniculata (t = 12.5, df = 8, P < 0.0001) and P. cordata (t = 5.42, df = 8, P = 0.0006) than for L. spongia (t = 1.4003, df = 8, P = 0.199). One-way ANOVA analysis showed no significant difference in efficacy between TSB-treated leaves of the 3 plants.

Inhibitory effects of Pontederia cordata on the growth of Microcystis aeruginosa.

This study investigated the effect of Pontederia cordata on Microcystis aeruginosa growth in three different experimental settings: (i) co-cultivation, (ii) exposure of cyanobacteria to culture water of P. cordata, and (iii) exposure of M. aeruginosa to organic extracts of P. cordata. Results showed that the growth of M. aeruginosa was significantly inhibited by co-cultivation, with the highest inhibition rate of 61.9% within 5 days. Moreover, 95% culture water with P. cordata could markedly inhibit the growth of M. aeruginosa, with inhibition rate of 98.3% on day 6, indicating that most of the algal cells died. The organic extracts of fibrous root showed stronger inhibition effect than the leaf and stalk extracts. Acetone extract of fibrous root showed the strongest inhibitory effect on M. aeruginosa. Different components of 80% acetone extracts from fibrous root exhibited varied effects on the growth of M. aeruginosa. Ethyl acetate and water components had strong inhibition effects on M. aeruginosa. By contrast, n-butyl alcohol components had weak inhibition effects, and hexane components even promoted the growth of M. aeruginosa. Allelochemicals of P. cordata were primarily released into the water through the fibrous root. Results indicated that P. cordata can be applied in environmentally friendly algal inhibition.

Phytoremedial Potential of Typha latifolia, Eichornia crassipes and Monochoria hastata found in Contaminated Water Bodies Across Ranchi City (India).

Phytoremediation is an emerging technology that uses green plants (living machines) for removal of contaminants of concern (COC). These plant species have the potential to remove the COC, thereby restoring the original condition of soil or water environment. The present study focuses on assessing the heavy metals (COC) present in the contaminated water bodies of Ranchi city, Jharkhand, India. Phytoremedial potential of three plant species: Typha latifolia, Eichornia crassipes and Monochoria hastata were assessed in the present study. Heterogenous accumulation of metals was found in the three plant species. It was observed that the ratio of heavy metal concentration was different in different parts, i.e., shoots and roots. Positive results were also obtained for translocation factor of all species with minimum of 0.10 and maximum of 1. It was found experimentally that M. hastata has the maximum BFC for root as 4.32 and shoot as 2.70 (for Manganese). For T. latifolia, BCF of maximum was observed for root (163.5) and respective shoot 86.46 (for Iron), followed by 7.3 and 5.8 for root and shoot (for Manganese) respectively. E. crassipes was found to possess a maximum BCF of 278.6 (for Manganese and 151 (for Iron) and shoot as 142 (for Manganese) and 36.13 (for Iron).

Remediation of Urban River Water by Pontederia Cordata Combined with Artificial Aeration: Organic Matter and Nutrients Removal and Root-Adhered Bacterial Communities.

Macrophyte combined with artificial aeration is a promising in situ remediation approach for urban rivers polluted with nutrients and organic matter. However, seasonal variations and aeration effects on phytoremediation performance and root-adhered microbial communities are still unclear. In this study, Pontederia cordata was used to treat polluted urban river water under various aeration intensities. Results showed that the highest removal efficiencies of chemical oxygen demand (COD(Cr)) and total nitrogen (TN) were attained under aeration of 30 L min(-1) in spring and summer and 15 L min(-1) in autumn, while total phosphorus (TP) removal reached maximum with aeration of 15 L min(-1) in all seasons. Moderate aeration was beneficial for increasing the diversity of root-adhered bacteria communities, and the shift of bacterial community structure was more pronounced in spring and autumn with varying aeration intensity. The dual effect, i.e. turbulence and dissolved oxygen (DO), of aeration on the removal of COD(Cr) and TN prevailed over the individual effect of DO, while DO was the most influential factor for TP removal and the root-adhered bacterial community diversity. P. cordata combined with 15 L min(-1) aeration was deemed to be the best condition tested in this study.

Experimental study on the survival of the water hyacinth (Eichhornia crassipes (Mart.) Solms--Pontederiaceae) under different oil doses and times of exposure.

