The crucial role of roots in increased cadmium-tolerance and Cd-accumulation in the pea mutant <Emphasis Type="Italic">SGECd</Emphasis><Superscript><Emphasis Type="Italic">t</Emphasis></Superscript>

Elucidation of mechanisms underlying plant tolerance to cadmium, a widespread toxic soil pollutant, and accumulation of Cd in plants are urgent tasks. For this purposes, the pea (Pisum sativum L.) mutant SGECd^t (obtained by treatment of the laboratory pea line SGE with ethylmethane sulfonate) was reciprocally grafted with the parental line SGE, and four scion/rootstock combinations were obtained: SGE/SGE, SGECd^t/SGECd^t, SGE/SGECd^t, and SGECd^t/SGE. They were grown in hydroponics in the presence of 1 μM CdCl₂ for 30 d. The SGE and SGECd^t scions on the SGECd^t rootstock had a higher root and shoot biomass and an elevated root and shoot Cd content compared with the grafts having SGE rootstock. Only the grafts with the SGE rootstock showed chlorosis and roots demonstrating symptoms of Cd toxicity. The content of nutrient elements in roots (Fe, K, Mg, Mn, Na, P, and Zn) was higher in the grafts having the SGECd^t rootstock, and three elements, namely Ca, Fe, and Mn, were efficiently transported by the SGECd^t root to the shoot of these grafts. The content of other measured elements (K, Mg, Na, P, and Zn) was similar in the root and shoot in all the grafts. Then, the non-grafted plants were grown in the presence of Cd and subjected to deficit or excess concentrations of Ca, Fe, or Mn. Exclusion of these elements from the nutrient solution retained or increased differences between SGE and SGECd^t in growth response to Cd toxicity, whereas excess of Ca, Fe, or Mn decreased or eliminated such differences. The obtained results assign a principal role of roots to realizing the increased Cd-tolerance and Cdaccumulation in the SGECd^t mutant. Efficient translocation of Ca, Fe, and Mn from roots to shoots appeared to counteract Cd toxicity, although Cd was actively taken up by roots and accumulated in shoots.     

Aluminum resistance in wheat involves maintenance of leaf Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript> content,decreased lipid peroxidation and Al accumulation,and low photosystem II excitation pressure

The phytotoxic aluminum species (Al³⁺) is considered as the primary factor limiting crop productivity in over 40 % of world’s arable land that is acidic. We evaluated the responses of two wheat cultivars (Triticum aestivum L.) with differential Al resistance, cv. Yecora E (Al-resistant) and cv. Dio (Al-sensitive), exposed to 0, 37, 74 and 148 μM Al for 14 days in hydroponic culture at pH 4.5. With increasing Al concentration, leaf Ca²⁺ and Mg²⁺ content decreased, as well as the effective quantum yield of photosystem II (PSII) photochemistry (Φ _PSII ), while a gradual increase in leaf membrane lipid peroxidation, Al accumulation, photoinhibition (estimated as F _v /F _m ), and PSII excitation pressure (1 ? q _p ) occurred. However, the Al-resistant cultivar with lower Al accumulation, retained larger concentrations of Ca²⁺ and Mg²⁺ in the leaves and kept a larger fraction of the PSII reaction centres (RCs) in an open configuration, i.e. a higher ratio of oxidized to reduced quinone A (Q_A), than plants of the Al-sensitive cultivar. Four times higher Al concentration in the nutrient solution was required for Al-resistant plants (148 μM Al) than for Al-sensitive (37 μM Al), in order to establish the same closed RCs. Yet, the decline in photosynthetic efficiency in the cultivar Dio was not only due to closure of PSII RCs but also to a decrease in the quantum yield of the open RCs. We suggest that Al³⁺ toxicity may be mediated by nutrient deficiency and oxidative stress, and that Al-resistance of the wheat cultivar Yecora E, may be due at least partially, from the decreased Al accumulation that resulted to decreased reactive oxygen species (ROS) formation. However, under equal internal Al accumulation (exposure Al concentration: Dio 74 μM, Yecora E 148 μM) that resulted to the same oxidative stress, the reduced PSII excitation pressure and the better PSII functioning of the Al-resistant cultivar was probably due to the larger concentrations of Ca²⁺ and Mg²⁺ in the leaves. We propose that the different sensitivities of wheat cultivars to Al³⁺ toxicity can be correlated to differences in the redox state of Q_A. Thus, chlorophyll fluorescence measurements can be a promising tool for rapid screening of Al resistance in wheat cultivars.     

