Abstract
Acceleration of flowering of Eustoma grandiflorum in early winter by day-extension treatments with far-red rich bulb-type fluorescent lamps was investigated after culturing short-day treatment was performed from transplant to the end of August, followed by under long-day treatment after the middle of September, which is appropriated for cool area in Japan. Far-red rich bulb-type fluorescent lamps were made for trial purposes and in addition to incandescent lamps and red rich bulb-type fluorescent lamps on the market were used as light sources. As a result, far-red rich bulb-type fluorescent lamps, as well as incandescent lamps, accelerated the flowering and development of flower buds compared to red rich bulb-type fluorescent lamps or intact natural daylength. When the intensity of far-red light exceeded 0.7 μmol·m−2·s−1, lateral flowers of the second order and higher increased, thus, cut flowers volume were enhanced. Furthermore, this promotion was further accelerated by continuous lighting compared to that under 16 h and 12 h photoperiods. These findings indicated that day-extension treatments from the middle term of growth until flowering time with more than 0.7 μmol·m−2·s−1 of far-red light promoted a high production of marketable cut flowers of the Eustoma grandiflorum and the effect was greatest with continuous lighting in early winter during the cool area.
