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Parker Laimbeer - One of the best experts on this subject based on the ideXlab platform.
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Age-specific responses to elevated salinity in the coastal marsh plant black needlerush (Juncus roemerianus Scheele) as determined through polyphasic chlorophyll a fluorescence transients (OJIP)
Marine Biology, 2012Co-Authors: Brant W. Touchette, Emily C. Adams, Parker LaimbeerAbstract:This study employed polyphasic chlorophyll a fluorescence transients (OJIP), a non-invasive marker of environmental stress in plants, to evaluate salt tolerance in three different Juncus roemerianus age classifications (6-, 24-, and 60-months). Following exposure to elevated salts (30 psu), the younger plants sustained growth, which was comparable to freshwater controls. While older (60-month) plants receiving only freshwater also grew over the 8-week study, the older salt-treated plants did not increase in size. Similarly, there were significant declines in variable chlorophyll a fluorescence parameters ( F _v/ F _m and F _v/ F _o), electron transport flux per reaction center (ET_o/RC), and photosystem II performance index (PI_ABS) for 60-month J. roemerianus following salt treatment. These responses were not evident in the two younger salt-treated age classifications. Our results suggest that older J. roemerianus are less tolerant to rapid and sudden increases in salinity relative to younger plants and that this age-specific response may help explain observed discrepancies in salt tolerance in J. roemerianus .
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Age-specific responses to elevated salinity in the coastal marsh plant black needlerush (Juncus roemerianus Scheele) as determined through polyphasic chlorophyll a fluorescence transients (OJIP)
Marine Biology, 2012Co-Authors: Brant W. Touchette, Emily C. Adams, Parker LaimbeerAbstract:This study employed polyphasic chlorophyll a fluorescence transients (OJIP), a non-invasive marker of environmental stress in plants, to evaluate salt tolerance in three different Juncus roemerianus age classifications (6-, 24-, and 60-months). Following exposure to elevated salts (30 psu), the younger plants sustained growth, which was comparable to freshwater controls. While older (60-month) plants receiving only freshwater also grew over the 8-week study, the older salt-treated plants did not increase in size. Similarly, there were significant declines in variable chlorophyll a fluorescence parameters (F \n v/F \n m and F \n v/F \n o), electron transport flux per reaction center (ET \n o/RC), and photosystem II performance index (PI \n ABS) for 60-month J. roemerianus following salt treatment. These responses were not evident in the two younger salt-treated age classifications. Our results suggest that older J. roemerianus are less tolerant to rapid and sudden increases in salinity relative to younger plants and that this age-specific response may help explain observed discrepancies in salt tolerance in J. roemerianus. © 2012 Springer-Verlag.
Brant W. Touchette - One of the best experts on this subject based on the ideXlab platform.
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Age-specific responses to elevated salinity in the coastal marsh plant black needlerush (Juncus roemerianus Scheele) as determined through polyphasic chlorophyll a fluorescence transients (OJIP)
Marine Biology, 2012Co-Authors: Brant W. Touchette, Emily C. Adams, Parker LaimbeerAbstract:This study employed polyphasic chlorophyll a fluorescence transients (OJIP), a non-invasive marker of environmental stress in plants, to evaluate salt tolerance in three different Juncus roemerianus age classifications (6-, 24-, and 60-months). Following exposure to elevated salts (30 psu), the younger plants sustained growth, which was comparable to freshwater controls. While older (60-month) plants receiving only freshwater also grew over the 8-week study, the older salt-treated plants did not increase in size. Similarly, there were significant declines in variable chlorophyll a fluorescence parameters ( F _v/ F _m and F _v/ F _o), electron transport flux per reaction center (ET_o/RC), and photosystem II performance index (PI_ABS) for 60-month J. roemerianus following salt treatment. These responses were not evident in the two younger salt-treated age classifications. Our results suggest that older J. roemerianus are less tolerant to rapid and sudden increases in salinity relative to younger plants and that this age-specific response may help explain observed discrepancies in salt tolerance in J. roemerianus .
