Effect of temperature on electron transport activities of glutaraldehyde-fixed pea thylakoids

Temperature-induced changes in Hill activity of glutaraldehyde-fixed pea ( Pisum sativum L. cv. Alaska) thylakoids have been examined. Using ferricyanide as electron acceptor, a temperature-induced change occurred at ca 12–14°C for both control and fixed thylakoids. In contrast to the controls, fixed thylakoids not only showed a change in slope of the Arrhenius plots but also a discontinuity which has not been observed in previous studies. A drop in activity coincided with the decrease in slope: the extent of the reduction depended on the concentration of glutaraldehyde used for fixation. Using a lipophilic electron acceptor, a temperature-induced change also occurred at 12–14°C, but there was no reduction in activities of fixed thylakoids at temperatures above the change in slope.
The results indicate that a temperature-induced change in fixed thylakoids restricts the access of ferricyanide to its reductant(s) in the membrane but that fixation does not affect the temperature-induced change per se. The results confirm that temperature has a general effect on the functioning of thylakoid membranes. The data demonstrate that calculations of the extent of inhibition by glutaraldehyde of Hill activity with ferricyanide should take into account the temperature at which assays are performed.