Photosynthesis, stomatal responses, and water potential in three species in an inland salt marsh in Kansas, USA

Interspecific variation of photosynthesis and water potential in inland salt marsh species has been largely unexplored. In this study, photosynthesis and water potential were measured in individuals of Spartina pectinata Link, Distichlis spicata (L.) Greene, and Bolboschoenus maritimus (L.) Palla in an inland salt marsh, possibly the first field measures of photosynthesis in inland salt marsh plants in North America. It was hypothesized that the C4 grasses S. pectinata and D. spicata would have a greater tolerance to salinity compared to the C3 sedge B. maritimus by stomata being less responsive to changing water status. During the study, B. maritimus was most sensitive to dry conditions, which was manifested as low photosynthesis, stomatal conductance, and water potential. Stomatal closure occurred in all species under dry conditions, but particularly in B. maritimus. Under dry conditions, S. pectinata maintained higher photosynthesis compared to other species. Water potential was lower in D. spicata compared to the other species. There were significant correlations between plant water potential and photosynthesis and water potential and stomatal conductance in B. maritimus, but not in S. pectinata or D. spicata. This is evidence of sensitivity of B. maritimus to dry conditions and tolerance in S. pectinata and D. spicata, largely due to stomatal responses.