NMR Study of Chloroplast Water in Acer platanoides: Water Exchange at Membrane-Bound Sites and Across the Chloroplast Envelope Membrane

Abstract: Nuclear magnetic resonance (NMR) spin relaxation techniques were used to measure the rate of water exchange across the chloroplast envelope membrane and to detect exchange of water-hydrogens between the bound and fluid states in Acer platanoides shade leaves. Results indicate that individual water molecules resided within a chloroplast for 320 ± 65 ms, on average, before exchanging through the envelope, and that exchangable bound hydrogens are at least six times more abundant in the chloroplast than in the nonchloroplast compartments.