Ethylene enhances gibberellin levels and petiole sensitivity in flooding-tolerant Rumex palustris but not in flooding-intolerant R-acetosa

The role of gibberellin (GA) and ethylene in submergence-induced petiole elongation was studied in two species of the genus Rumex. Analysis of endogenous Gas in the flooding-tolerant Rumex palustris Sm. and the intolerant Rumex acetosa L. by gas chromatography-mass spectrometry showed for both species the presence of GA(1), GA(4), GA(9), GA(19), GA(20) and GA(53). Gas chromatography-mass spectrometry analysis of R. palustris petiole tissue of submerged plants showed an increase in levels of 13-OH GAs, especially GA(1), compared with drained plants. This effect could be mimicked by application of 5 mu L L-1 ethylene. In R, acetosa, no differences between levels of GAs in drained or submerged plants were found. In R. palustris, both submergence and ethylene treatment sensitized petioles to exogenous gibberellic acid (GA(3)). In X. acetosa the effect was opposite? i.e. submergence and ethylene de-sensitized petioles to GA(3). Our results demonstrate the dual effect of ethylene in the submergence response related to flooding tolerance, i.e. in the flooding-tolerant R. palustris ethylene causes an increased concentration of and sensitivity to GA with respect to petiole elongation while in the intolerant R. acetosa ethylene reduces growth independent of GAs.