The effects of thiamine on in vitro organ development and anthocyanin accumulation in Raphanus sativus

Thiamine (Vitamin B1) has an important role as an enzymatic cofactor in metabolic processes such as central carbon pathways, which are necessary for biosynthesis and energy production in plants. The current study investigated concentration-dependent effects of in vitro thiamine treatments on seed germination, organ development, and anthocyanin accumulation in hypocotyls of Raphanus sativus (radish) 'Cherry Belle'. Radish seeds (30 per treatment across 6 replicates) were cultured for 15 days on Murashige and Skoog medium supplemented with six additional thiamine HCl concentrations: 0.4, 1.6, 6.4, 12.8, 25.6, and 51.2 mg L-1. Thiamine supplementation did not result in statistically significant changes in seed germination, whereas concentrations above 6.4 mg L-1 reduced leaf production (to 2.40 leaves per seedling at 12.8 mg L-1). All thiamine treatments enhanced hypocotyl elongation, while treatments above 6.4 mg L-1 induced root elongation, reaching a maximum length of 8.64 cm at 25.6 mg L-1. The treatment at 25.6 mg L-1 gave the maximum seedling vigor index (3737.23 ± 510.44). The treatment at 12.8 mg L-1 induced the highest anthocyanin accumulation in the hypocotyls (3136.05 ± 684.52 µg CGE g-1 DW). The findings suggested that thiamine treatment at specific concentrations may be useful for optimizing early in vitro seedling development and anthocyanin accumulation in radish. Also, the need for further studies to explain the underlying physiological mechanisms responsible for these concentration-dependent effects of thiamine in radish plants was suggested.