Effects of gibberellin on the growth and the flowering of several ornamental plants

Abstract

This experiment was conducted for the purpose of studying the effects of gibberellin on growth and flowering of several ornamental plants. Gib-berellin was applied to the plants with spraying as aqueous solution and single or repeated applica-tions were made. Concentrations of sprayed solution were 20, 40 and 50ppm. Comparison was made between treat-ed plants and non-treated control plants. In many cases, potted plants were treated in glasshouse. 1. Flowering of cyclamen (Cyclamen persicum MILL.) was hastend and this influnce was more remarkable in 40ppm than in 20ppm. Further-more, flower size and length of flower stalk were significantly increased. 2. Flowering of freesia (Freesia refracta KLATT.) was also hastened, but this influence was likely to be limited only to the plants possessing flower buds of fairly advanced stage. No damage or injury caused by the application of gibberellin was found among pollen grains of treated flowers. 3. Plant height and shoot length of petunia (Petunia hybrida VILM.) were both remarkably in-creased. 4. The effect of flower hastening upon winter daphne (Daphne odora THUNB.) became manifest within a week after single application of gibbere-llin. 5. Flower size and length of flower stem of sweet pea (Lathyrus odoratus L.) were increased, but the effect of flower hastening was indistinct. 6. Concerning the experiments with Japanese cherry (Prunus yedoensis MATSUM.) and thunberg spires (Spiraea Thunbergii SIEB.) from which flower budded twigs were pruned and dipped into glass bottles containing water or gibberellin solution, bud sprouting was remarkably hastened and length of flower stem was strikingly increased, but flowering was never hastened by the appli-cation (spraying only or both spraying and dipping) of gibberellin. 7. There were hardly any effects on flowering of potted Kurume azalea (Rhododendron obtusum PLANCH.) in glasshouse, or of Japanese apricot (Prunus Mume SIEB. et ZUCC.), peach (Prunus Persica SIEB. et ZUCC.) and Japanese cherry (Prunus yedoensis MATSUM.) which were planted in the field.