Investigation of white LED light intensity effects on the in vitro shoot organogenesis using the half-seed method in soybean (Glycine max)

Light-emitting diode (LED) technology is increasingly adopted in growth chambers for plant tissue culture. Given the distinct light spectrum of LED compared to fluorescent light, optimizing its integration under in vitro conditions becomes imperative. The in vitro explant usually grows under low light intensity. The potential advantage to shoot organogenesis and growth under high light intensity has been uninvestigated. Soybean ( Glycine max ) shoot organogenesis using half-seed explants is widely adopted for Agrobacterium -mediated transformation but remains as a lengthy process. The present study aims to address the adoption of LED technology for in vitro plant culture and investigate the effect of increasing light intensity of white LEDs over 100 \:mol·\:m⁻²·\:s⁻¹ on shoot organogenesis efficiency in soybean. In this study, two experiments were conducted. The initial experiment evaluated shoot induction across six light intensities: 40, 70, 100, 130, 160, and 190 \:mol·\:m⁻²·\:s⁻¹ of white LED light and one light intensity of 100 \:mol·\:m⁻²·\:s⁻¹ of fluorescent light. The subsequent experiment assessed three light intensities (40, 100, 190 \:mol·\:m⁻²·\:s⁻¹ ) of white LED during two phases (shoot induction and shoot elongation). Outcomes indicated that increasing light intensity during the shoot induction phase increased the biomass of induced shoot clusters. Additionally, increasing light intensity during shoot induction phase improved shoot elongation ratio, but only when shoot elongation was conducted under low light intensity (40 \:mol·\:m⁻²·\:s⁻¹ ). Furthermore, increasing light intensity during shoot elongation yielded enhancement in growth-related parameters, including shoot stem diameter, leaf area, and shoot biomass. The results underscore the pivotal role of LED lights in achieving a high light intensity that promotes soybean shoot growth in vitro.