STUDIES OF PLANT MEMBRANE-COMPONENTS USING PROTOPLASTS

Plant protoplasts have been used to study the composition of plasma membranes. Microelectrophoresis showed that beet protoplasts had a protein surface but those from petunia, tomato, tobacco, wheat and cultured apple cells were more acidic. There was no evidence that basic proteins caused lysis by reaction with negatively-charged surface groups. Charge measurements in medium containing sodium dodecyl sulphate showed that surface lipid was probably absent from petunia, tobacco and tomato protoplasts but present on those from beet. Polyene antibiotics reduced uptake of labelled amino acids and adenine by protoplasts, increased ion efflux, and caused lysis, confirming that sterols are present in some plant plasma membranes. © 1979.