Growth of Potato Plantlets In Vitro Is Different When Provided Concurrent Versus Alternating Blue and Red Light Photoperiods

Effects of concurrent vs. alternating blue and red light using light-emitting diodes (LEDs) on the photomixotrophic growth of potato plantlets in vitro were investigated. All seven treatments had the same 5.53 mol·m -2 daily light integral (DLI), photoperiod (16-hour day/8-hour night) and similar proportion of red light (45%) and blue light (55%). Results showed that the fresh/dry weight accumulation of potato plantlets in vitro under the concurrent blue and red light was superior than that under the alternating blue and red light, indicating that the simultaneous coexistence of blue and red light are necessary for optimum plantlet growth. Low PPF with long duration was better than high PPF with short duration under same DLI. Within the concurrent blue and red light treatments, when the duration of blue light was shorter than that of red light, timing of the blue light affected the growth of potato plantlets in vitro. Providing blue and red light together at the beginning of the photoperiod resulted in optimal growth, however plantlets illuminated with alternately blue and red light had significantly less fresh/dry weight accumulation.