Aquatic Plant Egeria Densa Research Articles

Red light mitigates Cd toxicity in Egeria densa by restricting Cd accumulation and modulating antioxidant defense system

Controlling light qualities have been acknowledged as an effective method to enhance the efficiency of phytoremediation, as light has a significant impact on plant growth. This study examined the effects of light qualities on cadmium (Cd) tolerance in aquatic plant Egeria densa using a combination of biochemical and transcriptomic approaches. The study revealed that E. densa exhibits higher resistance to Cd toxicity under red light (R) compared to blue light (B), as evidenced by a significant decrease in photosynthetic inhibition and damage to organelle ultrastructure. After Cd exposure, there was a significantly reduced Cd accumulation and enhanced levels of both glutathione reductase (GR) activity and glutathione (GSH), along with an increase in jasmonic acid (JA) in R-grown E. densa compared to B. Transcriptional analysis revealed that R caused an up-regulation of Cd transporter genes such as ABCG (G-type ATP-binding cassette transporter), ABCC (C-type ATP-binding cassette transporter), and CAX2 (Cation/H+ exchanger 2), while down-regulated the expression of HIPP26 (Heavy metal-associated isoprenylated plant protein 26), resulting in reduced Cd uptake and enhanced Cd exportation and sequestration into vacuoles. Moreover, the expression of genes involved in phytochromes and JA synthesis was up-regulated in Cd treated E. densa under R. In summary, the results suggest that R could limit Cd accumulation and improve antioxidant defense to mitigate Cd toxicity in E. densa, which might be attributed to the enhanced JA and phytochromes. This study provides a foundation for using light control methods with aquatic macrophytes to remediate heavy metal contamination in aquatic systems.

Impact Assessment of Flushing Flow from a Dam to Invasive Aquatic Plant Egeria densa in a Gravel-bed River

The implications of artificial water release, flushing flow, on the invasive aquatic plant Egeria densa in a gravel bed river, downstream of a dam, were investigated from the viewpoint of ecological characteristics, biomass change, open-channel hydraulics, and river engineering. To understand seasonal changes associated with Egeria densa, as well as the native species Hydrilla verticillata found within a reach, a series of surveys was conducted. A new method for assessing biomass flux during flushing flows is proposed. Our data indicated that Egeria densa biomass within the surveyed reach was reduced by approximately half following flushing flows conducted every March. Biomass flux was also evaluated using the proposed method. Our results imply that flushing flow supports native Hydrilla verticillata inhabitation within the downstream reach of a dam.

Impact of Mechanical Removal on the Regeneration and Colonization Abilities of the Alien Aquatic Macrophyte Egeria densa.

The development of aquatic plant beds can obstruct boat traffic, hinder the practice of water activities, and impact the functioning of freshwaters. In order to mitigate their effects, mechanical removal is often the preferred management solution. The objective of this study was to test, in mesocosms, the effect of frequency (none, one, and two cuts) and cutting dates (May and/or July) on the regeneration and colonization capabilities of the aquatic plant Egeria densa, an invasive alien species in France. The cutting date had no effect on the capabilities of E. densa, but the two cuts significantly reduced the plant's biomass. Removal produced numerous fragments, which exhibited very high survival and anchoring rates. However, summer removal produced fragments with lower regeneration and colonization abilities compared to fragments from spring cutting. Mechanical removal only temporarily reduced the biomass of the aquatic plant beds and could promote the formation of new beds from the fragments generated by management and dispersed by water flow.

