ACC-N-malonyltransferase activity during zygotic embryogenesis and germination of chick-pea seeds

Some physiological characteristics of ACC-N-malonyltransferase (ACC-N-MTase ) have been studied in the seeds of chick-pea (Cicer arietinum L.). This en zymatic activity was detectable during all periods of zygotic embryogenesis ; however, the highest values were found in the dry seed. in dry seeds, the enzymatic activity was greater in the embryonic axis than in the cotyledon s. During the onset of germination, activity increased more strongly in the cotyledons than in the embryonic axis, reaching its highest values in the storage organs coinciding with radicle emergence (18 to 24 h). Removal of t he cotyledons strongly diminished enzymatic activity in the embryonic axis. Low concentrations of ethrel (50 mu M) stimulated the axis ACC-N-MTase. Th e highest specific activity was found in the apical meristem of the embryon ic axis, declining over the length of the organ. The role of ACC-N-MTase ac tivity in the germinative process is discussed, together with the regulator y effect of ethylene on this ACC-conjugating enzyme.