Effets de L'acide abscissique exogène sur la levée de dormance au froid de tubercules de Topinambour cultivés in vitro

Abstract

In vitro cultured Helianthus tuberoses L. tubers were treated at low temperatures on a medium supplemented with ABA 1.7 × 10−5 M. Endogenous levels of ABA were measured by gas-liquid chromatography and electron capture. The existence of large quantities of this inhibitor does not appreciably modify the release of dormancy and subsequent germination at 24°C. At low temperatures, breaking of dormancy occurs with endogenous ABA levels of about 200–600 μg/kg fresh matter. Germination proceeds at 24°C with about 50–100 μg/kg fresh matter. The breaking of dormancy and the installation of the non dormant state by the low temperatures seem to be independent of the level of ABA in these tubers. The «boulage»: formation of tubers on a mother tuber, which is a perpetuation of the dormant state, is associated with a decreasing level of endogenous ABA. After 6 months, this level decreases to about that measured in non-dormant tubers. In our material, the ABA level does not appear to be involved in the perpetuation of the dormant state.