Application of environmental DNA analysis for detecting potential sources of invasive aquatic plant Egeria densa in a riverine network

Application of environmental DNA analysis for detecting potential sources of invasive aquatic plant Egeria densa in a riverine network

Influence of Invasive Submerged Aquatic Vegetation (E. densa) on Currents and Sediment Transport in a Freshwater Tidal System

AbstractWe present a field study combining measurements of vegetation density, vegetative drag, and reduction of suspended‐sediment concentration (SSC) within patches of the invasive submerged aquatic plant Egeria densa. Our study was motivated by concern that sediment trapping by E. densa, which has proliferated in the Sacramento–San Joaquin Delta, is impacting marsh accretion and reducing turbidity. In the freshwater tidal Delta, E. densa occupies shallow regions frequently along channel margins. We investigated two sites: Lindsey Slough, a muddy low‐energy backwater, and the lower Mokelumne River, with stronger currents and sandy bed sediments. At the two sites, biomass density, frontal area, and areal density of the submerged aquatic vegetation (SAV) were similar. Current attenuation within E. densa exceeded 90% and the vegetative drag coefficient followed , where is stem Reynolds number. The SAV reduced SSC by an average of 18% in Lindsey Slough. At the Mokelumne River the reduction ranged 0%–40%, with greatest trapping when discharge and SSC were elevated. This depletion of SSC decreases the transport of sediment to marshes by the same percentage, as the rising tide must pass through fringing SAV before reaching marshes. Sediment trapping in E. densa in the Delta is limited by low flux through the canopy and low settling velocity of suspended sediment (mostly flocculated mud). Sediment trapping by SAV has the potential to reduce channel SSC, but the magnitude and sign of the effect can vary with local factors including vegetative coverage and the depositional or erosional nature of the setting.

Application of environmental DNA methods for the detection and abundance estimation of invasive aquatic plant Egeria densa in lotic habitats

Estimating the presence and abundance of non-native species in the early stage of invasion is important to prevent further spread of non-native species in aquatic systems. Environmental DNA (eDNA) methods have been applied for aquatic plants; however, it is still questionable on the accuracy of the eDNA methods for the detection and abundance estimation of aquatic plants in lotic systems. Here, we studied the invasive aquatic plant Egeria densa in the tributaries of the Gonokawa River in Japan to compare the E. densa detection rate of the eDNA method with that of the three sampling methods and examine the relationships of the eDNA flux to the upstream plant coverage, plant stem fragment flux, and plant tissue DNA flux of E. densa in the study sites on each season. Our results indicated that the eDNA method better detected the presence of E. densa in our study sites than other methods. The eDNA flux was directly related to the coverage rank and the plant tissue DNA flux in the study sites in both months. These results suggest that the eDNA methods have a potential as monitoring tool for early detection and relative abundance estimation of invasive aquatic plants in lotic systems.

Recovery of black-necked swans, macrophytes and water quality in a Ramsar wetland of southern Chile: Assessing resilience following sudden anthropogenic disturbances

In 2004 migration and mortality for unknown reasons of the herbivorous Black necked swan (Cygnus melancorhyphus (Molina, 1782)) occurred within the Río Cruces wetland (southern Chile), a Ramsar Site and nature sanctuary. Before 2004, this wetland hosted the largest breeding population of this water bird in the Neotropic Realm. The concurrent decrease in the spatial occurrence of the aquatic plant Egeria densa Planch. 1849 - the main food source of swans - was proposed as a cause for swan migration and mortality. Additionally, post-mortem analyses carried out on swans during 2004 showed diminished body weight, high iron loads and histopathological abnormalities in their livers, suggesting iron storage disease. Various hypotheses were postulated to describe those changes; the most plausible related to variations in water quality after a pulp mill located upstream the wetland started to operate in February 2004. Those changes cascaded throughout the stands of E. densa whose remnants had high iron contents in their tissues. Here we present results of a long-term monitoring program of the wetland components, which show that swan population abundance, body weights and histological liver conditions recovered to pre-disturbance levels in 2012. The recovery of E. densa and iron content in plants throughout the wetland, also returned to pre-disturbance levels in the same 8-year time period. These results show the temporal scale over which resilience and natural restoring processes occur in wetland ecosystems of temperate regions such as southern Chile.

Particle bombardment and subcellular protein localization analysis in the aquatic plant Egeria densa.

