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Denise M Seliskar - One of the best experts on this subject based on the ideXlab platform.
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the response of plasma membrane lipid composition in callus of the halophyte Spartina patens poaceae to salinity stress
American Journal of Botany, 2005Co-Authors: Denise M Seliskar, John L GallagherAbstract:Callus cultures of the salt marsh grass Spartina patens were examined to determine changes and consistencies in membrane lipid composition in response to salt. Major membrane lipid classes remained stable at all salinity levels (0, 170, 340 mmol/L). However, the membrane protein to lipid ratio decreased significantly in response to elevated NaCl. Callus plasma membrane (PM) consisted predominantly of sterols, about 60% (mol%) of the total lipids. Glycolipid was the second largest lipid class, making up about 20% (mol%) of the total. With increasing salinity, the relative percentage of sitosterol decreased, while that of campesterol increased. The phospholipid species detected were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylinositol (PI). When callus was grown at 340 mmol/L NaCl, PC increased significantly. PI and PS were also significantly elevated in salinity treatments. Only 24-32% of the PM fatty acids were common plant membrane fatty acids, C16, C18, C20, and C22, while over 60% were the less common fatty acids, C11 and C14. Membrane fluidity remained stable in response to growth medium salinity. The findings on membrane responses to salinity will facilitate a better understanding of this halophyte's tactics for salt tolerance.
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the response of ammophila breviligulata and Spartina patens poaceae to grazing by feral horses on a dynamic mid atlantic barrier island
American Journal of Botany, 2003Co-Authors: Denise M SeliskarAbstract:Ammophila breviligulata, American beachgrass, and Spartina patens, salt meadow hay, have been grazed by feral horses on the dunes of Assateague Island for hundreds of years; however, because of a significant increase in the horse population since the 1960s, overgrazing and dune erosion have become, problems. Grazing was assessed on foredunes of four different morphologies along a 21-km stretch of the Maryland portion of the island using 17 exclosure plot pairs. In addition to decreased cover and biomass of the two species, plant structure was significantly affected by grazing. Leaf length and width, stem diameter, and stem density of A. breviligulata and stem diameter of S. patens were reduced in the grazed plots. Especially sensitive to grazing were reproductive characteristics. Percentage of plants in flower, height of flowering stems, and inflorescence length were all significantly reduced by grazing (nongrazed individuals measured). Species composition was not affected by horse accessibility.
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salinity adaptation of plasma membrane h atpase in the salt marsh plant Spartina patens atp hydrolysis and enzyme kinetics
Journal of Experimental Botany, 1998Co-Authors: Denise M SeliskarAbstract:Spartina patens, an intertidal C 4 grass, grows in the upper salt marsh and tolerates coastal seawater salinity. The regulation of ion movement across the plasma Introduction membrane (PM) for plant salt tolerance is thought to The C 4 grass, Spartina patens (Aiton) Muhl, grows in the be achieved by an electrochemical gradient generated upper part of salt and brackish marshes just above the by plasma membrane H+-ATPase. In this study, the Spartina alterniflora zone. It can tolerate coastal seawater change of PM H+-ATPase in response to NaCl was
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stress tolerance in the marsh plant Spartina patens impact of nacl on growth and root plasma membrane lipid composition
Physiologia Plantarum, 1998Co-Authors: Denise M Seliskar, John L GallagherAbstract:The C-4 salt marsh grass, Spartina patens, thrives in the upper portion of the marsh where soil salinities may be equal to coastal seawater. Spartina patens was grown in hydroponic culture in a greenhouse at 0, 340, and 510 mM NaCl, and measured for growth, tissue cation content, and root plasma membrane (PM) lipid composition. From 0 to 340 and 510 mM, the shoot growth decreased, but root growth was not affected. The Na + content increased in both shoots and roots when plants were grown in salt, while the shoots had a decreased K + content and the roots had a decreased Ca 2+ content. Spartina patens root plasma membrane was isolated with an aqueous polymer two-phase system. The purity of the plasma membrane was verified with cytochemical tests on membrane enzyme markers. Plasma membrane lipids were stable relative to the membrane protein content. Molar percentages of sterols (including free sterols) and phospholipid decreased with increasing salinity. However, glycolipid showed a statistically significant increase in the total lipid as salinity in the medium was increased from 0 to 510 mM. Even at a salinity of 510 mM, the plasma membrane sterol/phospholipid ratio was unaffected by NaCI. When the plants were grown in NaCI media, the plasma membrane had a decreased phosphatidylcholine (PC) and phosphatidylethanolamine (PE) content, but the PC/PE ratios were not affected. The plasma membrane molar percentage of sitosterol in total free sterol increased when plants were grown in salt media. The predominant membrane fatty acids were C11 and C14, and the major unsaturated one was C14:1. An increase in growth medium salinity resulted in a decreased root plasma membrane fluidity.