Improved salt tolerance in a wheat stay-green mutant <Emphasis Type="Italic">tasg1</Emphasis>

Salt stress inhibited the growth of both tasg1 and wild-type (WT) wheat seedlings, but the inhibition in tasg1 plants was relatively weaker than that of WT. Compared to the WT, the chlorophyll content, thylakoid membrane polypeptides, Hill reaction activity, actual photochemical efficiency of PSII (ΦPSII), and Mg²⁺- and Ca²⁺-ATPase activities were higher in tasg1 under salt stress. At the same time, the photosynthetic activity of the tasg1 was significantly higher than that of WT. In addition, tasg1 plants displayed relatively less accumulation of reactive oxygen species and oxidative damage accompanied by higher activity of some antioxidant enzymes, and the up-regulation of antioxidant genes further demonstrated the improvement of antioxidant activity in tasg1 under salt stress. Furthermore, tasg1 plants also showed relatively weaker Na⁺ fluorescence and lower Na⁺ content, but relatively higher content of K⁺ in their roots and shoots, and then, the roots of tasg1 plants enhanced net outward Na⁺ flux and a correspondingly increased net inward K⁺ flux during salt stress. This might be associated with the relatively higher activity of H⁺-ATPase in tasg1 plants. These results suggest that the improved antioxidant competence and Na⁺/K⁺ ion homeostasis play an important role in the enhanced salinity tolerance of tasg1 plants.     

Salt-induced changes in photosynthetic activity and growth in a potential medicinal plant Bishop’s weed (<Emphasis Type="Italic">Ammi majus</Emphasis> L.)

Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50 % reduction in shoot dry mass occurred at 156 mM (ca.15.6 mS cm^?1), whereas that in seed yield was at 104 mM (ca.10.4 mS cm^?1). As in most glycophytes, Na⁺ and Cl^? in both shoots and roots increased, whereas K⁺ and Ca²⁺ decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majusmaintained markedly higher K⁺/Na⁺ ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (P_N) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majusis a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K⁺/Na⁺ ratio and accumulation of proline in shoots, but P_N had a negative association with the salt tolerance of this crop.     

A nodule endophytic plant growth-promoting <Emphasis Type="Italic">Pseudomonas</Emphasis> and its effects on growth,nodulation and metal uptake in <Emphasis Type="Italic">Medicago lupulina</Emphasis> under copper stress

The aim of this study was to determine the plant growth-promoting potential of the nodule endophytic Pseudomonas brassicacearum strain Zy-2-1 when used as a co-inoculant of Medicago lupulina with Sinorhizobium meliloti under copper (Cu) stress conditions. Strain Zy-2-1 was capable of producing ACC deaminase activity, IAA and siderophores, and was able to grow in the presence of Cu²⁺ up to 2.0 mmol/L. Co-inoculation of S. meliloti with Zy-2-1 enhanced M. lupulina root fresh weight, total plant dry weight, number of nodules, nodule fresh weight and nitrogen content in the presence of 100 or 300 mg/kg Cu²⁺. In the presence of 500 mg/kg Cu²⁺, co-inoculation with S. meliloti and strain Zy-2-1 increased plant height, number of nodules, nodule fresh weight and nitrogen content in comparison to S. meliloti inoculation alone. Furthermore, a higher amount of Cu accumulation in both shoots and roots and a higher level of Cu translocation to shoots were observed in co-inoculated plants. These results demonstrate that co-inoculation of M. lupulina with S. meliloti and P. brassicacearum Zy-2-1 improves plant growth, nitrogen nutrition and metal extraction potential. This can be of practical importance in the remediation of heavy metal-contaminated soils.     