Particle bombardment is a powerful and relatively easy method for transient expression of genes of interest in plant cells, especially those that are recalcitrant to other transformation methods. This method has facilitated numerous analyses of subcellular localization of fluorescent fusion protein constructs. Particle bombardment delivers genes to the first layer of plant tissue. In leaves of higher plants, epidermal cells are the first cell layer. Many studies have used the epidermal cell layer of onion bulb (Allium cepa) as the experimental tissue, because these cells are relatively large. However, onion epidermal cells lack developed plastids (i.e., chloroplasts), thereby precluding subcellular localization analysis of chloroplastic proteins. In this study, we developed a protocol for particle bombardment of the aquatic plant Egeria densa, and showed that it is a useful system for subcellular localization analysis of higher plant proteins. E. densa leaflets contain only two cell layers, and cells in the adaxial layer are sufficiently large for observation. The cells in both layers contain well-developed chloroplasts. We fused fluorescent proteins to conventional plant localization signals for the nucleus, cytosol, mitochondria, peroxisome, and chloroplast, and used particle bombardment to transiently express these fusion constructs in E. densa leaves. The plant subcellular localization signals functioned normally and displayed the expected distributions in transiently transformed E. densa cells, and even chloroplastic structures could be clearly visualized.

Physical Controls on the Distribution of the Submersed Aquatic Weed Egeria densa in the Sacramento-San Joaquin Delta, California and Implications for Habitat Restoration

The invasive aquatic plant Egeria densa (Brazilian waterweed) is a submersed aquatic plant that has expanded its distribution in both its native and introduced range. Because the plant grows so densely, it can become a problem for management of waterways and habitat restoration projects. It is difficult to remove once established and mechanical and chemical controls have shown limited effectiveness. Here we analyze the distribution of E. densa in the Sacramento–San Joaquin Delta (the Delta) of California, USA, using environmental variables that include mean water velocity, mean water turbidity, and water column depth. We found that increasing water column depth strongly limited E. densa occurrence, especially when depth at mean lower low water (MLLW) exceeds 2 m. The highest probability of occurrence occurred at locations with a water column depth of −1 to 2 m at MLLW. Turbidity had a reliably negative effect on E. densa occurrence; as water clarity has increased in the Delta, it has likely favored the spread of the plant. Neither mean water velocity nor maximum water velocity had a reliable effect on E. densa probability, in spite of scientific and observational evidence that it is sensitive to flows. These results suggest potentially serious problems with restoration projects that emphasize shallow water habitat in the range favored by E. densa. Without some way to manage spread of the plant—through spraying, sediment loading, or gating—channels in such projects are at risk of being taken over by E. densa. However, these results should be interpreted in light of the fact that water outflow in water year 2008 was very low, and that E. densa abundance may be partially controlled by higher water flows than those considered here.

Organ-level analysis of idioblast patterning in Egeria densa Planch. leaves.

Leaf tissues of plants usually contain several types of idioblasts, defined as specialized cells whose shape and contents differ from the surrounding homogeneous cells. The spatial patterning of idioblasts, particularly of trichomes and guard cells, across the leaf epidermis has received considerable attention as it offers a useful biological model for studying the intercellular regulation of cell fate and patterning. Excretory idioblasts in the leaves of the aquatic monocotyledonous plant Egeria densa produced light blue autofluorescence when irradiated with ultraviolet light. The use of epifluorescence microscopy to detect this autofluorescence provided a simple and convenient method for detecting excretory idioblasts and allowed tracking of those cells across the leaf surfaces, enabling quantitative measurement of the clustering and spacing patterns of idioblasts at the whole leaf level. Occurrence of idioblasts was coordinated along the proximal–distal, medial–lateral, and adaxial–abaxial axes, producing a recognizable consensus spatial pattern of idioblast formation among fully expanded leaves. Idioblast clusters, which comprised up to nine cells aligned along the proximal–distal axis, showed no positional bias or regularity in idioblast-forming areas when compared with singlet idioblasts. Up to 75% of idioblasts existed as clusters on every leaf side examined. The idioblast-forming areas varied between leaves, implying phenotypic plasticity. Furthermore, in young expanding leaves, autofluorescence was occasionally detected in a single giant vesicle or else in one or more small vesicles, which eventually grew to occupy a large portion of the idioblast volume as a central vacuole. Differentiation of vacuoles by accumulating the fluorescence substance might be an integral part of idioblast differentiation. Red autofluorescence from chloroplasts was not detected in idioblasts of young expanding leaves, suggesting idioblast differentiation involves an arrest in chloroplast development at a very early stage, rather than transdifferentiation of chloroplast-containing epidermal cells.

