Germination Responses of Greasewood (Sarcobatus vermiculatus) to Temperature, Water Potential and Specific Ions

Abstract

Seeds of greasewood (Sarcobatus vermiculatus (Hook.) Torr.) were germinated at 5 degrees to 40 degrees C in 5-degree increments to determine temperature response. Seeds were also germinated in solutions of polyethylene glycol 6,000 (PEG), NaCl, and Na2 SO4, each at osmotic potentials of 0 to -4.2 MPa in -0.3 MPa decrements at 10, 20 and 30 degrees C to determine moisture stress, specific ion, and temperature interaction. Germination was high at all temperatures, 5 degrees C through 25 degrees C being optimal. A direct linear relationship existed between total germination and osmotic potential of each solution at each temperature. Mean germination at 30 degrees C was significantly different for each osmotica with NaCl highest and PEG lowest. Mean germination at 10 degrees C and 20 degrees was not different within osmotica; however, total germination was significantly lower in PEG than in NaCl and Na2SO4, indicating the difference between macromolecular PEG and ions (NA+, Cl-, and SO4=). Significant difference was observed in the coefficient of rate of germination between ions of Cl- and SO4=, with SO4= being more stressful.