Analysis of chromosome number and speculations on the origin of Arundo donax L. (Giant Reed)

Arundo donax (commonly called Giant Reed) is a perennial rhizomatous grass native to Asia, nowadays diffused all over the world. Due to its high biomass production and great adaptability to marginal land, interest in this species is increasing. In fact A. donax could represent an important and promising energy crop for heat and bioethanol second generation production. The propagation of A. donax is strictly agamic by rhizome fragmentation and cane node germination, strongly limiting the possibility of genetic improvement by breeding. The sterility could be caused by the fact that A. donax is a hybrid with uneven ploidy or a triploid species. It is difficult to propose an explanation for its sterility, because the chromosome number of A. donax is still a matter of debate, due to the high number and small size of the chromosomes; in the bibliography different counts ranging from 40 to 110 are reported. With the aim of establishing the chromosome number of A. donax we selected and counted 17 metaphase plates prepared from root tips obtained by hydroponic cultivation of cane nodes; our counts showed that A. donax most probably has 110 chromosomes. Our results suggested us two possible hypotheses, also based on SSR molecular marker results, concerning the evolutionary processes involved in the origins of A. Donax.     

Nutrient removal and biomass production in land treatment systems receiving domestic effluent

Land application of pre-treated wastewater is increasingly practiced to achieve both treatment and beneficial reuse of applied effluent. Vegetation is an important component of these systems, affecting hydraulic loading and nutrient uptake and hence treatment efficiency. This work investigated the effect of plant species (Acacia cyanophylla, Eucalyptus camaldulensis, Populus nigra and Arundo donax), on water requirements, nutrient removal, water use efficiency (WUE) and biomass production in land treatment systems (LTS) in which pre-treated wastewater was applied at rates to meet crop evapotranspiration. Vegetation had a strong effect on all the parameters monitored during this trial. A. cyanophylla produced the greatest amount of biomass and showed the highest irrigation requirements and WUE, followed by E. camaldulensis, A. donax and P. nigra. In addition, A. cyanophylla and A. donax achieved a higher leaf-N content compared to other species. As a result of the differences in tissue nutrient content and biomass, A. cyanophylla accumulated 23, 20, and 70% more N in hypergeous biomass than E. camaldulensis, A. donax and P. nigra, respectively. A. cyanophylla and E. camaldulensis accumulated 57 and 53% respectively more P than did P. nigra and A. donax. Therefore substantial improvement of the performance of the LTS in terms of nutrient removal can be achieved through the selection of appropriate plant species. Despite the enhanced growth rates observed in the study nutrient recovery by vegetation did not exceed 31 and 35% of the applied N and P, respectively. The relatively low percentages of removal are attributed to increased concentration of nutrients in effluent and the high ET rates prevailing in the study area. These findings suggest that additional practices are required to mitigate environmental impacts arising from excessive nutrient loads when effluent is applied at rates to meet crop water requirements.     

Restoring Soil Ecosystems and Biomass Production of Arundo donax L. under Microbial Communities-Depleted Soil

In recent years, giant reed (Arundo donax L) has received considerable attention as a promising plant for energy production. Giant reed is able to grow in a range of environments, including wetlands and marginal soils, and has shown promise in phytoremediation efforts. A pot experiment was carried out to investigate the ability of giant reed to restore ecosystems of different soils, including bauxite-derived red mud-amended soil and pure red mud (red mud—a waste generated by the Bayer process in the aluminum industry—is strongly alkaline and has a high salt content and electrical conductivity (EC) dominated by sodium). Samples were exposed to high temperatures, which simulate the effects of bushfires. Selected soil properties that were measured included soil dehydrogenase, alkaline phosphatase, urease and catalase activities, soil organic carbon, soil pH, EC, available soil macronutrients NPK, and above- and below-ground plant biomass yield. The results showed that giant reed reduced EC in all autoclaved soils and red mud-contaminated soils by 24–82 %. Significantly, available N was increased, and a slight increase was recorded for available K. The presence of giant reed enhanced the soils’ enzyme activities to recover in all tested autoclaved soils and red mud-contaminated soils; specifically, dehydrogenase activity increased by 262 and 705 % in non-autoclaved and autoclaved soils, respectively, and urease and catalase activities increased by 591 and 385 % in autoclaved soils, respectively. Total bacterial and fungal counts were higher in autoclaved soils than non-autoclaved soils after cultivating giant reed for 12 weeks. Autoclaved soils enabled higher biomass production for giant reed than non-autoclaved soils. These results demonstrate that giant reed is not only able to survive on soil that has lost its microbial community as a result of heat, but can also yield significant amounts of biomass while assisting recovering soil ecosystems after bushfires.     