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Age-specific responses to elevated salinity in the coastal marsh plant black needlerush (Juncus roemerianus Scheele) as determined through polyphasic chlorophyll a fluorescence transients (OJIP)
Marine Biology, 2012Co-Authors: Brant W. Touchette, Emily C. Adams, Parker LaimbeerAbstract:This study employed polyphasic chlorophyll a fluorescence transients (OJIP), a non-invasive marker of environmental stress in plants, to evaluate salt tolerance in three different Juncus roemerianus age classifications (6-, 24-, and 60-months). Following exposure to elevated salts (30 psu), the younger plants sustained growth, which was comparable to freshwater controls. While older (60-month) plants receiving only freshwater also grew over the 8-week study, the older salt-treated plants did not increase in size. Similarly, there were significant declines in variable chlorophyll a fluorescence parameters (F \n v/F \n m and F \n v/F \n o), electron transport flux per reaction center (ET \n o/RC), and photosystem II performance index (PI \n ABS) for 60-month J. roemerianus following salt treatment. These responses were not evident in the two younger salt-treated age classifications. Our results suggest that older J. roemerianus are less tolerant to rapid and sudden increases in salinity relative to younger plants and that this age-specific response may help explain observed discrepancies in salt tolerance in J. roemerianus. © 2012 Springer-Verlag.
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tolerance and avoidance two contrasting physiological responses to salt stress in mature marsh halophytes Juncus roemerianus scheele and spartina alterniflora loisel
Journal of Experimental Marine Biology and Ecology, 2009Co-Authors: Brant W. Touchette, Gracen Smith, Kirsten L Rhodes, M PooleAbstract:Abstract For most plants, elevated salinities can promote both hyperionic and hyperosmotic stress, often resulting in decreased growth and increased mortality. In previous studies involving plant–water relations, two contrasting physiological mechanisms to water stress have emerged: ( i ) stress-tolerance, which can be achieved through osmotic adjustment and changes in tissue elasticity, and ( ii ) stress-avoidance, which restricts further water loss through decreased stomatal conductance and changes in leaf morphology and/or orientation. While these processes have been well characterized in angiosperms during drought, few studies have considered these responses in halophytes during salt-stress. In this study, experimental microcosms were used to evaluate salt-tolerance and salt-avoidance in two contrasting coastal-marsh halophytes, Juncus roemerianus and Spartina alterniflora . In mature S. alterniflora , preacclimated to freshwater, only salt-tolerance mechanisms (osmotic adjustment and increased tissue rigidity) were observed during high salinity conditions. In contrast, physiological modifications observed in mature J. roemerianus involved salt-avoidance through decreased stomatal conductance. These physiological responses are consistent with zonation patterns in these plants, wherein S. alterniflora resides in the lower marsh and must contend with long-term salt exposure and J. roemerianus inhabits the upper reaches of salt-marshes where salinities tend to be lower and where salt-stress often involves transient exposure to high salinities.
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salt tolerance in a Juncus roemerianus brackish marsh spatial variations in plant water relations
Journal of Experimental Marine Biology and Ecology, 2006Co-Authors: Brant W. TouchetteAbstract:Abstract Halophytes residing in tidal marshes are often subjected to intense and varying environmental demands. These variations may occur in a matter of hours, with tidal-induced changes in hydrology and soil chemistry (including soil oxygen status, redox potentials, and salinity). Juncus roemerianus has been shown to occupy three dissimilar marsh zones, including lower marsh with minimally diluted saline waters, mid-marsh which undergoes periodic freshwater dilutions of tidal waters, and upper marsh which is principally maintained by upland freshwaters. The purpose of this study was to discern spatial patterns in plant water status of J. roemerianus . Leaf water potentials ( ψ leaf ) were 1–2 MPa less than soil-osmotic potential ( ψ π soil ), with the greatest ψ leaf (i.e., most negative; ca. − 4 MPa) generated within the lower marsh as plants experienced the highest salinities (18 ppt; during low tide). There was a 3–12% increase in relative water content ( θ ) in mid-marsh plants, in comparison to both lower- and upper-marsh individuals. Pressure–volume isotherms showed that plants along the shoreline (i.e., lower-marsh) had lower osmotic potential at full saturation ( ψ π sat ), lower osmotic potential at turgor loss point ( ψ π tlp ), and elevated bulk modulus of elasticity ( ϵ ). Whereas, no spatial differences in water content at turgor loss point ( θ tlp ) and symplastic water fraction ( θ sym ) were observed among the three marsh zones. Additionally, morphological and plant mass characteristics, including stomatal size, stomatal density, leaf abundance, and above-ground biomass, were greater in lower marsh plants compared to other two marsh zones. Overall, this study demonstrates the importance of soil–water salinity (as ψ π soil ) in shaping spatial variations in plant water status within a J. roemerianus brackish marsh.
