Morphogenic Response of Leaf Explants of Pleroma Heteromallum Under Different Combinations of In Vitro Growth Regulators

Objective: The study aimed to evaluate the morphogenic responses of leaf explants of Pleroma heteromallum cultured in vitro, with the goal of expanding the knowledge on micropropagation strategies for the species. Theoretical Framework: Pleroma heteromallum is an endemic species of Brazil with ornamental, medicinal, and phytoremediation potential. Its sexual propagation presents limitations, and the species is generally multiplied through stem cuttings. Micropropagation represents a promising alternative for large-scale production of seedlings with phytosanitary quality and continuous availability. Method: Five experiments were carried out testing MS media supplemented with different combinations of BAP, IBA, 2,4-D, PVP, and activated charcoal. The morphogenic responses of the leaf explants were evaluated throughout the culture period, with records of the percentages of callogenesis, rhizogenesis, and possible shoot formation. Results and Discussion: It was observed that PVP and activated charcoal did not inhibit oxidation and impaired callus formation. MS medium without growth regulators did not induce callogenesis, resulting in explant death. Treatments containing BAP alone showed inferior performance compared with those combined with IBA or 2,4-D. The peak of callogenesis and rhizogenesis occurred on the 20th day, followed by progressive callus oxidation. Only one explant, cultivated in BAP:IBA, formed callus, roots, and shoots, indicating potential for indirect organogenesis. Research Implications: The results support future micropropagation protocols for the species and contribute to its management and conservation. Originality/Value: This study provides unprecedented evidence on the in vitro morphogenesis of P. heteromallum, highlighting promising hormonal combinations for its propagation.