LED Light and Plant Growth Regulators Affect Callus Induction, Shoot Organogenesis, dl-Tetrahydropalmatine Accumulation, and Activities of Antioxidant Enzymes in Corydalis turtschaninovii Besser

The genus Corydalis, belonging to the Papaveraceae family, is widely distributed across the Northern Hemisphere, primarily in Asia. This study aimed to investigate the effect of plant growth regulators (PGRs) on callus induction, and of light quality and intensity on indirect shoot organogenesis, dl-Tetrahydropalmatine (dl-THP) accumulation, and activities of antioxidant enzymes in Corydalis turtschaninovii Besser. Calli were successfully induced from the leaf, tuber, and petiole explants with different PGR combinations. The best callus induction from leaf, tuber, and petiole explants were obtained in the medium supplemented with 3 mg·L−1 kinetin (Kn) combined with 0.8 mg·L−1 naphthalene acetic acid (NAA), 3 mg·L−1 benzyl adenine (BA) combined with 0.8 mg·L−1 NAA, and 2 mg·L−1 BA combined with 0.5 mg·L−1 NAA, respectively. For indirect shoot organogenesis, calli were cultured on the Murashige and Skoog (MS) medium under dark (D), white (W), red (R), blue (B), or 1:1 mixture of red and blue (RB) light-emitting diodes (LEDs) at an intensity of 25 or 50 µmol·m−2·s−1 photosynthetic photon flux density (PPFD) for six weeks. The RB treatment increased biomass accumulation of the callus, and promoted the induction of the shoot from the callus, whereas the R treatment promoted the dl-THP accumulation, especially with the higher light intensity. Light quality and intensity significantly influenced the activities of antioxidant enzymes and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity in calli, with the most pronounced effects observed under B or RB light treatments. Taken together, the application of monochromatic LED or combinations of red and blue LEDs could be used for the callus culture for different purposes in vitro.