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plant regeneration from callus cultures of salt marsh hay Spartina patens and its cellular based salt tolerance
Aquatic Botany, 1995Co-Authors: Denise M Seliskar, Jennifer A Moga, John L GallagherAbstract:Salt marsh hay, Spartina patens (Ait.) Muhl. (Poaceae), is a perennial salt-tolerant grass common in salt marshes and sand dunes of the Atlantic and Gulf coasts of the USA, and grows vigorously at coastal seawater salinity. To study the salt tolerance mechanisms that operate in S. patens at the cellular level, a tissue culture and regeneration protocol for this species was developed. Callus was initiated from seedling mesocotyl on ADM medium (Murashige and Skoog (MS) salts + 3% sucrose + 1 mg l−1 indoleacetic acid (IAA) and 1 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D)). Regenerable callus was selected from the several morphotypes that developed and was maintained on BND medium (MS salts + 3% sucrose + 0.5 mg l−1 6-benzylaminopurine (BAP), 1 mg l−1 1-naphthaleneacetic acid (NAA), 0.5 mg l−1 2,4-D, and 50 ml l−1 coconut water (CW)). Shoots formed from 90% of the cultures grown on shoot regeneration medium containing BAP and IAA. Roots formed from shoots when they were transferred to root regeneration medium containing indole-3-butyric acid (IBA) and activated charcoal or reduced strength MS medium. Plants regenerated via organogenesis have flowered and set viable seeds in a saltwater-irrigated field plot. Dry weight accumulation of unadapted callus at 510 mM NaCl is similar to that at 0 mM NaCl (control), indicating that S. patens has strong salt tolerance at the cellular level.
John L Gallagher - One of the best experts on this subject based on the ideXlab platform.
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the response of plasma membrane lipid composition in callus of the halophyte Spartina patens poaceae to salinity stress
American Journal of Botany, 2005Co-Authors: Denise M Seliskar, John L GallagherAbstract:Callus cultures of the salt marsh grass Spartina patens were examined to determine changes and consistencies in membrane lipid composition in response to salt. Major membrane lipid classes remained stable at all salinity levels (0, 170, 340 mmol/L). However, the membrane protein to lipid ratio decreased significantly in response to elevated NaCl. Callus plasma membrane (PM) consisted predominantly of sterols, about 60% (mol%) of the total lipids. Glycolipid was the second largest lipid class, making up about 20% (mol%) of the total. With increasing salinity, the relative percentage of sitosterol decreased, while that of campesterol increased. The phospholipid species detected were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylinositol (PI). When callus was grown at 340 mmol/L NaCl, PC increased significantly. PI and PS were also significantly elevated in salinity treatments. Only 24-32% of the PM fatty acids were common plant membrane fatty acids, C16, C18, C20, and C22, while over 60% were the less common fatty acids, C11 and C14. Membrane fluidity remained stable in response to growth medium salinity. The findings on membrane responses to salinity will facilitate a better understanding of this halophyte's tactics for salt tolerance.
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stress tolerance in the marsh plant Spartina patens impact of nacl on growth and root plasma membrane lipid composition
Physiologia Plantarum, 1998Co-Authors: Denise M Seliskar, John L GallagherAbstract:The C-4 salt marsh grass, Spartina patens, thrives in the upper portion of the marsh where soil salinities may be equal to coastal seawater. Spartina patens was grown in hydroponic culture in a greenhouse at 0, 340, and 510 mM NaCl, and measured for growth, tissue cation content, and root plasma membrane (PM) lipid composition. From 0 to 340 and 510 mM, the shoot growth decreased, but root growth was not affected. The Na + content increased in both shoots and roots when plants were grown in salt, while the shoots had a decreased K + content and the roots had a decreased Ca 2+ content. Spartina patens root plasma membrane was isolated with an aqueous polymer two-phase system. The purity of the plasma membrane was verified with cytochemical tests on membrane enzyme markers. Plasma membrane lipids were stable relative to the membrane protein content. Molar percentages of sterols (including free sterols) and phospholipid decreased with increasing salinity. However, glycolipid showed a statistically significant increase in the total lipid as salinity in the medium was increased from 0 to 510 mM. Even at a salinity of 510 mM, the plasma membrane sterol/phospholipid ratio was unaffected by NaCI. When the plants were grown in NaCI media, the plasma membrane had a decreased phosphatidylcholine (PC) and phosphatidylethanolamine (PE) content, but the PC/PE ratios were not affected. The plasma membrane molar percentage of sitosterol in total free sterol increased when plants were grown in salt media. The predominant membrane fatty acids were C11 and C14, and the major unsaturated one was C14:1. An increase in growth medium salinity resulted in a decreased root plasma membrane fluidity.