Campbell J Nairn - One of the best experts on this subject based on the ideXlab platform.
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broad scale patterns of genetic diversity and structure in a foundational salt marsh species black needlerush Juncus roemerianus
Conservation Genetics, 2019Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Campbell J NairnAbstract:Clonal and genetic diversity in foundational plant species are critical for species resiliency and ecosystem processes, both of which contribute to restoration success; however, genetic data is often lacking for common plant species used in many restoration practices. Only a few plant species dominate salt marshes, ecologically and economically valuable ecosystems targeted for restoration due to global decline. Despite being a foundational species in southeastern United States salt marshes black needlerush (Juncus roemerianus Scheele) is understudied, especially in comparison to the co-occurring smooth cordgrass (Spartina alterniflora Loisel). We used a panel of 18 microsatellite markers on 849 samples of J. roemerianus collected at 17 sites across a majority of the species range from Mississippi to South Carolina to measure clonal and genetic diversity and characterize population structure. Results are consistent with previous genetic studies on J. roemerianus and other clonal plant species in that clonal and genetic diversity were higher than expected based on life history literature, with an average genotypic diversity (GD) of 0.67 and average observed heterozygosity (HO) of 0.56. Differences in diversity between the ecologically and environmentally divergent Gulf (GD = 0.64, HO = 0.52) and Atlantic (GD = 0.80, HO = 0.45) coasts suggest that life history strategy may vary by environment. Hierarchical structure was apparent across the study area, with STRUCTURE analyses identifying three genetic clusters that further subdivided into five clusters and a broad transition zone. The scale of this genetic differentiation should be considered in sourcing plants for salt marsh restoration efforts.
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landscape genetics of the foundational salt marsh plant species black needlerush Juncus roemerianus scheele across the northeastern gulf of mexico
Landscape Ecology, 2018Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Nathan P Nibbelink, Richard B Chandler, Campbell J NairnAbstract:CONTEXT: Common species important for ecosystem restoration stand to lose as much genetic diversity from anthropogenic habitat fragmentation and climate change as rare species, but are rarely studied. Salt marshes, valuable ecosystems in widespread decline due to human development, are dominated by the foundational plant species black needlerush (Juncus roemerianus Scheele) in the northeastern Gulf of Mexico. OBJECTIVES: We assessed genetic patterns in J. roemerianus by measuring genetic and genotypic diversity, and characterizing population structure. We examined population connectivity by delineating possible dispersal corridors, and identified landscape factors influencing population connectivity. METHODS: A panel of 19 microsatellite markers was used to genotype 576 samples from ten sites across the northeastern Gulf of Mexico from the Grand Bay National Estuarine Research Reserve (NERR) to the Apalachicola NERR. Genetic distances (FST and Dcₕ) were used in a least cost transect analysis (LCTA) within a hierarchical model selection framework. RESULTS: Genetic and genotypic diversity results were higher than expected based on life history literature, and samples structured into two large, admixed genetic clusters across the study area, indicating sexual reproduction may not be as rare as predicted in this clonal macrophyte. Digitized coastal transects buffered by 500 m may represent possible dispersal corridors, and developed land may significantly impede population connectivity in J. roemerianus. CONCLUSIONS: Results have important implications for coastal restoration and management that seek to preserve adaptive potential by sustaining natural levels of genetic diversity and conserving population connectivity. Our methodology could be applied to other common, widespread and understudied species.
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microsatellite markers for population studies of the salt marsh species Juncus roemerianus juncaceae
Applications in Plant Sciences, 2017Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Campbell J NairnAbstract:Premise of the study: Juncus roemerianus (Juncaceae) is a foundational species and ecosystem engineer of salt marshes in the Gulf of Mexico. These ecosystems provide coastal flood attenuation, nurseries for important species, and other ecosystem services, but are experiencing significant decline. Nuclear microsatellite markers were developed for J. roemerianus to study genetic diversity and population structure for conservation and restoration efforts. Methods and Results: Illumina NextSeq high-throughput sequencing was used to develop a panel of 19 polymorphic microsatellite markers that were tested across individuals from three populations on the Gulf Coast. All markers were polymorphic, with observed and expected heterozygosities ranging from 0.212 to 0.828 and from 0.362 to 0.873, respectively. Allelic richness ranged from two to 13 alleles per locus with an average of 5.737. Conclusions: The 19 microsatellite markers are useful for population studies throughout the range of J. roemerianus. Three loci...
