Roots Of Aquatic Plants Research Articles

Structure of plant-associated microeukaryotes in roots and leaves of aquatic and terrestrial plants revealed by blocking peptide-nucleic acid (PNA) amplification.

Studies of plant-microbe interactions, including mutualistic, antagonistic, parasitic, or commensal microbes, have greatly benefited our understanding of ecosystem functioning. New molecular identification tools have increasingly revealed the association patterns between microorganisms and plants. Here, we integrated long-read PacBio single-molecule sequencing technology with a blocking protein-nucleic acid (PNA) approach to minimise plant amplicons in a survey of plant-eukaryotic microbe relationships in roots and leaves of different aquatic and terrestrial plants to determine patterns of organ, host, and habitat preferences. The PNA approach reduced the samples' relative amounts of plant reads and did not distort the fungal and other microeukaryotic composition. Our analyses revealed that the eukaryotic microbiomes associated with leaves and roots of aquatic plants exhibit a much larger proportion of non-fungal microorganisms than terrestrial plants, and leaf and root microbiomes are similar. Terrestrial plants had much stronger differentiation of leaf and root microbiomes and stronger partner specificity than aquatic plants.

COMPARISON OF PHYTOREMEDIATION AZOLLA MICROPHYLLA AND PISTIA STRATIOTES AGAINST CADMIUM (CD) ABSORPTION IN NGIPIK LAKE

Telaga Ngipik is water that is used by the community as a basic supply, and water supply to several industries. The content of heavy metal cadmium (Cd) in Ngipik lake can reduce water quality. The purpose of this study was to determine the phytoremediation ability of Azolla microphylla and Pistia stratiotes against the absorption of heavy metal Cd in Ngipik lake water samples. The method used in this study was a quasi-experimental method, with the independent variables being 5, 10, and 15 days of phytoremediation and types of aquatic plants. The research variables used were cadmium levels in the roots of aquatic plants. Sampling using random sampling. The sample used was 48 liters of Ngipik lake water for 4 replications. The results showed that Azolla microphylla was able to absorb the highest cadmium metal on day 15 with a level of 18.30 mg/kg, while Pistia stratiotes were able to absorb the highest cadmium metal on day 10 with a level of 11.28 mg/kg. Cadmium levels in water affect watercolor, water pH, and plant morphology. Following up on the findings in this study, it is suggested to use a wider variety of aquatic plants that have the potential to absorb Cd.

Rhithrops capensis gen. et sp. nov., a new aquatic dryopid beetle from the Western Cape of South Africa (Coleoptera: Dryopoidea: Dryopidae)

Rhithrops capensis gen. et sp. nov. is described from the Matjies River, in the Cedeberg range of the Western Cape Province, South Africa. The new genus is apparently related to the South African endemic genera Rapnus Grouvelle, 1899 and Strina Redtenbacher, 1867, but exhibits a number of distinct character states, including gibbosities outside the sublateral pronotal furrows and a transversely upturned labral apex, unique within the family. Rhithrops gen. nov. was collected from around the roots of aquatic plants in fast flowing deep water runs, as well as being sampled in nocturnal drift nets. The new species has relatively long legs and well-developed tarsal claws, and appears to be adapted to an entirely aquatic, benthic existence. A revised key is provided to the dryopid genera of South Africa.