Growth,ionic response,and gene expression of shoots and roots of perennial ryegrass under salinity stress

Growth, ionic responses, and expression of candidate genes to salinity stress were examined in two perennial ryegrass accessions differing in salinity tolerance. The salinity tolerant (PI265349) and sensitive accessions (PI231595) were subjected to 75-mM NaCl for 14 days in a growth chamber. Across two accessions, salinity stress increased shoot dry weight and concentrations of malondialdehyde (MDA) and Na⁺ in the shoots and roots, but decreased shoot Ca²⁺ and root K⁺ concentrations. Salinity stress also increased root expressions of SOS1, PIP1, and TIP1. Plant height and chlorophyll content were unaffected by salinity stress in the tolerant accession but significantly decreased in the sensitive accession. Shoot MDA content did not change in the tolerant accession but increased in the sensitive accession. A more dramatic increase in Na⁺ was found in the roots of the sensitive accession. Relative to the control, salinity stress reduced expression of SOS1, NHX1, PIP1, and TIP1 in the shoots but increased expression of these genes in the roots of the tolerant accession. Expression levels of SOS1 increased in the roots and expression of NHX1 increased in the shoots but decreased in the roots of the sensitive accession under salinity stress. A decline in PIP1 expression in the shoots and dramatic increases in TIP expression in both shoots and roots were found in the sensitive accession under salinity stress. The results suggested maintenance of plant growth and leaf chlorophyll content, lesser Na⁺ accumulation in the roots, and lower lipid peroxidation in the shoots which could be associated with salinity tolerance. The decreased expressions of SOS1, NHX1, and TIP1 in the shoots, and increased expressions of NHX1 and PIP1 in the roots might also be related to salinity tolerance in perennial ryegrass.     

Soil pH and electrical conductivity are key edaphic factors shaping bacterial communities of greenhouse soils in Korea

Soil microorganisms play an essential role in soil ecosystem processes such as organic matter decomposition, nutrient cycling, and plant nutrient availability. The land use for greenhouse cultivation has been increasing continuously, which involves an intensive input of agricultural materials to enhance productivity; however, relatively little is known about bacterial communities in greenhouse soils. To assess the effects of environmental factors on the soil bacterial diversity and community composition, a total of 187 greenhouse soil samples collected across Korea were subjected to bacterial 16S rRNA gene pyrosequencing analysis. A total of 11,865 operational taxonomic units at a 97% similarity cutoff level were detected from 847,560 sequences. Among nine soil factors evaluated; pH, electrical conductivity (EC), exchangeable cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), available P₂O₅, organic matter, and NO₃-N, soil pH was most strongly correlated with bacterial richness (polynomial regression, pH: R² = 0.1683, P < 0.001) and diversity (pH: R² = 0.1765, P < 0.001). Community dissimilarities (Bray-Curtis distance) were positively correlated with Euclidean distance for pH and EC (Mantel test, pH: r = 0.2672, P < 0.001; EC: r = 0.1473, P < 0.001). Among dominant phyla (> 1%), the relative abundances of Proteobacteria, Gemmatimonadetes, Acidobacteria, Bacteroidetes, Chloroflexi, and Planctomycetes were also more strongly correlated with pH and EC values, compared with other soil cation contents, such as Ca²⁺, Mg²⁺, Na⁺, and K⁺. Our results suggest that, despite the heterogeneity of various environmental variables, the bacterial communities of the intensively cultivated greenhouse soils were particularly influenced by soil pH and EC. These findings therefore shed light on the soil microbial ecology of greenhouse cultivation, which should be helpful for devising effective management strategies to enhance soil microbial diversity and improving crop productivity.     

Nutrient allocation and photochemical responses of <Emphasis Type="Italic">Populus</Emphasis> × <Emphasis Type="Italic">canadensis</Emphasis> ‘Neva’ to nitrogen fertilization and exogenous <Emphasis Type="Italic">Rhizophagus irregularis</Emphasis> inoculation

