Wetland Grass Research Articles

The Effects of Anthropogenic Stressors on Above- and Belowground Phytochemical Diversity of the Wetland Grass, Phragmites australis.

Coastal wetlands face threats from climate change-induced flooding and biological invasions. Plants respond to these stressors through changes in their phytochemical metabolome, but it is unclear whether stressors affecting one tissue compartment (e.g., leaves) create vulnerabilities in others (e.g., roots) or elicit similar responses across tissues. Additionally, responses to multiple simultaneous stressors remain poorly understood due to the focus on individual metabolites in past studies. This study aims to elucidate how the phytochemical metabolome of three Phragmites australis (Cav.) lineages, common in the Mississippi River Delta, responds to flooding and infestation by the non-native scale insect Nipponaclerda biwakoensis (Kuwana). Among these lineages, one is non-native and poses a threat to North American wetlands. Results indicate that metabolomic responses are highly specific, varying with lineage, tissue type, stressor type, and the presence of multiple stressors. Notably, the non-native lineage displayed high chemical evenness, while the other two showed stressor-dependent responses. The 10 most informative features identified by a machine learning model showed less than 1% overlap with known metabolites linked to water and herbivory stress, underscoring gaps in our understanding of plant responses to environmental stressors. Our metabolomic approach offers a valuable tool for identifying candidate plant genotypes for wetland restoration.

Effects of High Salinity and Water Stress on Wetland Grasses from the Spanish Mediterranean Coast.

The impacts of climate change are reaching unprecedented levels, heightening the risk of species loss and ecosystem service degradation. Wetlands, highly threatened ecosystems, serve vital ecological functions by capturing carbon, filtering water, and harbouring diverse wildlife. Coastal wetlands encounter many challenges, such as increased drought periods and escalating salinity levels, severely impacting plant biodiversity. Assessing how plants respond to various environmental stress factors is imperative for devising successful conservation strategies. In the present study, we examined three representative grass species found in various habitats within the Albufera Natural Park, close to the city of Valencia on the Spanish Mediterranean coast: Imperata cylindrica, Phragmites australis, and Saccharum ravennae. High salinity and water stress conditions were induced by subjecting the plants to irrigation with solutions containing 200, 400, 600, and 800 mM NaCl or withholding irrigation altogether to mimic coastal flooding and drought scenarios. The treatments were maintained until noticeable wilting of the plants occurred, at which point a range of stress biomarkers were determined, including photosynthetic pigments, ions, osmolytes, oxidative stress markers, and antioxidant metabolites, as well as antioxidant enzyme activities. Saccharum ravennae displayed the highest sensitivity to salt stress, whereas I. cylindrica appeared to be the most tolerant. The primary salinity tolerance mechanism observed in I. cylindrica and P. australis was a blockage of ion transport from the root zone to the aerial part, together with the salt-induced accumulation of proline and soluble sugars to high concentrations in the former. No significant effects of the water deficit treatment on the growth or biochemical parameters were observed for any of the analysed species. These findings offer valuable information for the effective management and conservation of coastal wetlands facing the challenges posed by climate change.

Analysis of nutrient loads, heavy metals and physicochemical properties of wastewater, wetland grass, and papaya samples: Gondar Malt factory, Ethiopia with global implication

Robust attention was brought to researchers due to deterioration of wastewater quality of lakes and reservoirs as major global concerns by industrial release. The uncontrolled releases of effluents impose serious impacts for both aquatic and terrestrial environments. In the current study, many parameters like nutrient loads, heavy metals and physicochemical properties of wastewater, wetland grass, and papaya samples were analysed. The investigated nutrients, alkalinity, and total hardness in fresh water samples were within the allowable limits except for phosphate in fresh wastewater and alkalinity in wastewater. The detected levels of heavy metals (mg/L) in wastewater samples were:- Cd (0.386–0.905), Cr (ND-0.074), Cu (0.064–0.096), Mn (0.184–1.528), Fe (0.167–4.636), Zn (0.175–0.333), and Pb (0.044–0.892) (mg/L). The studied metals in the wastewater sample, except Cd, Fe, and Pb were lower than the allowable limit. The level of heavy metals in the grass and papaya samples ranged from Cd (37.14–147.62), Cr (ND-8.82), Cu (3.14–8.33), Mn (2.89–85.46), Fe(5.0–65.15), Zn (3.44–36.84), and Pb (ND-60.36) (mg/kg). The detected metals were below the permissible limits, except Cd, Cr, and Pb. The findings of the physicochemical characteristics in wastewater samples were computed: pH (6.61–8.54), temperatures (21.63–26.57 °C), TDS (205.9–1896 mg/L), EC (359.9–3226.67 μs/cm), BOD (12.0–732.67 mg/L), COD (3.67–1691.33 mg/L). Except for temperature and pH, all levels in the wastewater were above the recommended limit for wastewater discharge by USEPA.

