Effects of LEDs on Photosynthesis and Secondary Metabolites in Roses, Chrysanthemums, and Campanulas

Integration of light emitting diodes (LEDs) in current growing systems receives full attention as they provide the opportunity to control light spectrum. In most cases, such research has focused on vegetables, whereas LED effects have not been extensively studied on ornamental plants. Potted Rosa hybrida 'Scarlet', Chrysanthemum morifolium 'Coral Charm', and Campanula portenschlagiana 'BluOne' were grown under a purpose-built LED array from Philips yielding approximately 200 μmol m ^-2 s ^-1 for 16 hours per day. The temperature in the greenhouse compartments was set to 24/18°C day/night, respectively. The four light treatments were (1) 40% Blue 60% Red, (2) 20% Blue 80% Red, (3) 100% Red, and (4) 100% White (Control). The plants were grown to flowering (except chrysanthemums) and plant growth was recorded at the end of the experiment. During the experiment photosynthetic parameters were measured and later leaf samples were analyzed by HPLC. The objective of the study was to characterize the effect of LEDs on the photosynthesis and the secondary metabolism of these plants. The leaf area was greater with increasing amount of blue light, while pure red light increased leaf area, total fresh, and total dry weight in chrysanthemums. In roses, HPLC analysis has shown that flavonoid and phenolic compounds were higher with increasing blue light ratio. In general, the differences between treatments were limited; however, in the pure red light, curled leaves and other abnormalities were observed in all species.