EFFECT OF GIBBERELLIC-ACID ON CARNATION FLOWER SENESCENCE - EVIDENCE THAT THE DELAY OF CARNATION FLOWER SENESCENCE BY GIBBERELLIC-ACID DEPENDS ON THE STAGE OF FLOWER DEVELOPMENT

Gibberellic acid at concentrations of 10(-5) M and 10(-4) M delayed the senescence of cut carnation flowers, when applied continuously via the stem, to flowers between the closed brush and fully open stages of development. Older flowers with reflexed petals were unresponsive. Treatment with paclobutrazol, an inhibitor of GA biosynthesis, prevented tight buds from opening fully, reduced the longevity of partially open flowers, but was ineffective when applied continuously to fully open flowers. Gibberellic acid-treated flowers did not show simultaneous petal inrolling, a known indicator of senescence, and the time to complete petal drying was extended. Gibberellic acid modified the climacteric ethylene rise in a manner consistent with the extension of longevity. These results provide evidence for a correlative role of gibberellins in flower development.