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Seasonal changes in the concentrations of trace elements (Ni, Cu, Pb, Zn, Cr and As) were analysed in shoots of macrophytes Myriophyllum spicatum, Najas marina, Potamogetoncrispus, Potamogeton lucens, Potamogeton nodosus, Potamogeton pectinatus and Nuphar lutea taken from lake Velenjsko jezero (Slovenia), an artificial lake resulting from mining activity. Lake lies in the vicinity of the Šoštanj Thermal Power Plant, from which fly ash slurry was transported by pipeline and emptied into Velenjsko jezero until 1983. The degree of concentration of elements in plant’s shoots varied according to the species of plant and the time of the season. The average concentrations of non-essential elements (Ni, Cr, Pb and As) in stems and leaves were the highest in Myriophyllum spicatum and the lowest in Nuphar lutea. Concentration of two essential elements Cu and Zn were the highest in the shoots of Potamogeton lucens and Potamogeton crispus respectively. Element concentration showed seasonal variation. For essential elements Zn and Cu there was a clear concentration decline from May to September in almost all macrophyte shoots, while non-essential elements remained at the same level or decreased through the season.

This research identified and characterized factors that influenced nanomaterial bioavailability to three aquatic plants: Azolla caroliniana Willd, Egeria densa Planch., and Myriophyllum simulans Orch. Plants were exposed to 4-, 18-, and 30-nm gold nanoparticles. Uptake was influenced by nanoparticle size, the presence of roots on the plant, and dissolved organic carbon in the media. Statistical analysis of the data also revealed that particle uptake was influenced by a 4-way (plant species, plant roots, particle size, and dissolved organic carbon) interaction suggesting nanoparticle bioavailability was a complex result of multiple parameters. Size and species dependent absorption was observed that was dependent on the presence of roots and nanoparticle size. The presence of dissolved organic carbon was found to associate with 4- and 18-nm gold nanoparticles in suspension and form a nanoparticle/organic matter complex that resulted in (1) minimized particle aggregation and (2) a decrease of nanoparticle absorption by the aquatic plants. The same effect was not observed with the 30-nm nanoparticle treatment. These results indicate that multiple factors, both biotic and abiotic, must be taken into account when predicting bioavailability of nanomaterials to aquatic plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigated invasive hybrid watermilfoil ability to reproduce sexually. [•] Hybrid artificial crosses produced viable seeds. [•] Genetic evidence for advanced generation hybrids was found in natural populations. [•] Sexual reproduction may impact management. [Copyright &y& Elsevier]

Myriophyllum aquaticum (Vell.) Verdc. produces two morphologically different forms of leaves based on whether they are aerial or aquatic. The objective of this study was to determine whether there are any similarities or differences between these two growth forms during their early stages of development. A comparative developmental study of aerial and aquatic growth forms of M. aquaticum was conducted from a qualitative and quantitative perspective using a scanning electron microscope. The pattern of leaf and lobe initiation such as their origin and shape were similar in both growth forms until the fourth plastochron (stage P4). Differences between the two growth forms became evident from stage P5 onward, where a larger shoot apical meristem (SAM), elongated epidermal cells, shorter and slightly more numerous lobes, as well as the presence of appendage-like structures characterized aquatic growth forms. On the other hand, aerial growth forms had smaller SAM, bulb-like epidermal cells, and longer and slightly less numerous leaf lobes. Significant differences between growth forms were noted for parameters such as volume of SAM, length of terminal, first, and middle lobes, as well as the length from first to last lobes. The volume of the SAM of aquatic shoot tips was always greater than aerial forms. On the other hand, lobes of aerial forms were always longer than the aquatic counterpart during early stages of development. This study on the development of M. aquaticum shows that the aerial and aquatic growth forms diverge from their early stages of development. [ABSTRACT FROM AUTHOR]

This paper considers certain elements relating to the ecological and economic importance of the aquatic macrophytes common in the Câmpia Română/Romanian Plain lakes, especially those species belonging to the genera Myriophyllum and Potamogeton, common in Bucharest's urban lakes. At present, the macrophytes of the Bucharest lakes are collected by personnel of the Lakes, Parks and Leisure Administration of Bucharest by mechanised and manual methods, which are sun-dried and transported as waste and deposited in a landfill. Thus these macrophytes are merely generating costs through harvest, transport and storage, instead of being a direct revenue source for the City hall. This study presents a review of international literature in support of the economic potential as fertiliser for open field crop, orchard and garden crop application, as well as food for farm animals. The last portion of the paper argues the vital need for the preservation of macrophyte stands in the lacustrine habitat for green, sustainable and integrated management of the urban lakes used for leisure and fishing. [ABSTRACT FROM AUTHOR]

