RESPONSE OF EXCISED ROOTS OF RAUVOLFIA SERPENTINA BENTH. TO GROWTH REGULATORY SUBSTANCES

Auxins, IAA and IBA were found to promote the root apex growth at low concentrations (below 0.5 mg/l) in calcium deficient medium. An interaction exists between phosphate ions and auxins. For lateral root formation, auxins were a limiting factor and were required in comparatively higher concentrations. Root tip meristem has an inhibitory effect on lateral root initiation in its proximity. The lateral root formation in response to auxins decreases with successive subculturing. Embryoid and shoot bud formation have been achieved by NAA with kinetin. NAA with kinetin and 2,4-D produced prominent subapical swelling in root apex by activating the division of the cortical tissue. Among the auxins used 2,4-D only was effective for callus formation. MH, TCPA and TIBA inhibited the root apex growth. After 9 to 12 successive transfers of the same explant, cambial activity appeared in the basal region in a IAA and sugar containing medium.