Effects of endogenous ABA levels and temperature on cedar (Cedrus libani Loudon) bud dormancy in vitro

Axillary and apical buds of in-vitro-propagated cuttings of Cedrus libani a re unable to burst at 24 degrees C, but this inhibition was overcome at 30 degrees C. Here we have used cedar microcuttings to investigate whether the levels of endogenous hormones vary with bud dormancy and temperature. We a nalysed the levels of abscisic acid, indole-3-acetic acid, zeatin, isopente nyladenine and their major metabolites using HPLC purification and fraction ation of the samples coupled to an ELISA method for hormonal quantitation i nvolving several antibodies elicited against each hormonal family. Abscisic acid levels in microcuttings with dormant buds were higher than those in m icrocuttings with growing buds. At 24 degrees C, needles accumulated more a bscisic acid than at 30 degrees C. In addition, when needles were removed, but growth release was achieved at 24 degrees C. Abscisic acid supplied at 30 degrees C induced the formation of dormant buds. These results suggest t hat abscisic acid accumulation in the needles can explain the bud dormancy of cedar microcuttings at 24 degrees C.