Side Lighting Enhances Morphophysiology and Runner Formation by Upregulating Photosynthesis in Strawberry Grown in Controlled Environment

The significant effects of lighting on plants have been extensively investigated, but research has rarely studied the impact of different lighting directions for the strawberry plant. To understand the optimal lighting direction for better growth and development, this study investigated how strawberries respond to variations in the lighting direction to help fine-tune the growth environment for their development. We examined how the lighting direction affects plant morphophysiology by investigating plant growth parameters, leaf anatomy, epidermal cell elongation, stomatal properties, physiological characteristics, and expressions of runner induction-related genes (FaSOC1 and FaTFL1) and gibberellin (GA) biosyntheses-related genes (FaGA20ox2 and FaGA20ox4). In closed-type plant factory units, the rooted cuttings of strawberry (Fragaria × ananassa Duch.) ‘Suhlyang’ were subjected to a 10-h photoperiod with a 350 μmol∙m−2∙s−1 photosynthetic photon flux density (PPFD) provided by light-emitting diodes (LEDs) from three directions relative to the plants: top, side, and bottom. Our results demonstrated that the side lighting profoundly promoted not only morphophysiology, but also runner formation, by upregulating photosynthesis in strawberries. Side lighting can bring commercial benefits, which include reduced economic costs, easier controllability, and harmlessness to plants. This will help provide new insights for the propagation of the most commonly cultivated strawberries in South Korea