Arbuscular mycorrhizal fungi (AMF) can promote plant growth performance, but their effectiveness varies depending on soil nitrogen (N) availability. To clarify the effectiveness of exogenous AMF along an N-fertilization gradient (0, 2, 10, 20, and 30 mM), the impacts of exogenous Rhizophagus irregularis and N on the growth, photochemical activity, and nutritional status of Populus?×?canadensis ‘Neva’ in natural soil were evaluated in a pot experiment. The results showed that the 10 mM N level was the optimal fertilization regime with the highest promotion effect on plant growth and the maximum quantum yield of photosystem II (PSII) (F_v/F_m). Excess N (20 and 30 mM) fertilization reduced the actual quantum yield of PSII (ФPSII) and the F_v/F_m of the plants. Regardless of the N availability, inoculated plants exhibited greater F_v/F_m values than did non-inoculated plants. The biomass of inoculated plants was significantly higher compared with the control under low N levels (0 and 2 mM). Under high N levels, inoculated plants showed significant increases in ФPSII. Moreover, the nutrient imbalance of plants inoculated with exogenous R. irregularis was eased by increasing P, Fe, Mn and Cu uptake in roots and higher P, Ca, Mg, Fe, Mn and Zn concentrations in leaves. Moreover, the F_v/F_m and ФPSII exhibited positive correlations with P, Ca, Mg and Zn concentrations in leaves. In conclusion, inoculation with exogenous R. irregularis can benefit plant fitness by improving the photochemical capacity and nutrient composition of poplar under different N levels.     

Enhanced salinity stress tolerance in transgenic chilli pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) plants overexpressing the wheat antiporter (<Emphasis Type="Italic">TaNHX2</Emphasis>) gene

Transgenic chilli pepper (Capsicum annuum L.) plants tolerant to salinity stress were produced by introducing the wheat Na⁺/H⁺ antiporter gene (TaNHX2) via Agrobacterium-mediated transformation. Cotyledonary explants were infected with Agrobacterium tumefaciens strain LBA4404 harboring a binary vector pBin438 that contains a wheat antiporter (TaNHX2) gene driven by the double CaMV 35S promoter and NPT II gene as a selectable marker. PCR and semiquantitative RT-PCR analysis confirmed that the TaNHX2 gene had been integrated and expressed in the T₁ generation of transgenic pepper plants as compared to the non-transformed plants. Southern blot analysis further verified the integration and presence of TaNHX2 gene in the genome of chilli pepper plants. Biochemical assays of these transgenic plants revealed enhanced levels of proline, chlorophyll, superoxide dismutase, ascorbate peroxidase, relative water content, and reduced levels of hydrogen peroxide (H₂O₂), malondialdehyde compared to wild-type plants under salt stress conditions. The present investigation clearly showed that overexpression of the TaNHX2 gene enhanced salt stress tolerance in transgenic chilli pepper plants.     

Consortium of Higher Aquatic Plants and Microalgae Designed to Purify Sewage of Heavy Metal Ions

We selected higher aquatic plants (HAP) and microalgae possessing a high sorption capacity in respect to heavy metals to form a consortium designed to purify contaminated aquatic ecosystems. Accumulation of heavy metals Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ was investigated in plants Pistia stratiotes, Elodea canadensis, and Lemna minor and green microalgae Chlorella vulgaris ВВ-2, Ankistrodesmus sp. ВI-1, Chlamydomonas reinhardtii В-4, and Scеnеdеsmus quadricauda В-1. It was found that intense accumulation of metals occurs in cultures of HAP Pistia stratiotes and Elodea canadensis. These plants are macroconcentrators of zinc, lead, and copper and microconcentrators of cadmium. Out of the examined cultures of microalgae, effective bioaccumulators of heavy metals were C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1. It was shown that heavy metals are selectively taken up from the medium in the series Zn²⁺ > Cu²⁺ > Cd²⁺ > Pb²⁺. In order to produce a consortium of higher aquatic plants and microalgae for purification of polluted aquatic ecosystems, we investigated interaction of HAP P. stratiotes and E. canadensis with microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 in the course of their cocultivation. Neutral relations were detected between the cells of microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 and HAP E. canadensis. At the same time, the cells of Ankistrodesmus sp. ВI-1 and HAP P. stratiotes formed a symbiosis. Microscopic examination showed numerous points where the cells of microalgae Ankistrodesmus sp. ВI-1 were attached to the roots of P. stratiotes plants. We tested an opportunity to employ the association between P. stratiotes and Ankistrodesmus sp. ВI-1 for purification of simulated wastewater polluted with heavy metal ions. This consortium proved to be capable of eliminating contaminants from the sewage, reducing their level in the sewage to standard values, and active accumulation of heavy metal ions.     