Characteristics of bioenergy grasses important for enhanced NaCl tolerance potential

Growing bioenergy grasses can contribute to a great extent towards the production of biomass, and it can be a potential source of renewable energy. Such grasses, if suitable for marginal land, will solve better the problem of its competition with the cultivation of food crops in arable land. Four different potential bioenergy grasses, e.g., Saccharum arundinaceum Retz., hybrid Napier var. CO-3, Saccharum spontaneum L., and Arundo donax L. were selected based on our earlier study, and these perennial grasses were subjected to NaCl stress, a characteristic feature of marginal lands. Various measurements to assess the NaCl tolerance mechanism, e.g., MDA content, antioxidant enzyme activity, photosynthetic pigments composition, chlorophyll fluorescence and photosystem I (PSI) and photosystem II (PSII) activities were analyzed after imparting NaCl stress and compared with the control plants. Among the grasses studied, a lower maximum quantum yield of PSII (F _v/F _m) and PSI and PSII activities were recorded in S. spontaneum and Napier var. CO-3 than in S. arundinaceum and A. donax. The latter two grasses showed less degradation of total chlorophyll and low MDA content. The maintenance of a better water status of A. donax and S. arundinaceum is attributed to the maintenance of favorable osmotic balance by the accumulation of the higher levels of compatible solutes, such as total soluble sugars and proline. The better performance of S. arundinaceum and A. donax under high NaCl conditions was also facilitated by the higher free radical-scavenging potential in them, as represented by the increase in peroxidase activity. These results suggest that S. arundinaceum and A. donax are better adapted to NaCl stress than S. spontaneum and Napier var. CO-3. The high NaCl tolerance potential, exhibited by S. arundinaceum and A. donax, makes them an appropriate choice for marginal lands affected by high levels of NaCl.     

Seasonal Dynamics of Aboveground and Belowground Biomass and Nutrient Accumulation and Remobilization in Giant Reed (Arundo donax L.): A Three-Year Study on Marginal Land

Giant reed (Arundo donax L.) is a perennial rhizomatous grass that shows promise as a bioenergy crop in the Mediterranean environment. The species has spread throughout the world, catalyzed by human activity, though also as a result of its intrinsic robustness, adaptability, and versatility. Giant reed is able to thrive across a wide range of soil types and is tolerant to drought, salinity, and flooding. This tolerance to environmental stresses is significant and could mean that growing energy crops on marginal land is one possible strategy for reducing competition for land with food production and for improving soil quality. We devised an experiment in which we cultivated giant reed in a sandy loam soil with low nutrient availability. Our goal was to evaluate the dynamics of aboveground and belowground biomass and assess the nutrient dynamics of this grass species, focusing particularly on nutrient accumulation and remobilization. The species demonstrated good productivity potential: In the third year, aboveground dry biomass yield reached around 20 t?ha^?1, with a corresponding rhizome dry biomass yield of 16 t?ha^?1. Results for this species were characterized by low nutrient contents in the aboveground biomass at the end of the growing season, and its rhizome proved able to support growth over the spring period and to store nutrients in the autumn. Nevertheless, the adaptability of giant reed to marginal land and the role of its belowground biomass should be investigated over the long-term, and any further research should focus on its potential to reduce greenhouse gas emissions and maintain soil fertility.     