In the course of re-oligotrophication in Lower Lake Constance, Germany, the tall-growing angiosperm Myriophyllum spicatum has been almost replaced by dense and lower-growing charophytes. We hypothesise that Chara globularis negatively affects the performance of M. spicatum due to density competition and nutrient interference. Intra- and interspecific competition was assessed using a response surface experimental design with different densities of both species in mono and mixed stands in an outdoor mesocosm experiment. After 8 weeks, we measured the growth and various functional traits of both species, including stoichiometry, ash-free dry mass and dry-matter content, and for M. spicatum, additionally chlorophyll content, leaf-mass fraction, formation of autofragments, and root/shoot ratio. With increasing density, C. globularis reduced the growth of M. spicatum much more strongly than that of conspecifics. Increasing density of C. globularis led to a lower chlorophyll a to b ratio and lower nitrogen content based on ash-free dry mass in M. spicatum as well as reduced autofragmentation. Established C. globularis meadows can negatively affect tall-growing angiosperms such as M. spicatum when the environmental conditions, such as low phosphorus availability and high water-clarity, are appropriate. These findings have implications for the management of lakes, specifically those where a nuisance growth of tall macrophytes occurs, e.g. in systems where M. spicatum is invasive. [ABSTRACT FROM AUTHOR]

Myriophyllum heterophyllum Michaux [Haloragaceae] in Haute-Vienne (Limousin, France), and the situation of this invasive plant in France and in Europe On the 10th of July 2011, in Saint-Sylvestre, a municipality of the Haute-Vienne French department, an unknown aquatic plant was observed which largely covered a private pond. After a collaborative identification by the authors and the national botanical conservatory of Massif Central ( CBNMC) office Limousin, it was concluded to be Myriophyllum heterophyllum Michaux. This article describes the situation of this species, which is considered an invasive alien species in Europe, but had not previously been the subject of an official report, or evaluation of its situation in France and in Europe in the natural environment. [ABSTRACT FROM AUTHOR]

ABSTRACT Relationships between water depths and density of submergent vegetation were studied in montane wetlands using statistical techniques based on clustering and an extension of regression trees. Sago pondweed ( Stuckenia pectinata) was associated with lower average water depths than water milfoil ( Myriophyllum sibiricum). We detected a nonlinear relationship when average water depths were used to predict percent cover in S. pectinata, with depths of 30-40 cm, producing the highest predicted average percent cover of S. pectinata; higher and lower depths resulted in lower percent cover predictions. For M. sibiricum, higher water depths were monotonically associated with higher average percent cover. To foster more S. pectinata and less M. sibiricum, managers might employ water control structures to reduce water depths below 1 m, using both temporary drawdowns and average depths of 30-40 cm. Other species responded less markedly to water depth variation. Should decreased water depths become more common, these results suggest an increase in S. pectinata and a decrease in M. sibiricum. Published in 2012. This article is a US Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Lemna spp. are the standard test species representing aquatic macrophytes in the current risk assessment schemes for herbicides and plant growth regulators in the European Union and North America. At a Society of Environmental Toxicology and Chemistry (SETAC) 2008 workshop on Aquatic Macrophyte Risk Assessment for Pesticides (AMRAP), a Species Sensitivity Distribution (SSD) working group was formed to address uncertainties about the sensitivity of Lemna spp. relative to other aquatic macrophyte species. For 11 herbicides and 3 fungicides for which relevant and reliable data were found for at least 6 macrophyte species, SSDs were fitted using lognormal regression. The positions of L. gibba (the most commonly tested Lemna species) and Myriophyllum spicatum (for which standardized test methods are under development) in each SSD were determined where data were available. The sensitivity of standard algal test species required for pesticide registration in the United States under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) relative to the macrophytes in each SSD was also examined (algae were not included in the SSD). L. gibba was among the most sensitive macrophyte species for approximately 50% of the chemicals examined. M. spicatum was among the most sensitive macrophytes for approximately 25% of the chemicals. In most cases, the lowest FIFRA algal species endpoint was lower than the most sensitive macrophyte endpoint. Although no single species consistently represented the most sensitive aquatic plant species, for 12 of 14 chemicals L. gibba and the FIFRA algae included an endpoint near or below the 5th percentile of the macrophyte SSD. For the other compounds, M. spicatum was the most sensitive species of all aquatic plants considered. Integr Environ Assess Manag 2013; 9: 308-318. © 2012 SETAC [ABSTRACT FROM AUTHOR]