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plant regeneration from callus cultures of salt marsh hay Spartina patens and its cellular based salt tolerance
Aquatic Botany, 1995Co-Authors: Denise M Seliskar, Jennifer A Moga, John L GallagherAbstract:Salt marsh hay, Spartina patens (Ait.) Muhl. (Poaceae), is a perennial salt-tolerant grass common in salt marshes and sand dunes of the Atlantic and Gulf coasts of the USA, and grows vigorously at coastal seawater salinity. To study the salt tolerance mechanisms that operate in S. patens at the cellular level, a tissue culture and regeneration protocol for this species was developed. Callus was initiated from seedling mesocotyl on ADM medium (Murashige and Skoog (MS) salts + 3% sucrose + 1 mg l−1 indoleacetic acid (IAA) and 1 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D)). Regenerable callus was selected from the several morphotypes that developed and was maintained on BND medium (MS salts + 3% sucrose + 0.5 mg l−1 6-benzylaminopurine (BAP), 1 mg l−1 1-naphthaleneacetic acid (NAA), 0.5 mg l−1 2,4-D, and 50 ml l−1 coconut water (CW)). Shoots formed from 90% of the cultures grown on shoot regeneration medium containing BAP and IAA. Roots formed from shoots when they were transferred to root regeneration medium containing indole-3-butyric acid (IBA) and activated charcoal or reduced strength MS medium. Plants regenerated via organogenesis have flowered and set viable seeds in a saltwater-irrigated field plot. Dry weight accumulation of unadapted callus at 510 mM NaCl is similar to that at 0 mM NaCl (control), indicating that S. patens has strong salt tolerance at the cellular level.
Dittmar Hahn - One of the best experts on this subject based on the ideXlab platform.
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seasonal analyses of arbuscular mycorrhizae nitrogen fixing bacteria and growth performance of the salt marsh grass Spartina patens
Plant and Soil, 2010Co-Authors: Allana Welsh, David J Burke, Erik P Hamerlynck, Dittmar HahnAbstract:Seasonal variation of arbuscular mycorrhizal fungi (AMF) in roots of the high salt marsh plant Spartina patens, the diversity of nitrogen-fixing bacteria in the rhizosphere and plant growth performance was studied at key stages of the growing season coinciding with major plant phenological stages, i.e., vegetative growth, reproduction and senescence. AMF colonization was highest during vegetative growth, with values declining during the growing season to the same level seen at plant dormancy. AMF colonization was reduced at lower depths in the sediments where anoxic conditions were observed and in plants treated with the systemic fungicide Benomyl. Only small changes in diversity of nitrogen-fixing bacteria in general and more specifically of those belonging to the e-subdivision of Proteobacteria were detected during the season or between treatments by PCR-RFLP of nifH gene fragments with DNA as template for amplification; however, greater seasonal changes were displayed when cDNA was used as template for amplification as a proxy for gene expression and thus active bacteria. DGGE analyses of nifH gene fragments representing nitrogen-fixing bacteria of the e-subdivision of Proteobacteria using both using DNA and cDNA as template showed highly diverse profiles that changed during the season and in response to treatment. Seasonal changes were observed for a suite of plant growth attributes and differences were observed between treatments, with higher values generally obtained on non-treated plants compared to Benomyl-treated plants. These differences were most pronounced during vegetative growth; however, differences between non-treated and Benomyl-treated plants were reduced seasonally and disappeared by the onset of senescence. This study demonstrates seasonal changes in AMF colonization on S. patens and in the community structure of nitrogen-fixing members of the e-subdivision of Proteobacteria in the plant root zone. Plant growth performance changed seasonally with some effects of Benomyl-treatment.
