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Publication Type J
Authors Hester, M. W., I. A. Mendelssohn and K. L. McKee
Title Species and population variation to salinity stress in Panicum hemitomon, Spartina patens, and Spartina alterniflora: morphological and physiological constraints
Source Environmental and Experimental Botany
Author Keywords Panicum hemitomon; Spartina patens; Spartina alterniflora; salt tolerance; morphology; osmotica; proline; glycine betaine; water relations SALT TOLERANCE; INTRASPECIFIC VARIATION; PROLINE DEHYDROGENASE; COMPATIBLE SOLUTES; GAS-EXCHANGE; GROWTH; MARSH; PHOTOSYNTHESIS; ACCUMULATION; HALOPHYTES
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 CO2 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 CO2 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 CO2 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. (C) 2001 Elsevier Science B.V. All rights reserved.
Author Address Univ New Orleans, Dept Biol Sci, New Orleans, LA 70148 USA Univ New Orleans, Dept Biol Sci, New Orleans, LA 70148 USA Louisiana State Univ, Wetland Biogeochem Inst, Baton Rouge, LA 70803 USA Louisiana State Univ, Dept Oceanog & Coastal Sci, Baton Rouge, LA 70803 USA US Geol Survey, Natl Wetlands Res Ctr, Lafayette, LA 70506 USA Hester MW Univ New Orleans, Dept Biol Sci, New Orleans, LA 70148 USA
29-Character Source Abbreviation Environ. Exp. Bot.
Publication Date Dec
Year Published 2001
Volume 46
Issue 3
Beginning Page 277-297
Unique Article Identifier ISI:000171990800009
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