Effect of selenium on growth and antioxidant capacity of <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. during development of lead-induced oxidative stress

Effects of two selenium concentrations—0.4 and 0.8 mg Se⁶⁺ per kilogram of soil (treatments Se0.4 and Se0.8)—on seedling growth, chlorophyll content (Chl (a + b)), the content of thiobarbituric acidreactive substances (TBARs) indicative of peroxidation rates, and the activities of antioxidant enzymes (ascorbate peroxidase, AsP; glutathione reductase, GR; and guaiacol peroxidase, GPX) were studied in roots and leaves of wheat (Triticum aestivum L., cv. Triso) plants that were exposed for 14 days to oxidative stress induced by 50 and 100 mg Pb²⁺ per kilogram of soil (treatments Pb50 and Pb100, respectively). The pollution of soil with Pb²⁺ inhibited growth, lowered Chl (a + b) content, and intensified peroxidation. The content of TBARs increased by 44 and 72% in leaves and by 25 and 45% in roots for treatments Pb50 and Pb100, respectively. Activities of the antioxidant enzymes GR and GPX were higher in Pb²⁺-treated than in untreated (control) plants. The introduction of Se⁶⁺ into Pb²⁺-free soil (treatment Se0.4) was found to promote growth, stimulate AsP activity by 40% in leaves, and enhance AsP, GR, and GPX activities in roots by 38, 33, and 74%, respectively. The content of TBARs was reduced in Se⁶⁺-treated plants. By contrast, the treatment Se0.8 suppressed growth, elevated TBARs content, and stimulated activities of antioxidant enzymes in roots and leaves. The addition of 0.4 mg Se⁶⁺/kg to Pb²⁺-contaminated soil alleviated the negative influence of lead on plant growth, whereas the addition of 0.8 mg Se⁶⁺/kg aggravated the effect of Pb²⁺ contamination, especially in treatment (Pb100+Se0.8). Thus, the effectiveness of exogenous Se⁶⁺ application on growth and adaptive potential of plants cultivated under optimal pollutant-free conditions and on soils contaminated with lead depended on the concentration of Se⁶⁺ supplemented to soil and on the content of the stressor agent.     

Deciphering the Mechanisms of Endophyte-Mediated Biofortification of Fe and Zn in Wheat

An investigation was carried out to understand the mechanism(s) underlying enhanced Fe or Zn uptake in low Fe–Zn accumulator wheat genotype 4HPYT-414, due to inoculation of siderophore-producing and zinc-solubilizing endophytes—Arthrobacter sulfonivorans DS-68 and Arthrobacter sp. DS-179. Root anatomical features, using transmission electron microscopy (TEM), qualitative and quantitative aspects of production of organic acids and sugars in root exudates, and expression of TaZIP genes were analysed to relate to endophyte-mediated higher concentrations of Fe and Zn in the roots and shoots of wheat plants. TEM studies revealed that the endodermis, cortical region, root hair extension, xylem and xylem vessels, pericycle and vascular bundles were more pronounced and thicker in inoculated treatments, as compared to control. The organic acid profile of root exudates revealed five types of organic acids, with citric acid being predominant. Inoculation of A. sulfonivorans and Arthrobacter sp. brought about 5- and eightfold increases in the amounts of acids, respectively, as compared to control, particularly citric acid, succinic acid and acetic acid. Among the four TaZIP genes targeted, expression was achieved only for TaZIP3 and TaZIP7 genes, which showed 1–2 fold increases in the inoculated treatments. The results clearly indicated that the endophyte-mediated overexpression of TaZIP3 and TaZIP7 genes in roots and shoots, and the observed anatomical and exudate changes were acting synergistically in facilitating higher Fe and Zn translocation in roots and shoots.     

Screening and selecting arbuscular mycorrhizal fungi for inoculating micropropagated apple rootstocks in acid soils