L-system based dynamic root growth model formulation of aquatic plants

植物根系在地球生物圈物质循环中起到关键性作用.陆生植物中目前基于根系具有对称性和自相似性假设建立的L系统已经做了较好研究，但在水生植物中相关的研究较少，更缺乏根系动态生长模型的构建.本文拟通过发展L系统来模拟水生植物从初生结构到次生结构，从简单根系到复合根系的动态生长过程.根系动态生长模型主要包含根系伸长规则和根系分支规则，并包含由主根与侧根的夹角θ和径向角γ确定初始根系生长方向.特别地，系统建立了2种代表性水生植物——世界上入侵严重的水生植物凤眼莲（Eichhornia crassipes）和被研究较多的水生植物穗状狐尾藻（Myriophyllum spicatum）根系动态生长模型.结果表明凤眼莲成熟根系总长度可达到2042.78 m，可能有利于其占据较多的空间和资源，使得凤眼莲在与本地植物的竞争中占有优势.穗状狐尾藻的总根系长度为73.08 m，由于穗状狐尾藻表现出最为典型的叉状分支构型，表明其对沉水生长环境有较好的适应性.;Root systems play a vital role in material circulation in the biosphere. Based on the two hypotheses of symmetry and self-similarity in the root system, the L-system of terrestrial plants has been well established. However, related research in aquatic plants, particularly for the dynamic root growth model, is rare. This study simulated the dynamic growth processes of a primary to secondary root structure from simple roots to complex roots of aquatic plants. The dynamic root growth model mainly includes root elongation and branching rules and determines the initial root growth direction of the intersectional angle θ and radial angle γ between the main and lateral roots. Specifically, the dynamic root growth model formulations of two representative aquatic plants, the cosmopolitan invasive aquatic plant, water hyacinth (Eichhornia crassipes), and the relatively most studied aquatic plant, Eurasian watermilfoil (Myriophyllum spicatum), were established by applying the L-system. The total length of the root system of mature E. crassipes can reach 2042.78 m, indicating that the species has a high nutrient absorption capability. This may favor resource exploitation, facilitating its competitive ability with native plants. The total length of the M. spicatum root system is 73.08 m; owing to its typical dichotomous branching, this plant has a relatively high adaptation to the aquatic environment.

Evaluation of Water Quality and Heavy Metal Pollution in the Shoots and Roots of Aquatic Plants

The safety of vegetables has been an issue of public concern in recent years. Thus, heavy metals (Cu, Cd, Mn, Pb, Zn and Fe) in the shoot and root of Sacciolepis africana, Ceratophyllun demersum and Pistia stratiotes in Owena reservoir, Nigeria were tested using Atomic Absorption Spectrophotometer while some Physico-chemical parameters of water were measured using multi parameter hand-held meter. The water quality result revealed that the average temperature, turbidity, conductivity, dissolved oxygen and pH were 27.77oC, 7.21NTU, 101.83Ω/S, 6.95mg/l and 6.55 respectively. The single factor pollution index showed that Temperature (0.93), DO (0.99) and pH (0.99) fell within the category of slight pollution while turbidity (1.20) and conductivity (1.02) fell within the medium pollution category. Sacciolepis africana bio-concentrated more heavy metals than Ceratophyllun demersum and Pistia stratiotes. The HRIs of Cu, Cd, Mn, Zn and Fe indicated no risk since all values were less than 1. However, there was a potential risk for Pb through the consumption of the plants despite that the HRI of the shoot of Ceratophyllun demersum (0.65) and root of Pistia stratiotes (0.46) were less than 1. The THQ and HI values for the root and shoot of all the vegetables were less than 1, indicating that they are unlikely to result in any chronic systemic risk-averse health effects.

Cable bacteria at oxygen‐releasing roots of aquatic plants: a widespread and diverse plant–microbe association

Summary Cable bacteria are sulfide‐oxidising, filamentous bacteria that reduce toxic sulfide levels, suppress methane emissions and drive nutrient and carbon cycling in sediments. Recently, cable bacteria have been found associated with roots of aquatic plants and rice (Oryza sativa). However, the extent to which cable bacteria are associated with aquatic plants in nature remains unexplored.Using newly generated and public 16S rRNA gene sequence datasets combined with fluorescence in situ hybridisation, we investigated the distribution of cable bacteria around the roots of aquatic plants, encompassing seagrass (including seagrass seedlings), rice, freshwater and saltmarsh plants.Diverse cable bacteria were found associated with roots of 16 out of 28 plant species and at 36 out of 55 investigated sites, across four continents. Plant‐associated cable bacteria were confirmed across a variety of ecosystems, including marine coastal environments, estuaries, freshwater streams, isolated pristine lakes and intensive agricultural systems. This pattern indicates that this plant–microbe relationship is globally widespread and neither obligate nor species specific.The occurrence of cable bacteria in plant rhizospheres may be of general importance to vegetation vitality, primary productivity, coastal restoration practices and greenhouse gas balance of rice fields and wetlands.

