Abstract

Seeds of seabeach amaranth (Amaranthus pumilus Raf.) stored at 4C (39F) for approximately 1 year (harvested September 2003) and freshly harvested seeds (October 2004) were soaked in November 2004 in solutions of the potassium (K) salt (K-salt) of gibberellin A₃ (K-GA₃) at 0, 100, 500, or 1000 mg/liter (ppm) for 24 hr in darkness. After treatment, seeds were germinated at 25C (77F) or at an 8/16-hr thermoperiod of 30/20C (86/68F) with daily photoperiods at each temperature of 0 (total darkness) or 16 hr. Germination was recorded every 3 days for 30 days. Stored and fresh seeds responded similarly. However, the 2003 seeds had greater viability (percent germination) and vigor (germinated faster) and these data are presented. Regardless of germination temperature and photoperiod, nontreated seeds [0 mg/liter (ppm) K-GA₃] did not germinate. When germinated at 25C (77F) the response of seeds to K-GA₃ treatment was linear for both photoperiods with significantly greater total (30-day) germination occurring in the dark for seeds treated with 100, 500, or 1000 mg/liter (ppm) K-GA₃. At 25C (77F), the greatest total germination (84%) was observed for seeds treated with 1000 mg/liter (ppm) K-GA₃ and maintained in darkness, whereas for seeds exposed to a 16-hr photoperiod, maximum germination was 72%. At 30/20C (86/68F) the response to K-GA₃ was quadratic with maximum germination at predicted rates of 882 and 875 mg/liter (ppm) KGA₃ (88 and 92%, respectively) for photoperiods of 0 and 16 hr, respectively. Treatment of nonstratified seeds of seabeach amaranth with K-GA₃ removed physiological (embryo) dormancy and eliminates the need for stratification (moist-prechilling). Treatment also reduced sensitivity of the seeds to light, and appeared to broaden the range of temperatures for germination.