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uptake and translocation of heavy metals in salt marsh sediments by Spartina patens
Bulletin of Environmental Contamination and Toxicology, 2007Co-Authors: Kallaya Suntornvongsagul, David J Burke, Dittmar HahnAbstract:The Hackensack Meadowlands is a coastal marsh system in northeastern New Jersey, located approximately 10 km west of New York City. Within the Meadowlands, twelve destructed or degraded estuarine wetland sites are currently part of ecological restoration projects that are in various phases of development from planning to completion (http:// www.meadowlands.state.nj.us/naturalresources/wetlands/ Wetlands.cfm). A completed restoration site is Harrier Meadow (North Arlington, NJ) where mitigation work included the creation of channels, impoundments, low marsh habitat and upland habitat islands. Important salt marsh plant species such as salt-meadow grass (Spartina patens), and spike grass (Distichlis spicata) dominate portions of the marsh. The sediments of Harrier Meadow contain heavy metals at concentrations that are below regulatory action limits (e.g., cadmium (Cd) 0–1 ppm; chromium (Cr) 10–18 ppm; copper (Cu) 13–60 ppm; nickel (Ni) 7–15 ppm; lead (Pb) 0–87 ppm; zinc (Zn) 28–94 ppm) (http:// www.meri.njmeadowlands.gov/ecorisk/), but above those typically found in uncontaminated environments (van Driel et al. 1995; Swaileh et al. 2004). Since Spartina species have been shown to take up heavy metals into roots and translocate them into aboveground parts (see Weis and Weis (2004) for review), we had investigated the fate and the effects of selected heavy metals (i.e., Cd, Cr, Cu, Ni, Pb, and Zn) in sediment cores that were densely covered with Spartina patens in a recent short-term study (Suntornvongsagul et al. 2007). Since levels of metals taken up and translocated had been shown to vary depending on the metal concentration in the substrate (Vogel-Mikus et al. 2005), and to be affected by the presence of other metals (McKenna et al. 1993; Podar et al. 2004), half of these cores were artificially amended with Ni in order to increase its availability, and to assess potential effects on uptake of other metals. Ni was chosen since it was the most accumulated metal in shoots from a mixture containing Cd(II), Cu(II), Ni(II) and Zn(II) in identical concentrations (Peralta-Videa et al. 2002), and was assumed to persist in hydrated form in pore water. We demonstrated that Ni-amendment had no significant effect on the fate of other metals in sediments, however, observed increased root-uptake of certain metals. Although translocation of Ni into shoots reflected the 10-fold higher concentrations in sediments and roots in Ni-amended cores, metal translocation into shoots was generally small for all metals (Suntornvongsagul et al. 2007). The goal of the current study was to extend the observations beyond the first growing season, and to assess whether Ni-amendment had effects on metal uptake and translocation after three growing seasons.
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interactions between the salt marsh grass Spartina patens arbuscular mycorrhizal fungi and sediment bacteria during the growing season
Soil Biology & Biochemistry, 2003Co-Authors: David J Burke, Erik P Hamerlynck, Dittmar HahnAbstract:Abstract The interaction between the salt marsh plant Spartina patens , arbuscular mycorrhizal fungi (AMF) and bacteria in salt marsh sediment was examined in a long-term arbuscular mycorrhizas (AM) suppression study by applying the systemic fungicide benomyl to field-collected sediment cores with and without S. patens plants. Microbial populations were sampled four times corresponding to major plant phenological stages (dormancy, vegetative growth, reproduction, and senescence) previously linked to changes in microbial populations under field conditions. Benomyl-treatment of soil cores significantly suppressed AM colonization on S. patens , keeping values relatively consistent throughout the growing season (11.5%) whereas plants in non-treated cores experienced seasonal increases and declines in AM colonization (26.6% during vegetative growth to 11.5% during dormancy). Soil physicochemical parameters were not affected by benomyl application. In unvegetated cores, no benomyl- or seasonal effects were displayed by cell numbers and specific biomass of DAPI-stained organisms, members of the domain bacteria and here especially members of the α-, β-, γ- and δ-subdivisions of proteobacteria that were the most abundant bacterial groups. In vegetated cores, the microbial community as well as specific bacterial populations were at least twice as large in terms of number and biomass than in samples from unvegetated cores with significant seasonal changes for DAPI-stained cells, for members of the domain bacteria and for members of the α- and γ-subdivisions of proteobacteria. In benomyl-treated cores, the population of γ-subdivision of proteobacteria was significantly smaller than in non-treated cores, and a positive association was found between this bacterial group and root length colonized by AM suggesting that AM-suppression can affect populations of specific soil bacterial populations in salt marsh sediment. Benomyl-treatment had no effect on the diversity of N-fixing bacteria as evidenced by PCR-RFLP analysis, but seasonal changes were noted in vegetated cores with populations during active plant growth substantially different from populations during dormancy and senescence.
