Arbuscular mycorrhizal fungi effect growth and photosynthesis of Phragmites australis (Cav.) Trin ex. Steudel under copper stress

• Arbuscular mycorrhizal fungi (AMF) is an effective way to remove heavy metals’ inhibition on plants, however, few relevant research attempts have been made to determine the contribution of AMF to the physiological and biochemical changes related to the enhanced copper tolerance of Phragmites australis under metal‐stressed conditions.
• In this study, the effects of AMF inoculation on P. australis under different concentrations of copper stress were investigated according to the changes in the parameters related to growth and development, and photosynthetic charateristics. Then, differentially expressed proteins (DEPs) were evaluated by the Isobaric Tag for Relative and Absolute Quantification (iTRAQ) system, which could accurately quantify the DEPs by measuring peak intensities of reporter ions in tandem mass spectrometry (MS/MS) spectra.
• It was found that AMF inoculation may relieve the photosynthesis inhibition caused by copper stress on P. australis and thus promote growth. Proteomic analysis results showed that under copper stress, the inoculation of R. irregularis resulted in a total of 459 differently‐expressed proteins (200 up‐regulated and 259 down‐regulated) in root buds. In addition, the photosynthetic changes caused by AMF inoculation mainly involve the up‐regulated expression of transmembrane protein–pigment complexes CP43 (photosystem II) and FNR (ferredoxin‐NADP+ oxidoreductase related to photosynthetic electron transport).
• These results indicate that AMF could effectively improve the growth and physiological activity of P. australis under copper stress, and thus provides a new direction and instructive evidence for determining the mechanisms by which AMF inoculation enhances the copper tolerance of plants.

     

The Use of DNA Fingerprinting in Ecological Studies of Phragmites australis (Cav.) Trin. ex Steudel

A number of reed populations (Phragmites australis) from natural locations on the shore of Lake Ammersee in the south of Bavaria as well as artificially grown reed plants were analyzed for restriction fragment length polymorphisms (RFLPs) in order to evaluate for further ecological studies the dynamics of the restriction pattern within the genome of plants which propagate themselves asexually. The artificially grown reed plants were raised in four ponds supplemented with different phosphate concentrations (8 μg, 16 μg, 50 μg, and 200 μg/l) from rhizomes taken from a neighbouring fish pond. The genomic DNA of 25 of these plants and the DNA from 37 plants out of 18 stands from the lakeshore was isolated and restricted with the enzyme EcoRI, EcoRV, XbaI and HindIII and hybridized to three probes from a shot-gun cloned reed plasmid library. The probes gave between 15 and 26 bands (DNA fingerprints) of high polymorphic frequency (68% ? 100%) after hybridization with repetitive sequences of restricted DNA. A cluster analysis based on the banding pattern as a measure of genetic similarity (GS) was performed with the two sets of reed plants. The plants from the lakeshore exhibited a clear formation of clusters with GS up to 100%; the 20 plants grown from rhizomes, in contrast, did not show any clear correlation among themselves, neither to the phosphate concentration they grew in, nor to the five plants tested from the pond their rhizomes came from. The value of genetical investigations of the plant genome in context with environmental impact on plants is being discussed.     

Nitrogen and carbohydrate pools of two rhizome types of Phragmites australis (Cav.) Trin. ex Steudel

Carbohydrate and total nitrogen contents as well as free amino acid (FAA) concentrations were determined in distinct types of rhizomes of two genetically homogeneous stands of reed (Phragmites australis (Cav.) Trin. ex Steudel) differing in morphology, productivity and nutrient supply in order to evaluate the storage capacity of vertical rhizomes and expansion rhizomes. The expansion rhizomes possess significantly higher amounts of FAA and of total nitrogen but similar carbohydrate concentrations in comparison to the vertical rhizomes. However, no significant differences were found for total nitrogen, FAA and total carbohydrates between both investigated stands indicating a comparable storage capacity of rhizomes independent of nutrient availability. Only the composition of the FAA pool varied in the alanine/asparagine ratio probably influenced by the oxygen supply of the rhizome/root system.     

