Regulation in rhizome transition to storage organ in lotus (Nelumbo nucifera Gaertn.) with exogenous gibberellin, gibberellin biosynthesis inhibitors or abscisic acid

Effects of exogenous gibberellin (GA), gibberellin biosynthesis inhibitors, and abscisic acid (ABA) on rhizome morphogenesis (transition to storage organ) were examined in seed-derived lotus (Nelumbo nucifera Gaertn.) plants. Exogenous 1 mg·L^-1 GA₃ promoted rhizome elongation without swelling under short-day conditions, whereas uniconazole with 0.1 mg·L^-1 and paclobutrazole with 0.1, 1, and 10 mg·L^-1 stimulated rhizome enlargement under long-day conditions. Rhizomes of the plants grown with 10 and 25 mg·L^-1 ABA also enlarged under long-day conditions. Rhizome enlargement was closely related to cell enlargement and starch grain accumulation. In all the experiments, starch grain accumulation in expanded cells was recognized in the enlarged rhizomes, but not in the elongated rhizomes. It was suggested that rhizome transition to the storage organ was regulated via biosynthesis of GA and/or ABA.