High frequency plant regeneration with histological analysis of organogenic callus from internode explants of Asteracantha longifolia Nees

Asteracantha longifolia Nees is an ayurvedic medicinal herb. The internode explants of this plant were used for high frequency plant regeneration on Murashige and Skoog (MS) medium supplemented with various plant growth regulators (PGRs) in different concentrations. Apical meristem and leaf primordium formations were confirmed through microscopic analysis of histological sections of the organogenic callus tissues. The synergistic effect of α-naphthaleneacetic acid (NAA) 0.5 mg/l with N6 benzyladenine (BA) 0.25 mg/l increased the percentage of explants response for callus induction while comparing other treatments. Various concentrations of NAA were also found to be best for explants response to callus induction than 2,4-dichlorophenoxyacetic acid (2,4-D). The callus morphology (color and texture) was different according to the growth regulators and their concentrations. The highest percentage of response per culture for shoot bud regeneration was noted for the concentration of NAA 0.5 mg/l with BA 2.0 mg/l, the same concentration effectively increased the number of shoots per culture. Different concentrations of indol-3-butyric acid (IBA) and NAA were used in half strength MS medium for in vitro rooting of regenerated shoots. The maximum percentage of shoot response for rooting and the highest number of root formations per shoot were observed on the medium containing 0.5 mg/l of IBA. The survival rate (86.7%) of the regenerated plants was noted after 20 days of transplantation.