METABOLISM OF (-ABSCISIC ACID TO DIHYDROPHASEIC-ACID-4'-BETA-D-GLUCOPYRANOSIDE BY SUNFLOWER EMBRYOS())

(+)-[2-C-14]Abscisic acid [(+) ABA], prepared from (+/-)-[2-C-14] ABA by HPLC on a chiral column, at an initial concentration of 10 muM, was absorbed and metabolized very quickly by sunflower embryos. Oxidative products showed a small transient accumulation as their free forms af ter an incubation of 16 hr; at this time they accounted for about 16% of the total radioactivity absorbed. Whatever the incubation time, the ir esterified forms were detected only in small amounts. The major met abolite which accumulated with incubation time was acidic, of a highly polar nature and resistant to hydrolysis. It was isolated by reversed phase HPLC, HPTLC and TLC and characterized by mass spectrometry as d ihydrophaseic acid glucopyranoside. Such a conjugate of an oxidative c atabolite could not play the role of a potential source of ABA upon hy dration. So our results do not support the hypothesis of an eventual i nvolvement of ABA conjugates in the maintenance of embryo dormancy in sunflower.