Endogenous Abscisic Acid as a Key Switch for Natural Variation in Flooding-Induced Shoot Elongation    

Abstract

Elongation of leaves and stem is a key trait for survival of terrestrial plants during shallow but prolonged floods that completely submerge the shoot. However, natural floods at different locations vary strongly in duration and depth, and, therefore, populations from these locations are subjected to different selection pressure, leading to intraspecific variation. Here, we identified the signal transduction component that causes response variation in shoot elongation among two accessions of the wetland plant Rumex palustris. These accessions differed 2-fold in petiole elongation rates upon submergence, with fast elongation found in a population from a river floodplain and slow elongation in plants from a lake bank. Fast petiole elongation under water consumes carbohydrates and depends on the (inter)action of the plant hormones ethylene, abscisic acid, and gibberellic acid. We found that carbohydrate levels and dynamics in shoots did not differ between the fast and slow elongating plants, but that the level of ethylene-regulated abscisic acid in petioles, and hence gibberellic acid responsiveness of these petioles explained the difference in shoot elongation upon submergence. Since this is the exact signal transduction level that also explains the variation in flooding-induced shoot elongation among plant species (namely, R. palustris and Rumex acetosa), we suggest that natural selection results in similar modification of regulatory pathways within and between species.

The Submergence Tolerance Regulator SUB1A Mediates Crosstalk between Submergence and Drought Tolerance in Rice

“…In the case of deepwater rice, the decline in ABA augments GA-mediated internode elongation and ethylene-dependent adventitious root formation during submergence (Hoffmann-Benning and Kende, 1992;Steffens et al, 2006). Recently, it was reported that modulation of internal ABA levels is a key determinant in the rate of underwater petiole elongation in submergence-tolerant Rumex palustris ecotypes, allowing escape of leaves from floodwaters (Chen et al, 2010). It appears that submergence-induced ABA degradation is a prerequisite for escape of submergence through rapid shoot elongation.…”

Waterproofing Crops: Effective Flooding Survival Strategies

“…Underwater escape by Rumex palustris and quiescence of Rumex acetosa are conferred by distinctions in the elongation of leaf petioles involving the same ethylene, ABA, and GA hierarchy established for rice (Benschop et al, 2005;Bailey-Serres and Voesenek, 2008). For example, ABA insensitivity corresponded to greater underwater petiole elongation in R. palustris ecotypes (Chen et al, 2010). In this species, elongation growth toward the water surface is complemented by upward hyponastic curvature of the petiole.…”

Anatomical and morphological modifications in response to flooding by six Cerrado tree species

“…However, when subjected to extended periods of flooding and the water column is relatively shallow, it may be more beneficial to the plant to undergo rapid shoot elongation to escape submersion. Some species rapidly elongate their stems or petioles keeping leaves above the water surface, facilitating gas exchange and light interception (Voesenek et al 2004;Kolb & Joly 2009;Manzur et al 2009;Chen et al 2010).…”

“…Vegetation that occurs in these areas is subject to flooding in the rainy season, when the water table reaches or almost reaches the surface. Flooding may induce multiple physiological dysfunctions in plants, such as inhibition of photosynthesis and transport of carbohydrates, reduced absorption of nutrients (due to root death and loss of mycorrhiza in plants with these associations) and hormonal changes such as increase in ethylene (He et al 1996;Kozlowski 1997) and abscisic acid (ABA) (Benschop et al 2005;Chen et al 2010) concentrations or decrease in cytokinin biosynthesis (Zhang et al 2000). Flooding also induces premature senescence resulting in leaf chlorosis, necrosis and leaf loss (Zhang et al 2000).…”