Phenotypic plasticity variations in Phragmites australis under different plant–plant interactions influenced by salinity

Abstract Coastal wetland ecosystems are increasingly threatened by escalating salinity levels, subjecting plants to salinity stress coupled with interactions in the community. Abiotic factors can disrupt the balance between competition and facilitation among plant species. Investigating the effects of different neighboring species and trait plasticity could extend the stress gradient hypothesis and enhance understanding of vegetation distribution and diversity in salt marshes. We conducted a greenhouse experiment and investigated the plastic response of wetland grass Phragmites australis to seven neighboring plants of three functional types (conspecifics, graminoids and forbs) under soil salinity (0 and 10 g/L). Plant height, base diameter, density, leaf thickness, specific leaf area and total and part biomasses were measured. Additionally, the relative interaction index (based on biomass) and the relative distance plasticity index (RDPI) were calculated. Salinity significantly reduced the biomass, height, density and diameter of P. australis. The functional types of neighboring plants also significantly affected these growth parameters. The influence of graminoids on P. australis was negative under 0 g/L, but this negative effect shifted to positive facilitation under 10 g/L. The facilitation effect of forbs was amplified under salinity, both supporting the stress gradient hypothesis. The growth traits of P. australis had a plastic response to salinity and competition, such as increasing belowground biomass to obtain more water and resources. The RDPI was higher under salt conditions than in competitive conditions. The plant–plant interaction response to stress varies with plant functional types and trait plasticity.

An evaluation of the wetland grass flora of Mizoram, India

Mizoram, a diminutive state in northeastern India forms a major segment of the Indo-Burma biodiversity hotspots. The wetland grasses in the ecosystem are elements adapted in assorted habitat as one of the primary producers. This present assessment is principally focused to augment and evaluate information on the current status of the aquatic and semi-aquatic grasses from the taxonomic and ecological perspectives from this ecoregion. The paper encompasses the present taxonomic account of the wetland grasses with recent citations, protologue, type, basionym, phenology, growth forms, field status, worldwide distribution and specimens examined. The present investigation revealed the occurrence and distribution of 16 genera including 23 species of wetland grasses from this state. This kind of study always sets the ground for launching in-depth ecological projects for working out the present ecological characteristics and status of the wetlands and their restoration and conservation.

Evaluation of Phragmites australis for Environmental Sustainability in Bahrain: Photosynthesis Pigments, Cd, Pb, Cu, and Zn Content Grown in Urban Wastes

Modern urban societies generate tremendous amounts of hazardous wastes, including toxic organics and metals. Toxic metals harm plants and pose a risk to human health; examples of them are copper (Cu), zinc (Zn), palladium (Pb), and cadmium (Cd). Wetland plants are excellent for the ecological restoration of toxic metal-affected environments. Phragmites australis (common reed) belongs to the family Poaceae and is a broadly distributed wetland grass that is native to Bahrain, Europe, and America. P. australis shows a high content of chlorophyll. This study aimed to assess percentages of water, chlorophyll, and toxic metal content using acetone extraction; the calculation of the concentrations was performed according to the equations proposed by Lichtenthaler and the percentage of water content was calculated. After the metal exposure, the reed plants were digested, and their total mineral analysis was accomplished by atomic absorption spectroscopy; statistical analysis was conducted by Statistical Package for the Social Sciences (SPSS) version 21. The results revealed that the immature stage showed the highest chlorophyll a (mean 1641.5 (µg/g)) carotenoids (mean 359.75 (µg/g)) and total chlorophyll (mean 2183.93 (µg/g)), and the mature flowering stem had the highest chlorophyll b (mean 676.45 (µg/g)). The mature flowering stem stage showed the highest Pb (mg/L) and Cd (mg/L) values; on the other hand, Cu was the highest in the fully elongated non-flowering stage (0.108 mg/L), and the highest Zn content was found in the immature stage (mean 2.083). Owing to its growth in contaminated environments, P. australis can be considered a potential source of phytonutrients; higher concentrations were mostly available in the immature and mature flowering stages, with a favorable immature stage. The use of such marginal wetland plants may be very useful in reducing the pollution burden of urban built environments. These plants offer a green and sustainable solution for the disposal of waste from urban areas. Hence, further planning and execution of such a green solution are pivotal for creating environmental sustainability.

