Increasing the ratio of red to blue light as supplemental light improves growth, photosynthesis, and yield of cut roses

Abstract

During the seasons with limited light intensity, reductions in growth, yield and quality are challenging issues for commercial cut rose production in greenhouses. Using artificial supplemental light is recommended for maintaining commercial production in regions with limited light intensity. Nowadays, replacement of traditional lighting sources with LEDs attracted lots of attentions. Since red (R) and blue (B) light spectra present the important wavelengths for the photosynthesis and growth, in the present study different ratios of supplemental R and B lights including 90% R: B 10% (R90B10), 80% R: 20% B (R80B20), 70% R: 30% B (R70B30) with an intensity of 150 µmol m^-2 s^-1 together with natural light and without supplemental light (control) were applied on two commercial rose cultivars. According to the obtained results, supplemental light improved growth, carbohydrate levels, photosynthesis capacity, and yield when compared to the control. R90B10 in both cultivars reduced the time required for flowering compared to the control treatment. The highest number of harvested flower stems was obtained by R90B10 and R80B20 in both cultivars. Chlorophyll and carotenoid levels were the highest under control and higher ratio of B light, while carbohydrate and anthocyanin contents increased by having high ratio of R light in the supplemental light. Analysis of chlorophyll fluorescence were indicative of better photosynthetic performance under high ratio of R light in the supplemental light. In conclusion, R90B10 light regime is recommended as suitable supplemental light recipie to improve growth and photosynthesis, to accelerate flowering, and to improve the yield and quality of cut roses.