Endogenous hormone alteration during callus and adventitious root formation through thin cell layer culture system in Phyllanthus amarus

This study investigates the endogenous hormone variation in the callus and adventitious root formation of Phyllanthus amarus using the thin cell layer (TCL) culture system. By employing longitudinal thin cell layer (lTCL) internode explants, this study examined the changes in key plant hormones, including auxin (AUX), cytokinins (CKs), gibberellin A3 (GA3), abscisic acid (ABA), and melatonin (MEL), using ultra-high-performance liquid chromatography (UHPLC). This experiment highlighted that the position of the internode had a significant impact on both callus and adventitious root formation. Internode explants closer to the root base (3rd internode) favored adventitious root formation, attributed to higher endogenous AUX levels, while the 2nd internode exhibited superior callus formation efficiency, associated with a more balanced AUX/CKs ratio. TCL explants demonstrated faster morphogenesis and higher efficiency compared to internode explants due to better nutrient and plant growth regulator absorption. The lTCL explants facilitated a more rapid and extensive formation of callus and adventitious roots. Hormonal analysis revealed dynamic changes in endogenous hormone levels throughout the culture period, with notable peaks of AUX and CKs at critical stages of callus and adventitious root development. The ratios between AUX and CKs, as well as interactions with GA3, ABA, and MEL, played a pivotal role in regulating morphogenesis. The findings provide valuable insights into the intricate hormonal mechanisms controlling in vitro morphogenesis in P. amarus and underline the potential of TCL culture systems for improving tissue culture strategies in medicinal plants. Internode position significantly influenced callus and adventitious root formation on Phyllanthus amarus. Thin cell layer culture positively impacted morphogenesis. Endogenous hormone alterations correlated with morphogenesis in Phyllanthus amarus.