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effect of arbuscular mycorrhizae on soil microbial populations and associated plant performance of the salt marsh grass Spartina patens
Plant and Soil, 2002Co-Authors: David J Burke, Erik P Hamerlynck, Dittmar HahnAbstract:The effect of arbuscular mycorrhizae (AM) on soil microbial populations and on growth performance of the high salt marsh plant Spartina patens was investigated in a AM suppression study on field-collected soil cores with S. patens. The application of benomyl resulted in a significant reduction of AM colonization on roots of S. patens, but did not completely suppress AM. Non-treated cores had significantly greater colonization (26 ± 6%) than either benomyl- (12 ± 7%) or benomyl-phosphorus-treated (7 ± 3%) cores at a depth of 2.5 cm. Colonization differences between cores declined with depth (5.0 and 7.5 cm), however, so that at 7.5 cm there was no difference between treatments. This decline was attributed to a reduction in oxygen availability with depth as evidenced by decreasing redox potential. Basic environmental conditions generally resembled those found at the field site. There were no environmental differences between treatments at the depths examined. Cell numbers and specific biomass of DAPI-stained organisms as well as members of the Domain Bacteria were significantly higher when AM colonization was suppressed, while those of the Domains Eucarya and Archaea were not significantly influenced. The increase in both microbial and bacterial population size and biomass in the presence of lower levels of AM colonization is most likely due to increases in carbon exudation to soil and rhizosphere populations that accompany AM suppression. PCR-RFLP analysis of nifH amplicons in bulk soil and rhizosphere at varying depths through the soil cores showed differences in banding patterns between rhizosphere and soil material in the presence of AM. The lack of such strong differences in the benomyl-treated cores suggests that AM colonization more strongly affects the nitrogen-fixing population than do physicochemical conditions (e.g. redox potential) alone. Plant growth performance assessed by analyzing root and leaf biomass, as well as excitation transfer efficiency of open photosynthesis system II (PS II) reaction centers (Fv/Fm) was not significantly influenced by AM. Significant differences were found between treatments for C/N ratios and nitrogen content in leaf tissue, indicating that suppression of AM increased plant nitrogen acquisition.
Lisamarie Windham - One of the best experts on this subject based on the ideXlab platform.
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net impact of a plant invasion on nitrogen cycling processes within a brackish tidal marsh
Ecological Applications, 2003Co-Authors: Lisamarie Windham, Joan G EhrenfeldAbstract:Using comparative analysis of the rates of key processes, we have documented the net effect of a shift in plant species composition on nitrogen cycles with the example of the rapid expansion of Phragmites australis (common reed) and its replacement of short grasses (e.g., Spartina patens) in coastal marshes of the eastern United States. In this study, we measured nitrogen (N) uptake by marsh plants, N adsorption from the water column by litter, changes in N content of litter, sediment N mineralization, nitrification, and nitrate consumption in adjacent plots dominated either by P. australis or by historically dominant S. patens. Rates of individual processes were generally greater in P. australis than in S. patens, but the magnitude of difference varied greatly among processes. Seasonal measurements of standing stock nitrogen in plant tissue indicate that P. australis took up ∼60% more N than did S. patens, and annual rates of N immobilization were nearly 300% greater in P. australis litter than in S. pat...
