Indoor microgreen production systems are becoming increasingly popular because they can achieve high yields and quality, especially in unfavorable climates and urban settings. Light is a critical environmental factor that influences plant development; however, limited information exists on the effects of photoperiod (PP) on the growth of chia and arugula microgreens and on the associated electricity costs. The objective of this study was to evaluate the impact of different blue LED light (Light-Emitting-Diode) PPs, 24:0, 18:6, 12:12, and 6:18 h of light: dark compared with natural light, on the growth and biomass production of Salvia hispanica (chia) and Eruca sativa (arugula) grown indoors under controlled conditions (25 °C and 189.4 μmol·m−2·s−1). In chia, shoot length increased (p ≤ 0.05) with shorter PP, particularly under the 6:18 and 12:12 h·d−1 photoperiods, while arugula showed no significant response. Root length and total plant length were unaffected by photoperiod in either species. Leaf area was the most responsive growth parameter, with larger leaves produced under PP of 18 h or more per day. Total chlorophyll content was highest at 12:12 and 18:6 h light: dark. Fresh biomass reached its maximum at 18:6, with 637.6 g m−2 in chia and 883.7 g m−2 in arugula. TOPSIS was used as a multi-criteria decision-making tool for comprehensive treatment evaluation, showing that the 6:18 treatment achieved the highest overall ranking, whereas the 18:6 treatment resulted in the greatest biomass production.
Sánchez-Villegas et al. (Thu,) studied this question.