Identification and Quantification of Abscisic Acid, Indole-3-acetic Acid and Gibberellins in Phloem Exudates ofPharbitis nil

Abstract

Abscisic acid (ABA) and indole-3-acetic acid (IAA) were identified by full-scan GC-MS in phloem exudates collected from cotyledons of Pharbitis nil Chois., strain Violet. The occurrence of gibberellin A1 (GA1), GA19, and GA20 was also demonstrated by gas chromatography-selected ion monitoring (GC-SIM). The levels of these plant hormones were analyzed by HPLC or GC-SIM in the phloem exudates, and in the cotyledons from seedlings grown under conditions that were inductive and non-inductive for flowering. The amounts of plant hormones in the phloem exudates collected for 6 h were 3–50% of those originally present in the cotyledons. The levels of plant hormones were higher in the phloem exudates collected from cotyledons grown under the inductive conditions. These results suggest that the transport of plant hormones from the cotyledon via the phloem is significant, and that endogenous plant hormones are involved in regulating the flowering of P. nil.