Medicinal Plant Research 2025, Vol.15, No.3, 119-128 http://hortherbpublisher.com/index.php/mpr 121 and prevent contamination (Yu et al., 2025). Besides, the selection of midsection stem tissues without terminal buds and without basal roots, has been proven to have a higher survival rate and proliferation rate. The combination of culture medium and growth regulator, is a key factor affecting bud cluster proliferation and rooting efficiency. Murashige and Skoog (MS) media are usually used in combination with cytokinins (6-BA) and auxin (like NAA, IBA) (Wang et al., 2022; Zhang et al., 2025a). On this basis, additives such as banana puree and activated carbon can further promote root growth and the vigorous growth of seedlings. Light quality also has a significant impact on plant growth and secondary metabolism, especially the combination light of red and blue leds, which helps promote biomass accumulation and metabolite synthesis (Wang et al., 2018; Gam et al., 2020; Wu et al., 2024). Leds with a 1:1 ratio of red and blue light have been proven to simultaneously optimize plant growth and polyamine metabolism (Wu et al., 2022; 2024). 2.3 Bottlenecks and improvement needs Despite the continuous advancement of tissue culture propagation techniques, domestication and transplantation remain the difficult links in the expansion and propagation of A. roxanensis. The survival rate of tissue culture seedlings when transplanted into soil is often limited by poor root development and environmental stress. Even under the optimized scheme, the survival rate can reach 80% to 95%, but it often decreases significantly under uncontrolled conditions (Yu et al., 2025; Zhang et al., 2025a). The current main problems are concentrated on insufficient root development and weak stress resistance, which limit the successful establishment and long-term growth of propagating plants (Yu et al., 2025; Zhang et al., 2025a; b). Compared with wild plants, the root system of tissue culture seedlings is weaker, and their tolerance to drought, salt and extreme temperature environments is poorer (Zhang et al., 2025b; Zhong et al., 2025). So, in the future, it is urgently necessary to further optimize the application strategies of growth regulators, light quality regulation and domestication techniques, etc., in order to improve the root structure and stress resistance (Wang et al., 2018; Wu et al., 2022). 3 Types and Mechanisms of Growth Regulators 3.1 Auxin-based regulators Auxin, especially indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), play a fundamental role in root induction in the tissue culture of A. roxanensis. In which, the effect of IBA is particularly obvious. Studies have shown that when 1.0 mg/L IBA and 1.0 mg/L NAA were added to the MS medium, the rooting rate could reach 92%, and an average of 2.62 roots were produced per plant, which was superior to other auxin treatments (Zhang et al., 2025a). IAA can also promote root formation, but since IBA is more stable and has a better induction effect on adventite roots under in vitro conditions, it is usually more favored (Hong et al., 2020). These auxin mainly promote the elongation and division of cells at the root origin, eventually forming a strong root system. The concentration of auxin directly affects the length and quantity of roots. The optimal concentration, like 1.0 mg/L IBA, can maximize the rooting efficiency, while concentrations that are too high or too low may inhibit root growth or cause abnormal root morphology (Zhang et al., 2025a). Excessive auxin can cause callus formation or root dwarfing, while insufficient concentration leads to low rooting efficiency. Therefore, precisely regulating the auxin concentration is the key to achieving a uniform and robust root system in the rapid tissue propagation of A. roxanensis. 3.2 Cytokinin-based regulators 6-benzylaminopine (6-BA) is an artificially synthesized cytokinin that also plays a key role in the proliferation and differentiation of bud clusters in A. roxanensis. Studies have shown that when the concentration of 6-BA is 1.0-2.0 mg/L and combined with a low concentration of NAA, the best bud cluster proliferation effect can be achieved, with a high induction rate and an increase in the number of buds produced by a single explant (Zhang et al., 2025a). Although cytokinin mainly promotes bud formation, it also affects root structure in rooting culture media. Therefore, it is often necessary to maintain a reasonable balance with auxin. For instance, 1.0 mg/L 6-BA + 0.05 mg/L NAA is most suitable for bud cluster proliferation, while high concentrations of cytokinin may inhibit rooting.
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