RESPONSE TO PHOTOPERIOD AND TEMPERATURE BY SPARTINA ALTERNIFLORA (POACEAE) FROM NORTH CAROLINA AND SPARTINA FOLIOSA FROM CALIFORNIA

Seedlings of Spartina alterniflora Loisel. from Oregon Inlet, North Carolina were generally taller and produced significantly more culms and total dry weight than those of S. foliosa Trin. from two California populations (Alameda Beach and Marin County) in eight photoperiodtemperature treatments over a 1 7-wk period. Seedlings of S. alterniglora produced maximal biomass in 30-26 C whereas those of S. foliosa produced maximal biomass in 22-18 C, both under long-day conditions. The average photosynthesis rate for S. alterniflora (3.0 mg C g dry wt-l hr-l) was 1.6 times higher than that for S. foliosa (1.9 mg C g dry wt-l hr-'), but the dark respiration rates (0.3 and 0.4 mg C g dry wt-l hr-l, respectively) were not significantly different. The proportion of rhizomes was greater under short than long-day conditions for both species in most temperature regimes. The average shoot soluble carbohydrate and starch concentrations were higher for S. foliosa (8.4 and 0.9%, respectively) than those for S. alterniflora (6.0 and 0.4%, respectively). The average rhizome soluble carbohydrate concentration (18%) for S. alterniglora under long-day conditions was significantly lower than that under short-day conditions (28%) and also lower than those for S. foliosa under both long (26%) and short-day (25%) conditions. Rhizome starch concentrations of S. alterniflora were significantly higher in the short than in most long-day temperatures and were generally higher for S. alterniflora than for S. foliosa under short-day conditions. The root starch concentration of S. alterniflora under short-day conditions (1.3%) was higher than that under long-day conditions (0.2%) and also higher than those of S. foliosa under both long (0.2%) and short-day (0.7%) conditions. The two species exhibited similar patterns of carbohydrate storage in belowground organs, similar flower initiation processes not under strict photoperiod control, and similar respiration rates, but significantly difl^erent photosynthetic rates and growth responses with S. alterniflora having the potential to be the more productive species. THE TWO PERENNIAL salt marsh grasses, Spartina alterniflora Loisel. and S. foliosa Trin. form almost monospecific stands in the lower portion of the intertidal zone on the Atlantic and Pacific coasts of North Amertca, respectively. Spartina alterniflora occurs from Newfoundland southward along the Atlantic coast to Texas (Hitchcock, 1950), while S. foliosa ' Received for publication 27 January 1983; revision accepted 18 August 1983. Paper number 8661 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. We wish to express appreciation to Ms. A. A. Hines for technical assistance in the phytotron and in carbohydrate analyses. We are also grateful to Dr. R. J. Monroe, Professor of Statistics, N.C. State Univ., for assistance in analysis of data. The research was supported in part by appropriations from the N.C. Coastal Research Program; the Univ. of N.C. Sea Grant College Program, Office of Sea Grant, NOAA, Department of Commerce, Grant No. GH103; and NSF Grant 2895 1. Mention of a trade mark or proprietary product by North Carolina State University does not imply approval to the exclusion of other products that may be suitable. occurs from Baja, California northward along the Pacific coast to Del Norte County, California (Munz and Keck, 1959). Although the species are disjunct in distribution, the respective habitats of these grasses both dictate tolerance to inundation, salinity, and anaerobic sediments. The primary means of reproduction by both species is vegetative (by rhizomes); however, colonization of new areas and filling in of stands can be accomplished by