This article explores the interrelations between flow, fluctuating drag forces, and dynamic reconfiguration experienced by four freshwater plant species in response to turbulent open-channel flow. The study is based on experiments conducted in a laboratory flume using single specimens ofRanunculus penicillatus, Fontinalis antipyretica, Myriophyllum alterniflorum, andCallitriche stagnalis. A significant correlation between drag fluctuations, plant movements, and upstream turbulence was found. The data also revealed that the plants in general exhibited spatial flapping-like motion, with the propagation velocity of perturbations along the plant being approximately constant and comparable to the upstream flow velocity. The analysis of statistical moments, spectra, cross-correlations, and coherence functions provided strong support to the conclusion that the dynamic reconfiguration directly affects the drag force exerted on the plants, in addition to the effect of the upstream turbulence. [ABSTRACT FROM AUTHOR]

Excessive nutrient loading may cause a shift from submerged macrophyte dominance to free-floating macrophyte dominance. Tolerance and persistence of submerged plants in response to shade may be key characteristics in determining when/if such a shift occurs in shallow eutrophic lakes. This study examines how the cover of floating macrophyte ( Lemna minor) and shade of dark mesh affect the growth and photosynthetic efficiency of two submerged plants ( Vallisneria natans and Myriophyllum spicatum) on different nutrient substrates. We found that low- and mid-cover intensities generally enhanced the leaf/shoot growth of both submerged plants under all cover and substrate types. The relative growth rates (RGR) were slightly enhanced under the treatment of Lemna with low- and mid-intensity cover on both nutrient-rich substrates. The leaf/shoot growth and RGR of both submerged macrophytes generally increased more under Lemna cover than mesh cover. The photosynthetic efficiency ( F/ F value) typically increased with the duration of treatment and the cover densities. In addition, these two macrophytes with contrasting growth forms have markedly different growth and survival strategies in response to covers. These results strengthen the hypothesis that submerged plants can successfully develop under a low-intensity cover of floating vegetation on nutrient-rich substrate. [ABSTRACT FROM AUTHOR]

Biological invasions are regarded as threats to global biodiversity. Among invasive aliens, a number of plant species belonging to the genera Myriophyllum, Ludwigia and Cabomba, and to the Hydrocharitaceae family pose a particular ecological threat to water bodies. Therefore, one would try to prevent them from entering a country. However, many related species are commercially traded, and distinguishing invasive from non-invasive species based on morphology alone is often difficult for plants in a vegetative stage. In this regard, DNA barcoding could become a good alternative. In this study, 242 samples belonging to 26 species from 10 genera of aquatic plants were assessed using the chloroplast loci trn H- psb A, mat K and rbc L. Despite testing a large number of primer sets and several PCR protocols, the mat K locus could not be amplified or sequenced reliably and therefore was left out of the analysis. Using the other two loci, eight invasive species could be distinguished from their respective related species, a ninth one failed to produce sequences of sufficient quality. Based on the criteria of universal application, high sequence divergence and level of species discrimination, the trn H-psb A noncoding spacer was the best performing barcode in the aquatic plant species studied. Thus, DNA barcoding may be helpful with enforcing a ban on trade of such invasive species, such as is already in place in the Netherlands. This will become even more so once DNA barcoding would be turned into machinery routinely operable by a nonspecialist in botany and molecular genetics. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study is to model, under controlled laboratory conditions, the effect of submerged aquatic vegetation (SAV) on turbulence generated in a water column by an oscillating grid turbulence (OGT). Velocity profiles have been measured by an acoustic Doppler velocimeter (MicroADV). Experimental conditions are analysed in two canopy models (rigid and semi-rigid), using nine plant-to-plant distances (ppd), three stem diameters (d), four types of natural SAV (Cladium mariscus, Potamogeton nodosus, Myriophyllum verticillatum and Ruppia maritima) and two oscillation grid frequencies (f). To quantify this response, we have developed a non-dimensional model, with a specific turbulent kinetic energy (TKE), f, stroke (s), d, ppd, distance from the virtual origin to the measurement (zm ) and space between grid bars (M). The experimental data show that, at zm /z c <1 the turbulent kinetic energy decays with zm , according to the well-known power law, zm −2, and does not depend on the vegetation characteristics. In contrast, at z m/z c >1, TKE decreases faster with z m and scales to the model variables according to . Therefore, at zm /zc >1 the TKE is affected by the geometric characteristics of the plants (both diameter and plant-to-plant distance), an effect called sheltering. Results from semi-rigid canopies and natural SAV are found to scale with the non-dimensional model proposed for rigid canopies. We also discuss the practical implications for field conditions (wind and natural SAV). [Copyright &y& Elsevier]

