Mannitmetabolismus in der marinen Braunalge Fucus serratus

Abstract

Summary Kinetic studies on 14 C-photoassimilation in Fucus serratus L. provided evidence that mannitol is significantly stronger 14 C-labelled after photosynthesis at 22° C than at 4° C. At lower temperatures phosphate esters as precursors in the pathway of mannitol biosynthesis show higher percentage labelling. After pulse labelling by photosynthesis in 14 C-bicarbonate (10 min) and subsequent light periods from 10 min to 3 h the insoluble fraction is rather slowly labelled. In the soluble fraction percentage labelling of mannitol amounts to a constant level of 95% of total 14 C-labelling. Under these conditions mannitol content shows no remarkable changes. During subsequent dark periods, however, specific activity of 14 C-mannitol decreases continuously, whereas the total amount of 14 C-TCA cycle intermediates increases. From these data it is concluded that mannitol serves as a quickly available substrate of respiration in brown algae.