Adaptation of the thylakoid membranes of pea chloroplasts to light intensities. I. Study on the distribution of chlorophyll-protein complexes.
The effect of light intensity (16 h white light and 8 h dark) during growth of pea plants at 20°C on the chlorophyll composition and on the relative distribution of chlorophyll amongst the various chlorophyll-protein of pea thylakoids was studied. The chl a/chl b ratios increased from 2.1 to 3.2 as light intensity during growth varied from 10 to 840 μEm(-2) s(-1). This function can be described by two straight lines intersecting at a transition point of approximately 200 μEm(-2) s(-1). Similar discontinuities in the responses were observed in the changes in the relative distribution of chlorophyll amongst the various chlorophyll-protein complexes. This demonstrates that the chl a/chl b ratio of the various thylakoids is a good indicator of changes in the relative distribution of chlorophyll. As the chl a/chl b ratio decreased, the amount of chlorophyll associated with photosystem I complexes decreased, that with photosystem II core reaction centre complex was halved, and that with the main chl a/b-proteins of the light-harvesting complex was markedly increased.
Division of Plant Industry, CSIRO, GPO Box 1600, 2601, Canberra, ACT, Australia.
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Leong
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Anderson