Variation in photosynthetic pigments and plastoquinone contents in sugar beet chloroplasts with changes in leaf copper content.

The changes in the contents of chlorophyll (Chl) a, Chl b, carotenoid, and plastoquinone in sugar beet (Beta vulgaris) chloroplasts were investigated during Cu deficiency and resupply. With the onset of Cu deficiency, extrachloroplastic Cu decreased more rapidly than chloroplast Cu, which eventually accounted for all of the Cu present in the leaf. The ultrastructure of Cu-deficient chloroplasts did not differ from the control except in very young, severely deficient leaves. During Cu depletion and resupply, Chl a, Chl b, carotenoid, and plastoquinone contents changed concomitantly. Because of the concurrent changes in the contents of terpenoid-containing pigments and plastoquinone with Cu depletion and resupply, we suggest that Cu might be involved in the regulation of the early steps of terpenoid biosynthesis prior to the formation of geranyl-geranyl-pyrophosphate.