Temperature dependence of the membrane resistance in Characeae cells

Changes in the electrical resistance of internodal cells of Nitellopsis obtusa (Desv. in Lois) J. Gr. and Lychnothamnus barbatus (Meyen) Leonh., produced by short-lasting temperature changes (3-min intervals) in the range of 4⇌48°C were measured. In the whole temperature range examined the electrical resistance of the cell membranes underwent from 5 to 9 distinct changes; the overall changes were approximately hyperbolic, while in certain narrow temperature ranges they were non-monotonic, and in others linear. Arrhenius plots of these dependencies provide data which suggest a specific, stepwise character of changes in the permeability to ions, produced by temperature alterations and probably connected with corresponding modifications of cell membrane fluidity. This seems to support the view that the cell membranes of the examined plant species may exist in different, discrete, physiological states characteristic of certain temperature ranges.