EFFECT OF LIGHT INTENSITY ON GROWTH AND QUALITY OF CUT ROSES

The yield and quality of different cultivars of greenhouse roses grown under different levels of supplementary lighting up to 370 μmol.m^-2s^-1, PPF, were studied.
The highest light levels contributed to a photosynthetic active radiation which exceeded the natural radiation during summer.
Generally the yield increased as the PPF increased up to 370 μmol.m^-2s^-1, which was given for 20 h a day from September to June.
During the summer period the yield increased with 40–50 % given 210 μmol.m^-2s^-1 when the natural light inside the greenhouse decreased below 300 μmol.m^-2s^-1. The percentage class 1 roses increased by increasing the PPF up to 250 μmol.m^-2s^-1, particulary in mid-winter.
The percentage of long-stem roses (> 40 cm) was significantly increased by PPF up to 370 μmol.m^-2s^-1 during winter, but decreased by lighting during summer.
The dry weight per shoot or weight per cm stem increased as the PPF increased during winter.

III International Symposium on Artificial Lighting in Horticulture

Hans R. Gislerod, Leiv M. Mortensen

https://doi.org/10.17660/ActaHortic.1997.418.2