TO DETERMINE the optimum in vitro conditions for callus induction and plant regeneration from in vitro leaf and stem of Catalpa (Catalpa bignonioides) seedlings, the explants were cultured on Murashige and Skoog (MS) or woody plant medium (WPM) medium supplemented with different concentrations (4.5, 6.7, 9.0, 18.0, and 27.1 μM) of 2,4-dichlorophenoxyacetc acid (2,4-D) or naphthalene acetic acid (NAA) (5.4, 8.1, 10.7, 21.4, and 32.2 μM) along with 2.2 μM benzyl adenine (BA). The highest rate of whitish, compact, and nodular calli were induced when the leaf explants cultured on MS medium supplemented with 32.22 μM NAA plus 2.2 μM BA (74.5%). Weigh calluses out showed that the callus produced from this medium had the most weigh (2.9 gram). The nodular, compact and organogenic callus tissues regenerated into shoots following 5 weeks on MS medium supplemented with 17.7–26.6 μM BA and then these were transferred for an additional 3 weeks on MS medium with Gamborg B5 vitamins supplemented with same plant growth regulators and 20% coconut water for shoot elongation by culture under 16-h photoperiod. The adventitious formed shoots then were rooted on MS medium containing four different concentrations of IBA or NAA. The adventitious root formation as high as 82.5% was occurred on MS medium supplemented with 4.9 μM BA. The regenerated plants were successfully acclimatized under greenhouse conditions.