Metabolomic Evenness Underlies Intraspecific Differences Among Lineages of a Wetland Grass.

The metabolome represents an important functional trait likely important to plant invasion success, but we have a limited understanding of whether the entire metabolome or targeted groups of compounds confer an advantage to invasive as compared to native taxa. We conducted a lipidomic and metabolomic analysis of the cosmopolitan wetland grass Phragmites australis. We classified features into metabolic pathways, subclasses, and classes. Subsequently, we used Random Forests to identify informative features to differentiate five phylogeographic and ecologically distinct lineages: European native, North American invasive, North American native, Gulf, and Delta. We found that lineages had unique phytochemical fingerprints, although there was overlap between the North American invasive and North American native lineages. Furthermore, we found that divergence in phytochemical diversity was driven by compound evenness rather than metabolite richness. Interestingly, the North American invasive lineage had greater chemical evenness than the Delta and Gulf lineages but lower evenness than the North American native lineage. Our results suggest that metabolomic evenness may represent a critical functional trait within a plant species. Its role in invasion success, resistance to herbivory, and large-scale die-off events common to this and other plant species remain to be investigated.

Causal impact of fire on a globally rare wetland plant: a 40-year Bayesian time series analysis

BackgroundCanby’s dropwort (Oxypolis canbyi (J.M. Coult. & Rose) Fernald) was listed as federally endangered in 1986, yet the species has continued to decline and is no longer found in 11 counties throughout its former range. The seasonal wetlands in which this forb occurs are disappearing from the landscape, often closing in and transitioning to wet forest or are drained and converted to agriculture. We document the effects of reintroducing fire to the only population of O. canbyi in Maryland and examine the resulting population increase using Bayesian interrupted time series analysis with a counterfactual.ResultsAfter cutting woody vegetation, 3.74 times more stems of dropwort per year were produced over the baseline of no intervention. Subsequently, after fire was reintroduced, 10.80 times more dropwort stems per year were produced in comparison to the time period after cutting woody vegetation. The counterfactual prediction showed that in the absence of intervention with fire, dropwort stem production would likely have declined.ConclusionsCutting woody vegetation set the stage for the growth of fine fuels by increasing sun exposure on wetland grasses. It was only after fire was reintroduced that the population of plants expanded significantly in extent and flower production. A process for model selection with a directed acyclic graph followed by Bayesian interrupted time series analysis and a counterfactual was useful for causal inference. Application of fire is an important step in the recovery of the federally endangered dropwort.

First records of Calamagrostis purpurea (Poaceae) in the Carpathians, a relict species new to the flora of Slovakia, Ukraine, and Romania

The first records of Calamagrostis purpurea, an apomictic wetland grass species with a Euro-Siberian, predominantly boreal distribution, are reported for the Carpathians. This significantly expands the species’ range in Central Europe eastwards from the known localities in Austria and Czechia. Due to in situ finds and revision of the herbarium vouchers, C. purpurea was discovered in the Western Carpathians in Slovakia (the Nízke Tatry Mts) as well as in the Eastern Carpathians in Ukraine (the Chornohora Mts) and Romania (Dorna Depression, the Harghita, Bodoc Mts, Intorsura Buzaului Depression) at 6 sites in total. All these newly found localities are situated within 870–1570 m a.s.l. The locality in the Nízke Tatry Mts is at the highest elevation, while those in the Romanian Carpathians are the southeasternmost in Central Europe. In the Carpathians, C. purpurea is confined to undisturbed wetland habitats, which implies its relict origin in the region. A distribution map, habitat characteristics, morphological description, and images of the plants from the Carpatians are provided. Carpathian populations tested with flow cytometry are DNA-octoploid (the predominant ploidy level of the species in Europe). Because of the species’ rarity and vulnerability, it is suggested to include C. purpurea in the next editions of the Red Data Books and/or Red Lists of the corresponding countries.

