Seed Germination of Rhododendron chapmanii: Influence of Light and Temperature

Abstract

Abstract Seeds of Rhododendron chapmanii A. Gray (Chapman's rhododendron) were germinated at 25C (77F) or 8/16 hr thermoperiods of 25/15C (77/59F) or 30/20C (86/68F) with daily photoperiods of 0 (total darkness), ¼, ½, 1, 2, 4, 8, 12 or 24 hr. For all temperatures, no germination occurred during a 30-day period for seeds not subjected to light. At 25C (77F) germination was a function of photoperiod. The longer the photoperiod the greater the germination with 30-day germination ≥90% for photoperiods ≥8 hr. Alternating temperatures, particularly 25/15C (77/59F), enhanced germination when light was limiting. The highest germination (80%) by day 30 for seeds at 30/20C (86/68F) was realized with a 24-hr photoperiod, whereas 30-day germination ≥ 90% occurred at 25/15C (77/59F) and 25C (77F) for photoperiods of 8 and 12 hr and 8, 12, and 24 hr, respectively.