Impact of the biological control agent Tetramesa romana (Hymenoptera: Eurytomidae) on Arundo donax (Poaceae: Arundinoideae) along the Rio Grande River in Texas

Five years post-release of the arundo gall wasp, Tetramesa romana, into the riparian habitats of the lower Rio Grande River, changes in the health of the invasive weed, Arundo donax, or giant reed, have been documented. These changes in plant attributes are fairly consistent along the study area of 558 river miles between Del Rio and Brownsville, TX, and support the hypothesis that the arundo wasp has had a significant impact as a biological control agent. Plant attributes were measured prior to release in 10 quadrats at each of 10 field sites in 2007, and measured again at the same undisturbed sites, 5 years after the release of T. romana, in 2014. Above ground biomass of A. donax decreased on average by 22% across the 10 sites. This decline in biomass was negatively correlated to increased total numbers of T. romana exit holes in main and lateral shoots per site in 2014 compared to 2007. Changes in biomass, live shoot density and shoot lengths, especially the positive effect of galling on main and lateral shoot mortality, appear to be leading to a consistent decline of A. donax. Economically, this reduction in A. donax biomass is estimated to be saving 4.4 million dollars per year in agricultural water. Additional impacts are expected as populations of the wasp increase and as other biological control agents such as the arundo scale, Rhizaspidiotus donacis, become more widespread.     

Allocation pattern,ion partitioning,and chlorophyll a fluorescence in Arundo donax L. in responses to salinity stress

Biometric and physiological analyses of salt stress responses were performed in two time-course experiments on giant reed (Arundo donax L). Experiment I evaluated biomass production in plants exposed to 128, 256, 512 mM NaCl for 84 days. For Experiment II, plants grown under 256 mM NaCl were further assessed for chlorophyll a fluorescence, ionic partitioning, and proline content at 14 and 49 days after treatment (DAT). Biomass allocation was affected with all the concentrations of NaCl used from 28 DAT onward. Proline biosynthesis in leaves was more stimulated than that in roots after salt stress. Photosynthetic efficiency of photosystem II (PSII) was not affected by salt stress up to 42 DAT, while 49 DAT plants exhibited a significant reduction of both potential (Φ_PSII) and maximal (F_v/F_m) PSII quantum yield. A. donax resulted a moderately sensitive species in response to 256 and 512 mM NaCl, concentrations that are however higher than that commonly found in most marginal lands (such as 128 mM or lower), where the biomass yield is appreciable, especially in short-term cultivation (56 DAT here). Altogether, this study indicates that A. donax can be considered as a promising and valuable energy crop for exploiting the Mediterranean marginal land.     

Screening of giant reed (Arundo donax L.) ecotypes for biomass production under salt stress

Given its high biomass and plasticity, Arundo donax L. is a promising ligno-cellulosic crop for cultivation in marginal lands in temperate climates. In order to test for adaptation to salinity, growth parameters of several A. donax clones were evaluated under two salt regimes in hydroponics. Mild NaCl stress (50 mM NaCl, 5.6 mS cm^?1 EC, for 10 days) failed to discriminate between ecotypes, while a more severe NaCl treatment (150 mM, 18.8 mS cm^?1 EC, for 21 days) enabled the identification of ecotypes maintaining plant growth under high salinity. Among several biometric parameters, 4th leaf width, and shoot and root DW consistently highlighted differences between ecotypes. Gas-exchange parameters also responded to severe NaCl treatment, while the photosystem efficiency was good, regardless of treatment. The results confirm that A. donax can be considered moderately tolerant to NaCl stress, with variation between ecotypes. Our screening protocol identified ecotypes with higher biomass production under severe NaCl treatment and can be useful for preliminary evaluation of NaCl tolerant clones for increasing productivity under salinity. The detected inter-ecotype variability could also be investigated to identify suitable clones for different environments.     

Molecular evidence for a single genetic clone of invasive Arundo donax in the United States

Arundo donax (giant reed) is an aggressive invasive weed of riparian habitats throughout the southern half of the United States from California to Maryland. Native to Asia, the species is believed to have been initially introduced into North America from the Mediterranean region although subsequent introductions were from multiple regions. To provide insight into the potential for biological control of A. donax, genetic variation in plants sampled from a wide geographical area in the United States was analyzed using Sequence Related Amplification Polymorphism (SRAP) and transposable element (TE)-based molecular markers. Invasive individuals from 15 states as well as four populations in southern France were genetically fingerprinted using 10 SRAP and 12 TE-based primer combinations. With the exception of simple mutations detected in four plants, A. donax exhibited a single multilocus DNA fingerprint indicating a single genetic clone. The genetic uniformity of invasive A. donax suggests that classical biological control of the species could be successful. A lack of genetic diversity in the invaded range simplifies identification of native source populations to search for natural enemies that could be used as biocontrol agents.     

