The potential use of photoperiod during transplant production under artificial lighting conditions on floral development and bolting, using spinach as a model

Spinach (Spinacia oleracea L.) was chosen to demonstrate that the respectiv e vegetative or reproductive conditions of transplants can be controlled in their early stages Of development under artificial light in a closed syste m. Transplant production under artificial light was divided into three grow th phases and the photoperiod during each of these phases was varied. The r ate of floral development was controlled by photoperiod, but floral initiat ion itself was not affected. Short photoperiod treatments (80 or 12 hours/d ay) retarded floral development and stem elongation (bolting), This delay c ontinued even after the transplants were transferred to natural long-day (1 5.5 hours/day on average) conditions with high temperatures (17 and 37 degr ees C minimum and maximum). We concluded that by using short photoperiods d uring transplant production, marketable plants with reduced bolting could b e produced under natural long-day conditions. In Japan, spinach with this r esetting capacity would be of greater value. Further,: this Concept opens t he possibility of producing better quality transplants of several species u nder artificial lighting conditions of appropriate length, and thereby cont rolling their floral development and/or bolting.