THE DIFFERENTIAL EFFECTIVENESS OF TWO SYNTHETIC AUXINS IN DELAYING FLORET ABSCISSION IN RED CESTRUM CUT FLOWERS DEPENDS ON THEIR TRANSPORT AND METABOLISM

摘要

Floret abscission in Red Cestrum (Cestrum elegans Schlecht) cut flower shoots was significantly delayed by a pulse treatment of 2,4-dichlorophenoxyacetic acid (2,4-D) while 1-naphthaleneacetic acid (NAA) was less effective. This phenomenon is attributed to the findings showing that significant amount of 2,4-D moved acropetally and accumulated in florets, leaves, and upper parts of the stem, while NAA remained in the lower parts of the stem. In addition, a significant amount of the accumulated 2,4-D remained in the active free form for a relatively longer period of time during vase life, while NAA was quickly metabolized. 2,4-D induced higher rates of ethylene evolution and increased expression levels of Aux/IAA homologous genes, cloned from the floret abscission zone, compared to those observed in response to NAA. This suggests that ethylene evolution and expression of Aux/IAA homologous genes may serve as markers for the activity of these two synthetic auxins.