Nonstructural carbohydrates are those that can be accumulated and then readily mobilized in order to be metabolized or translocated to other plant parts. This method quantitatively determines the amount of the total glucose following enzymatic hydrolysis. Total non-structural carbohydrates (TNC) is the sum of total glucose, free fructose and free sucrose. Starch is the total glucose minus the free glucose multiplied by 0.9. The free carbohydrates are determined by a separate analysis. The samples for total glucose are enzymatically hydrolyzed at 55°C with amyloglucosidase for 12 hours and analyzed by HPLC with mass selective detection. The analysis uses a Phenomenex Luna NH2 (250 mm x 4.6 mm) HPLC column at a flow rate of 2.75 mL min-1 acetonitrile:water (78:22). The method has a detection limit of 0.5% and is reproducible to within 10% (relative).
Smith, Dale. Removing and Analyzing Total Nonstructural Carbohydrates from Plant Tissue. Wisconsin Agric. Exp. Sta. Res. Report 41. 1969.