Factors affecting iron plaque on the roots ofPhragmites australis (Cav.) Trin. ex Steudel

Phragmites australis (the common reed) was collected at six sites in southern Québec and Ontario, Canada, in order to study the accumulation of iron plaque on the roots. The deposition of iron oxides on roots ofP. australis did not correlate directly with soil measurements; however, the amounts of iron-bound-to-carbonates fraction of the soil/sediment, responsible for the iron plaque accumulation, correlated with the % of water, % of organic matter, % of clay and pH of the substrate. Plants located very near flowing water accumulated more iron plaque on the roots than plants in other habitats through the summer; it is hypothesized that carbonates associated with iron come from the flowing water. In wetlands or sites near flowing water, most root iron was found on the surface, as iron plaque, while there was more iron inside the root in dry environments. Radial oxygen loss from the roots is probably the most important source of oxygen for the oxidation of iron.     

Tissue culture and long-term regeneration of Phragmites australis (Cav.) Trin. ex Steud.

Phragmites australis tissue cultures were initiated from mature seeds on MS medium supplemented with 1 mgl^-1 each of 2,4-D and IAA. Cultures displayed typical embryogenic callus that was compact and bright yellow. Selection for embryogenic callus established long-term regenerable cultures. Removal of auxin from the basal medium allowed numerous complete plants to be recovered from the cultures. Histological study indicated both the presence of embryogenic-type cells and the bipolar development of regenerated plants.     

Some Aspects of the Importance of Genetic Diversity in Phragmites australis (Cav.) Trin. ex Steudel for the Development of Reed Stands

Various sites of Phragmites australis in Germany (Uckermark and Mark Brandenburg) and sites in Hungary and Denmark were investigated by PCR fingerprinting in order to determine their genetic diversity. Genetic similarities were calculated and, based on this, a cluster analysis was performed. The genetic similarity of reed clones around one lake ranged from between 70 to 100%, that of clones from different lakes was clearly lower. The further apart the clones were situated from each other, the less similar they were. At a wetland site near the shore a sudden colonisation by several new Phragmites clones was observed. This site was located in front of a well established genetically almost homogenous stand within the eulittoral. All the results are discussed in connection with a proposed model of establishment and development of water reed stands: colonization, selection of best adapted clones by competition and the stability of stands.     

The Effect of pH and Plaque on the Uptake of Cu and Mn in Phragmites australis(Cav.) Trin ex. Steudel

The physico-chemical properties of iron oxyhydroxide plaquesformed on the roots of Phragmites australis under field andlaboratory conditions were determined using electron microscopyand energy dispersive spectrometry (EDS) analysis. Plaques werepresent as an amorphous coating on roots with an uneven distribution.They were shown to be composed of iron in both the field andlaboratory, and phosphorus was found to be adsorbed onto thesurface of plaques formed in the laboratory. The uptake of copperand manganese in the presence and absence of plaque was investigatedunder two different pH regimes. Concentrations of Cu were lowerin the shoots of P. australis in the presence of plaque (565mg kg^-1) than when it was absent (1400 mg kg^-1), under growthconditions of higher pH (6.0). The adsorption of Cu and Mn ontothe plaque surface was not the mechanism by which plaque reducedthe uptake of other metals. Alternatively, the plaque may simplyact as a physical barrier. Under conditions of lower pH (3.5)the activity of hydrogen ions at the root surface interferedwith the movement of metals into the root and masked any potentialeffect of iron plaque. Copyright 2000 Annals of Botany Company Phragmites australis, iron oxyhydroxide plaque, pH, manganese, copper, EDS, SEM, wetlands     

The effect of sewage sludge flooding on growth and morphometric parameters of Phragmites australis (Cav.) Trin. ex Steudel