L-DONAX,a growth model of the invasive weed species,Arundo donax L.

Arundo donax L. is a perennial reed and is an invasive weed of riparian systems in North America. A structural model (L-DONAX) of the species was constructed using L-system modelling in order to assist in understanding and demonstrating the complexities of the plant's development and structure. The model produces a realistic number of plant components from a single rhizome segment over the course of the first year of growth, using empirical relationships derived from outdoor experiments. Biomass production is also simulated, through the use of relationships found between aerial plant portion sizes and masses. L-DONAX demonstrates that control of A. donax clumps is likely to require more than annual biomass removal, due to the bulk of biomass being present underground, and the ability of remaining rhizome or stem segments to produce large clumps quickly. The model extrapolates to years of growth beyond the first, but is found to require some re-parameterisation to improve accuracy.     

Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus x giganteus), giant reed (Arundo donax L.), weeping lovegrass [Eragrostis curvula (Shrad.) Nees], kleingrass (Panicum coloratum L.), and Johnsongrass (Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168?kg?N?ha^?1) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate (p?=?0.08), but was affected by year and species interactions (p?<?0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0?Mg?ha^?1 in 2009, but only 13.0?Mg?ha^?1 and 9.8?Mg?ha^?1 in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0?Mg?ha^?1, respectively. Giant miscanthus established poorly, producing only 4.7?Mg?ha^?1. Across years, giant reed had the highest biomass yield, 33.2?Mg?ha^?1 at 168?kg?N?ha^?1, and the highest nutrient concentrations and removal rates (162 to 228?kg?N?ha^?1, 23 to 25?kg?P?ha^?1, and 121 to 149?kg?K?ha^?1) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75?kg?N?ha^?1, 5 to 12?kg?P?ha^?1, and 44 to 110?kg?K?ha^?1) across years, demonstrating its merits as a low-input bioenergy crop.     

Impacts of the invader giant reed (<Emphasis Type="Italic">Arundo donax</Emphasis>) on riparian habitats and ground arthropod communities

Riparian areas have experienced long-term anthropogenic impacts including the effects of plant introductions. In this study, 27 plots were surveyed across three Mediterranean rivers in north-eastern Spain to explore the effects of the invader giant reed (Arundo donax) on riparian habitat features and the diversity, trophic structure, body size, and abundances of epigeal and hypogeal arthropods in riparian areas. Using pitfall traps and Berlese funnels, this study detected a significant increase in collembola abundance and a decrease in the abundance, body size and diversity of macro-arthropods at order and family levels in invaded plots compared to native stands. Invaded and un-invaded areas also differed in the taxonomical structure of arthropod assemblies but not in trophic guild proportions. However, the fact that arthropods were smaller in A. donax soils, together with the absence of particular taxa within each trophic guild or even an entire trophic group (parasitoids), suggests that food-web alterations in invaded areas cannot be discarded. Habitat features also differed between invaded and un-invaded areas with the poorest herbaceous understory and the largest leaf litter deposition and soil carbon stock observed in A. donax plots. The type of vegetation in riparian areas followed by the total native plant species richness were identified as major causal factors to changes in the abundance, diversity and composition of macro-arthropods. However, our analyses also showed that some alterations related to A. donax invasion were inconsistent across rivers, suggesting that A. donax effects may be context dependent. In conclusion, this study highlights an impoverishment of native flora and arthropod fauna in A. donax soils, and suggests major changes in riparian food webs if A. donax displaces native riparian vegetation.     

L-DONAX,a growth model of the invasive weed species,Arundo donax L.

