Effect of gibberellin biosynthesis inhibitors on shoot regeneration from hypocotyl explants of Albizzia julibrissin.

Hypocotyl explants of Albizzia julibrissin were placed on Gamborg's B5 medium supplemented with various levels of paclobutrazol, uniconazole, prohexadione calcium, or GA3. Callus formation was evident within one week after placement of the explants on the culture media. Green nodule-like structures protruded from the distal end of the explants within 10 days and developed into shoots within a month. These shoots readily formed adventitious roots when placed on fresh culture medium. All three of the gibberellin biosynthesis inhibitors increased shoot formation compared to the control. The number of shoots per explants was increased 107, 79, and 168% by 0.3-0.4 μM paclobutrazol, uniconazole, and prohexadione calcium, respectively. In contrast to the gibberellin biosynthesis inhibitors, GA3 decreased shoot formation. These results indicate that modification of gibberellin status can have a strong impact on the number of shoots formed.