Phragmites australis is the most frequently used species in constructed wetlands (CW) for dewatering and mineralization of sludge. Such CW create a very hostile environment for plants because their roots are exposed to permanently anaerobic conditions. Our working hypothesis assumed a simple relationship between the success of reed in colonising sludge flood stands and maximalisation of shoot oxygen production and transport to rhizomes and roots. Morphometric parameters and density of common reed shoots growing in reed bed systems inundated with sewage sludge were investigated. It was proved that flooding with sewage sludge significantly influenced characteristics of common reed populations. In comparison with natural stands, on stands treated with sewage sludge, maximal density of shoots was higher, biomass was twice as high, shoot diameter was significantly greater, and leaf weight ratio of an individual shoot was also significantly higher. Tendency to shorten shoots was noted. Growing period was longer for reed shoots treated with sewage sludge than on natural stands.     

Interaction of cadmium with glutathione and photosynthesis in developing leaves and chloroplasts of Phragmites australis (Cav.) Trin. ex Steudel

We investigated how the presence of cadmium (Cd) at the emergence of Phragmites australis Trin. (Cav.) ex Steudel plants from rhizomes interacted with leaf and chloroplast physiological and biochemical processes. About 8.5 nmol Cd mg-1 chlorophyll was found in leaves, and 0.83 nmol Cd mg-1 chlorophyll was found in chloroplasts of plants treated with 50 microm Cd. As a result, a 30% loss of chlorophyll was measured concomitantly with a comparable percentage reduction in light-saturated photosynthesis. Rubisco content and activity were lowered by 10% and 60%, respectively. Antioxidant activity was stimulated by Cd treatment and was associated with an increase in the glutathione and pyridine pools, and with a larger pool of reduced glutathione. It is suggested that the glutathione pool and its predominance in the reduced state protected the activity of many key photosynthetic enzymes against the thiophilic binding of Cd. Chloroplast ultrastructure was not significantly altered with 50 microm treatment and the efficiency of photosystem II, measured as the fluorescence ratio Fv/Fm, remained high because F0 and Fm were proportionally decreased. In plants treated with 100 microm Cd, all effects were exacerbated, but Fv/Fm remained close to that of control leaves and the glutathione and pyridine nucleotides pools were lowered. The results suggest that glutathione exerted a direct important protective role on photosynthesis in the presence of Cd.     

Effects of external iron concentration upon seedling growth and uptake of Fe and phosphate by the common reed, Phragmites australis (Cav.) Trin ex. Steudel

The objectives of this study were to determine whether, and to what degree, the aqueous iron concentration in the growing medium affects the growth of, and Fe uptake by, Phragmites australis, and whether the presence of iron in the growing environment affects the uptake of the essential element phosphate. The wetland macrophyte P. australis was grown under laboratory conditions in nutrient solution (0.31 mg L(-1) phosphate) containing a range of iron concentrations (0-50 mg L(-1) Fe). A threshold of iron concentration (1 mg L(-1)) was found, above which growth of P. australis was significantly inhibited. No direct causal relationship between iron content in aerial tissues and growth inhibition was found, which strongly suggests that iron toxicity cannot explain these results. Phosphate concentrations in aerial tissues were consistently sufficient for growth and development (2-3 % d. wt) despite significant variation in concentration of phosphate associated with roots. External Fe concentration had a significant effect on the growth of P. australis and on both Fe and phosphate concentrations associated with roots. However, neither direct toxicity nor phosphate deficiency could explain the reduction in growth above 1 mg L(-1) external Fe concentration     

Desodification from calcareous saline sodic soil through phytoremediation with Phragmites australis (Cav.) Trin. ex Steud. and gypsum

