14C-Assimilate pattern and kinetics of photosynthetic 14CO2-assimilation of the marine red alga Bostrychia scorpioides

Summary Occurrence and metabolism of dulcitol and sorbitol in the marine red alga Bostrychia scorpioides (Huds.) Mont. (Ceramiales: Rhodomelaceae) were investigated. Both hexitols are rapidly ¹⁴C-labelled during photosynthesis in a H¹⁴CO₃-seawater medium and are accumulated at comparable rates. The absolute quantity amounts to about 3.2% on a dry weight basis; the percentage of ¹⁴C-labelling after 60 min is 30% for dulcitol and 40% for sorbitol. Additionally small amounts of free ¹⁴C] glucose were found. Pulse labelling experiments and changes in specific activity provide evidence that both hexitols are rapidly available respiratory substrates, which, however, are probably not interconvertible with polymeric compounds. Some chemotaxonomic aspects are discussed.