Abstract
We quantified how the spectral distributions ranging from red [R (600 to 699 nm)] to far-red [FR (700 to 799 nm)] influenced flowering and stem extension of stock (Matthiola incana (L.) R. Br.). ‘Yukinami’ and ‘White Iron’ plants were grown under a natural photoperiod with or without exposure throughout the entire night (continuous lighting) by LEDs with seven different R/FR ranging from all R to all FR (Experiment 1). Light exposure treatments promoted flowering and stem extension. The effects on flowering and stem extension increased as R/FR of the continuous lighting decreased, reaching a maximum at R/FR of 0.7 or lower in ‘Yukinami’. Exposure to R/FR ranging from 0.15 to 0.7 was more effective than FR-only continuous lighting for promoting flowering in ‘White Iron’. ‘White Iron’ plants were grown under a natural photoperiod with or without continuous lighting by LEDs with seven different peak wavelengths between 628 and 742 nm (Experiments 2 and 3). All exposure conditions promoted flowering and stem extension. Exposure to 709, 725, and 742-nm LEDs with peak wavelengths in the FR region strongly promoted flowering and stem extension. Flowering nodes were the lowest under continuous lighting with the 709-nm LED, which was the most effective for the promotion of flowering. The analysis using estimated values of phytochrome equilibrium established by LEDs with different peak wavelengths indicated the possibility of phytochrome control in the flowering and stem extension of stock.
