Abstract
When the upper part of main shoot of morning glory is bent down, an axillary bud situated on the uppermost node starts to elongate. Using an agravitropic mutant of morning glory, weeping, we previously found that this release from apical dominance requires graviresponse. However, the molecular mechanism of this phenomenon, as well as whether this release from apical dominance is triggered by the same mechanism as one induced by decapitation are unclear. In this report, we examined the involvement of cytokinin and auxin in the two modes of axillary bud growth. In wild-type morning glory, decapitation caused an increase in cytokinin level and a reduction of auxin response. In contrast, significant change of neither cytokinin nor auxin action was observed with shoot bending treatment. These results suggest that mechanism for gravity-regulated release from apical dominance is independent of decapitation one.