Hayley R Tumas - One of the best experts on this subject based on the ideXlab platform.
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broad scale patterns of genetic diversity and structure in a foundational salt marsh species black needlerush Juncus roemerianus
Conservation Genetics, 2019Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Campbell J NairnAbstract:Clonal and genetic diversity in foundational plant species are critical for species resiliency and ecosystem processes, both of which contribute to restoration success; however, genetic data is often lacking for common plant species used in many restoration practices. Only a few plant species dominate salt marshes, ecologically and economically valuable ecosystems targeted for restoration due to global decline. Despite being a foundational species in southeastern United States salt marshes black needlerush (Juncus roemerianus Scheele) is understudied, especially in comparison to the co-occurring smooth cordgrass (Spartina alterniflora Loisel). We used a panel of 18 microsatellite markers on 849 samples of J. roemerianus collected at 17 sites across a majority of the species range from Mississippi to South Carolina to measure clonal and genetic diversity and characterize population structure. Results are consistent with previous genetic studies on J. roemerianus and other clonal plant species in that clonal and genetic diversity were higher than expected based on life history literature, with an average genotypic diversity (GD) of 0.67 and average observed heterozygosity (HO) of 0.56. Differences in diversity between the ecologically and environmentally divergent Gulf (GD = 0.64, HO = 0.52) and Atlantic (GD = 0.80, HO = 0.45) coasts suggest that life history strategy may vary by environment. Hierarchical structure was apparent across the study area, with STRUCTURE analyses identifying three genetic clusters that further subdivided into five clusters and a broad transition zone. The scale of this genetic differentiation should be considered in sourcing plants for salt marsh restoration efforts.
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landscape genetics of the foundational salt marsh plant species black needlerush Juncus roemerianus scheele across the northeastern gulf of mexico
Landscape Ecology, 2018Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Nathan P Nibbelink, Richard B Chandler, Campbell J NairnAbstract:CONTEXT: Common species important for ecosystem restoration stand to lose as much genetic diversity from anthropogenic habitat fragmentation and climate change as rare species, but are rarely studied. Salt marshes, valuable ecosystems in widespread decline due to human development, are dominated by the foundational plant species black needlerush (Juncus roemerianus Scheele) in the northeastern Gulf of Mexico. OBJECTIVES: We assessed genetic patterns in J. roemerianus by measuring genetic and genotypic diversity, and characterizing population structure. We examined population connectivity by delineating possible dispersal corridors, and identified landscape factors influencing population connectivity. METHODS: A panel of 19 microsatellite markers was used to genotype 576 samples from ten sites across the northeastern Gulf of Mexico from the Grand Bay National Estuarine Research Reserve (NERR) to the Apalachicola NERR. Genetic distances (FST and Dcₕ) were used in a least cost transect analysis (LCTA) within a hierarchical model selection framework. RESULTS: Genetic and genotypic diversity results were higher than expected based on life history literature, and samples structured into two large, admixed genetic clusters across the study area, indicating sexual reproduction may not be as rare as predicted in this clonal macrophyte. Digitized coastal transects buffered by 500 m may represent possible dispersal corridors, and developed land may significantly impede population connectivity in J. roemerianus. CONCLUSIONS: Results have important implications for coastal restoration and management that seek to preserve adaptive potential by sustaining natural levels of genetic diversity and conserving population connectivity. Our methodology could be applied to other common, widespread and understudied species.
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microsatellite markers for population studies of the salt marsh species Juncus roemerianus juncaceae
Applications in Plant Sciences, 2017Co-Authors: Hayley R Tumas, Brian M Shamblin, Mark S Woodrey, Campbell J NairnAbstract:Premise of the study: Juncus roemerianus (Juncaceae) is a foundational species and ecosystem engineer of salt marshes in the Gulf of Mexico. These ecosystems provide coastal flood attenuation, nurseries for important species, and other ecosystem services, but are experiencing significant decline. Nuclear microsatellite markers were developed for J. roemerianus to study genetic diversity and population structure for conservation and restoration efforts. Methods and Results: Illumina NextSeq high-throughput sequencing was used to develop a panel of 19 polymorphic microsatellite markers that were tested across individuals from three populations on the Gulf Coast. All markers were polymorphic, with observed and expected heterozygosities ranging from 0.212 to 0.828 and from 0.362 to 0.873, respectively. Allelic richness ranged from two to 13 alleles per locus with an average of 5.737. Conclusions: The 19 microsatellite markers are useful for population studies throughout the range of J. roemerianus. Three loci...