The reclamation of saline sodic soils requires sodium removal and the phytoremediation is one of the proven low-cost, low-risk technologies for reclaiming such soils. However, the role of Phragmites australis in reclaiming saline sodic soils has not been evaluated extensively. The comparative reclaiming role of P. australis and gypsum was evaluated in a column experiment on a sandy clay saline sodic soil with EC_e 74.7 dS m^?1, sodium adsorption ratio (SAR) 63.2, Na⁺ 361 g kg^?1, and pH 8.46. The gypsum at 100% soil requirement, planting common reed (P. australis) alone, P. australis + gypsum at 50% soil gypsum requirements, and leaching (control without plant and gypsum) were four treatments applied. After 11 weeks of incubation, the results showed that all treatments including the control significantly reduced pH, EC, exchangeable Na⁺, and SAR from the initial values, the control being with least results. The gypsum and P. australis + gypsum were highly effective in salinity (EC_e) reduction, while sodicity (SAR) and Na⁺ reductions were significantly higher in P. australis + gypsum treatment. The reclamation efficiency in terms of Na⁺ (83.4%) and SAR (86.8%) reduction was the highest in P. australis + gypsum. It is concluded that phytoremediation is an effective tool to reclaim saline sodic soil.     

Plant regeneration from embryogenic cultures of Phragmites australis (Cav.) Trin. Ex Steud.

Embryogenic cultures of the common reed [Phragmites australis (Cav.) Trin. Ex. Steud.] were induced on Murashige and Skoog (1962)-based medium with 2% (w/v) sucrose, B5 vitamins and 4.5 μM 2,4-dichlorphenoxyacetic acid. Four independent culture lines, two initiated from stem nodes and two from roots, were established. These cultures underwent somatic embryogenesis. In one line of stem node origin, the somatic embryos germinated and developed into plants, following transfer of embryogenic cultures to Murashige and Skoog (1962)-based medium lacking growth regulators, with 108 ± 17 plants being recovered per 100 mg fresh weight of culture. In other lines, the somatic embryos developed roots, but not shoots. Shoot regeneration via somatic embryogenesis offers potential as anin vitro system for physiological studies, including assessments of the response of common reed to environmental pollutants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Zinc, Lead and Cadmium Tolerance, Uptake and Accumulation by the Common Reed,Phragmites australis(Cav.) Trin. ex Steudel

Zinc (Zn), lead (Pb) and cadmium (Cd) tolerance in populationsof seedlings ofPhragmites australisraised from seeds collectedfrom a mine site (Plombières, Belgium) contaminated withZn, Pb and Cd and three ‘clean’ sites (Felixstowe,UK; Wisbech, UK; and Mai Po, Hong Kong) were studied under glasshouseconditions. Small differences were found between the metal-contaminatedpopulation and the three ‘clean’ populations whenseedlings were grown in 1.0 µg  ml^-1Zn and 10.0 µgml^-1Pb treatment solutions. In general, however, different populationsof seedlings showed similar growth responses, metal uptake andindices of Zn, Pb and Cd tolerance when cultured in the samemetal-contaminated media for 89 d or in the same metal treatmentsolutions (ZnSO₄:1.0 and 4.0 µg ml^-1Zn; Pb(NO₃)₂: 10.0and 25.0 µg ml^-1Pb; CdSO₄: 0.5 and 1.0 µg ml^-1Cd)for 3 weeks. There was insufficient evidence to support thehypothesis that the metal-contaminated population has evolvedto a Zn-, Pb- or Cd-tolerant ecotype but the results indicatedsome differentiation between the populations with that fromHong Kong being the least productive under the experimentalconditions used. The implications of the findings on selectionof provenances for use in constructed wetlands for wastewatertreatment are discussed. Metal accumulation; heavy metal tolerance; Phragmites australis; population differentiation     

Invasive Phragmites australis management outcomes and native plant recovery are context dependent

