Effects of auxin, gibberellin, and cytokinin on petal blackening and flower opening in cut lotus flowers (Nelumbo nucifera)

Abstract

Cut lotus flowers (Nelumbo nucifera Gaertn. cv. Saddabutra), which are sold as closed buds, fail to open and show rapid petal blackening when placed in vase water. We investigated the effect on bud opening and petal blackening of treatments with an auxin, a gibberellic acid, and two cytokinins. Continuous treatment of cut flowers placed in an aqueous solution containing ≥0.1mM naphthylacetic acid (NAA) hastened petal blackening and resulted in stem curvature, but lower concentrations (0.01–10μM) had no effect. Depending on the experiment, continuous treatment with 0.03–0.45mM of the gibberellin GA3 delayed petal blackening by 0.5–1.5d (controls lasted 4d), but in experiments during the hot/rainy season (May–September) GA3 had no effect. At 25–100μM the cytokinin benzyladenine (6-benzylaminopurine; BA) delayed petal blackening by about 1.0d. Similarly, the cytokinin thidiazuron (TDZ) delayed petal blackening by about 1.0d, at 1.25–2.5μM. Pulse treatments had similar or better effects. A 3–12h pulse treatment with 0.45mM GA3 or with 10μM TDZ delayed the time to petal blackening by 1.1–2.3d. However, none of these treatments promoted bud opening. It is concluded, nonetheless, that a pulse treatment with GA3 or TDZ seems promising for practice.