Hybridization may be important in the evolution of invasiveness, but few empirical studies compare introduced hybrid and parental lineages. Invasive 'variableleaf watermilfoil' (Myriophyllum heterophyllum) in the northeastern United States consists of at least three distinct lineages: an interspecific hybrid (M. heterophyllum × Myriophyllum laxum) and two historically allopatric lineages of pure M. heterophyllum. Previous observations suggested that hybrid populations of variable-leaf watermilfoil may be comparatively more 'invasive' than pure lineages. However, no quantitative data comparing hybrid and parental lineages have been collected, nor has invasiveness been compared between parental lineages. Here, we demonstrate that these distinct lineages are also ecologically distinct. We find some support for the hypothesis that hybridization has played a role in the evolution of invasiveness: hybrids exhibited higher biomass, individual plant size, and greater branching than at least one parental lineage of M. heterophyllum. However, parental lineages did not differ from the hybrid for some traits, demonstrating that pure parental lineages can also be invasive. In addition, we found no evidence for a role of intraspecific hybridization in the evolution of invasiveness in these lineages of variable-leaf watermilfoil, even where they cooccurred locally. Our study suggests that distinguishing among cryptic lineages will help prioritize rapid response control efforts. [ABSTRACT FROM AUTHOR]

Abstract: Freshwater macrophytes stimulate rhizosphere-associated coupled nitrification–denitrification and are therefore likely to influence the community composition and abundance of rhizosphere-associated denitrifiers and nitrate reducers. Using the narG gene, which encodes the catalytic subunit of the membrane-bound nitrate reductase, as a molecular marker, the community composition and relative abundance of nitrate-reducing bacteria were compared in the rhizosphere of the freshwater macrophyte species Littorella uniflora and Myriophyllum alterniflorum to nitrate-reducing communities in unvegetated sediment. Microsensor analysis indicated a higher availability of oxygen in the rhizosphere compared to unvegetated sediment, with a stronger release of oxygen from the roots of L. uniflora compared to M. alterniflorum. Comparison of narG clone libraries between samples revealed a higher diversity of narG phylotypes in association with the macrophyte rhizospheres compared to unvegetated sediment. Quantitative PCR targeting narG- and 16S rRNA-encoding genes pointed to a selective enrichment of narG gene copies in the rhizosphere. The results suggested that the microenvironment of macrophyte rhizospheres, characterized by the release of oxygen and labile organic carbon from the root system, had a stimulating effect on the diversity and relative abundance of rhizosphere-associated nitrate reducers. [Copyright &y& Elsevier]

Environmental heterogeneity is universal and occurs at various spatial scales. Many studies have examined effects of environmental heterogeneity on growth of individual species, but few have tested the effects on species composition and biomass of plant communities, especially those consisting of submerged macrophytes. Moreover, no study has tested effects of scale of heterogeneity on plant communities. We constructed communities with four submerged macrophytes (i.e., Ceratophyllum demersum, Hydrilla verticillata, Egeria densa and Myriophyllum verticillatum) and subjected the communities to three homogeneous light treatments (100%, 65% and 30% of full light and coded as high, medium and low light treatment, respectively) and two heterogeneous light treatments differing in patch size (large vs. small patch treatment). The total amount of light received by the whole communities in the two patchy treatments was the same as that in the homogeneous medium light treatment. Under homogeneous treatments, decreasing light intensity significantly decreased total biomass, total number of nodes and total shoot length of the submerged macrophyte communities and of H. verticillata and E. densa, but did not significantly affect growth of M. verticillatum or C. demersum. Light heterogeneity, i.e., light patchiness or patch scale, did not affect these three growth variables of the community as well as those of the individual macrophytes. Therefore, light intensity can affect structure and biomass of submerged macrophyte communities, but light heterogeneity may not. [ABSTRACT FROM AUTHOR]

We investigated the effects of turion size and water depth on the emergence and size of the submerged macrophyte Myriophyllum oguraense Miki subsp, yangtzense in an outdoor experiment in order to determine the underlying factors affecting its persistence at early life-history stages. Turions were sampled and sorted into three groups (small, medium, and large) and buried in plastic pots with unsterilized lake sediment under four different water depth treatments. Percent emergence, total plant biomass and plant height were strongly affected by turion size, increasing with increasing turion size. Emergence time was significantly affected by both turion size and size × water depth interaction and was delayed with decreasing turion size. Plant emergence of both small and large turions was significantly delayed with increasing water depth. The results indicate that large turions and shallow water might favor the early establishment and survivorship of the immature plant. Allocation to sprouting appears to enhance the ability of immature plants to survive unfavorable conditions. We propose that turion size and water depth play an important role in influencing the abundance and distribution of this endemic population. [ABSTRACT FROM AUTHOR]

