Stage-Specific Evaluation of Plant Growth Regulators for In Vitro Regeneration of Four Himalayan Medicinal Plants: Explant Effects and Trade-offs Between Multiplication, Elongation and Rooting

In vitro propagation can reduce wild harvesting of medicinal plants, but optimisation is often reduced to naming a single “best” medium. This study evaluates the regeneration of Bergenia ligulata, Thalictrum foliolosum, Selinum tenuifolium and Wulfenia amherstiana on Murashige and Skoog medium with cytokinins (BAP, kinetin, TDZ) and auxins (IAA, NAA, IBA), alone and in combination, using leaf, nodal, rhizome and root explants. Shoot number, shoot length, the percentage of responding explants and rooting were analysed as separate stages. The treatment giving the most shoots rarely gave the longest shoots or the highest response. For B. ligulata leaf explants, BAP 0.8 + NAA 0.2 mg/l gave the most shoots (8.5) but only a 30% response, whereas BAP 1.0 + NAA 0.2 mg/l gave 8.0 shoots, 7.1-cm shoots and a 70% response, so the expected yield per inoculated explant was more than twice as high (5.6 versus 2.6 shoots). Auxin alone supported multiple shoots in T. foliolosum (NAA 0.5 mg/l: 11.25 shoots, 10.9 cm) and S. tenuifolium. Explant origin altered outcomes: root-derived T. foliolosum cultures reached an 89.6% response compared with 62.5% for leaf cultures. B. ligulata shoots rooted best without growth regulators (87.2%, 12.8 roots), and added auxins reduced rooting. Candidate two-stage protocols are proposed for each species, together with the acclimatisation, genetic-fidelity and chemical-consistency tests needed before they can support conservation or supply.