Effect of Supplementary Lighting and Heat Lamps on Greenhouse Environment and Flowering of Cut Roses

Abstract

The characteristics of several types of supplementary light sources and one heat lamp, which are currently used in cut rose production, were investigated to determine their influence on the meteorological environment of a greenhouse and the flowering time and quality of plants grown for cut roses. Supplemental lighting was installed above the growing bed of the cut rose (Rosa hybrida ‘ Feel L ip’) p lants using light emitting d iode ( L ED) lamps, metal halide (MH) l amps, high pressure sodium (HPS) lamps, and nano carbon fiber infrared (NCFI) heat lamps. The luminosity of the LED and NCFI lamps was very low (6.8 μmol·m-1·s-1 PPF and 0.4 μmol·m-1·s-1 PPF, respectively), whereas MH and HPS lamps had a significantly higher luminosity the lamps had a luminosity of 79 – 100 μmol·m-1·s-1 PPF. The LED and MH lamps did not produce a wavelength in the infrared region, and generated little heat. However, the HPS and NCFI lamps radiated more heat due to having a large wavelength in the infrared region. The experiment was performed by dividing the treatment plot in the same space, and daily minimum temperature was increased by 2°C under the MH, HPS and NCFI lamp treatments. However, there was no difference in relative humidity between any of the treatments. Regardless of light intensity, all lamp types promoted flowering of the cut rose plants, resulting in shortening in the days to flowering by 5 – 7 days at least, or 12 - 14 days as many compared with that of control. In the spring when there was a sufficient amount of natural light, the length of the flower stalk of plants grown under supplemental light treatments was shorter than that of the control as the days to flowering was shortened by the supplemental lighting. However, in the winter when there was an insufficient amount of natural light, the length of the flower stalk on the treated plants was longer than that of control, showing an improvement in flower quality.