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 on e week after placement of the explants on the culture media. Green nod ule-like structures protruded from the distal end of the explants with in 10 days and developed into shoots with in a month. These shoots rea dily formed adventitious roots when placed on fresh culture medium. Al l three of the gibberellin biosynthesis inhibitors increased shoot for mation compared to the control. The number of shoots per explant was i ncreased 107, 79, and 168% by 0.3-0.4 muM 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 im pact on the number of shoots formed.