Literature Review: The Role of Plant Growth Regulators in Embryogenic Callus Induction in Curcuma sp.

Embryogenic callus development in Curcuma species depends on the type, concentration, and proportion of plant growth regulators (PGRs), particularly the interaction between auxins and cytokinins. These hormones regulate tissue dedifferentiation and influence subsequent regeneration. Although tissue culture is widely used for Curcuma propagation and conservation, callus induction efficiency varies according to species, explant type, and hormonal composition. This review discusses the effects of auxins, such as 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthaleneacetic acid (NAA), alongside cytokinins, including benzylaminopurine (BAP), thidiazuron (TDZ), and kinetin, on embryogenic callus formation. Previous studies have reported promising PGR combinations, including 2,4-D at 2.0 mg/L combined with TDZ at 0.5 mg/L, although their effectiveness may differ among species. Appropriate hormonal balance is essential for improving the regenerative capacity of cultured tissues and supporting embryogenic or organogenic development. By comparing findings across Curcuma species, this review examines hormone-mediated physiological responses and challenges in protocol standardization. Further research is needed to clarify species-specific PGR requirements, the mechanisms underlying embryogenic competence, and the long-term stability of regenerated plants. Future efforts should prioritize hormone optimization, alternative PGR systems, and reproducible protocols for mass propagation, phytochemical production, and genetic resource conservation.