Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Utrecht, The Netherlands.
Plant Physiol. 2010 Oct;154(2):969-77. doi: 10.1104/pp.110.162792. Epub 2010 Aug 10.
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.
叶片和茎的伸长是陆生植物在浅水但长时间淹没芽的洪水期间生存的关键特征。然而，不同地点的自然洪水在持续时间和深度上差异很大，因此来自这些地点的种群受到不同的选择压力，导致种内变异。在这里，我们确定了导致湿地植物酸模叶蓼两个品系芽伸长反应变化的信号转导组分。这两个品系在淹没时叶柄伸长率差异 2 倍，河流洪泛区种群的伸长速度较快，而来自湖岸的植物的伸长速度较慢。水下快速叶柄伸长会消耗碳水化合物，并依赖于植物激素乙烯、脱落酸和赤霉素的（相互）作用。我们发现，快速和慢速伸长植物之间的芽中碳水化合物水平和动态没有差异，但叶柄中乙烯调节的脱落酸水平，以及这些叶柄对赤霉素的反应性，解释了淹没时芽伸长的差异。由于这正是解释植物物种（即酸模叶蓼和酸模）中洪水诱导的芽伸长变异的精确信号转导水平，因此我们假设自然选择导致了种内和种间调节途径的相似修饰。