Simultaneous carbon dioxide reduction and methane generation in biogas for rural household use via anaerobic digestion of wetland grass with cow dung

In the present study, wetland grass (common reed) and cow manure were used as substrates for biogas production during 45-days hydraulic retention reaction. The fermenter has a total volume of 200 L and a working volume of 150 L. Following biogas generation, methane enhancement processes were combined with a chemical process. The solvents including H2O, NaOH, and Ca(OH)2 were taken in two consecutive columns for 3 h, and variation of components was measured after every 15 min. The results showed 2,254 L of biogas as 343.08 ml CH4g-1VSremoved of yields, with concomitant removal of H2S by H2O, NaOH, and Ca(OH)2 absorbers. The total removal of H2S using H2O, NaOH, and Ca(OH)2 was observed to be were 55.56, 98.89, and 98.75 %, respectively. A total enhancement of methane production using NaOH and Ca(OH)2 was observed to be 88.04 and 85.9%, respectively. As a result, H2S and CO2 emissions are significantly decreased, while low-cost chemical treatments improve bio-methane generation. This study also highlights the environmental implications of co-digesting wetland grass with cow dung, and the findings indicated that the strategy is highly effective in increasing biogas production and methane contents.

Using rapid repeat SAR interferometry to improve hydrodynamic models of flood propagation in coastal wetlands

The propagation of tides and riverine floodwater in coastal wetlands is controlled by subtle topographic differences and a thick vegetation canopy. High-resolution numerical models have been used in recent years to simulate fluxes across wetlands. However, these models are based on sparse field data that can lead to unreliable results. Here, we utilize high spatial-resolution, rapid repeat interferometric data from the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) to provide a synoptic measurement of sub-canopy water-level change resulting from tide propagation into wetlands. These data are used to constrain crucial model parameters and improve the performance and realism of simulations of the Wax Lake wetlands in coastal Louisiana (USA). A sensitivity analysis shows that the boundary condition of river discharge should be calibrated first, followed by iterative correction of terrain elevation specified originally by a Digital Terrain Model derived from LiDAR measurements. The calibration of bed friction becomes important only with the boundary and topography calibrated. With the model parameters calibrated, the overall Nash-Sutcliffe model efficiency for water-level change increases from 0.15 to 0.53 with the RMSE reduced by 26%. In areas with dense wetland grasses, the LiDAR signal is unable to reach the soil surface, but the L-band UAVSAR instrument detects changes in water levels that can be used to infer the true ground elevation. The high spatial resolution and repeat-acquisition frequency (minutes to hours) observations provided by UAVSAR represent a groundbreaking opportunity for a deeper understanding of the complex hydrodynamics of coastal wetlands.

Shade and salinity responses of two dominant coastal wetland grasses: implications for light competition at the transition zone.

Coastal wetlands are threatened by the increased salinity that may result from sea level rise. Salinity stress alters species zonation patterns through changes in competitive outcome between species differing in salinity tolerance. This study therefore aimed to understand how salinity and light affect two dominant and competing coastal wetland grasses that differ in salt tolerance, height and photosynthetic metabolism. The C4 species Spartina anglica and the C3 species Phragmites australis were grown at five salinity levels (0, 7, 14, 21 and 28 ppt) and two light fluxes (100 % and 50 % of natural daylight) in an outdoor experimental setup for 102 d with full access to nutrients. Salinity reduced the biomass, height and shoot density of P. australis from 81.7 g dry weight (DW), 0.73 m and 37 shoots per pot at a salinity of 0 ppt to 16.8 gDW, 0.3 m and 14 shoots per pot at a salinity of 28 ppt. Biomass, height and shoot density of S. anglica did not respond or were only slightly reduced at the highest salinity of 28 ppt. High salinity also resulted in a higher tissue concentration of N and P in P. australis. Both species had low ability to acclimate to the lower light flux. Shade acclimation in S. anglica occurred via modest changes in specific leaf area, pigment content and biomass allocation. High salinity reduced traits important for light competition and increased the nutrient concentration in P. australis leaf and root biomass, while this was overall unaffected in S. anglica. This is likely to reduce the competitive ability of P. australis over S. anglica for light because at high salinities the former cannot effectively shade the lower-growing S. anglica. Neither species effectively acclimates to shade, which could explain why S. anglica does not occur in the understorey of P. australis at low salinities.

