An attempt was made to induce rooting from nodal cuttings of Saraca asoca under controlled conditions and study its biochemical changes during rooting. The nodal cuttings were pretreated with different concentrations of IAA, NAA and IBA and kept in a growth chamber [25±2°C, 16 h photoperiod (55 µmolm-2s-1) with cool, white fluorescent lamps and 65% relative humidity] for 12 h. Among the three auxins used for pretreatment, IBA showed more positive response on rooting as compared to IAA and NAA within 4 weeks of transfer to growing medium under mist condition. Among four concentrations of IBA tested, 500 ppm gave maximum percentage of rooting, number of roots and root length. Therefore, IBA was used further in experiments for biochemical investigation. The adventitious rooting was obtained in three distinct phases that is induction (0 to 10 d), initiation (10 to 20 d) and expression (20 to 30 d). IAA-oxidase activity of IBA-treated cuttings increased slightly as compared to control. The activity was found to decrease during induction and initiation phases and increase during expression phase. The peroxidase activity in IBA-treated cuttings increased up to initiation phase and declined at the expression phase. Polyphenol oxidase activity increased both in IBA-treated and control cuttings during induction and initiation phase but declined slowly during expression phase. Total phenolic content was higher in IBA-treated cuttings, particularly in initiation and expression phases and it also correlated with peroxidase activity. Phenolics might be playing key role for induction of adventitious rooting, and phenolic compounds can be used as rooting enhancer in S. asoca, an important medicinal plant.
Key words: Auxins, enzyme activity, nodal cuttings, Saraca asoca, propagation.