2002 Volume 71 Issue 2 Pages 272-276
To determine environmental factors involved in rosette formation of Elatum hybrids of Delphinium, bolting behavior in response to temperatures, photoperiods, and light intensities was investigated. Seedlings rosetted under a natural 10-12 hr photoperiod during winter at 22°C. Seedlings subjected to 25/20°C (day/night) for 40 days just after germination formed rosettes after they were transferred to below 20/15°C, whereas they bolted quickly when they were kept at the continuously high temperature. A high percentage of seedlings bolted when they were transferred to a greenhouse kept above 18°C in early October, but those kept at a minimum temperature of 10°C formed rosettes. This rosette formation was also accelerated by exposing seedlings to 50% shading. We conclude that short days induce rosette formation in Elatum hybrids of Delphinium and that cool temperature accelerated it. Exposure of seedlings to high temperatures during the early seedling stage and/or low light intensity after planting also enhanced rosette formation.