In the last decades, petroleum activities have increased in the Brazilian Amazon where there is oil exploration on the Urucu River, a tributary of the Amazon River, about 600 km from the city of Manaus. Particularly, transportation via the Amazon River to reach the oil refinery in Manaus may compromise the integrity of the large floodplains that flank hundreds of kilometers of this major river. In the Amazon floodplains, plant growth and nutrient cycling are related to the flood pulse. When oil spills occur, floating oil on the water surface is dispersed through wind and wave action in the littoral region, thus affecting the vegetation of terrestrial and aquatic environments. If pollutants enter the system, they are absorbed by plants and distributed in the food chain via plant consumption, mortality, and decomposition. The effect of oil on the growth and survival of vegetation in these environments is virtually unknown. The water hyacinth [Eichhornia crassipes (Mart.) Solms] has a pantropical distribution but is native to the Amazon, often growing in high-density populations in the floodplains where it plays an important role as shelter and food source for aquatic and terrestrial biota. The species is well known for its high capacity to absorb and tolerate high levels of heavy metal ions. To study the survival and response of water hyacinth under six different oil doses, ranging from 0 to 150 ml l(-1), and five exposure times (1, 5, 10, 15, and 20 days), young individuals distributed in a completely randomized design experiment composed of vessels with a single individual each were followed over a 50-day period (30-day acclimatization, 20 days under oil treatments). Growth parameters, biomass, visual changes in the plants, and pH were recorded at 1, 5, 10, 15, and 20 days. Increasing the time of oil exposure caused a decrease in biomass, ratio of live/dead biomass and length of leaves, and an increase in the number of dead leaves. Dose of oil and time of exposure are the most important factors controlling the effects of petroleum hydrocarbons on E. crassipes. Although the species is able to survive exposure to a moderate dose of oil, below 75 ml l(-1) for only 5 days, severe alterations in plant growth and high mortality were observed. Therefore, we conclude that Urucu oil heavily affects E. crassipes despite its known resistance to many pollutants.

Effects of planting densities on water quality improvements and Pontederia cordata's physiology.

Various planting densities (5, 10, or 20 plants per tank) of Pontederia cordata were water-cultivated in purifying tanks to treat polluted water. Seasonal effects of the planting densities on the water quality improvement and the morphology and physiology of the plant were analyzed. Results indicated that planting densities affected the nitrogen and phosphorus removal of water, and the morphology and physiology of plants, including activity of peroxidise and catalase, content of chlorophyll and soluble protein (SP), the length of root, stem and leaf, tiller number and root density. When planting density increased from 10 to 20 plants per tank, the morphology and physiology of plants, and the nitrogen and phosphorus removal by plants improved slowly, but caused a tiller number decline in individual plants. This variation was significant in autumn, and associated with seasonal variations of plant physiology. During autumn, there were 26 tillers in each plant with 10 plants per tank, compared to 14 tillers per plant with 20 plants per tank. Increase in the nitrogen and phosphorus contents of the plants for 5-10 plants per tank was 5.41 and 0.79 g kg(-1), compared to 1.17 and 0.12 g kg(-1) for 10-20 plants per tank, respectively.

Assessment of the nutrient removal effectiveness of floating treatment wetlands applied to urban retention ponds.

The application of floating treatment wetlands (FTWs) in point and non-point source pollution control has received much attention recently. Although the potential of this emerging technology is supported by various studies, quantifying FTW performance in urban retention ponds remains elusive due to significant research gaps. Actual urban retention pond water was utilized in this mesocosm study to evaluate phosphorus and nitrogen removal efficiency of FTWs. Multiple treatments were used to investigate the contribution of each component in the FTW system with a seven-day retention time. The four treatments included a control, floating mat, pickerelweed (Pontederia cordata L.), and softstem bulrush (Schoenoplectus tabernaemontani). The water samples collected on Day 0 (initial) and 7 were analyzed for total phosphorus (TP), total particulate phosphorus, orthophosphate, total nitrogen (TN), organic nitrogen, ammonia nitrogen, nitrate-nitrite nitrogen, and chlorophyll-a. Statistical tests were used to evaluate the differences between the four treatments. The effects of temperature on TP and TN removal rates of the FTWs were described by the modified Arrhenius equation. Our results indicated that all three FTW designs, planted and unplanted floating mats, could significantly improve phosphorus and nitrogen removal efficiency (%, E-TP and E-TN) compared to the control treatment during the growing season, i.e., May through August. The E-TP and E-TN was enhanced by 8.2% and 18.2% in the FTW treatments planted with the pickerelweed and softstem bulrush, respectively. Organic matter decomposition was likely to be the primary contributor of nutrient removal by FTWs in urban retention ponds. Such a mechanism is fostered by microbes within the attached biofilms on the floating mats and plant root surfaces. Among the results of the four treatments, the FTWs planted with pickerelweed had the highest E-TP, and behaved similarly with the other two FTW treatments for nitrogen removal during the growth period. The temperature effects described by the modified Arrhenius equation revealed that pickerelweed is sensitive to temperature and provides considerable phosphorus removal when water temperature is greater than 25 °C. However, the nutrient removal effectiveness of this plant species may be negligible for water temperatures below 15 °C. The study also assessed potential effects of shading from the FTW mats on water temperature, DO, pH, and attached-to-substrate periphyton/vegetation.