A New Method to Capture the Spatial and Temporal Heterogeneity of Aquatic Plant Iron Root Plaque In Situ.

The roots of aquatic plants, including rice, release oxygen into the subsurface, precipitating reduced metals, such as iron (Fe) and manganese (Mn), as plaques that form on the surface of the roots. These plaques are a unique habitat for microorganisms and a hotspot for biogeochemical cycling, including the toxic trace metalloid arsenic (As). However, studying plaque deposition and mineral composition in this spatially and temporally heterogeneous environment is challenging, particularly in situ. Here, we describe a new technique for nondestructive and repeated rhizosphere sampling. We placed vinyl films that adhere Fe deposits from roots growing adjacent to the films into soil. The films were removed and replaced throughout plant growth and were characterized using a variety of spectroscopic (XRF imaging and Fe EXAFS) and microscopic (SEM and confocal) techniques. Fe deposits were most concentrated at lateral junctions and heterogeneity was apparent in the location and speciation of Fe-associated As in both pot and field studies. XRF imaging at multiple incident beam energies revealed that this As was mostly arsenate, although arsenite was present on the edge of the Fe deposit. Iron deposits were typically micron sized and consisted mostly of ferrihydrite, consistent with the data reported using conventional techniques. Moreover, Fe deposits were occupied by a variety of microorganisms. These films are a suitable technique to study a range of spatial and temporal questions regarding the biogeochemistry of aquatic plant roots.

Diverse fungal communities associated with the roots of isoetid plants are structured by host plant identity

Abstract We examined fungi associated with roots of isoetid plants collected from six Norwegian lakes. The composition of the diverse fungal communities was shaped mainly by host identity, while abiotic factors had negligible effects. The communities associated with roots of Subularia aquatica, Isoetes echinospora and Isoetes lacustris were dominated by Ascomycota, Chytridiomycota, and Basidiomycota while Glomeromycota were infrequent and the proportion of unidentified fungal taxa was relatively high. In contrast, Lobelia dortmanna and Littorella uniflora roots associated mainly with Glomeromycota, Ascomycota, and Basidiomycota. Chytridiomycota and unidentified fungi were rare. Glomeromycota comprised 39 phylotypes spanning nine families, with the second most abundant phylotype belonging to a yet undescribed sister lineage to the family Archaeosporaceae, repeatedly reported from aquatic environments. Our results indicate that fungal communities in roots of aquatic plants might be diverse as in terrestrial plants, and that they comprise a high proportion of yet undescribed taxa.

Distribution and trophic transfer of engineered nanoparticles along aquatic food chains and related influencing factors: A review

Nanotechnology is developing rapidly and has been widely applied in chemical engineering, electronic engineering, energy sources, environmental protection and other fields. Engineered nanoparticles (ENPs) are inevitably releasing into the aquatic environment during the entire life cycle of nano-products, thus exposing to aquatic organisms, which has been well investigated in the past decade. ENPs could be internalized by different types of aquatic organisms including algae, plants, and fish. Therefore, the possible transfer of ENPs between different aquatic organisms has attracted attentions, and many important publications reported the trophic transfer of ENPs through aquatic food chains. This review first provided the internalization and distribution of ENPs in different aquatic organisms including microorganism, aquatic plants, invertebrate and fish: (1) For microorganisms, ENPs are mainly adsorbed on the cellular surface, and then be internalized, and the internalization could lead to subsequent toxicity; (2) ENPs could be taken up by the roots of aquatic plants, and then be migrated to stem and leaves by evapotranspiration; (3) ENPs were mainly located in the hepatopancreas and gut of invertebrates; (4) ENPs could be accumulated in the gill and digestive tract of fish, and then distributed into other tissues such as liver and spleen. Secondly, the research status of ENPs in aquatic food chain were summarized and analyzed. The transfer of ENPs was observed in both freshwater and marine food chains, and current investigations on freshwater food chains contributed a larger proportion than in the marine. Most of the researches proved that ENPs can transfer along the food chain, but the biomagnification was only reported in a few publications. Thirdly, the influence of water chemistry factors and ENPs properties on the transfer of ENPs via aquatic food chains was discussed. For the water chemistry factors, like light illumination, solution pH, co-existing compounds such as natural organic matter, ionic strength, and oxidation–reduction potential all altered the bioavailability of ENPs and played important roles in the trophic transfer of ENPs. For the properties of ENPs, it is observed that: (1) the metal ions which were released from metal-containing ENPs can improve the bioavailability of ENPs in aquatic organisms; (2) different coatings of ENPs brought different or opposite surface charge on the surface, thus changing the internalization and bioavailability of ENPs. For example, ENPs with positively charged surface could be easily adsorbed on the surface of aquatic organisms than the negatively charged particles; (3) different size and shape influenced the contacting area between the ENPs and organisms, and ENPs with smaller size were usually more readily enter aquatic organisms, which were deeply discussed in this review. Finally, the current researches, prospects and challenges on ENPs transfer in the aquatic food chains are addressed.

