The contrasting role of auxin in submergence‐induced petiole elongation in two species from frequently flooded wetlands

Abstract

The contrasting role of auxin in submergence-induced petiole elongation in two species from frequently flooded wetlands J a n G . H . M . R ijn d e rs , G e r a r d W. M. B a re n d se , C o rn e lis W. P. M . B lom a n d L a u r e n s A. C. J. V oesenek naphthylphthalamic acid (NPA) had no effect on petiole elongation. The elongation response after NAA or NPA treatment was comparable for plants in both submerged and drained conditions. Pre-ageing of detached petioles of Rumex paliistris for 3 h in light or in dark conditions had no effect on the submergence-induced elongation. In comparison to intact plants, detached petioles of Rumex paliistris, with or without lamina, did not show significant differences in responsiveness to IAA between drained or submerged conditions. This was in contrast to Ranunculus sceleratus where submergence caused a clear increase in responsiveness towards IAA. Removal of the lamina, the putative source of auxin, or treatment with NPA did not hinder the submergence-induced elongation of detached Rumex paliistris petioles, but severely inhibited elongation of detached Ranunculus sceleratus petioles. This inhibition could be restored by application of NAA, suggesting the specific involvement of auxin in the submergence response of Ranunculus sceleratus. It is concluded that, in contrast to Ranunculus sceleratus, auxin is probably not involved in the submergence-induced petiole elongation of Rumex paliistris.

The stimulating effects of ethylene and auxin on petiole elongation and on hyponastic curvature are independent processes in submerged Rumex palustris

“…From these experiments, we conclude that the dependence of submergence‐induced petiole elongation on auxin remains during the entire elongation response and is not restricted to the onset of the process. Figure 1 also explains why in previous studies on submergence‐induced petiole elongation (Rijnders et al . 1996), no role for auxin in petiole elongation was found.…”

“…These earlier studies showed that pretreatment with the auxin transport inhibitor naphthylphtalamic acid (NPA), or removal of the leaf blade (a putative source of auxin) (Ljung, Bhalerao & Sandberg 2001), did not affect petiole length when this was measured after 48 h of submergence (Blom et al . 1994; Rijnders et al . 1996).…”

Survival tactics of Ranunculus species in river floodplains

“…The physiology of the stimulation of shoot elongation of R. sceleratus by submergence has been well studied, and is linked to entrapment of the gaseous plant hormone ethylene. Some leaf-borne auxin together with an enhanced endogenous level of ethylene is required to stimulate petiole elongation in this species (Samarakoon and Horton 1984;Rijnders et al 1996). R. repens was by far the most tolerant Ranunculus species under submerged conditions in complete darkness.…”

Submergence induces expansin gene expression in flooding-tolerant Rumex palustris and not in flooding-intolerant R. acetosa

“…We show in this report that¯ooding-induced cell elongation, which is an ethylene-and GA-regulated process (Rijnders et al 1996(Rijnders et al , 1997, is accompanied by the induction of genes encoding for expansins in R. palustris. These genes are not induced in R. acetosa, suggesting that ethylene induces expansin expression only in¯ooding-tolerant Rumex species as an essential part of the¯ooding-resistance mechanism.…”