The outcomes of invasive plant removal efforts are influenced by management decisions, but are also contingent on the uncontrolled spatial and temporal context of management areas. Phragmites australis is an aggressive invader that is intensively managed in wetlands across North America. Treatment options have been understudied, and the ecological contingencies of management outcomes are poorly understood. We implemented a 5‐year, multi‐site experiment to evaluate six Phragmites management treatments that varied timing (summer or fall) and types of herbicide (glyphosate or imazapyr) along with mowing, plus a nonherbicide solarization treatment. We evaluated treatments for their influence on Phragmites and native plant cover and Phragmites inflorescence production. We assessed plant community trajectories and outcomes in the context of environmental factors. The summer mow, fall glyphosate spray treatment resulted in low Phragmites cover, high inflorescence reduction, and provided the best conditions for native plant recruitment. However, returning plant communities did not resemble reference sites, which were dominated by ecologically important perennial graminoids. Native plant recovery following initial Phragmites treatments was likely limited by the dense litter that resulted from mowing. After 5 years, Phragmites mortality and native plant recovery were highly variable across sites as driven by hydrology. Plots with higher soil moisture had greater reduction in Phragmites cover and more robust recruitment of natives compared with low moisture plots. This moisture effect may limit management options in semiarid regions vulnerable to water scarcity. We demonstrate the importance of replicating invasive species management experiments across sites so the contingencies of successes and failures can be better understood.     

Slashing Phragmites (Phragmites australis) prior to planting does not promote native vegetation establishment

Phragmites or Common Reed (Phragmites australis) is a tall rhizomatous cosmopolitan grass. While native to Australia, it can be invasive in wetlands, forming dense monocultures and reducing their ecological integrity. We assessed the potential for the cutting of Phragmites reeds prior to planting to promote the establishment of indigenous shrubs that might ultimately outcompete Phragmites. We established ten 5 m × 5 m quadrats in an area dominated by Phragmites, brush‐cut the reeds to ground level in five of them and left five uncut as controls. Within each quadrat, we planted 20 plants (~40 cm tall) of each of five indigenous shrub species, unguarded (4 plants/m²). We surveyed the plants one month after planting and annually for the following four years for survival, height and browsing damage. Browsing damage to plants was common (>50%) and unaffected by cutting. After four years, overall plant survival rates were ~25% and mean plant heights for the five shrub species ranged between 120 and 174 cm. Cutting of Phragmites had no positive effect on plant survival or height. In fact, two Melaleuca species grew taller in the uncut quadrats. Cutting of Phragmites reed beds prior to planting is unlikely to promote the establishment of woody plantings. However, planting within established Phragmites with or without prior brush‐cutting is worthy of further trialling as a potential tool for reinstating native diversity at Phragmites‐dominated sites.     

Genetic and epigenetic changes during the invasion of a cosmopolitan species (Phragmites australis)

While many introduced invasive species can increase genetic diversity through multiple introductions and/or hybridization to colonize successfully in new environments, others with low genetic diversity have to persist by alternative mechanisms such as epigenetic variation. Given that Phragmites australis is a cosmopolitan reed growing in a wide range of habitats and its invasion history, especially in North America, has been relatively well studied, it provides an ideal system for studying the role and relationship of genetic and epigenetic variation in biological invasions. We used amplified fragment length polymorphism (AFLP) and methylation‐sensitive (MS) AFLP methods to evaluate genetic and epigenetic diversity and structure in groups of the common reed across its range in the world. Evidence from analysis of molecular variance (AMOVA) based on AFLP and MS‐AFLP data supported the previous conclusion that the invasive introduced populations of P. australis in North America were from European and Mediterranean regions. In the Gulf Coast region, the introduced group harbored a high level of genetic variation relative to originating group from its native location, and it showed epigenetic diversity equal to that of the native group, if not higher, while the introduced group held lower genetic diversity than the native. In the Great Lakes region, the native group displayed very low genetic and epigenetic variation, and the introduced one showed slightly lower genetic and epigenetic diversity than the original one. Unexpectedly, AMOVA and principal component analysis did not demonstrate any epigenetic convergence between native and introduced groups before genetic convergence. Our results suggested that intertwined changes in genetic and epigenetic variation were involved in the invasion success in North America. Although our study did not provide strong evidence proving the importance of epigenetic variation prior to genetic, it implied the similar role of stable epigenetic diversity to genetic diversity in the adaptation of P. australis to local environment.