Bacterial periphytic communities related to mercury methylation within aquatic plant roots from a temperate freshwater lake (South-Western France).

Macrophyte floating roots are considered as hotspots for methylmercury (MeHg) production in aquatic ecosystems through microbial activity. Nevertheless, very little is known about periphyton bacterial communities and mercury (Hg) methylators in such ecological niches. The ability to methylate inorganic Hg is broadly distributed among prokaryotes; however, sulfate-reducers have been reported to be the most important MeHg producers in macrophyte floating roots. In the present work, the periphyton bacterial communities colonizing Ludwigia sp. floating roots were investigated through molecular methods. Among the 244 clones investigated, anaerobic microorganisms associated with the sulfur biogeochemical cycle were identified. Notably, members of the sulfur-oxidizing prokaryotes and the anoxygenic, purple non-sulfur bacteria (Rhodobacteraceae, Comamonadaceae, Rhodocyclaceae, Hyphomicrobiaceae) and the sulfate reducers (Desulfobacteraceae, Syntrophobacteraceae, and Desulfobulbaceae) were detected. In addition, 15 sulfate-reducing strains related to the Desulfovibrionaceae family were isolated and their Hg-methylation capacity was tested using a biosensor. The overall results confirmed that Hg methylation is a strain-specific process since the four strains identified as new Hg-methylators were closely related to non-methylating isolates. This study highlights the potential involvement of periphytic bacteria in Hg methylation when favorable environmental conditions are present in such ecological micro-niches.

A New Approach to Sampling Intact Fe Plaque Reveals Si-Induced Changes in Fe Mineral Composition and Shoot As in Rice.

The Fe (oxyhydr)oxide rind, or Fe plaque, that forms on aquatic plant roots is an important sorbent of metal(loid)s and plays a role in the attenuation of metal(loid) uptake into higher plants. However, the mineral composition of Fe plaque and thus its potential to sorb metal(loid)s is affected by solution chemistry. The predominant strategy to characterize Fe plaque using dithionite-citrate-bicarbonate (DCB) extraction and elemental analysis reveals total Fe quantity but misses the mineral structure of the Fe (oxyhydr)oxide. Here, we developed a new technique using gentle sonication to sample intact Fe plaque from the root system and concentrate it for subsequent mineralogical characterization using synchrotron-based X-ray diffraction and X-ray absorption spectroscopy. We then coupled that data with conventional DCB extraction. The sample preparation method was effective at concentrating As-bound Fe plaque minerals in a uniform coating onto membranes that could easily be analyzed with X-ray techniques. Using these methods, we show that the percentage of poorly ordered Fe minerals in Fe plaque increases with increasing pore-water Si in flooded rice paddy soils. These findings have implications for understanding mineral controls on As cycling in the soil-rice nexus, and the sampling approach can be adopted for other aquatic plant systems.

