Suppression of scape elongation by paclobutrazol and ancymidol of potted `Paul Richter' tulips (Tulipa gesneriana, L.) under greenhouse and low light postharvest environments were compared. Soil” drench applications of paclobutrazol at 0.25 or 0.50 mg/15-cm pot were as effective as ancymidol at 0.50 or 0.75 mg/pot in limiting scape lengths at colored bud stage and at senescence. Paclobutrazol pre-plant bulb soaks at 2.5 or 5.0 mg·liter-1 prevented excessive scape elongation during low light exposure, whereas ancymidol bulb soaks were ineffective. Neither plant growth regulator reduced flower size or affected petal color. Paclobutrazol applied as a soil drench or as a bulb soak increased days required up colored bud stage up to 4 days, whereas neither chemical affected post-greenhouse, life of tulips. Chemical names used: (R*, R*)-(±)-β-[(4-chlorophenyl) methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazol-1-ethanol (paclobutrazol) and α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).
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