Abstract: No PAO activity was detected in ungerminated cowpea (Vigna unguiculata L. ) seeds (form 0 to 24 h after imbibition) , but it could be detected in the plumule , cotyledons and embryonic axis of the germinatingseeds whose radicles were just visible (36 h after imbibition) . The PAO activities in these three parts increased at different rates during germination , while no PAO could be detected in radicle at all times. Soaking with Act2D only inhibited the seed germination by 27. 6 % , but CHM could inhibit the germination by 90. 6 %. Moreover , the inhibitions of the PAO activity in the plumule and cotyledons by Act2D were just 29. 1 % and 33. 3 % , and those by CHM were up to 87. 2 % and 85. 4 % respectively. Light had a remarkable inhibitory effect on the PAO activity in plumule and cotyledons. Soaking with putrecine (0. 1 and 0. 5 mmol/ L) or CuCl₂ (10μmol/ L) for 6 h could enhance the activity of PAO.

Key words: Cowpea ( Vigna unguiculata L. ), Polyamine, Polyamine oxidase, Seed germination, Cu²⁺