Callus Culture System from Lonicera japonica Thunb Anthers: Light Quality Effects on Callus Quality Evaluation

<i>Lonicera japonica</i> Thunb has significant edible and medicinal value, possessing heat clearing, detoxification, antibacterial, and blood pressure reduction properties. Currently, its quality is constrained by factors such as climate, environment, flowering period, and germplasm degradation. The strategy of using bioreactors and abiotic inducers to produce bioactive metabolites has not yet been implemented. This study reports, for the first time, the induction of an embryogenic callus from <i>L. japonica</i> anthers, the identification of tissue morphological structures, and the effects of light induction on the callus morphology, metabolite accumulation, and antioxidant activity. The results showed that the MS medium, supplemented with 1.0 mg·L^-1 6-BA, 1.5 mg·L^-1 NAA, 1.5 mg·L^-1 2,4-D, and 0.2 mg·L^-1 KT, induced 89% embryogenic callus formation. Uniform callus lines were obtained using 2.0 mg·L^-1 6-BA, 0.5 mg·L^-1 NAA, and 0.2 mg·L^-1 KT in each subcultivation. Embryogenic cells were observed to have closely arranged spherical protruding granules on their surface, along with visible nuclei and numerous starch grains. After 15 days of blue light induction, active metabolites and antioxidant activities peaked. This experimental system not only provides support for germplasm innovation but also indicates that abiotic inducers can be utilized as a means to achieve higher yields of metabolic products.