Effect of the light spectrum of white LEDs on the productivity of strawberry transplants in a plant factory with artificial lighting

The application of plant factory with artificial lighting (PFAL) for producing strawberry transplants (S-PFAL) was recently introduced due to the capacity for high quality and year-round transplant production. To achieve greater efficiency with this system, it is essential to select lighting sources that have a suitable spectrum for runner plant propagation. This study was conducted to investigate the effects of the light spectrum of white light-emitting diodes (LEDs), which have a different correlated color temperature compared with that of white fluorescent lamps, on the growth of strawberry (Fragaria × ananassa Duch. cv. Maehyang) propagules and runner plants in a PFAL. Uniform propagules with one fixed runner each were placed into a PFAL for transplant production and were grown under either warm-white LEDs (WWL), mint-white LEDs (MWL), or cool-white fluorescent lamps (CWF) for 21 days. The propagules in the MWL treatment group had the greatest number of leaves, leaf area, top/root dry weight ratio and number of newly formed runners per propagule among the treatments. The dry weight of the newly formed runners of each propagule was also greatest after MWL treatment, whereas it was lowest after CWF treatment. However, there was no significant difference in the growth parameters of the runner plants among the three treatments. The photosynthetic photon efficacy of WWL and MWL was 5.40 µmol s⁻ ¹ W⁻ ¹, which was 62.6% higher than that of CWF (3.38 µmol s⁻ ¹ W⁻ ¹). The dry weight efficacies of the MWL, WWL, and CWF treatments were 23.5, 22.1, and 10.0 g kWh⁻ ¹, respectively. These results indicate that MWL with high photosynthetic photon efficacy can have positive effects on the runner formation and growth of strawberry propagules and can replace cool-white fluorescent lamps in an S-PFAL.