In vivo time‐resolved X‐ray fluorescence mapping measurements of Egeria densa immersed in Cr(VI) aqueous solution

In vivo time‐resolved Cr and Ca X‐ray fluorescence (XRF) mapping measurements were performed in a laboratory over a period of 69 days on a living common aquatic plant Egeria densa that was immersed in 5 mM K2CrO4 aqueous solution. The time and spatial resolution for each time‐resolved XRF map were ~1.6 days and 1 × 1 mm2, respectively. The obtained XRF maps exhibited characteristic localized Cr and Ca areas where the XRF signals were especially strong (‘hot spots’), and this indicated the necessity of preliminary millimeter‐resolution surveying in XRF microscopy. Ca hot spots were detected prior to Cr(VI) immersion and nearly disappeared after immersion in deionized water for 2 weeks and the Cr(VI) solution for 1 week. After these immersions, a Cr hot spot was formed at approximately the same location of the missing Ca hot spot, which suggests that the original Ca‐accumulated regions were substituted for the isolation of Cr species when they were introduced. The sizes and intensity distributions of the Cr hot spots were sensitive to the Cr(VI) exposure approximately 1 week prior to each XRF measurement. This sensitivity suggests potential applications of E. densa as a Cr(VI) biomonitor in aquatic environments. Copyright © 2014 John Wiley & Sons, Ltd.

Regulatory effect of stems on sucrose-induced chlorophyll degradation and anthocyanin synthesis in Egeria densa leaves

Detached green leaves of the aquatic plant Egeria densa showed chlorophyll degradation and turned red due to induced anthocyanin synthesis incubated in 0.1M sucrose under continuous light for 7-10days. If the leaves were placed in water, only chlorophyll degradation occurred and the detached leaves turned yellow. The levels of endogenous total carbohydrates increased in detached leaves cultured in the sucrose solution but only increased marginally in water. If the leaves were still attached to a piece of stem, with a node on either side of the single leaf whorl, then they did not accumulate anthocyanin in culture with 0.1M sucrose. These leaves showed a similar increase in total carbohydrates and degradation of chlorophyll as detached leaves. Attached leaves, in which the midrib had been cut in situ, showed localized accumulation of anthocyanin in the leaf tissue distal to the cut in the midrib when cultured in 0.1M sucrose. These results suggest that the stem plays a regulatory role in anthocyanin synthesis in attached leaves cultured in a sucrose solution but does not influence chlorophyll degradation or carbohydrate accumulation.

EFFECT OF PROLONGED EXPOSITION TO PULP MILL EFFLUENTS ON THE INVASIVE AQUATIC PLANT EGERIA DENSA AND OTHER PRIMARY PRODUCERS: A MESOCOSM APPROACH

