Germination Response to Temperature and Salinity of Four Dune Grasses from the Outer Bank of North Carolina

At four constant thermoperiods (65°, 75°, 85° and 95°F) and three alternating diurnal thermoperiods (65° —75°, 65° —95°F), good germination (above 70%) was obtained with seed of Ammophila breviligulata Fern., Panicum amarulum Hitch. and Chase., and Spartina patens (Ait.) Muhl. without cold treatment under certain temperature conditions. None of the constant temperature treatments yielded good germination. All attempts to obtain good germination with Uniola paniculata L. without cold treatment were unsuccessful. Various periods of cold treatment had no effect upon subsequent germination in the 65° —95°F alternating diurnal thermoperiod in A. brevilligulata and S. patens. In P. amarulum cold treatment for 15 days was sufficient to ensure good germination. Cold treatment for 30 days was adequate for good germination in U. paniculata, but 15 days was not always sufficient. When cold treatment for 30 days at 43°F preceded germination in the seven temperature conditions, germination was increased in all species. Maximum tolerance limits for A. breviligulata and U. paniculata to NaCl lie between 1.0% and 1.5%. The upper limit of NaCl concentration for germination of P. amarulum is between 1.5% and 2.0% and for S. patens about 4.0%. Germination response to salinity was primarily an inverse linear relationship for A. breviligulata, P. amarulum, and U. paniculata, but a curvilinear relationship in S. patens. In this species germination was successful at 2.0% NaCl. Germination inhibition in A. breviligulata, P. amarulum, and S. patens was apparently primarily an osmotic effect. Based on germination response, S. patens is the most salt tolerant, followed by P. amarulum which is more than U. paniculata. A. breviligulata is the most salt sensitive.