Ethylene Binding in Wild Type and Mutant Arabidopsis thaliana (L.) Heynh

At least two classes of ethylene binding site are shown to exist in Arabidopsis thaliana (L.) Heynh. The affinites of the sites for ethylene are essentially identical (KD ∼ 7 × 10−11 M) but the sites differ markedly in their rate constants of association and dissociation. Measurement of ethylene binding in a range of mutants differing in their sensitivity to ethylene suggests that in some cases at least, the mutation may affect ethylene receptors or transduction mechanisms but that the effect may be reflected in either fast or slow associating sites. The importance of suppressing ethylene biosynthesis when measuring ethylene binding in vivo is demonstrated.