Santa Catarina state is the largest producer of apples in Brazil. Soils in this region have low pH and high levels of aluminum and manganese, requiring high inputs of fertilizers and amendments increasing costs of apple production. Inoculation of arbuscular mycorrhizal fungi can improve the establishment of micropropagated apple plants in such adverse soil conditions. Soil samples were collected from apple orchards in the Caçador, Fraiburgo and São Joaquim regions to develop a corn bioassay to identify mycorrhizal communities with high infectivity. Eleven fungal species were identified from one Caçador soil with the highest infectivity. Glomus etunicatum SCT110, Scutellospora pellucida SCT111, Acaulospora scrobiculata SCT112 and Scutellospora heterogama SCT113 were brought into single-species culture and used in a plant growth and nutrient uptake experiment using micropropagated apple (Malus prunifolia), cultivated at three soil pH. Colonization by fungal isolates significantly affected plant height, shoot and root dry weights, and root:shoot ratio. Soil pH also significantly affected all growth parameters except shoot dry weight. Mycorrhizal inoculation also significantly altered tissue concentrations of P, Zn, Cu, Ca, S, Na, N, K, Fe and Al. Association with mycorrhizal fungi increased P concentration and also decreased Al concentrations in the shoots. Overall, G. etunicatum and S. pellucida were the most effective isolates to promote plant growth and nutrient uptake. Inoculation of apple rootstock with selected fungal isolates during the acclimatization stage represents a useful strategy for producing micropropagated apples that can withstand acidic soil conditions.     

Nutrient and water dynamics of Amazonian <Emphasis Type="Italic">canga</Emphasis> vegetation differ among physiognomies and from those of other neotropical ecosystems

Ferriferous savannas, also known as cangas in Brazil, are nutrient-impoverished ecosystems adapted to seasonal droughts. These ecosystems support distinctive vegetation physiognomies and high plant diversity, although little is known about how nutrient and water availability shape these ecosystems. Our study was carried out in the cangas from Carajás, eastern Amazonia, Brazil. To investigate the N cycling and drought adaptations of different canga physiognomies and compare the findings with those from other ecosystems, we analyzed nutrient concentrations and isotope ratios (δ¹³C and δ¹⁵N) of plants, litter, and soils from 36 plots distributed in three physiognomies: typical scrubland (SB), Vellozia scrubland (VL), and woodland (WD). Foliar δ¹⁵N values in cangas were higher than those in savannas but lower than those in tropical forests, indicating more conservative N cycles in Amazonian cangas than in forests. The lower δ¹⁵N in savanna formations may be due to a higher importance of mycorrhizal species in savanna vegetation than in canga vegetation. Elevated δ¹³C values indicate higher water shortage in canga ecosystems than in forests. Foliar and litter nutrient concentrations vary among canga physiognomies, indicating differences in nutrient dynamics. Lower nutrient availability, higher C:N ratios, and lower δ¹⁵N values characterize VL, whereas WD is delineated by lower δ¹³C values and higher soil P. These results suggest lower water restriction and lower P limitation in WD, whereas VL shows more conserved N cycles due to lower nutrient availability. Differences in nutrient and water dynamics among physiognomies indicate different ecological processes; thus, the conservation of all physiognomies is required to ensure the maintenance of functional diversity in this unique ecosystem.     

Deep rooting and global change facilitate spread of invasive grass

Abiotic global change factors, such as rising atmospheric CO₂, and biotic factors, such as exotic plant invasion, interact to alter the function of terrestrial ecosystems. An invasive lineage of the common reed, Phragmites australis, was introduced to North America over a century ago, but the belowground mechanisms underlying Phragmites invasion and persistence in natural systems remain poorly studied. For instance, Phragmites has a nitrogen (N) demand higher than native plant communities in many of the ecosystems it invades, but the source of the additional N is not clear. We exposed introduced Phragmites and native plant assemblages, containing Spartina patens and Schoenoplectus americanus, to factorial treatments of CO₂ (ambient or +300 ppm), N (0 or 25 g m^?2 year^?1), and hydroperiod (4 levels), and focused our analysis on changes in root productivity as a function of depth and evaluated the effects of introduced Phragmites on soil organic matter mineralization. We report that non-native invasive Phragmites exhibited a deeper rooting profile than native marsh species under all experimental treatments, and also enhanced soil organic matter decomposition. Moreover, exposure to elevated atmospheric CO₂ induced a sharp increase in deep root production in the invasive plant. We propose that niche separation accomplished through deeper rooting profiles circumvents nutrient competition where native species have relatively shallow root depth distributions; deep roots provide access to nutrient-rich porewater; and deep roots further increase nutrient availability by enhancing soil organic matter decomposition. We expect that rising CO₂ will magnify these effects in deep-rooting invasive plants that compete using a tree-like strategy against native herbaceous plants, promoting establishment and invasion through niche separation.