The Role of Ethylene in Shoot Elongation with Respect to Survival and Seed Output of Flooded Rumex maritimus L. Plants

Abstract

Abstract. Rum ex m aritim us L. occurs in fre quently flooded sites of lowland flood plains. Upon submergence this species exhibited rapid elongation of shoots, but the response depended upon the developmental stage when flooding was initiated. In the rosette stage, petioles showed a fast and large response; during early stem elonga tion the response of petioles was less, but the extension of the lower internodes considerable; during flowering stem development, high internodes extended and the contribution to final stem length diminished. Ethylene production by an intact plant before, during and after submergence was measured with a laser-driven photoacoustic technique. Internal ethylene concentrations increased within 12 h of submergence. Ethylene accumulated in the submerged plant due to increased synthesis as well as a reduced diffusion from the plant to the water (instead of air). The elongation response could in part be mimicked by exogenous ethylene. Directly after submergence a further increase of ethylene synthesis was observed, which may be of vital importance in causing shoots to continue their rapid elongation even after the water surface is reached. The $ responses of shoots were related to fitness in experimental field plots. Survival of submerged R. maritim us depended on its ability to emerge above the water surface, while seed production was positively correlated with shoot height above the water.

An amalgamation between hormone physiology and plant ecology: A review on flooding resistance and ethylene

“…This is ac companied by a significant stimulation of the growth rate of both petioles and laminae. The strongest growth enhancement is achieved in the youngest petioles , Van der Sman et al 1991, Voesenek andBlom 1989A, B). This shoot elongation response is observed in many other species occurring in the interface regions be tween land and water (see Table 1; Osborne 1984, Ridge 1987, Schwegler and Brándle 1991.…”

“…The latter will al low the shoot to gain access to atmospheric oxygen if the shoot reaches the water surface. Since most oxygen will enter the plant via stomata (Gaynard and Armstrong 1987) or via micropores (see Nouchi et al 1990), the importance of a large leaf area re gaining a position above the water surface is un doubted , Van der Sman et al 1991). In order to achieve this shootatmosphere contact, petioles and/or internodes must maintain or enhance their elongation rate.…”

“…Due to the low dif fusion rate of gases in water, concentrations of ox ygen, carbon dioxide, and ethylene may signifi cantly change in response to flooding. Regardless of daily fluctuations and circadian rhythms, carbon di oxide and ethylene levels generally increase under submerged conditions, whereas oxygen concentra tions decrease (Van der Sman et al 1991, Stiinzi and Kende 1989. The ele vated ethylene levels may stimulate formation of lysigenous aerenchyma and enhanced shoot growth to restore leaf-atmosphere contact after submer gence.…”

“…3). Due to strong absorption by ethylene at the C 0 2 laser wavelengths it has been possible to detect very low ethylene concentrations in air (Harren et al 1990A, Van der Sman et al 1991, Voesenek et al 1990A, Woltering and Harren 1989, Woltering et al 1988. To improve the sensitivity of the photoa coustic system further, the acoustic cell was placed inside the C 0 2 laser cavity.…”

“…However, plants that germinate in April and May will give the largest seed production (Van der Sman et al 1991). Since seed germination in Rum ex is obligately aerobic , timing of seedling emergence in the field depends on withdrawal of the flood water.…”