Arundo donax L. is a perennial reed and is an invasive weed of riparian systems in North America. A structural model (L-DONAX) of the species was constructed using L-system modelling in order to assist in understanding and demonstrating the complexities of the plant's development and structure. The model produces a realistic number of plant components from a single rhizome segment over the course of the first year of growth, using empirical relationships derived from outdoor experiments. Biomass production is also simulated, through the use of relationships found between aerial plant portion sizes and masses. L-DONAX demonstrates that control of A. donax clumps is likely to require more than annual biomass removal, due to the bulk of biomass being present underground, and the ability of remaining rhizome or stem segments to produce large clumps quickly. The model extrapolates to years of growth beyond the first, but is found to require some re-parameterisation to improve accuracy.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Characterization of phenology,physiology, morphology and biomass traits across a broad Euro‐Mediterranean ecotypic panel of the lignocellulosic feedstock Arundo donax

Giant reed (Arundo donax L.) is a perennial rhizomatous grass, which has attracted great attention as a potential lignocellulosic feedstock for bioethanol production due to high biomass yield in marginal land areas, high polysaccharide content and low inhibitor levels in microbial fermentations. However, little is known about the trait variation that is available across a broad ecotypic panel of A. donax nor the traits that contribute most significantly to yield and growth in drought prone environments. A collection of 82 ecotypes of A. donax sampled across the Mediterranean basin was planted in a common garden experimental field in Savigliano, Italy. We analysed the collection using 367 clumps representing replicate plantings of 82 ecotypes for variation in 21 traits important for biomass accumulation and to identify the particular set of ecotypes with the most promising potential for biomass production. We measured morpho‐physiological, phenological and biomass traits and analysed causal relationships between traits and productivity characteristics assessed at leaf and canopy levels. The results identified differences among the 82 ecotypes for all studied traits: those showing the highest level of variability included stomatal resistance, stem density (StN), stem dry mass (StDM) and total biomass production (TotDM). Multiple regression analysis revealed that leaf area index, StDM, StN, number of nodes per stem, stem height and diameter were the most significant predictors of TotDM and the most important early selection criteria for bioenergy production from A. donax. These traits were used in a hierarchical cluster analysis to identify groups of similar ecotypes, and a selection was made of promising ecotypes for multiyear and multisite testing for biomass production. Heritability estimates were significant for all traits. The potential of this ecotype collection as a resource for studies of germplasm diversity and for the analysis of traits underpinning high productivity of A. donax is highlighted.     

Growth and nutrients accumulation potentials of giant reed (Arundo donax L.) in different habitats in Egypt

Arundo donax L. has a high biomass production and a tendency toward community dominance in many habitats and thereby a tolerance to a wide range of environmental conditions. Therefore, the present study investigated the potentiality of A. donax to accumulate nutrients and trace metals in its biomass. Six main habitats (Nile Bank, Drain Bank, Canal Bank, Field Edges, Railways and Roadsides) were recognized. At each habitat, six quadrats (each 1 m²), distributed equally in two sites, were selected for growth measurements (e.g., density, shoot height, diameter, leaf area and biomass), plant and soil analyses. Plants from Nile, Canal and Drain Banks had the highest values of most growth measurements, while those from Railways and Roadsides had the lowest. Canal Bank plants accumulated the highest concentrations of P, Cu and Pb in their leaves; Zn in the stem; and Mg, Cd and Fe in the rhizome. The bioaccumulation factor (BF) of A. donax, for Cd, Fe, Mn and Zn, was greater than 1, while the translocation factor (TF) of most trace metals was less than unity in most habitats. In conclusion, A. donax showed morphological plasticity in response to habitat heterogeneity, and its growth was most vigorous in the riparian habitats. The high BF, as well as the significant positive correlations between trace metals, especially Cd, in soil and plant, renders A. donax a powerful phytoremediator.     