The recent disappearance of the aquatic plant Egeria densa, a Brazilian native invasive species, from a wetland in southern Chile prompted several efforts to unveil the origin of this phenomenon. Because these changes occurred by the time a newly built pulp mill started its operations in the area, a reasonable doubt for a cause-effect relationship is plausible. We implemented a mesocosm approach to directly evaluate the effect of treated pulp mill effluents (PMEs) on several growth-related parameters of E. densa as well as other primary producers. We hypothesize that effluent, at a dilution similar to that detected in the zone of the wetland where the negative environmental impacts were evident, has a significant negative effect on this aquatic plant as well as on other primary producers inside a mesocosm system. After a prolonged (months) exposure to both 0% PME with pure river water and a 4 to 5% (v/v) dilution of treated PME, no effect on E. densa was measured. Furthermore, plants exposed to effluent exhibited a significantly greater general growth rate. Coincidently, chlorophyll a concentration in the water column and periphyton biomass also changed over time, but without any pattern attributable to the effluent. Values of the autotrophic index obtained from the periphyton growth pattern did not suggest enrichment of the system with organic matter. Our results only refer to the direct effect of mill effluents on several biotic responses, but they represent an important advance toward generation of the scientific knowledge necessary to understand how the ecosystem functions while receiving this and other unquantified sources of water.

Causes of the disappearance of the aquatic plant Egeria densa and black-necked swans in a Ramsar sanctuary: comment on Mulsow & Grandjean (2006)

Causes of the disappearance of the aquatic plant Egeria densa and black-necked swans in a Ramsar sanctuary: comment on Mulsow & Grandjean (2006)

Effect of Prolonged Exposition to Pulp Mill Effluents on the Invasive Aquatic Plant Egeria Densa and Other Primary Producers: A Mesocosm Approach

Effect of Prolonged Exposition to Pulp Mill Effluents on the Invasive Aquatic Plant Egeria Densa and Other Primary Producers: A Mesocosm Approach

Concentraciones de elementos minerales en Egeria densa Planch. Colectada en el santuario de la naturaleza Carlos Anwandter, Valdivia, Chile

A preliminary study of the accumulation of mineral elements was carried out on the aquatic plant Egeria densa Planch., collected from the Carlos Andwandter Sanctuary, as a potential cause of the decrease in plant population observed over the last two years. Plants with and without visible damage were collected from different areas of the Sanctuary. The results showed that iron concentration is abnormally high in all plants and it is particularly high in plants with visible tissue damage. Iron concentrations in damaged plants was on average 40090 mg kg-1 while plants with little or no tissue damage had average values of 13251 mg kg-, which were 17.1 times higher than the average values reported for plants growing in their native areas. It is concluded that the high concentrations of iron could be the cause of the population decrease of Egeria densa observed over the last two years.

The Membrane Potential as Indicator for Transport and Energetic Processes of Leaf Cells of the Aquatic Plant Egeria densa: IV. Reactions with synthetic redox substances

Summary The effect of 3 redox substances on the membrane potential, membrane integrity and proton extrusion of illuminated leaf cells of Egeria densa has been investigated. The herbicide, O,O-di-n-butyl-(1-n-butylamino-cyclohexyl)-phosphonate (PABT, 0.29 mol m-3), depolarizes the plasma membrane and inhibits the proton pumping in the initial phase followed by electrolyte leakage from the cells after about 90 min. For the formulation of PABT, nonylphenol-poly-oxyethylene adducts (EO) are used as nonionic surfactants. EO prove to be non-penetrating exogenous electron acceptors, causing membrane depolarization and a stimulation of H+-extrusion as is the case with ferricyanide. Concentrations up to two orders of magnitude above the cmc of the EO do not significantly disturb the membrane integrity in Egeria leaf cells. 1,4-Naphthoquinone (NQ), a general lipophilic electron acceptor, is used to modify plasmalemma electron transport. After accepting one electron, the resulting semiquinone radicals cause membrane disruption. NQ (0.1 mol m-3) depolarizes the membrane, inhibits the H+-extrusion, and leads to membrane disruption. Subtoxic concentrations (10-2 mol m-3) of NQ cancel the effects of PABT. Non-penetrating electron acceptors (EO, ferricyanide), however, do not impair PABT action. The effects of EO, PABT, and NQ are prevented by fusicoccin (FC, 10-3 mol m-3). A plasmalemma redox system in Egeria is considered to be the common site of action of EO, PABT, and NQ.

