ABA content and sensitivity during the development of dormancy in lily bulblets regenerated in vitro

We measured ABA content and sensitivity in bulblels of Lilium speciosum Thunb , regenerating from scale explants in vitro at temperatures (15, 20 or 25°C) that allowed the development of various levels of dormancy (very low, intermediate or high, respectively). The one-step purification and the accuracy of the immunoassay were confirmed by HPLC and by liquid chromatography/mass spectrometry. ABA content was not correlated with dormancy development. Sensitivity to ABA was determined as the difference in sprouting performance of excised bulblets on medium with and without ABA. In bulblets regenerating at 20 or 25°C. ABA sensitivity was high during the period of dormancy establishment and decreased thereafter. Dormant hulblets were almost completely insensitive to ABA. The changes in sensitivity to ABA were confirmed by measuring the level of ABA in bulblets at the time of sprouting. This level was, as expected, highest in bulhlels with low ABA-sensitivity. Briefly cold-treated bulblets, in which dormancy may he re-established by culture at 20°C, again became sensitive to ABA. ABA sensitivity decreased with increasing temperature bulblets that regenerated at I5°C and hardly developed any dormancy, were very sensitive to ABA. It was concluded that in addition to ABA sensitivity another, still unknown, factor played a key role in dormancy development.