Formation and transport of 1-aminocyclopropane-1-carboxylic acid in pea plants

The formation and transport of free 1-aminocyclopropane-1-carboxylic acid (ACC) and conjugated ACC 1-(malonylamino)cyclopropane-1-carboxylic acid; M-ACC] was studied in pea plants. Excision and dark incubation induced ACC and M-ACC synthesis in stem segments, including the second node. At similar rates as in segments, ACC and M-ACC were formed near the cut surface in stems after decapitation, leading to a transient increase in both compounds in the node adjacent to the cut. The maximum level of M-ACC at 6 hr exceeded that of ACC at 3 hr. Seven days after decapitation, total M-ACC in the shoot returned to the level in the control plants. Over the same period of time, M-ACC accumulated in the roots in amounts comparable to those previously observed in the shoot. It is concluded that M-ACC formed near the cut is transported basipetally, and that the roots act as a sink. Both the increase in ACC and M-ACC in the node after decapitation and the degree to which growth of lateral shoots was inhibited by ACC applied to the cut end increased with advancing age of the plant.