The laccase-catalyzed modification of lignin for enzymatic hydrolysis

The efficient use of cellulases in the hydrolysis of pretreated lignocellulosic biomass is limited due to the presence of lignin. Lignin is known to bind hydrolytic enzymes nonspecifically, thereby reducing their action on carbohydrate substrates. The composition and location of residual lignin therefore seem to be important for optimizing the enzymatic hydrolysis of lignocellulosic substrates. The use of lignin-modifying enzymes such as laccase may have potential in the modification or partial removal of lignin from the biomass. In this study, the effect of lignin modification by laccase on the hydrolysis of pretreated spruce (Picea abies) and giant reed (Arundo donax) was evaluated. The substrates were first treated with laccase and then hydrolyzed with commercial cellulases. Laccase modification improved the hydrolysis yield of spruce by 12%, but surprisingly had an adverse effect on giant reed, reducing the hydrolysis yield by 17%. The binding properties of cellulases on the untreated and laccase-treated lignins were further studied using isolated lignins. The laccase treatment reduced the binding of enzymes on modified spruce lignin, whereas with giant reed, the amount of bound proteins increased after laccase treatment. Further understanding of the reactions of laccase on lignin will help to control the unspecific-binding of cellulases on lignocellulosic substrates.     

Origin of the invasive Arundo donax (Poaceae): a trans-Asian expedition in herbaria

Background and Aims

The hypothesis of an ancient introduction, i.e. archaeophyte origin, is one of the most challenging questions in phylogeography. Arundo donax (Poaceae) is currently considered to be one of the worst invasive species globally, but it has also been widely utilzed by man across Eurasia for millennia. Despite a lack of phylogenetic data, recent literature has often speculated on its introduction to the Mediterranean region.

Methods

This study tests the hypothesis of its ancient introduction from Asia to the Mediterranean by using plastid DNA sequencing and morphometric analysis on 127 herbarium specimens collected across sub-tropical Eurasia. In addition, a bioclimatic species distribution model calibrated on 1221 Mediterranean localities was used to identify similar ecological niches in Asia.

Key Results

Despite analysis of several plastid DNA hypervariable sites and the identification of 13 haplotypes, A. donax was represented by a single haplotype from the Mediterranean to the Middle East. This haplotype is shared with invasive samples worldwide, and its nearest phylogenetic relatives are located in the Middle East. Morphometric data characterized this invasive clone by a robust morphotype distinguishable from all other Asian samples. The ecological niche modelling designated the southern Caspian Sea, southern Iran and the Indus Valley as the most suitable regions of origin in Asia for the invasive clone of A. donax.

Conclusions

Using an integrative approach, an ancient dispersion of this robust, polyploid and non-fruiting clone is hypothesized from the Middle East to the west, leading to its invasion throughout the Mediterranean Basin.     

A salt on the bioenergy and biological invasions debate: salinity tolerance of the invasive biomass feedstock Arundo donax

Arundo donax L., commonly known as giant reed, is promising biomass feedstock that is also a notorious invasive plant in freshwater ecosystems around the world. Heretofore, the salt tolerance of A. donax had not been quantified even though anecdotal evidence suggests halophytic qualities. To test whole-plant and leaf level responses, we established a pot experiment on 80 scions propagated from an A. donax population that has naturalized on the shore of the San Francisco Bay Estuary. To quantify growth and physiological responses to salinity (NaCl), A. donax scions were divided into eight treatments and grown for 60 days across a range of salinities (0–42 dS m⁻¹). Classic growth analysis showed >80% reduction in overall growth at the highest salinities. Yet, there was zero mortality indicating that A. donax is able to tolerate high levels of salt. Declining photosynthesis rates were strongly correlated (R² > 0.97) with decreasing stomatal conductance, which was in turn closely related to increasing salinity. Leaf gas exchange revealed that stomata and leaf limitations of carbon dioxide were three times greater at high salinities. Nonetheless, even when salinities were 38–42 dS m⁻¹ A. donax was able to maintain assimilation rates 7–12 μmol m⁻² s⁻¹. Further, by maintaining 50% relative growth at salinities ~12 dS m⁻¹ A. donax can now be classified as ‘moderately salt tolerant’. A. donax leaf gas exchange and whole-plant salt tolerance are greater than many important food crops (i.e. maize, rice), the bioenergy feedstock Miscanthus × giganteus, as well as some uncultivated plant species (i.e. Populus and Salix) that are indigenous in regions A. donax currently invades. The results of this study have implications for both agronomists wishing to expand A. donax to fields dominated by saline soils, and for others who are concerned about the spread of A. donax with altered stream hydrology or sea-level rise.