In Vitro Morphogenesis of Tobacco: Modulation of Endogenous Growth Regulators by Tulsi (Holy Basil)

Plant growth regulators (PGRs) play a vital role in the induction of morphogenesis in vitro. Synthetic PGRs are commonly used to induce organogenesis and somatic embryogenesis from various explants, while natural substances are rarely utilized. This study aimed to enhance the regenerative response in Nicotiana tabacum leaf explants using Tulsi (Ocimum sanctum) leaf extract and to elucidate the biochemical interactions during modulation of endogenous plant growth regulators, including indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin, and 6-(γ, γ-dimethylallylamino) purine (2iP). Tulsi leaf extract significantly improved shoot production through interactions between endogenous hormones and those present in the extract, which enhanced stress mitigation. The 20% Tulsi leaf extract treatment produced significantly more shoots than the control, coinciding with increased endogenous IAA and zeatin levels starting on day 10 in culture. Furthermore, ABA and zeatin concentrations increased on days 15 and 25, respectively, in the 20% Tulsi extract treatment, suggesting their role in the induction of somatic embryo-like structures. ABA likely acts as an activator of stress responses, encouraging the development of these structures. Additionally, 2iP was involved in the induction of both forms of regeneration in the 10% and 20% extract treatments, especially in combination with ABA. These results suggest that Tulsi leaf extract holds promising potential as a natural supplement for increasing plant regeneration in vitro and advancing our understanding of how natural extracts of plant origin can be harnessed to optimize plant regeneration processes in vitro.