ABA CONTENT AND SENSITIVITY DURING THE DEVELOPMENT OF DORMANCY IN LILY BULBLETS REGENERATED IN-VITRO

We measured ABA content and sensitivity in bulblets of Lilium speciosu m Thunb. regenerating from scale explants in vitro at temperatures (15 , 20 or 25 degrees C) that allowed the development of various levels o f dormancy (very low, intermediate or high, respectively). The one-ste p purification and the accuracy of the immunoassay were confirmed by H PLC and by liquid chromatography/mass spectrometry. ABA content was no t correlated with dormancy development. Sensitivity to ABA was determi ned as the difference in sprouting performance of excised bulblets on medium with and without ABA. In bulblets regenerating at 20 or 25 degr ees C, ABA sensitivity was high during the period of dormancy establis hment and decreased thereafter. Dormant bulblets were almost completel y insensitive to ABA. The changes in sensitivity to ABA were confirmed by measuring the level of ABA in bulblets at the time of sprouting. T his level was, as expected, highest in bulblets with low ABA-sensitivi ty. Briefly cold-treated bulblets, in which dormancy may be re-establi shed by culture at 20 degrees C, again became sensitive to ABA. ABA se nsitivity decreased with increasing temperature: bulblets that regener ated at 15 degrees C and hardly developed any dormancy, were very sens itive to ABA. It was concluded that in addition to ABA sensitivity ano ther, still unknown, factor played a key role in dormancy development.