Population differentiation in Spartina patens: gas-exchange response to salinity

Abstract

Greenhouse and laboratory studies were conducted to evaluate the effects of gradual vs sudden increase in salinity from 5 to 25 ppt on leaf conductance and net carbon assimilation of 2 Spartina patens populations (Ferblanc and Clovelly) from USA Gulf Coast marshes. Results indicated that the 2 populations had quite similar gas-exchange responses to salinity treatments. However, with progression of each experiment, some differences in responses became apparent. The Ferblanc population (which grows under high salinities in a brackish-saltmarsh zone) maintained greater net carbon assimilation than did the Clovelly population (which grows under low salinities of a freshbrackish zone) in 5 and 15 ppt salinity treatment. At 25 ppt salinity, net carbon assimilation was reduced by 10% for Ferblanc, which was not statistically significant (p = 0.05), and by 22% for Clovelly population, which was statistically significant (p 5 0.05). In addition, Ferblanc plants produced significantly (p 5 0.05) greater leaf area than did the Clovelly population. The observed responses are in accord with the habitat characteristics where these populations grow naturally. Results indicate a potential differentiation between the 2 populations under the salinity-flooding combinations tested. However, there is no evidence of restricted gene flow between these populations. Thus differences found may be due to differential survival of offsprings from a common gene pool rather than evolutionary divergence of isolated populations

Diversity in leaf anatomy, and stomatal distribution and conductance, between salt marsh and freshwater species in the C4 genus Spartina (Poaceae)

“…300 µbar substomatal levels). Measured CO 2 assimilation rates were similar to measurements of short‐form S. alterniflora in its natural habitat (Giurgevich & Dunn, 1979, 1982) and glasshouse‐grown Spartina species by Pezeshki (1991), Ewing et al . (1995), Nieva et al .…”

“…The low marsh species S. alterniflora and S. anglica and freshwater S. cynosuroides exhibit a C 4 type response to varying CO 2 , including a low compensation point and saturation of photosynthesis at relatively low CO 2 levels (c. 300 µbar substomatal levels). Measured CO 2 assimilation rates were similar to measurements of short-form S. alterniflora in its natural habitat (Giurgevich & Dunn, 1979 and glasshousegrown Spartina species by Pezeshki (1991), Ewing et al (1995), Nieva et al (1999Nieva et al ( , 2003, and Maricle et al (2007b), but lower than those reported in S. × townsendii (Long & Woolhouse, 1978) or S. cynosuroides (Giurgevich & Dunn, 1981). Rates of photosynthesis can be influenced by growth and measurement conditions, and adaptations for conserving water.…”