Abstract
The effect of three-stage spraying of 200 mg/l ethephon in the flower bud stage with leaf primordium and involucre was studied for chemical control of growth and flowering in summer-to-autumn-flowering chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura) cultivars under open field conditions. Leaf primordium and young leaf numbers of ‘Iwanohakusen’,‘Madobe’,‘Seiun’ and ‘Summer-yellow’ with and without ethephon spraying were 17.3–18.2 in the early growing stage, and maximum leaf primordium and young leaf numbers were 19.8–22.8 in the starting involucre formation stage, and decreased after that. The development of leaf primordium and young leaf numbers under ethephon spraying was inhibited by 15–30 days compared to without ethephon. Leaf primordium development and young leaf numbers of ‘Summer-yellow’ with ethephon were more inhibited than other cultivars. The budding was also markedly inhibited and the leaf numbers were increased. As a result, the transformation from leaf primordium to involucre was inhibited by ethephon application in summer-to-autumn-flowering chrysanthemum.