Numerous invasive aquatic species introductions can be traced to the aquarium trade. Many potentially harmful aquarium species may be difficult to identify based on morphology alone. As such, some prohibited or invasive species may be available for purchase if they are mislabeled as species without restrictions. Here we compare molecular identifications to internet vendors' identifications for accessions of a popular genus of aquarium plants that are difficult to distinguish morphologically ( Myriophyllum; watermilfoils). Specifically, we identified the extensive mislabeling of M. heterophyllum-an invasive species in the northeastern and western US. Furthermore, genotypes of M. heterophyllum found in our aquarium survey have also been found in invasive populations, suggesting their potential introduction through escape from aquaria, water gardens, or nurseries. Two additional taxa were sold under incorrect names. Finally, our survey revealed that Myriophyllum taxa present in the aquarium trade generally have poorly known distributions and ecologies, and therefore their invasive potential is unknown. Our study confirms that molecular identification methods can provide a valuable tool to survey commercial pathways for potentially harmful species that are otherwise difficult to identify. [ABSTRACT FROM AUTHOR]

The partitioning of 4- and 18-nm gold nanoparticles (AuNPs) to aquatic macrophytes was investigated in vivo with exposure suspension in well water. Three morphologically distinct aquatic macrophytes were studied. Myriophyllum simulans Orch. and Egeria densa Planch. are submerged aquatic vascular plants, whereas Azolla caroliniana Willd. is a free-floating aquatic fern. Because aquatic plants absorb the majority of their nutrients from the water column, it is logical to hypothesize that they may absorb nanomaterials in suspension, potentially facilitating trophic transfer. Each plant was exposed to two different-sized gold nanospheres at a nominal concentration of 250 µg/L AuNPs for 24 h. Macrophytes were harvested at six time points (1, 3, 6, 12, 18, and 24 h), dried, and then analyzed for gold concentration via inductively coupled plasma-mass spectrometry. Concentrations were normalized to whole-plant dry tissue mass. The present study shows that absorption of AuNPs through root uptake was size and species dependent. Electron microscopy revealed that 4- and 18-nm AuNPs adsorbed to the roots of each species. Root tissue was sectioned, and transmission electron microscopy indicated that 4-nm and 18-nm AuNPs were absorbed by A. caroliniana, whereas only 4-nm AuNPs were absorbed by M. simulans. Egeria densa did not absorb AuNPs of either size. Gold nanoparticles were confirmed in tissue by using energy-dispersive X-ray spectroscopy. Absorption of AuNPs by plants may be a function of the salinity tolerance of each species. Environ. Toxicol. Chem. 2012;31:194-201. © 2011 SETAC [ABSTRACT FROM AUTHOR]

The article focuses on a study which investigated the nature and persistence of substrate at a mesohabitat scale matter for Chironomidae assemblages. The study included 60 samples collected using a Surber sampler, and a set of 23 environmental descriptors, such as physicochemical parameters and different fractions of particulate organic matter. It found that stable substrates such as boulders, cobbles and rooted plants supported higher chironomids richness, abundance and diversity.

Abstract: Paleoenvironmental reconstructions from Little Llangothlin Lagoon have been used to argue for early European impact on the eastern Australian landscape. In particular, these studies have argued for European arrival on the New England Tablelands at about 1800 AD, with significant impacts including the clearance of one species of Casuarina before 1820 AD and significant erosion by 1836 AD (; ; , ). We have re-cored the lagoon, dated the cores using 210Pb and radiocarbon, and counted pollen and other proxies. Our 210Pb results indicate that 210Pb background was achieved stratigraphically later than the erosion event and we have three early Holocene radiocarbon ages in the erosion event interval. We conclude that the ‘erosion event’ predates European settlement. The 210Pb results indicate much less erosion in response to European settlement than suggested by these earlier studies. We also find no notable decline in Casuarina in the pollen record spanning the time of initial European impact, and in fact we find very little Casuarina in the record. Instead of a Casuarina dominated vegetation we conclude that the area was dominated by open Eucalypt forest prior to European settlement. Rather than changes in the regional vegetation in the early 19th century, we attribute changes in the palynoflora spanning the ‘erosion event’ to changes within the lake/wetland and in particular to changes in the dominance of different species of Myriophyllum; most likely due to water depth fluctuation. This site has stood out as indicating an earlier European impact than other localities in eastern Australia, beyond the original limits of settlement near Sydney. Our findings suggest that a more traditional interpretation of this site is warranted and that no very early impact is discernable. [Copyright &y& Elsevier]