Assessing changes to ecosystem structure and function following invasion by Spartina alterniflora and Phragmites australis: a meta-analysis

Biological invasions resulting from anthropogenic activities are one of the greatest threats to maintaining ecosystem functioning and native biodiversity. Invasions are especially problematic when the invading species behaves as an ecosystem engineer that is capable of transforming ecosystem structure, function, and community dynamics. Of particular concern is the spread of emergent wetland grasses whose root systems alter hydrology and structural stability of soils, modify ecosystem functions, and change community dynamics and species richness. To address the threats posed to ecosystems across the globe, management practices focus on the control and removal of invasive grasses. However, it remains unclear how severely invasive grasses alter ecosystem functions and whether alterations persist after invasive grass removal, limiting our ability to determine if management practices are truly sufficient to fully restore ecosystems. Here, we conducted a meta-analysis to quantify ecological alterations and the efficacy of management following the invasion of Spartina alterniflora and Phragmites australis, two common and pervasive invaders in coastal wetlands. Our results indicate that S. alterniflora and P. australis significantly alter measures of ecosystem functioning and organismal abundance. Invaded ecosystems had significant elevations in abiotic carbon and nitrogen fixation and uptake in areas with invasive grasses, with differential photosynthetic pathways of these two grass species further explaining carbon fluxes. Moreover, evidence from our analyses indicates that management practices may not adequately promote recovery from invasion, but more data are needed to fully assess management efficacy. We call for future studies to conduct pairwise comparisons between uninvaded, invaded, and managed systems and provide research priorities.

Response to salt stress of two wetland grasses of forage potentialities

The growth of two wetland forage grasses Leptochloa fusca (L.) Kunth. and Echinochloa stagnina (L.) P. Beauv. was investigated under NaCl salinity regarding the morphological traits, plant chemical composition, photosynthesis and the antioxidant enzymes POD and CAT. Plants of both species were irrigated with 0, 50, 100, 200, 300 and 400 mM NaCl in a sand/perlite mixture of 1:1 (v/v). Salinity negatively affected morphological traits and plant biomass of both species, particularly E. stagnina. Soluble sugars and proline within limits, protein contents of the foliage were increased to different extents by increasing salinity, but insoluble sugar decreased. K+/Na+ ratio of shoot and root of both species was decreased as a consequence of Na+ accumulation and restricted K+ uptake. NaCl salinity adversely affected photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency of both species particularly E. stagnina. Tolerance of L. fusca and E. stagnina to salinity stress can be based on stomatal closure and reduction in leaf area, in order to minimize water loss via transpiration and increase the activity of some antioxidant enzymes to detoxifying ROS generated during stress.

Resilience of trees and the vulnerability of grasslands to climate change in temperate Australian wetlands

Observations from wetlands across the globe suggest a consistent pattern of woody encroachment into wetland grasslands, altering habitat structure and ecological function. The extent to which hydrological changes have contributed to woody invasion of wetland grasslands is unclear. Our objective was to compare rates of woody encroachment in Australian floodplain wetlands between wet and dry hydrological phases. We test the hypothesis that contraction of non-woody wetland vegetation (grasses and rushes) would be concentrated in dry phases, co-incident with recruitment of the River Red Gum Eucalyptus camaldulensis lower in the floodplain. We conduct the first detailed mapping of habitat change in two of the largest forested wetlands in inland Australia, comparing wet and dry hydrological phases. Detailed photogrammetry, supported by extensive ground survey, allowed the interpretation of high resolution aerial photography to vegetation community level. We found a consistent pattern of decline in non-woody vegetation, particularly amongst grasses utilising the C4 photosynthetic pathway. The C4 grasses Pseudoraphis spinescens and Paspalum distichum showed steep declines in the Barmah Millewa and Macquarie Marshes respectively, being replaced by River Red Gum E. camaldulensis. C3 sedges proved more resilient in both systems. Our results suggest that a pattern of tree expansion into non-woody wetland vegetation, characteristic of wetlands across the globe, is a major habitat structural change in the Australian floodplain wetlands studied. Projected hydrological impacts of climate change are likely to further restrict wetland grass foraging habitat in these semi-arid floodplain wetlands.

