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

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 >= 0.1 mM naphthylacetic acid (NAA) hastened petal blackening and resulted in stem curvature, but lower concentrations (0.01-10 mu M) had no effect. Depending on the experiment, continuous treatment with 0.03-0.45 mM of the gibberellin GA(3) delayed petal blackening by 0.5-1.5 d (controls lasted 4 d), but in experiments during the hot/rainy season (May-September) GA(3) had no effect. At 25-100 mu M the cytokinin benzyladenine (6-benzylaminopurine; BA) delayed petal blackening by about 1.0 d. Similarly, the cytokinin thidiazuron (TDZ) delayed petal blackening by about 1.0 d, at 1.25-2.5 mu M. Pulse treatments had similar or better effects. A 3-12 h pulse treatment with 0.45 mM GA(3) or with 10 mu M TDZ delayed the time to petal blackening by 1.1-2.3 d. However, none of these treatments promoted bud opening. It is concluded, nonetheless, that a pulse treatment with GA(3) or TDZ seems promising for practice. (c) 2012 Elsevier B.V. All rights reserved.