Abstract
Cyclamen (Cyclamen persicum Mill.), whose growth and flowering are retarded by high temperatures during the summer season, was used in this experiment to investigate the effect of root-zone cooling on growth and flowering. Root-zone temperatures were preset at 20, 23, and 26°C during the summer season. The control was without root-cooling. Each root-zone temperature was maintained at ±1 to 2°C of the preset temperature. The averages of minimum and maximum temperatures of the control were about 25 and 28°C, respectively. Vegetative growth was promoted at 23°C compared with that of the control. Flowering at 20°C started in the middle of October, and the number of flowers per plant reached about 7 after 20 days. Flowering rates increased with a drop in the root-zone temperature: 20% at the control temperature, 44% at 26°C, 60% at 23°C, and 88% at 20°C. The number of flower buds per plant was maximal at 23°C, and was about 65, having 25 and 10 more than those at 20°C and the control temperature, respectively. In conclusion, root-zone cooling at 23°C significantly promoted both vegetative growth and flower bud formation of cyclamen, and that at 20°C accelerated the flowering rate. Thus, controlling the root-zone temperature between 23 and 20°C may be markedly advantageous for cyclamen cultivation during the hot summer season.