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effects of phragmites australis common reed invasion on aboveground biomass and soil properties in brackish tidal marsh of the mullica river new jersey
Estuaries, 1999Co-Authors: Lisamarie Windham, Richard G LathropAbstract:Phragmites australis (common reed) has been increasing in brackish tidal wetlands of the eastern United States coast over the last century. Whereas several researchers have documented changes in community structure, this research explores the effects of Phragmites expansion on aboveground biomass and soil properties. We used historical aerial photography and a global positioning system (GPS) to identify and age Phragmites patches within a high marsh dominated by shortgrasses (Spartina patens and Distichlis spicata). Plots along transects were established within the vegetation types to represent a gradient of species dominance and a variety of ages of the Phragmites plots. In comparison to neighboring shortgrass communities, Phragmites communities were found to have nearly 10 times the live aboveground biomass. They also had lower soil salinity at the surface, a lower water level, less pronounced microtopographic relief, and higher redox potentials. These soil factors were correlated with the age and biomass of Phragmites communities, were increasingly different with increasing Phragmites dominance along the transects, and were increasingly altered by the ages of Phragmites communities until the factors stabilized in plots of 8 yr to 15 yr of age. We propose that Phragmites expansion plays an important role in altering these soil properties and suggest a variety of mechanisms to explain these alterations.
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microscale spatial distribution of phragmites australis common reed invasion into Spartina patens salt hay dominated communities in brackish tidal marsh
Biological Invasions, 1999Co-Authors: Lisamarie WindhamAbstract:Over the last century, Phragmites australis (common reed) has been expanding rapidly from the marsh–upland boundary into Spartina patens (salt hay)-dominated high marsh communities of the eastern US coast. Whereas direct and indirect human disturbances and changes in hydrology or salinity are likely to influence rates of spread at the landscape scale, the susceptibility of specific plant communities to invasion also influence rates of Phragmites expansion at the local scale. I measured microscale (0.25 m2) spatial patterns of culms (emerging buds and mature stems) in October 1993 at both expanding and stable boundaries of Phragmites populations within a S. patens-dominant matrix. In both expanding and stable plots, Phragmites culms were observed more frequently than expected on hummocks that were created by S. patens tussock-forming root structure. Culm density within a plot was correlated with the percent hummock cover within a plot. Further, Phragmites culms, particularly mature stems, were concentrated along the perimeter of the hummocks. Because the culms were not evenly distributed between hummocks and hollows, I suggest that invasion rates of Phragmites are limited in S. patens communities by microscale differences in hummock availability. The pattern of emergence suggests that expanding rhizomes of Phragmites encounter both competition with S. patens roots on the hummocks and physiological stressors (salinity, anoxia, sulfide concentrations) in the hollows.
Mark W. Hester - One of the best experts on this subject based on the ideXlab platform.
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species and population variation to salinity stress in panicum hemitomon Spartina patens and Spartina alterniflora morphological and physiological constraints
Environmental and Experimental Botany, 2001Co-Authors: Mark W. Hester, Irving A. Mendelssohn, Karen L MckeeAbstract:Abstract Panicum hemitomon , Spartina patens , and Spartina alterniflora are wide-spread dominant grasses of fresh, brackish, and salt marsh plant communities, respectively. Our previous research identified significant intraspecific variation in salt tolerance and morphology among populations within each species. In this study our objectives were to determine shorter-term physiological/biochemical responses to salinity stress and identify potential indicators of salt tolerance, with the ultimate goal of discerning similarities and differences in the mechanisms of salinity stress resistance. We subjected a subset of six populations within each species, ranging from high to low salt tolerance, to sublethal salinity levels (4, 20, and 30 ppt, respectively, for species) and monitored physiological and growth responses after 1 week (early harvest) and 5 weeks (late harvest). In all three species sublethal salinity levels generally resulted in significantly reduced net CO 2 assimilation, leaf expansion, midday leaf xylem pressure, water use efficiency, and live and total biomass; and significantly increased leaf Na + /K + ratio, leaf proline, leaf glycine betaine, leaf sucrose, root-to-shoot ratio, and dead:total aboveground biomass ratio. All three species displayed significant population (intraspecific) variation in net CO 2 assimilation, leaf expansion, water use efficiency, midday leaf xylem pressure, leaf proline, leaf glycine betaine (except Panicum , where it could not be accurately determined), leaf Na + /K + ratio, leaf sucrose, total plant biomass, dead:total aboveground biomass ratio, and root-to-shoot ratio. General indicators of salt tolerance (regardless of species) included high net CO 2 assimilation rates and water use efficiencies, and low ratios of root-to-shoot and dead:total aboveground biomass. Factor analysis and a-priori linear contrasts revealed some unique differences between species in terms of the relative importance of morphology and physiology in explaining intraspecific variation in salt tolerance. Plant morphology (size attributes) were strongly associated with salt tolerance in P. hemitomon , weakly associated with salt tolerance in S. patens , and not associated with salt tolerance in S. alterniflora . Highly salt-tolerant populations of Spartina alterniflora displayed the greatest ion selectivity (lower leaf Na + /K + ratios), which was not displayed by the other two species. These results suggest that plant size attributes can be very important in explaining population differences in salt tolerance in glycophytes, but may be independent of salt tolerance in halophytes, which have specialized physiological (and/or anatomical) adaptations that can confer salinity stress resistance through mechanisms such as selective ion exclusion and secretion.
