Glycerol permeability of rye leaf protoplasts as affected by temperature and electroporation

The permeability of rye leaf protoplasts to glycerol was determined using 1,3-¹⁴C glycerol and liquid scintillation spectrometry. Estimates were 1.0 x 10^-8 m s^-1 at 0 °C and 4.1 x 10^-8 m s^-1 at 22 and 31 °C. The activation energy for glycerol permeability was 32.8 kJ/mol. The effect of electroporation on glycerol uptake was also explored. Treatments were performed with a field strength of 100 V/cm and an exponential decay constant of 5.8 ms. At 22 °C, electroporation affected the rate and extent of glycerol permeation, causing an increase in the intercept of the glycerol uptake curve and a decrease in the slope. Electroporation had no significant effect on glycerol uptake when performed at 0 °C, when the cells were electroporated at 0 °C then warmed to 31 °C, or when the cells were electroporated at 22 °C then cooled to 0 °C. The results at 22 °C were consistent with an influx of glycerol during electroporation.