6 Fetguany 2007 ronzurnerde.rustoo A G Protein-Coupled Receptor Is a Plasma Membrane Receptor for the Plant Hormone Abscisic Acid Xigang Liu,1*3 Yanling Yue,' Bin Li,3 Yanli Hie/ Wei Litz Wei-Hua Wu,3 Ligeng Ma" The plant hormone abscisic add (ABA) regulates many physiological and developmental processes