ABA Involvement in the Psychrolabile Dormancy of Fagus Embryo

Abstract

Embryos of Fagus sylvatica isolated from fruits at harvest were dormant. After a cold-treatment in restricted water conditions, embryos were able to germinate at a percentage which increased with chilling duration. Embryo ABA content decreased during the dormancy-releasing treatment at 4 degrees C; it also decreased in the same proportions during embryo culture at 23 degrees C, a temperature allowing dormancy to be strongly expressed. It thus appears that embryo ABA content was not correlated with the physiological potentialities of the embryo. The significant decrease in ABA level observed during culture at 23 degrees C could be explained by a very rapid ABA metabolism, revealed by the results of [H-3]ABA feeding experiments. Also, when fluridone, an inhibitor of carotenoid synthesis, was applied directly to axes, dormant embryos were able to germinate after a one-week culture. The comparison between axis ABA content in the absence or in the presence of fluridone after a 6-day culture gave an estimation of the axis capacity for a de novo ABA synthesis. Consequently, it appears that the psychrolabile dormancy of Fagus is associated with the ability of the axis to synthesize its own ABA.