The use of degraded peatlands for biomass production

The goal of this research is an assessment of the possible use of peatlands biomass and straw for the production of mixed bio-pellets. Peaty soils are a specific type of soils formed as the result of wetlands drainage. Peat mining is completed by the factory if the layer of the peat is less than 1-2 meters and not enough deep for effective mechanical excavation. After the peat excavation is finished, the biggest problem is the use of these lands for other purposes. One of the perspective directions is rewetting of post-mining peatlands to stimulate the growth of common reed, cattail, fescue, sedge, and other grasses which may grow in natural conditions, and also improve conditions for the cultivation of other plants, including trees. The yield of wetland grass in Belarus varies from 8.1 to 14 DM g ha-1 per year. The yield of willow wood can reach 8-10 of DM g ha-1 per year. The highest prime cost of biomass is obtained for willow wood, but it will be lower with the enlargement of the plantation area. Pellets with a high content of wood residues (sawdust) have the best technological parameters including calorific value when compared to pellets from only peat and peat plus straw. Biomass production on degraded peaty soils has also an ecological effect. The cost of carbon quotas on the market varies from 20 to 25 euro per ton, and biomass production can provide additional profit in the case of CO2 emissions trading depending on the biomass content in the fuel.

With a little help from my friends: physiological integration facilitates invasion of wetland grass Elymus athericus into flooded soils

Tidal wetlands worldwide are undergoing rapid invasions by tall‐growing clonal grasses. Prominent examples are invasions by species of the genera Spartina, Phragmites and Elymus. The responsible physiological and ecological drivers of these invasions are poorly understood. Physiological integration (PI) is a key trait of clonal plants, which enables the exchange of resources among ramets. We investigated PI in Elymus athericus, which has been rapidly spreading from high‐marsh into low‐marsh environments of European salt marshes during the last decades. We applied a nitrogen stable‐isotope approach to trace nutrient translocation between ramets in a factorial mesocosm experiment. The experiment was set up to mimic an invasion pattern commonly found in tidal wetlands, i.e. from high‐elevated and rarely flooded into low‐elevated and frequently flooded microenvironments. We tested for intraspecific variability in PI by including two genotypes of Elymus that naturally occur at different elevations within the tidal frame, a high‐marsh (HM) and a low‐marsh (LM) genotype. PI strongly increased offspring ramet aboveground and belowground biomass by 62 and 81%, respectively. Offspring ramets under drained conditions had 95% greater belowground biomass than those under flooded conditions. LM genotype offspring ramets produced 27% more aboveground biomass than HM genotypes. Offspring ramets were clearly more enriched in 15N under flooded versus drained conditions; however, this positive effect of flooding on δ15N was only significant in the LM genotype. Our findings demonstrate the importance of PI for the growth of Elymus offspring ramets and thereby for the species' capacity for fast vegetative spread. We show that offspring ramets under stressful flooded conditions are more dependent on nutrient supply from parent ramets than those under drained conditions. Our data furthermore suggest a higher degree of adaptation to flooding via PI in the LM versus HM genotype. In conclusion, we highlight the importance of assessing PI and intraspecific trait variability to understand invasion processes within ecosystems.