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Intraspecific variation in salt tolerance and morphology in the coastal grass Spartina patens (poaceae)
American Journal of Botany, 1996Co-Authors: Mark W. Hester, Irving A. Mendelssohn, Karen L MckeeAbstract:Clones of Spartina patens were collected from 19 locations throughout Gulf coast marshes of Texas, Louisiana, and Florida. Following three vegetative generations of de-acclimation from field conditions, genotypes were subjected to a salinity screening protocol in which salinity was increased in weekly increments of 5%o (gram salt/kilogram solution). Plants were harvested when there was 50% death of aboveground tissue, which we defined as the lethal salinity level. The genotypes displayed highly significant intraspecific variation in lethal salinity level, which ranged from 63%o to 93%o. Significant intraspecific variation was also observed in all plant morphological variables, as well as leaf rolling, leaf expansion rates at 2%o and 20%o salinity, aboveground, belowground, and total biomass, and belowground-to-aboveground biomass ratio. An ANOVA of principal component scores from a PCA of lethal salinity level and covariable-adjusted total plant dry mass further illustrated intraspecific variation within this species in these two traits expressed as one principal component. Correlation analysis revealed that intraspecific variation in salt tolerance was not strongly associated with intraspecific variation in plant morphological traits, leaf rolling, or leaf expansion rates.
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a comparison of indicators of sublethal salinity stress in the salt marsh grass Spartina patens ait muhl
Aquatic Botany, 1995Co-Authors: Kern Ewing, Karen L Mckee, Irv Mendelssohn, Mark W. HesterAbstract:Wetland plant communities in coastal Louisiana are degrading, resulting in the loss of live emergent vegetation and subsequent succession to open water. Saltwater intrusion has resulted from the construction of navigation canals through the marshes; the subsequent salinity increase is one of the potential sources of sublethal stress on plants. Greenhouse experiments were conducted on Spartina patens (Ait.) Muhl. to compare the usefulness of several indicators for the detection of salinity stress. CO2 uptake, leaf expansion, proline concentration and live aboveground biomass displayed significant responses to the salinity levels employed as treatments (0, 7, 14, 21 and 28 ppt.). CO2 exchange was the only indicator showing a significant response within 7 days of the initiation of treatments (measurements were made at 7, 14 and 42 days).
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a comparison of indicators of sub lethal untrient stress in the salt marsh grass Spartina patens
Environmental and Experimental Botany, 1995Co-Authors: Kern Ewing, Irving A. Mendelssohn, Karen L Mckee, Mark W. HesterAbstract:Abstract Wetland plant communities in coastal Louisiana are degrading, resulting in the loss of live emergent vegetation and subsequent succession to open water. Nutrient deprivation caused by compartmentalization of marsh parcels and impaired water exchange is one of the potential sources of sub-lethal stress on plants. Greenhouse experiments were conducted on Spartina patens (Ait.) Muhl. to compare the usefulness of several indicators for the detection of nutrient stress. Responses were measured at the end of 7, 14 and 35 days, with experiments timed to end simultaneously. Leaf expansion rate, aboveground biomass, leaf spectral reflectance, adenine nucleotide levels and CO 2 exchange rate all detected significant differences among treatments (0, 25, 50 and 100% Hoagland's solution). All but aboveground biomass were able to detect some treatment differences as early as 7 days after initiation of treatments; aboveground biomass detected differences after 14 days. Adenine nucleotide levels showed the best ability to discriminate among the 0, 25, 50 and 100% Hoagland's treatments, while all other indicators were able to detect differences only between the 0% treatment and the higher levels of nutrient application.
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clonal integration in Spartina patens across a nitrogen and salinity gradient
Botany, 1994Co-Authors: Mark W. Hester, Karen L Mckee, David M Burdick, Marguerite S Koch, K M Flynn, S Patterson, Irving A. MendelssohnAbstract:We investigated physiological integration among ramets of Spartina patens when clones spanned a salinity gradient. Clones of S. patens were grown in paired pots with the ramets of the parent pot co...