Effects of Ethephon Application on Plant Height and Leaf Color in Summer-to-Autumn-Flowering Chrysanthemum

Abstract

The effects of ethephon spraying on the growth development, flower bud stage and leaf color were studied in a summer-to-autumn-flowering chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura) under open field conditions. The growth of all cultivars was slow until the last ethephon spraying stage, but that from the involucre formation stage to the floret formation stage was fast and growth before flowering was slow again. Leaf segments grew after rosette formation at high positions under a schedule of three 200 mg/l ethephon sprayings with 1000 mg/l for strong inhibition of flower bud differentiation. The plant height overtook that achieved with three 200 mg/l ethephon sprayings in 'Seiun' and 'Summer-yellow' cultivars. First growth using ethephon sprays with pinching was slower than that without pinching. Leaf color of flowers treated with ethephon sprays and pinching was more inhibited than that without pinching in all cultivars. Our results showed that, ethephon spraying inhibited early flower bud differentiation, growth of stems and change of leaf color to dark green, however, the stem length was longer than controls because the growth of stems is fast in summer-to-autumn-flowering chrysanthemum.