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Plant Physiology 62:146-151 (1978)
© 1978 American Society of Plant Biologists

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Articles

Water Permeability of Chlorella Cell Membranes by Nuclear Magnetic Resonance

Measured Diffusion Coefficients and Relaxation Times 1

Darryl G. Stout2 and Peter L. Steponkus3

Larry D. Bustard and Robert M. Cotts

Department of Floriculture and Ornamental Horticulture, Cornell University, Ithaca, New York 14853, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853

Measurement by two nuclear magnetic resonance (NMR) techniques of the mean residence time {tau}a of water molecules inside Chlorella vulgaris (Beijerinck) var. "viridis" (Chodot) is reported. The first is the Conlon and Outhred (1972 Biochim Biophys Acta 288: 354-361) technique in which extracellular water is doped with paramagnetic Mn2+ ions. Some complications in application of this technique are identified as being caused by the affinity of Chlorella cell walls for Mn2+ ions which shortens the NMR relaxation times of intra- and extracellular water. The second is based upon observations of effects of diffusion on the spin echo of intra- and extracellular water. Echo attenuation of intracellular water is distinguished from that of extracellular water by the extent to which diffusive motion is restricted. Intracellular water, being restricted to the cell volume, suffers less echo attenuation. From the dependence of echo amplitude upon gradient strength at several values of echo time, the mean residence time of intracellular water can be determined. From the mean residence time of intracellular water, the diffusional water permeability coefficient of the Chlorella membrane is calculated to be 2.1 ± 0.4 x 10–3 cm sec–1.

2 Present address: Agriculture Canada, Range Research Station, 3015 Ord Road, Kamloops, B.C., V2B 8A9 Canada.

3 Present address: Agronomy Department, Cornell University, Ithaca, New York 14853.

1 Supported by Grant DMR-73-07521 from the National Science Foundation and by a National Research Council of Canada Scholarship.






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Copyright © 1978 by the American Society of Plant Biologists