Abstract: We tested the effects of the herbicide metsulfuron-methyl on growth of the submerged macrophyte Myriophyllum spicatum under laboratory conditions using different exposure scenarios. The exposures of each scenario were comparable in the concentration×time factor, viz., the same 21-d time-weighted average (TWA) concentrations but variable in peak exposure concentrations (ranging from 0.1 to 21000ngaiL−1) and exposure periods (1, 3, 7, 14 or 21d). To study recovery potential of the exposed M. spicatum plants we continued the observation on shoot and root growth for another 21d in herbicide-free medium so that the total observation period was 42d. Non-destructive endpoints, length and number of new shoots and roots, were determined weekly from day 14 onwards. Destructive endpoints, dry-weight (DW) of main shoots, new shoots and new roots, were measured at the end of the experiment (t =42d). Metsulfuron-methyl exposure in particular inhibited new tissue formation but was not lethal to main shoots. On days 21 and 42 after start exposure, EC10/EC50 values for new tissues expressed in terms of peak concentration (=measured concentration during exposure periods of different length) showed large differences between exposure scenarios in contrast to EC10/EC50 values for days 21 and 42 expressed in terms of 21-d and 42-d TWA concentrations, respectively. At the end of the experiment (day 42), 42-d TWA EC x values were remarkably similar between exposure scenarios, while a similar trend could already be observed on day 21 for 21-d TWA EC x values. For the macrophyte M. spicatum and exposure to the herbicide metsulfuron-methyl the TWA approach seems to be appropriate to use in the risk assessment. However, the data from the toxicity experiment suggest that on day 21 also the absolute height of the pulse exposure played a (minor) role in the exposure – response relationships observed. [Copyright &y& Elsevier]

Allelopathic effects of C. alternifolius (Cyperus alternifolius), M. aquaticum (Myriophyllum aquaticum), C. alternifolius and M. aquaticum were investigated in coexistance experiments, and the algae biomass, chlorophyll a, community change and organic matters of the coexistance samples were monitored and analyzed. Cell numbers and Chl - a were significantly inhibited by C. alternifolius and M. aquaticum. The peak biomass of algae is 2.4 x 107/L, while that of the control, C. alternifolius, M. aquaticum is 4.48,1.15, 2.03 x 108/L respectively. The organic matters analysis show that only 75 kinds of organic matter exist in the C. alternifolius and M. aquaticum coexistance samples while 131 kinds of organic matter exist in the control sample. Acetone cyanohydrin, Triethyl phosphate, Camphene and 4 - methyl -4 - Phenol were new produced matters by C. alternifolius and M. aquaticum which maybe the potential allelopathic matters. [ABSTRACT FROM AUTHOR]

Abstract: Cadmium stress on aquatic macrophytes is currently few documented and no studies were conducted on clonal populations in controlled conditions. Our aim is to assess the effect of cadmium stress on Myriophyllum alterniflorum from physiological, anatomical and phenotypical parameters among different developmental stages. An experiment was carried out in order to test the hypothesis that a high external dose of Cd affects differentially young and old leaves of watermilfoil in terms of (1) anatomical and biological parameters, (2) physiological parameters and (3) that these differences result from the overall level of oxidative stress. Cadmium stress strongly affects the morphology of chlorophyllian organs and decreases the xylem-vessel number and diameter in matures leaves. Moreover we first report a new cadmium-induced anatomical feature: a double endodermis with separated layers which limits water and gaseous losses in mature leaves. From a physiological point of view, cadmium induces at all developmental stages a reduction in chlorophyll contents, a malondialdehyde production indicating a drastic lipoperoxydation, an enhanced production of reactive-oxygen-species scavengers (free proline and in lesser parts carotenoids) and a perturbation in hydric status in M. alterniflorum clones. The results obtained support the initial hypotheses. Indeed, it should be noted that cadmium stress mainly disturbs mature-leave structure and function, increasing their ageing and senescence. This mechanism probably contributes to limit the cadmium impact on young and growing parts as cadmium is known to preferentially accumulate in senescent leaves. [Copyright &y& Elsevier]

