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

D.C. McCain


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.