Micropropagation of nodal explants from adult trees of Cleistanthus collinus

The micropropagation of adult Cleistanthus collinus was accomplished. The nodal segments from terminal twigs of a 15-year-old tree and basal sprouts of a comparable chronological age were used for initiating shoot bud cultures. Washing explants with sterile mixtures of citric acid (520.5 μM) and PVP 40 (3.75 μM) three to four times controlled the leaching of brown inhibitory substances into the establishment medium. Axillary shoots proliferated best on MS medium containing citric acid (104.1 μM), and PVP 40 (12.5 or 25 μM) supplemented with 0.44 μM BA. The number of new shoots from nodal segments of explants placed on MS medium supplemented with 0.44 μM BA increased when the remaining lengths of nodal segments were transferred to fresh medium after the longer microshoots were harvested. The microshoots derived from basal sprouts rooted best (50%) when treated with 11.4 mM IAA for 2 min, whereas only 40% of the microshoots derived from terminal twigs produced roots after a 2-min exposure to 28.5 mM IAA. The placement of BA-soaked agar cubes on the apex-decapitated shoots controlled shoot-tip necrosis considerably. In general, explants from basal sprouts were more suitable than terminal twig explants for the micropropagation of adult trees of C. collinus. Received: 26 February 1997 / Revision received: 13 September 1997 / Accepted: 29 September 1997