담수에 자생하는 수생식물에서 분리된 내생균류의 지베렐린 생산과 동정

수생식물 샘플은 낙동강과 금호강이 만나는 달성습지에서 자라풀을 채집하였다. 자라풀의 뿌리에서 내생균류를 분리하고 형태가 다른 균주를 관찰하여 최종적으로 16개 균주를 선발하였다. 내생균류의 배양여과액은 식물생장촉진활성 검정을 위하여 난장이벼에 처리하여 스크리닝하였으며, HD1008 균주가 식물생장촉진활성이 가장 높은 것으로 확인되었다. HD1008 균주의 배양여과액을 HPLC와 GC/MS-SIM을 이용하여 분석하였고, HD1008 균주가 식물호르몬인 지베렐린 <TEX>$GA_1$</TEX> (1.2 ng/100 mL)과 <TEX>$GA_4$</TEX> (5 ng/100 mL) 를 생산하는 것을 정량분석을 통하여 확인하였다. 또한, HD1008균주의 beta-tubulin 유전자 염기서열을 이용하여 동정에 이용하였으며, 분자적인 방법과 형태적인 방법으로 관찰하였을 때, 지베렐린을 생산하는 새로운 P. trzebinskii로 동정되었다. Aquatic plant Hydrocharis dubia (Blume) Backer was collected from the Dalsung wetland in Daegu. Sixteen endophytic fungi with different colony morphologies were isolated from the roots of aquatic plants. Waito-c rice (WR) seedlings were treated with fungal culture filtrates (FCF) for screening plant growth-promoting activity. In the results, HD1008 strain isolated from aquatic plant showed highest plant growth-promoting activity. The FCF of HD1008 strain was analyzed using gas chromatography mass spectrometry (GC/MS) with selected ion monitoring (SIM). Analysis of the FCF of HD1008 strain found that it contained gibberellins (GA) (<TEX>$GA_1$</TEX>, 1.2 ng/100 mL; <TEX>$GA_4$</TEX>, 5 ng/100 mL). Phylogenetic tree of HD1008 strain was constructed by partial internal transcribed spacer (ITS) region and partial beta-tubulin gene sequences. Therefore, we describe HD1008 strain as a new gibberellin-producing Penicillium trzebinskii based on morphological and molecular characteristics.

ZINC AND LEAD IN BOTTOM SEDIMENTS AND AQUATIC PLANTS IN RIVER NAREW

Aquatic ecosystems are a valuable part of natural environment. The increasing level of pollution in waters transforming biocoenoses and other adverse effects of the impact of toxic substances have contributed to the development of biological monitoring. The aim of the study was to determine the changes in contents of zinc and lead in bottom sediments and roots of aquatic plants: Phragmites australis and Acorus calamus in the river Narew. There were 14 points on the river, from where samples of bottom sediments and plant material were collected. The contents of lead and zinc were determined by means of flame atomic absorption spectrophotometry using Varian device. It was proven that bottom sediments were characterized by low contents of zinc and lead except from two sampling points: in Bondary and Narew. Achieved results of analyzes of plant material showed a slight exceeding in the case of lead. Spatial distribution of zinc and lead contents in examined roots of plants coincided with their contents in bottom sediments, which was also confirmed by statistical analysis. It was proven that aquatic plants had greater tendency for accumulation of metals than bottom sediments.

Free-living culturable bacteria and protozoa from the rhizoplanes of three floating aquatic plant species

Terrestrial plant roots exude compounds that promote the proliferation of microorganisms, a phenomenon called the rhizosphere effect. However, little is known about the influence of roots of aquatic plants on microbial populations. We compared cultivable bacteria and protozoa from the rhizoplanes of Azolla filiculoides Lam., Lemna gibba L., and Ricciocarpus natans L., collected at the Tecocomulco Lagoon (Hidalgo, Mexico). The functional bacterial groups isolated from A. filiculoides, L. gibba and R. natans, were macro- and microscopically characterized, and phylogenetically identified using the 16S rDNA gen. About 96% of isolates corresponded to Gram-negative bacteria, and potential N-fixing free-living bacteria (diazotrophic bacteria) were the most abundant. Molecular analysis detected 15 bacterial genera in the rhizoplane of R. natans, whereas A. filiculoides and L. gibba only yielded five genera, among which Aeromonas was predominant. Twenty-five genera of flagellated and 20 genera of ciliated protozoa were identified. Bodo was the more abundant flagellated, whereas Halteria was the most frequent ciliate. All three aquatic plants showed the rhizospheric effects. The most abundant and diverse community of protozoa was found in A. filiculoides, which also had the most abundant bacterial community, but the highest bacterial diversity was found in R. natans.

