Optimization of factors affecting in vitro regeneration, flowering, ex vitro rooting and foliar micromorphological studies of Oldenlandia corymbosa L.: a multipotent herb

Abstract

The conditions were optimized for efficient in vitro regeneration of shoots and roots of Oldenlandia corymbosa L. using nodal shoot explants. Murashige and Skoog’s (MS) medium augmented with additives and 2.0 mg L−1 BAP was recorded optimum for shoot bud induction from the nodal meristems. The shoots were proliferated by subsequent subcultures on half strength MS medium fortified with 1.0 mg L−1 BAP and 0.5 mg L−1 kinetin + additives. This media combination yielded maximum number of shoots (223 ± 4.12 shoots/culture bottle) with 13.4 cm average length. Flower buds were induced (4.2 ± 0.28 flowers) from the in vitro multiplied shoots on MS medium contained 1.0 mg L−1 BAP and 0.5 mg L−1 of kinetin and IAA under 50 µmol m−2 s−1 SFPD light intensity for 12 h/day photoperiod. In vitro regenerated shoots were rooted on half strength MS medium conjunct with IAA, IBA and NAA singly at different concentrations. The best rooting response was observed on half strength MS medium containing IBA at 2.0 mg L−1 with activated charcoal. Roots were also induced from the cut ends of the shoots using ex vitro rooting techniques in O. corymbosa by pulse treating the shoots with 300 mg L−1 IBA for 4 min. Better roots were achieved in this method than the in vitro roots in terms of numbers (14.7 ± 0.21) and firmness. The foliar micromorphological studies could help to understand the structural adaptations of micropropagated O. corymbosa plantlets towards field environments. The in vitro induced anomalies in stomatal apparatus were repaired during hardening of plantlets in the greenhouse and after field transfer. Decrease in stomatal density (from 70.78 ± 0.55 to 55.6 ± 0.10), and increase in veins, trichomes and crystals/raphides densities revealed the developments of structural changes in the leaves to withstand in the harsh field conditions. The acclimatized plantlets with well developed root systems were successfully shifted to the natural soils with 98% survival rate.