Figure 8.

Incorporation of ¹⁴C-labeled carbohydrates into constituents of potato tuber discs from wild-type plants. A, Potato tuber discs were incubated with [U-¹⁴C]Suc (Suc), [U-¹⁴C]Glc (Glc), [U-¹⁴C]Glc-1-P (G1P), [U-¹⁴C]Glc plus unlabeled Glc-6-P (G1P/G6P), or [U-¹⁴C]Glc-1-P plus unlabeled Gal-1-P (G1P/Gal1P). After 45 or 60 min of incubation (see inset), discs were removed and processed. Subsequently, the ¹⁴C contents of the pellet, the supernatant, and the polysaccharides were determined. B, In a similar experiment, tuber discs were incubated with [U-¹⁴C]Glc (Glc), [U-¹⁴C]Glc-1-P (G1P), or [U-¹⁴C]Glc-1-P plus unlabeled Glc (G1P/Glc). At intervals (see inset), discs were removed and processed (see A). In A and B, the vast majority of the pellet consists of starch, and minor constituents are compounds derived from the cell wall. The polysaccharides are essentially SHG_L. The supernatant contains low molecular mass compounds, such as SHG_S monosaccharides and disaccharides. C, Tuber discs were incubated for 30 min in [U-¹⁴C]Glc-1-P. Subsequently, SHG_L was isolated and subjected to acid hydrolysis. The monosaccharides released were separated by HPAEC-PAD. In the eluate, each monosaccharide was collected separately and monitored for ¹⁴C content. Bars 1 and 2 represent unidentified compounds that elute early during HPAEC. All data shown are averages of three independently performed experiments and sd.