THE ROLE OF AQUATIC PLANTS AND MICROORGANISMS IN DOMESTIC WASTEWATER TREATMENT

This study aimed to assess the ability of microorganism populations and two aquatic plant species (water hyacinth - Eichhornia crassipes Solms and water morning glory - Ipomoea aquatica) to treat domestic wastewater in Nhue Giang pond, Tay Mo village, Tu Liem District, Hanoi City in Vietnam. The results showed that microorganism populations in the pond water contained all of groups of microorganisms including bacteria, Actinomycetes, mold and yeast. In water inlet and outlet samples, bacteria has the largest number in population (2.1x10 6 and 8.7x10 5 CFU/mL at inlet and outlet), accounting for 99.91% of total microorganisms. Regarding the number of microorganisms attached on roots of aquatic plants, the highest number was recorded for bacteria, while the numbers of Actinomycetes, mold and yeast were quite small. The total number of microorganisms attached on water hyacinth roots is 2.5x10 6 CFU/g and 1.5x10 6 CFU/g (at inlet and outlet sample) higher than that on water morning glory roots in both sampling sites. The wastewater treatment efficiency for TSS, COD, NH4 + and PO4 3- parameters at the site without aquatic plants was in the range of 1% to 5% only, while treatment efficiency for those parameters at location with aquatic plants was much higher. Particularly, it was in range of 37.8% - 53.3% for TSS; 44.4% - 53.4% for COD; 56.7% - 61.4% for PO4 3- and 26.8% - 32.6% for NH4 + . All the lower values belonged to water morning glory sample and the higher values belonged to water hyacinth sample at the outlet.

Bioaugmentation involving a bacterial consortium isolated from the rhizosphere of Spirodela polyrhiza for treating water contaminated with a mixture of four nitrophenol isomers

A flask-scale laboratory study was performed to assess the bioaugmentation of water contaminated with a mixture of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and 2,4-dinitrophenol by using a bacteria consortium consisting of three nitrophenol-degrading bacteria strains (Pseudomonas sp. strain MFR-1, Pseudomonas sp. strain PFR-1 and Rhodococcus sp. strain DFR-1), reinoculated into the roots of Spirodela polyrhiza. The selected strains were colonized into the root at approximately 104 to 106 colony-forming units (CFU per plant). The high populations remained stable through five sequential two-days degradation cycles and complete nitrophenol removal was achieved within five-repeated cycles. Hence, inoculation of subjected degraders into the roots of aquatic plants is an effective treatment for nitrophenol-contaminated effluents or aquatic resources.

Some Aspects of the Biology ofDistichodus rostratus (GUNTHER, 1864) in River Rima, North-western Nigeria

Study was carried out to determine some aspects of the biology of Distichodus rostratus (GUNTHER, 1864) in River Rima, North-western Nigeria. This is with a view to provide information on the species in River Rima which has not been documented elsewhere. These include morphometric measurements, growth pattern, diet composition, gonad maturation stages, gonadosomatic index (GSI) and fecundity of the species. A total of 66 samples were collected from Kwalkwalawa fish landing site of River Rima between July and December, 2012. Total length of the samples ranged from 18.70±0.99SE to 46.20±0.99SE with a mean value of 31.18±0.99SE while total weight ranged from 104.20±32.65SE to 892.60±32.65SE with a mean value of 473.92±32.65SE. The b values of 2.461, 2.476 and 2.292 for all samples, females and males respectively indicate negative allometry. Mean condition factor was 1.52±0.517SD, indicating that the species are in good condition. Analysis of the stomach contents revealed that the species are herbivorous feeding mainly on leaves and roots of aquatic plants, grasses, algae and deadwood. Observation of the structural feeding adaptations such as the sub-inferior mouth, the fine and numerous gill rakers, the U-shaped stomach and the long intestine further confirms the herbivorous nature of the fish. Four stages of gonad maturation were established in females and three stages in males. Gonadosomatic index values for males ranged from 0.08 to 1.20% with mean value of 0.25±0.0211SE and for females 0.25 to 2.29%, with a mean value of 1.89±0.829SE. Fecundity ranged from 2,980 – 21,010 eggs.

