Metabolism of [2- 14C]abscisic acid in dormant and Afterripened Apple Embryos

Abstract

Summary Dormant and after-ripened embryos of Pyrus malus L. var. Golden delicious were incubated with (±) [2- 14 C]abscisic acid at 10 -5 M (947 MBq mmol -1 ) for various periods (2, 6, 9,12 days) at 24 °C in darkness. The embryos were extracted in 80 % ethanol. Two acidic diethyl-ether phases which contained the free acids and the acids released after mild alkaline hydrolysis, respectively, were analysed as well as the radioactivity which remained in the final aqueous phase. The results obtained indicated that ABA metabolism was very active in both cases since, despite continuing absorption, the percentage of the radioactivity represented by abscisic acid decrease as a function of time. Greater amounts of abscisic acid remained in after-ripened embryos than in dormant embryos. The surplus of abscisic acid metabolized was found almost exclusively in the form of a-D-glucopyranoside abscisate while distribution of the radioactivity corresponding to other metabolites was not modified. There is, therefore, a tendency in dormant embryos towards the formation of β-D-glucopyranoside abscisate, a substance the role of which as a potential source of ABA has already been demonstrated in this material.