The Membrane Potential as Indicator for Transport and Energetic Processes of Leaf Cells of the Aquatic Plant Egeria densa: III. Evidence for Electron Transport through the Plasmalemma

Summary Plasmalemma redox reactions are investigated by microelectrode technique and by means of redoxactive compounds using leaves of E. densa. Ferricyanide (0. 33 mol m−3) is extracellularly reduced by leaves in the light (ca.9 μmol gFW−1 h−1) as well as in darkness (ca.5. 3 μmol gFW−1 h−1) . Its reduction is accompanied by a depolarization of the plasmalemma. Both effects together are a strong argument for trans -plasmalemma electron transport. The hydrophilic ferrocyanide and oxidized or reduced pyridine nucleotides did not show significant effects on the electric cell potential; on the contrary, the lipophilic electron acceptor, menadione, also depolarizes the plasmalemma. The question is discussed to what extent electron transport at the plasmalemma is involved in electrogenesis of plants.

Electrophysiological evidence for the herbicidal mode of action of phosphonic acid esters

The electrical membrane potential of leaf cells of the higher aquatic plant Egeria densa Planchon, measured with microelectrodes, was immediately depolarized after treatment with 0.29 mM of the dialkyl phosphonic ester, O, O‐di‐n‐butyl‐(1‐n‐butylamino‐cyclohexyl)‐phosphonate (PABT). This depolarization was followed by a strong electrolyte efflux after ca 90 min. Active photosynthesis or respiration as well as an intact plasma membrane was essential for this effect. An increased concentration of thiobarbituric acid (TBA)‐reactive agents observed within this period suggests that membrane destruction by lipid peroxidation was responsible for the electrolyte efflux. Antioxidants such as α‐tocopherol (0.25 mM) and ascorbic acid (1 mM) stopped electrolyte efflux, but did not affect the depolarization.Fusicoccin (1 μM) prevented PABT‐induced membrane depolarization and the subsequent electrolyte efflux. Also, the ATPase inhibitor, DES (50 üM), as well as substances which stimulate the proton pump such as sucrose (30 mM), AIB (10 μM), and acetate (1 mM), prevented PABT‐mediated electrolyte efflux. The depolarizing effect of PABT was also obviated above pH 7.5. Thus, if the PABT‐induced depolarization was inhibited no membrane destruction occurred whereas depolarization alone was not a sufficient condition for the development of the PABT action. The initial depolarizing effect of PABT cannot be explained by a physical interaction with the lipid part of the plasma membrane. Thus, a metabolism‐driven mode of action connected to plasma membrane energization has to be assumed.

The Membrane Potential as Indicator for Transport and Energetic Processes of Leaf Cells of the Aquatic Plant Egeria densa: II. The Effect of the Specific Energy Transfer Inhibitor Tentoxin and its Derivative Dihydrotentoxin

Summary The effect of tentoxin, an energy transfer inhibitor produced by the phytopathogenic fungus Alternaria alternata, and of its natural derivative, dihydrotentoxin, on the membrane potential of leaf cells of the fresh-water plant Egeria densa was investigated. Tentoxin reversibly depolarizes the membrane potential in the light down to its dark level after a lag-phase of some 10 min. A second application of the phytotoxin shortens this lag-phase considerably. Dihydrotentoxin also depolarizes the membrane potential, but less effectively. In the dark, no influence on the PD of both substances could be observed. Fusicoccin repolarizes the membrane in the presence of tentoxin or dihydrotentoxin or, when first added, suppresses the toxin-induced response. Tentoxin as well as d1hydrotentoxin lower the ATP content of Egeria leaves significantly. The tentoxin action on the cell potential is discussed as a result of inhibition of photophosphorylation.