Light quality effects on subsequent dark 14CO2-fixation in Fucus serratus

The intensity and fate of ¹⁴CO₂-fixation in the dark are studied on Fucus serratus apices previously maintained under low illumination conditions using white, blue, red or yellow isoquantic lights.In the case of a 180 s pulse, light quality affected dark carbon-fixation, with a higher level of incorporation into ethanol-soluble organic matter in the case of yellow light cultivated apices. After a 30 s pulse ¹⁴C was mainly fixed into glycerate and aspartate-malate pools whatever the pre-treatment light conditions, with a higher level into glycerate when apices were pre-illuminated with blue or yellow light. After a 180 s pulse, ¹⁴C was mainly transferred into amino acids (glutamate and alanine) at the expense of aspartate and malate in red and yellow pre-illumination conditions, as found in the white light reference experiment, and only at the expense of glycerate in blue light pre-illumination conditions.The metabolic pathway of glycerate formation, principally enhanced by blue light preillumination, remains unexplained under these non-photosynthetic conditions. Results are discussed with reference to CO₂-fixation via phosphoenolpyruvate carboxykinase and light quality effects on its in vitro activity.