Abstract
When floating rice (Oryza sativa L. cv Habiganj Aman II) plants are grown under submergence, the levels of endogenous gibberellin and ethylene increase. We examined the role of gibberellin in the increase of the level of endogenous ethylene in the internodes of floating rice. When excised stem sections were treated with gibberellic acid in ambient air or in water, internodal elongation and ethylene production were induced. Also, the activities of 1-aminocyclopropane-1-carboxylic acid synthase and ethylene-forming enzyme were stimulated in the internodes. In stem sections submerged in a solution of 0.1 mM ancymidol, an inhibitor of gibberellin biosynthesis, internodal elongation and ethylene level in the internodes were reduced to about half and two-thirds, respectively, compared with stem sections submerged in distilled water. These results indicate that gibberellin has a promotive effect on ethylene synthesis in floating rice internodes.
