Effect of Ethephon Application on Growth and Morphology of Summer-to-Autumn-Flowering Chrysanthemums in Open Culture

Abstract

The effect of ethephon applications on growth and morphology in summer-to-autumn-flowering chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura = Chrysanthemum morfolium Ramat.) was studied for forced cut flower production under open culture. Flower bud differentiation of ‘Madobe’ and ‘Summer-yellow’ was strongly inhibited by 200-400 mg·liter⁻¹ ethephon applications when sprayed at 0-1,000 mg·liter⁻¹ ethephon concentrations. Leaf increasing terms of some cultivars were more elongated by 800-1,000 mg·liter⁻¹ ethephon applications than by 200 mg·liter⁻¹ and others were the same elongation when sprayed with 0-1,000 mg·liter⁻¹ ethephon concentrations. Cultivars with longer internodes showed more stem elongation using 200 mg·liter⁻¹ ethephon sprays than those with shorter internodes showed. Leaf numbers and stem lengths were not incleased and malformations occurred when they were sprayed with 200 and 1,000 mg·liter⁻¹ ethephon after bud differentiation in flower buds, flower and peduncle of those cultivars.
As a result, cultivars showing strongly inhibited flower bud differentiation and longer internodes after ethephon applications should be used for cut flower growing for flowering inhibition in summer-to-autumn-flowering chrysanthemums, ethephon sprays should be avoided after flower bud differentiation.