Pulse timing control for LED plant growth unit and effects on carnation

•The effects of LED with different modulations on the carnation plant are investigated.•Control of the pulse timing between red and blue light in PWM dimming was examined.•Stomata and chlorophyll content of the carnation are examined and compared to control. In this study, the effect of LED plant growth units at different working modes on carnation is examined. The applications are performed in a tunnel-type full-automatic greenhouse environment. LED plant growth units involving red and blue LEDs at different wavelengths (Mod1, Mod2, Mod3, Mod4) are fed at different modes and their effects on carnation are observed in comparison with the control. Thus, applications are performed with four different working modes. Control of the pulse timing (phase of wave pattern) between red and blue light in PWM light dimming has been examined. Morphological and physiological changes in carnation development, growth and blooming stages have been compared among different treatments. In different light application, several changes in stomatal responses, leaf area, chlorophyll content and flowers in carnation have been observed when compared with control. We have obtained the best results in all studied parameters, especially in Mod 2 while we have obtained relatively worse results in Mod 3 implementation than the control implementation. Chlorophyll quantities in carnations are measured by the pedicle lengths of the flowers and the flower quantities and the results are compared with the carnations grown under sun in a greenhouse. The changes on growth and development of carnation exposed to different light have been determined as more sensitive parameters to detect its effects.