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Abbreviations: c -carotenes; Chl -chlorophyll; Chl (a+b) -total chlorophyll content; CPa -chlorophyll-protein of photosystem II; CPI -chlorophyll-protein of photosystem I; LHCPs -light-harvesting chlorophyll-proteins of photosystem II; x -leaf xanthophylls; x+c -total carotenoids.

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The partition of phylloquinone (vitamin K1), of chlorophylls a and b and of the two main carotenoids, β-carotene and lutein, in subthylakoid particles (digitonin treatment) and chlorophyll protein complexes (sodium dodecylsulfate polyamide-gel electrophoresis) isolated from tobacco chloroplasts (Nicotiana tabacum L.) is described. 1. The “light particle” fractions (S 90 000, S 150 000) of digitonin fragmented chloroplasts are enriched in CP I and contain a higher proportion of phylloquinone, chorophyll a and β-carotene as compared to whole chloroplasts. This is visualized by high values for the ratio a/b (6 -8) and for β-carotene/lutein (1.7) as well as about 3 mol of K1 per 100 mol of total chlorophyll. The “heavy digitonin particle” fraction (10 000 x g sediment), in turn, contains a higher proportion of chlorophyll b and lutein, but a lower level of phylloquinone than whole chloroplasts. 2. The chlorophyll a-protein CP I of pigmentsystem I, isolated by preparative gel electrophoresis using 0.5% and 4% SDS, is characterized by a stable level of phylloquinone (1 mol K1 per 100 mol of total chlorophyll), high chlorophyll a/b ratios (7 -10) and high values for β-carotene/lutein (~ 6.0). The light-harvesting chlorophyll a/b-protein LHCP of photosystem II (chlorophyll a/b = 1.1 - 1.5, β-carotene/lutein = < 0.1) contains either low amounts of phylloquinone (0.5% SDS) or only trace amounts of K1 (4% SDS). The free pigment fraction (FP) contains at 0.5% SDS 57% of the total phylloquinone of thylakoid membranes. At 4% SDS the K1 amount in the free pigment fraction increases to 84%. 3. The phylloquinone partition studies in digitonin particles and SDS chlorophyll proteins indicate that there exist at least two localization sites for phylloquinone K1 in the photosynthetic membrane. The CP I complex and a second site, presumably near photosystem II (CPa?)

Ivana Štětinová, Prague, for their decision to publish a special issue on fluorescence imaging of plants and also my colleague Roland Valcke, Diepenbeek, Belgium, the editor of this special issue, for his encouraging and valid endeavors to edit this issue. In addition, I thank Claus Buschmann, Karlsruhe, a former member of my group, for his valid help during the preparation of several figures and for reading the manuscript.