Figure 4.

Redistribution of Radiolabel and Calculation of Absolute Rates of Glycolysis and Starch and Cell Wall Biosynthesis after Incubation of Tuber Discs Excised from Wild-Type and UMPS Antisense Lines in 10 mM [U-¹⁴C]Sucrose.

Discs were cut from developing tubers of 10-week-old plants and washed three times in buffer and were then incubated in 10 mM 2-(N-morpholino)-ethane-sulfonic acid (Mes)-KOH, pH 6.5, containing [U-¹⁴C]sucrose to a final specific activity of 1.1 kBq/mol. The discs were incubated for 2 h, washed three times, extracted, and fractionated to determine the metabolic fate of the ¹⁴C. Absolute rates of glycolysis, starch, and cell wall biosynthesis within the tuber discs were calculated from the label incorporation data using the specific activity of the hexose phosphate pool to account for isotopic dilution factors. The specific activity was estimated by dividing the label retained in the hexose phosphate pool by the sum of carbon in phosphorylated sugars. Data are presented as means ± se of determinations on six individual plants per line. Values marked with asterisks were determined to be significantly different from wild-type values by t test.