Summary 1. Many animals that consume freshwater macrophytes are omnivorous (i.e., they include both plant and animal matter in their diet). For invertebrate omnivorous consumers, selection of macrophyte species depends partly on the presence of secondary metabolites in plants, plant carbon/nutrient balances and/or physical structure of plants. However, little is known about the mechanisms influencing consumption of macrophytes in aquatic vertebrates. 2. For two fish species, the omnivorous rudd ( Scardinius erythrophthalmus) and herbivorous grass carp ( Ctenopharyngodon idella), feeding preferences were determined in three choice experiments. We tested (i) whether the presence of secondary metabolites and macrophyte stoichiometry affects macrophyte species selection by fish, (ii) the importance of macrophyte stoichiometry by manipulating the macrophytes experimentally and (iii) the rate of herbivory when the most palatable macrophyte is offered simultaneously with a common animal prey. 3. In a choice experiment with five species of submerged macrophytes ( Callitriche sp., Chara globularis, Elodea nuttallii, Myriophyllum spicatum and Potamogeton pectinatus), Myriophyllum was clearly consumed least by both fishes, which strongly correlated with the highest phenolic concentration of this macrophyte. Additionally, a significant negative relationship was found between consumption and C : N ratio of the five macrophytes. The two most consumed macrophytes also had the lowest dry matter concentration (DMC). 4. In a second choice experiment, the C : N ratio of the least ( Myriophyllum) and most ( Potamogeton) palatable plants was manipulated by growing the macrophytes under fertilised and unfertilised conditions and subsequently feeding them to rudd. The avoidance of consumption of the chemically defended Myriophyllum by rudd was partly alleviated by the lowered C : N ratio. 5. The third choice experiment showed that both fishes preferred animal prey (the amphipod Gammarus pulex) over the most palatable macrophyte ( Potamogeton) when offered simultaneously. The C : N ratio of the amphipods was about half that of the lowest C : N ratio measured in the macrophytes. Consumption by the fishes could not clearly be related to C : P or N : P ratios of prey items in any of the experiments. 6. We conclude that omnivorous fish avoid macrophytes that are chemically defended. However, when these defences are only minor, stoichiometry (C : N ratio) in combination with DMC may be a determining factor for consumption by vertebrate facultative herbivores. [ABSTRACT FROM AUTHOR]

The misidentification of Myriophyllum aquaticum (Vell.) Verdc. in the Kashmir Himalaya, India is corrected. In addition to its taxonomic description and illustration, the paper discusses the range expansion of this invasive plant species into different aquatic habitats and management implications in the region. [ABSTRACT FROM AUTHOR]

Resprouting ability may increase a plant's resistance to recurrent disturbances in aquatic ecosystems. We investigated the effect of mechanical disturbances on survival and regrowth patterns in three clonal aquatic species of similar growth form but with different ecological ranges in terms of flooding ( Myriophyllum verticillatum, Myriophyllum spicatum and Potamogeton coloratus). P. coloratus prefers to colonize stable habitats, whereas M. verticillatum occurs in intermediately flooded habitats and M. spicatum is tolerant to a high flooding frequency. Two cutting treatments (single cuts or repeated cuts) were applied under controlled conditions. We hypothesized that M. verticillatum and M. spicatum would be resistant to cutting displaying either a tolerant or an escape strategy whereas P. coloratus would be sensitive to cutting. Our hypothesis was validated, as the three species displayed contrasting responses to disturbance. M. verticillatum displayed efficient clonal propagation following breakage (escape strategy), but its growth rate decreased after recurrent disturbances. P. coloratus displayed a close response but was unable to compensate biomass loss even after one cut. M. spicatum maintained a similar growth rate by developing a densely branched form despite recurrent disturbances but with a low investment in clonal growth (tolerance strategy). Both biomass compensation and clonal propagation influence plant fitness, but their relative advantage differs depending on the flooding frequency experienced by plants in their natural habitats. Clonal propagation may promote recolonization after disturbances in infrequently flooded sites, but seems less efficient than a tolerance strategy for survival in frequently flooded sites. [ABSTRACT FROM AUTHOR]

Nuisance growth of Myriophyllum aquaticum has often been attributed to high amounts of nutrients. The uptake of nitrogen and phosphorus from sediments and their allocation have been documented in both natural and laboratory populations. However, nutrient loading to surface water is increasingly becoming an important issue for water quality standards. Aquatic macrophytes that develop adventitious roots may be able to survive through the uptake of water column nutrients. Our objectives for this study were to assess M. aquaticum growth when combinations of nitrogen and phosphorus were added to the water column. Mesocosm experiments were conducted where nitrogen (1.8, 0.8, and 0.4 mg l; high, medium, and low) and phosphorus (0.09, 0.03, 0.01 mg l; high, medium, and low) concentrations were paired and added to the water column. After 12 weeks, the combination of 1.80:0.01 N:P resulted in greater ( P < 0.01) total biomass and greater biomass for all plant tissues. Total biomass at the 1.80:0.01 N:P combination was 53% greater than biomass at all other combinations. The yield response of M. aquaticum was a quadratic function of tissue nutrient content. Yield was positively ( r = 0.82) related to increasing nitrogen content, whereas a negative ( r = 0.89) relationship was determined for increasing phosphorus content. We propose the negative relationship is due to increased nutrient competition and shading by algae resulting in reduced M. aquaticum growth. Tissue nutrient content indicated that critical concentrations (1.8% nitrogen and 0.2% phosphorus) for growth were not attained except for nitrogen in plants grown in the 1.80:0.01 N:P combination. These data provide further evidence that M. aquaticum requires high levels of nitrogen to achieve nuisance growth. Survival through uptake of water column nutrients may be a mechanism for survival during adverse conditions, a means of long distance dispersal of fragments, or may offer a competitive advantage over species that rely on sediment nutrients. [ABSTRACT FROM AUTHOR]

