Change in pH regimes and adventitious root induction in semi-hardwood cuttings of Gmelina arborea Roxb.

Change in pH regimes (pH 5.5-8.5), IBA (0.5 mM) and their interactions significantly influenced adventitious root induction and growth in semi-hardwood shoot cuttings collected from annually hedged Gmelina arborea Roxb. stockplants of 4 years of age and maintained in earthen pots. Acidic pH 5.5 administered for 4 h as 5.0 mM potassium phosphate buffer significantly promoted rooting ability (%) and root number cutting(-1) and was the second best for root biomass after neutral pH 7.0. The effectiveness for induction and growth of adventitious roots was as follows: pH 5.5 > pH 8.5 > pH 7.0. Addition of IBA was ineffective at pH 5.5-7.0 and inhibitory at pH 8.5 for induction and growth of adventitious roots. The findings suggest a direct role of acidic pH, independent of auxin, in the process of adventitious root formation, encouraging in depth investigation for detection and characterization of pH dependent expression of early transcriptomes and their association with functioning of auxin signal transduction system in the process.