Red and white LED light improve vegetative propagation of Dysophylla yatabeana in closed-type smart farm

Efficient artificial lighting is essential for optimizing plant growth and propagation in closed-type smart farms. This study aimed to evaluate the effects of light-emitting diode (LED) combinations using red (R), blue (B), and white (W) light on physiological responses and rhizome-based vegetative propagation in Dysophylla yatabeana, a poorly seed-propagable aquatic species. Plants were cultivated under five different spectral treatments and a natural light control. Key physiological indicators-including net photosynthetic rate (Pn), substomatal CO₂ partial pressure (Ci), transpiration rate (E), photo-synthetic quantum efficiency (Φ), and leaf-to-air temperature difference (ΔT)-were measured. Path analysis was conducted to clarify the direct and indirect relationships among these variables and growth traits such as shoot dry weight (SDW), rhizome dry weight (RDW), and number of rhizomes (RN). The addition of W significantly enhanced both SDW and RN, whereas high R: B ratios increased Pn but suppressed RDW. Light quality was found to influence growth not only through direct spectral effects but also via complex physiological pathways regulating internal CO₂ dynamics and assimilate allocation. These results provide insight into light management strategies for controlled-environment agriculture, especially for species requiring vegetative propagation, and support the development of sustainable indoor cultivation systems using LED lighting.