In vitro Propagation and Foliar Micromorphological Studies of Dillenia indica L.: An Underutilized Fruit Tree

The present study describes an improved, efficient method for in vitro propagation of the underutilized fruit tree, Dillenia indica L. Nodal segments obtained from a mature tree were used as initial explants for in vitro regeneration. Among the various cytokinin types (BAP, Kin, mT, and TDZ) and concentrations tested, MS medium containing 0.5 mg·L⁻¹ 6-benzylaminopurine was optimal for shoot induction. Subculturing mother explants into fresh medium during subsequent passages significantly influenced shoot multiplication. A maximum of 5–7 shoots were regenerated after the third subculturing on MS medium containing 0.5 mg·L⁻¹ 6-benzylaminopurine. Maximum rooting was achieved in MS medium containing 2 mg·L⁻¹ indole-3-butyric acid. Approximately 80% of the plants survived acclimatization. A comparative study revealed significant changes in leaf micromorphology and architecture, including developmental and structural changes in venation patterns, trichomes, and stomata, in both in vitro-grown and fully acclimatized plants. This foliar micromorphological study elucidated the mechanism of adaptation of in vitro-regenerated plantlets during acclimatization. The current investigation could provide a foundation for the large-scale propagation and conservation of this medicinally important and underutilized fruit tree species.