Jan Kohlmeyer - One of the best experts on this subject based on the ideXlab platform.
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fungi on Juncus roemerianus 17 new ascomycetes and the hyphomycete genus kolletes gen nov
Botanica Marina, 2005Co-Authors: Jan Kohlmeyer, Brigitte Volkmannkohlmeyer, Clement K M TsuiAbstract:Three new fungi are described from the halophyte, Juncus roemerianus, an endemic species in saltmarshes of the United States east coast. Pseudohalonectria halophila sp. nov. is an obligate marine fungus, whereas Phaeosphaeria anchiala sp. nov. is facultative, and Kolletes undulatus gen. et sp. nov. a terrestrial, but halotolerant hyphomycete. The taxonomic classification of P. anchiala in Phaeosphaeria is supported by phylogenetic analysis of the SSU and ITS region of the rDNA.
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Fungi on Juncus and Spartina: New marine species of Anthostomella, with a list of marine fungi known on Spartina*
Fungal Biology, 2002Co-Authors: Jan Kohlmeyer, Brigitte Volkmann-kohlmeyerAbstract:All 39 marine species described so far from Spartina spp. are listed. Anthostomella torosa sp. nov. is described from culms of Juncus roemerianus in North Carolina, and A. spissitecta sp. nov. is described from leaf sheaths of saltmarsh Spartina alterniflora in the USA (Connecticut, Florida, North Carolina, Rhode Island) and from S. densiflora in Argentina (Buenos Aires). Both species occur close to the rhizome and are classified as obligate marine fungi. The new species are compared with similar taxa, and a table comprises characteristics of the nine known aquatic Anthostomella species.
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fungi on Juncus roemerianus new coelomycetes with notes on dwayaangam junci
Fungal Biology, 2001Co-Authors: Jan Kohlmeyer, Brigitte VolkmannkohlmeyerAbstract:Pycnodallia dupla gen. sp. nov. and Hymenopsis chlorothrix sp. nov. are described from saltmarsh Juncus roemerianus in North Carolina. Conidiomata of P. dupla develop on senescent inflorescences and involucral leaves, between 40 and 60 cm above the rhizome, therefore, the species can be considered as facultative marine. Conidiomata of H. chlorothrix are found on dead culms, 16–43 cm above the rhizome. This species is classified as obligately marine. Dwayaangam junci , the anamorph of Orbilia junci , has been found for the first time in nature. Conidia develop on the medulla of leaves, in lesions caused by grasshoppers.
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fungi on Juncus roemerianus 11 more new ascomycetes
Botany, 1998Co-Authors: Jan Kohlmeyer, Brigitte Volkmannkohlmeyer, Ove ErikssonAbstract:Anthostomella atroalba sp.nov., Phaeosphaeria roemeriani sp.nov., and Rivilata ius gen. et sp.nov. are described from the endemic needlerush, Juncus roemerianus Scheele, in salt marshes of the U.S. east coast. Phaeosphaeria roemeriani is an obligate marine species growing in the base of the plant, whereas A. atroalba and R. ius can be considered terrestrial, because they develop exclusively in the upper, not inundated, part of the leaves. Rivilata, a member of Saccardiaceae, is compared with representatives of Phillipsiella and Schizothyrium.Key words: Anthostomella, Juncus, marine fungi, marsh, Phaeosphaeria, Rivilata.
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fungi on Juncus roemerianus 10 a new orbilia with ingoldian anamorph
Mycologia, 1998Co-Authors: Jan Kohlmeyer, Hansotto Baral, Brigitte VolkmannkohlmeyerAbstract:Orbilia junci sp. nov., belonging to the subgenus Hemiorbilia, is described from the endemic halophyte Juncus roemerianus from North Carolina. This small discomycete grows on the brittle tips of old standing leaves, where it is exposed to extreme climatic conditions, including drought, soaking by rain or dew, freezing in the winter, high summer tem- peratures and salt spray. The species forms a stauro- sporous hyphomycete in culture, Dwayaangam junci sp. nov., characterized by conidia that are branched dichotomously twice at the apex and consist of a cy- lindric-ellipsoidal main axis and four curved and ta- pering side arms that are pointing upwards and downwards. The new anamorph is compared with the other six species assigned previously to Dwayaangam and is the first member of this genus to be linked with a teleomorph.
