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Articles

Studies on Effects of Certain Quinones

II. Photosynthetic Incorporation of ¹⁴CO₂ by Chlorella¹

^a Life Sciences Division, Syracuse University Research Corporation, Syracuse, New York 13210

The effects of various quinone herbicides and fungicides on the photosynthetic ¹⁴CO₂ fixation and the incorporation of ¹⁴C among the products of photosynthesis in Chlorella pyrenoidosa was investigated. Addition of 30 µM 2,3-dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), or 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited CO₂ fixation, whereas 1,4-benzoquinone had no effect. Treatment with 3 µM or higher concentrations of dichlone, 06K-quinone or 1,4-benzoquinone also produced marked changes in the pattern of ¹⁴C distribution. A noticeable effect was an increase in the proportion of ¹⁴C in sucrose and glycine accompanied by a reduction in ¹⁴C lipids and glutamic acid. These changes appear to occur as a result of shifts in the flow of carbon along various biosynthetic pathways of photosynthetic CO₂ fixation. It is suggested that inactivation of coenzyme A and shortage of reduced triphosphopyridine nucleotide in the quinone-treated cells inhibited the synthesis of lipids and glutamic acid, thereby diverting more carbon into sucrose and glycine.

¹ This work was supported by Grant ES 00223-05 from the National Institutes of Health.