S05 - Session P2 - Effect of raising duration and root zone volume on bolting and cut flower quality of Delphinium grandiflorum var. sinensis

Authors: Goto Tanjuro *, Yoshikuni Kitamura, Ken-ichiro Yasuba, Yuichi Yoshida, Mika Kawai, Reimi Kai

On transplants production of Delphinium grandiflorum var. sinensis in the high temperature season in Japan, bolting in cell tray and early flowering after planting have been big problems. So, heat pomp cooling is conducted generally, but the running costs are very high. In previous experiment, we found when the plants were grown in 406 cell trays with 4 ml root zone volume, bolting and flowering in cell tray was not seen for one year. There is a possibility that high-quality cut flowers can be produced as bolting can be suppressed by limiting the root zone volume. Therefore, in this experiment, we investigated the effects of the raising duration and root zone volume on bolting, flowering and cut flower quality. Seeds were sown in 406 (root zone volume 4 mL), 228 (9 mL), 200 (12 mL), 128 (20 mL) and 72 (46 mL) cell trays every month from May 1st to August 1st. On September 15, 5 seedlings were planted in a planter with a capacity of 12 L. They were harvested when three flower opened. Regardless of sowing time, bolting before planting was found in 72, 128, and 200 cell trays, but not in 288 and 406 cell trays. Regardless of raising duration, plants grown in 200, 288 and 406 cell trays have not seen early flowering after planting, and there was no significant difference in cut flower quality among them. Bolting is affected not by the raising period but by the root zone volume during raising in the high temperature season. It was considered possible to produce high-quality cut flowers by raising under root restriction.