Copper is an essential element for the function of metabolic pathways in many living organisms like photosynthesis in plants. But, for the last decades, anthropogenic sources and release of Cu lead to environmental pollution particularly in aquatic ecosystems. The aquatic plant, Myriophyllum alterniflorum, known as a bioindicator of metal pollution, could be used as biomonitor. The aim of this study is to evaluate biomarkers responses of watermilfoil during Cu pollution at high environmental levels (100 μg l CuSO) in controlled conditions. Morphological and anatomical features like a new double endodermis (DE) layer were evidenced in response to Cu treatment. Moreover, physiological parameters like pigments contents, osmotic potential and proline content present a differential response to Cu stress in young and old leaves of watermilfoil. Finally, despite a rapid and strong phytoaccumulation of Cu, only young leaves are slightly affected in their cell membrane integrity as indicated by MDA content. In comparison with the Cu effect on other aquatic macrophytes, M. alterniflorum develops particular protection mechanisms like the ROS scavenging using proline rather than carotenoids, the reduction of water loss with the DE and the heavy metal elimination through senescence to protect preferentially the photosynthetic components of the young leaves and the main-stem elongation. Due to its Cu sensitivity, M. alterniflorum appears as important in the field of environmental studies using plant biomarkers. [ABSTRACT FROM AUTHOR]

Background and Aims The mature morphology of most plants can usually be said to consist of three mutually exclusive organs: leaves, stems, and roots. The vast majority of mature morphologies may be easily grouped into one of these mutually exclusive categories. However, during very early stages of development and in many instances from inception, the division between organ categories becomes fuzzy due to the overlap in developmental processes that are shared between the aforementioned mutually exclusive categories. One such overlap has been described at the gene level where KNOXI homologues, transcription factors responsible for maintaining indeterminate cell fate, are expressed in the shoot apical meristem and during early stages of compound leaf development. This study characterizes the occurrence and spatial localization of mRNA of a KNOXI homologue, MaKN1, during the early stages of development in the simple leaves of Myriophyllum aquaticum, an aquatic angiosperm from the family Haloragaceae exhibiting pentamerous whorls of finely lobed leaves. Methods A 300-bp KNOXI fragment was sequenced from M. aquaticum and used in an RNA localization study to determine the temporal and spatial expression of KNOXI during the early stages of leaf lobe development in M. aquaticum. The developmental sequence of leaves of M. aquaticum was also described using scanning electron microscopy. Key Results Lobe development of M. aquaticum occurs in two very distinct regions at the leaf base in an alternating fashion reminiscent of a distichous shoot system. It was discovered that MaKN1 expression is localized to both the shoot apical meristem and early stages of leaf primordia development (P1–P7). Initially, MaKN1 is expressed ubiquitously throughout primordia (P1–P3); however, as lobes develop, MaKN1 becomes localized to recently emerged lobe primordia, and disappears as lobes develop basipetally. Conclusions The pattern of gene expression is indicative of shared developmental processes during early development between shoots, compound leaves, highly lobed simple leaves and unifoliate simple leaves which lack KNOXI expression. These findings are supportive of Arber's less rigid ‘partial shoot’ theory, which conceptualizes compound leaves as having shoot-like elements. [ABSTRACT FROM PUBLISHER]

As a contribution to the continuing discussion of the ecological differentiation and stable coexistence of species, we investigated the extent to which the two sister species, Macroplea mutica and M. appendiculata, use the host plants Myriophyllum spicatum and Potamogeton sp. Specimens from four populations differing in host plant experience were used for behavioural observations. Both species did not feed on Myriophyllum but on Potamogeton. Beetles kept on Myriophyllum or without plant lost weight, while those on Potamogeton maintained or increased their weight. Only M. appendiculata laid eggs on this plant, as well as on Potamogeton, where M. mutica exclusively oviposited. In choice experiments, all larvae preferred the roots of Potamogeton over Myriophyllum for attachment (also the M. mutica larvae that had been collected from Myriophyllum). The data are discussed in the light of the unusual occasional occurrence of M. mutica on Myriophyllum and the speciation in the genus Macroplea. [ABSTRACT FROM AUTHOR]