The role of irradiance and/or ethylene in inducing mortality and self-branching disorders in Gerbera jamesonii Bolus. seedlings was studied. Seedling mortality increased from 8% to 57% when seed was covered with vermiculite than left uncovered during germination. Supplemental lighting for 30 days after germination decreased seedling mortality and decreased the time to visible bud compared to seed germinated under natural light only. In subsequent experiments, seeds were germinated and then seedlings were water logged or sprayed with ethephon (0.69, 3.45, or 17.25 mM) at four different stages of seedling development. Half of the ethephon-treated seedlings were sprayed with silver thiosulfate (STS). Seedling mortality was greatest after cotyledon expansion but before expansion of the first tree leaf. The highest ethephon concentration caused reduced seedling dry weight after 42 days. Applying STS did not overcome self-branching or meristem necrosis.
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