In continuous treatments naphthylacetic acid (NAA) hastened petal blackening at 10 mM, 1 mM and 0.1 mM. At these concentrations it also induced a curvature in the upper part of the peduncle, which is growing during the first day of vase life. NAA had no effect on petal blackening when applied at 0.01 mM (10 M), 1 M, 0.1 M, or 0.01 M. A control for the solvent also had no effect (results not shown).
Depending on the experiment GA3 delayed petal blackening at 0.03–0.60 mM or had no effect (Table 1). Petal blackening was delayed by 0.8–1.5 d (average 1.1 d; n = 4) in experiments carried out in November, December and March, which is during the dry and cooler season, and 0.7 d in an experiment carried out in April, which is the beginning of the hot/rainy season. In experiments during the hot/rainy season (May and September) GA3 had no effect (Table 1). A control for the solvent had no effect (not shown)