Changes in Membrane Lipids of Roots Associated with Changes in Permeability: I. EFFECTS OF UNDISSOCIATED ORGANIC ACIDS.

Previous work has shown that undissociated forms of organic acids, such as formic, acetic, and propionic acids, increase the permeability of barley roots to ions. The work here was undertaken to test whether these undissociated acids affect the lipids from the root membranes in such a way as to account for the permeability increase. Relative amounts of the principal fatty acids from barley root membranes were measured as a function of organic acid concentration, pH, and time of treatment of barley roots under conditions similar to those of the previous studies.Undissociated formic, acetic, and propionic acids all rapidly increase the proportions of palmitic, stearic, and oleic acids and decrease proportions of linoleic and linolenic acids. Only the undissociated species are effective. The effects on the fatty acids from membrane lipids parallel effects on ion permeability. It is concluded that the increase in permeability produced by undissociated organic acid is due to changes in the lipids of barley root membranes.