TITLE	Population differentiation in Spartina patens: Responses of photosynthesis and biomass partitioning to elevated salinity
AUTHOR	S.R. Pezeshki Division of Ecology and Organismal Biology, Department of Biology, University of Memphis, Memphis, TN 38152, USA R.D. DeLaune Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803, USA
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ABSTRACT	Populations of Spartina patens (Ait) Muhl. were collected from three distinct habitats in Louisiana Gulf Coast marshes. The Lake Tambour and Ferblanc populations are associated with saltmarsh and saltmarsh-brackish marsh interface, respectively, where soil salinity is greater than at the brackish-freshwater transition zone where the Clovelly population occurs. The effects of salinity at 0, 5, and 15 ppt on gas exchange, growth and biomass partitioning were evaluated. All study populations performed well under the elevated salinities for 12 weeks (the duration of the study). However, differences in gas exchange, growth, biomass production, and patterns of biomass partitioning in response to the treatments were evident among the populations. For example, in the Lake Tambour population, there was no significant change in leaf conductance or net photosynthesis in response to the elevated salinities whereas, in others, significant reductions in net photosynthesis were found at the 15 ppt treatment. Generally, all populations had comparable gas exchange rates under control (0 ppt) treatment. However, the Clovelly and Lake Tambour populations exhibited significantly (p < 0.05) greater net photosynthesis compared to the Ferblanc population under the 5 ppt salinity treatment. In 5 and 15 ppt treatments, the Lake Tambour population maintained the greatest number of shoots, leaf area, and dry weight among the study populations. The population-by-treatment interaction was significant for all size-related traits except the gas exchange properties. Although certain measured parameters appeared to reflect the relative position of these populations in the natural range of S. patens, based on the present data salt-tolerance in this species can not generally be inferred from the field position. In addition, the within- and between-population variation in the characteristics studied suggest that collection of germplasm from a wide range of sites is needed to increase the likelihood of capturing the maximum salinity tolerance. Thus finding the greatest level of salt-tolerance among the population of this and other important coastal macrophyte species remains as a major task.
KEYWORD	Marsh restoration; Marsh vegetation; Photosynthesis; Population differentiation; Salinity stress;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 38 Number 2 April 1997, page 115-120, 6 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China