Abstract: INTRODUCTION: Parrotia subaequalis, is a critically endangered wild plant species listed in the National Key Protected Wild Plants List of China and classified as Critically Endangered (CR) by the International Union for Conservation of Nature (IUCN). As a relic species from the Tertiary period, it holds significant scientific value for studying the early origin and differentiation of the Hamamelidaceae family in China. Despite its ecological and ornamental importance, P. subaequalis faces numerous threats to its survival, including low natural survival rates due to limited light adaptation, difficulties in pollination and seed set, and challenges in vegetative propagation methods such as cutting and seed sowing. Tissue culture technology offers a promising approach to rapidly propagate this endangered species, overcoming the limitations of traditional propagation methods.   RATIONALE: This study aimed to establish an efficient tissue culture and rapid propagation system for P. subaequalis by investigating the effects of different disinfection methods, basic media, and combinations of plant growth regulators (PGRs) on lateral bud germination, proliferation, and adventitious root formation. By optimizing these factors, we sought to increase the survival rate and proliferation coefficient of P. subaequalis in vitro, thereby providing a reliable source of plant material for conservation and production purposes.   RESULTS: Disinfection effects: The optimal disinfection method involved treating the shoot segments with 75% ethanol for 30 seconds followed by 0.52% NaClO for 5 minutes, resulting in an 83.33% survival rate. Lateral Bud Germination: The WPM basic medium showed the highest germination rate (72%) among the tested media (MS, 1/2MS, WPM). The addition of 1.0 mg∙L–1 KT significantly increased the germination rate to 91%, but without inducing multiple shoots. The combination of 1.5 mg∙L–1 6-BA and 0.003 mg∙L–1 TDZ yielded the best proliferation results, with a proliferation coefficient of 4.17. Adventitious root formation: Inducing adventitious roots in P. subaequalis was challenging, with high concentrations of auxins causing browning and death of shoots. The addition of 0.2 mg∙L–1 NAA to 1/2MS medium resulted in a 60% rooting rate. Acclimatization and transplantation: Rooted plantlets were successfully acclimatized and transplanted into a mixed substrate of peat moss and perlite (3:1, v/v) with a survival rate exceeding 90% after 30 days.   CONCLUSION: This study successfully established a tissue culture and rapid propagation system for P. subaequalis, significantly improving its survival rate and proliferation coefficient. The optimized protocols, including the use of WPM medium for lateral bud germination, a combination of 1.5 mg∙L–1 6-BA and 0.003 mg∙L–1 TDZ for proliferation, and 0.2 mg∙L–1 NAA for root induction, provide a reliable method for the large-scale propagation of this endangered species. This system not only contributes to the conservation of P. subaequalis but also facilitates its utilization in landscaping and timber production. Future research could focus on exploring the regeneration capacity of different color morphs and geographical populations of P. subaequalis to further enhance its conservation and sustainable use.

Key words: Parrotia subaequalis, endangered protected plants, tissue culture, tufted buds, multiplication