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Plant Physiology 64:721-726 (1979) © 1979 American Society of Plant Biologists Stabilization of Thylakoid Membranes by Spermine during Stress-induced Senescence of Barley Leaf Discs 1a Department of Plant Science, University of Alberta, Edmonton, Alberta T6G 2E3 Canada
The effect of spermine on photochemical activity and polypeptide composition of chloroplasts from barley leaf discs during senescence in the dark was studied. Chloroplast membranes did not show photosystem II activity after spermine treatment when water was the electron donor, but in the presence of diphenylcarbazide, this activity was observed. The diphenylcarbazide-stimulated photoreduction of dichloroindophenol was 3-fold greater in leaf discs incubated for 72 hours in spermine than in water. Photosystem I activity was reduced by about 90% within the first 24 hours in the spermine-treated samples. This reduction, however, was not due to a decrease in the photosynthetic unit size. A preferential loss of polypeptides other than those associated with photosystem II was observed during senescence of the leaf discs in water, but this loss was reduced by spermine. Spermine treatment also prevented the appearance of several additional chlorophyll proteins found in the controls during senescence. The results have been interpreted on the basis of the interaction of spermine with thylakoid membranes resulting in stabilization of membrane function during senescence.
2 Present Address: Department of Plant Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2 Canada. 1 This work was supported by a National Research Council of Canada grant to SZ. DJK is recipient of a National Research Council of Canada scholarship.
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