Microbial Community Analysis in the Roots of Aquatic Plants and Isolation of Novel Microbes Including an Organism of the Candidate Phylum OP10

A number of molecular ecological studies have revealed complex and unique microbial communities in various terrestrial plant roots; however, little is known about the microbial communities of aquatic plant roots in spite of their potential use for water quality improvement in aquatic environments (e.g. floating treatment wetland system). Here, we report the microbial communities inhabiting the roots of emerged plants, reed (Phragmites australis) and Japanese loosestrife (Lythrum anceps), collected from a floating treatment wetland in a pond by both culture-independent and culture-dependent approaches. Culture-independent analysis based on 16S rRNA gene sequences revealed that the microbial compositions between the two aquatic plant roots were clearly different (e.g. the predominant microbe was Betaproteobacteria for reed and Alphaproteobacteria for Japanese loosestrife). In comparisons of microbial communities between the plant roots and pond water taken from near the plants, the microbial diversity in the plant roots (e.g. 4.40–4.26 Shannon-Weiner index) were higher than that of pond water (e.g. 3.15 Shannon-Weiner index). Furthermore, the plant roots harbored 2.5–3.5 times more phylogenetically novel clone phylotypes than pond water. The culture-dependent approach also revealed differences in the microbial composition and diversity among the two plant roots and pond water. More importantly, compared to pond water, we succeeded in isolating approximately two times more novel isolate phylotypes, including a bacterium of candidate phylum OP10 (recently named Armatimonadetes) from the plant roots. These findings suggest that aquatic plants roots are significant sources for a variety of novel organisms.

Characteristics of aquatic plant roots, soil microbes and agricultural non-point source pollutant mitigation in riparian buffer zones

An experiment was conducted on the characteristics of root morphology and vitality, and soil microbial community diversity of three typical aquatic plants to determine their mitigation efficiency of agricultural non-point source pollutants in riparian buffer zones. All the aquatic plants used have significantly differences in the characteristics of root morphology and vitality. Root vitality values of the aquatic plants are in the following order: Iris pseudacorus Acorus calamus Lythrum salicaria. Root vitality has a significant correlation with root tip number. The aquatic plants show significant rhizosphere effect, soil microbial biomass in rhizosphere is markedly higher than that in bulk soils. Furthermore, microbial community in rhizosphere soils of the riparian buffer zone has the composition sequence as: bacteria actinomycetes fungi. Soil microbial community diversity index is as follows: I. pseudacorus A. calamus L. salicaria, having the same tendency as that of root vitality. The order of removal efficiency of TN, TP and CODCr by the aquatic plants in the riparian buffer zone is I. pseudacorus A. calamus L. salicaria. The results suggest that variations in root vitality caused by differences in root structure of aquatic plants influence soil microbial community structure and diversity. This results in the differences in removal efficiencies of agricultural non-point source pollutants in riparian buffer zones.

Stream plant chemistry as indicator of acid sulphate soils in Sweden

Results from the biogeochemical mapping (roots of aquatic plants and Fontinalis antipyretica) conducted by the Geological Survey of Sweden (SGU) reflects the metal load of surface waters draining acid sulphate (AS) soils in Sweden. In this study, results from the biogeochemical, soil geochemical and Quaternary mapping programmes at SGU were used to investigate the impact of fine-grained deposits hosting AS soils on stream water trace element chemistry in two separate areas. In the area around Lake Mälaren, postglacial sediments contain the highest levels of most trace elements studied. Owing to the low pH of AS soils and subsequent leaching, levels of nickel (Ni), cobalt (Co), copper (Cu), sulphur (S), yttrium (Y), uranium (U), tungsten (W), and molybdenum (Mo) were significantly elevated in aquatic roots. Levels were lower in the Skellefteå area, which may be explained by lower concentrations in source deposits. Concentrations of arsenic (As) and lead (Pb) were normal or impoverished in biogeochemical samples from postglacial, finegrained sediment areas. Maps based on ratios (Ni:Pb or Y:Pb) in biogeochemical samples can, together with results from Quaternary mapping, be used to predict areas with AS soils in Sweden.;