Title: Low concentrations of glyphosate in water and sediment after direct over-water application to control an invasive aquatic plant

When an invasive wetland grass degrades a Ramsar wetland and Important Bird Area, decisive management action is called for. To limit the extent and spread of European Phragmites australis, the Ontario government began the first, large-scale application of glyphosate (Roundup CustomⓇ) over standing water to control an invasive species in Canadian history. Between 2016 and 2018, over 1000 ha of marsh were treated. To assess the concentration, movement and longevity of this herbicide in treated marshes, we measured the concentration of glyphosate, its primary breakdown product aminomethylphosphonic acid (AMPA), and the alcohol ethoxylate-based adjuvant AquasurfⓇ in water and sediments in areas of the highest exposure and up to 150 m into adjacent bays. The maximum observed concentration of glyphosate in water was 0.320 mg/L, occurring within 24 hr of application. The maximum glyphosate concentration in sediment was 0.250 mg/kg, occurring within about 30 days of application. AMPA was detectable in water and sediment, indicating microbial breakdown of glyphosate in the marsh, but at low concentrations (maxwater = 0.025 mg/L, maxsed = 0.012 mg/kg). The maximum distance from the point of application that glyphosate was detected in the water was 100 m, while AMPA was detectable only at the edge of where glyphosate was applied (0 m). Concentrations in water returned to pre-treatment levels (<DL) within 20–30 days of application. In sediment, glyphosate residue persisted above detection limits (>0.005 mg/kg) for over one year but less than two years. Concentrations of alcohol ethoxylates were variable in space and time, following a pattern that could not be attributed to AquasurfⓇ use. The direct, over-water application of Roundup CustomⓇ with AquasurfⓇ to control invasive P. australis did not reach concentrations deemed to pose toxicological concern to aquatic biota by the Canadian Council of Ministers of the Environment.

EFFECTS OF SALT STRESS ON PLANT GROWTH AND BIOMASS ALLOCATION IN SOME WETLAND GRASS SPECIES IN THE MEKONG DELTA

Salt stress causes serious damage to many cellular and physiological processes that leads to yield reduction. The study induced salt stress using Hoagland solution added NaCl to evaluate its effects on plant growth and biomass allocation of some wetland grass species in order to identify salt-tolerant species for replacing and/or supplementing rice/grass in rice-shrimp model and salt-affected area in the Mekong Delta. The study also seeks to evaluate the response of leaf chlorophyll (SPAD unit) and proline content in salt-treated plants to varying application of salinity. Typha orientalis, Lepironia articulata, Eleocharis dulcis and Scirpus littoralis were studied in hydroponics condition with four levels of NaCl of 5, 10, 15, 20‰ and the control treatment (without adding NaCl). The experiment was arranged in a completely randomized design with 3 replications. The salt-treated plants showed visually clear responses of inhibited growth under salt stress condition compared to the control plants. Among the four studied species, T. orientalis produced the highest dry shoot biomass (15.5 g DW/plant), while E. dulcis had the lowest value (2.8 g DW/plant). However, only T. orientalis showed significantly decreased in biomass as salinity increased with 9.3 and 4.6 times lower of fresh and dry biomass in plants grown at the salinity level of 20‰ compared to those grown in the control treatment. The other three plant species did not affect by salinity levels. The results indicated that S. littoralis, L. articulata and E. dulcis could tolerate at high salinity of 20‰ (eq. to the EC value in the nutrient solution of 38.0 dS/m) and could be potential candidate to grow in the rice-shrimp model or in the salt-affected soils.

Water quality and transpiration responses of Eichornia crassipes at Lake Tana, Ethiopia

Lake Tana is the largest freshwater body in Ethiopia, and it is a multi-use water body. However, currently the lake size reduced by different pressures, of these the occurrence of aquatic invasive weeds specifically, water hyacinth (Eichornia crassipes). The study was focused to evaluate the physiology of water hyacinth and its effect on water transpiration and quality in Lake Tana. In addition to water hyacinth, two wetland grasses (Cyperus papyrus and Typha latifolia) were selected based on predominance along the lake shore line. Plant physiology parameters (e.g., leaf width, height, and number of leaves) and transpiration data were collected in every week and day, respectively. In situ field measurements were also taken to observe vegetation treatments response for water quality. The result showed that transpiration of water hyacinth was two times higher than papyrus and T. latifolia. The number of leaves and leaf widths are significantly (p < 0.1) increased in water hyacinth weed compared to the corresponding wetland vegetations. Dissolved oxygen and temperature were statistically significant (p < 0.05) due to water hyacinth compared to the corresponding treatments, and the values were also beyond the desirable standard. Therefore, Lake Tana water alterations due to water hyacinths will be continued where effective controlling mechanisms have not been taken there.