13C-NMR SPECTROSCOPY TO MONITOR SUGARS IN PITH OF INTERNODES OF A SH2CORN AT DEVELOPMENTAL STAGES

Sugars move through stalks to he deposited in kernels in sweet corn (Z ea mays L.). Concentrations of sugars in stalks change as plants pass through developmental stages. To follow such changes, carbon-13 nuclea r magnetic resonance spectroscopy (C-nmr), a technology that can measu re concentrations of sugars in tissues, was compared with analysis by high-performance liquid chromatography (HPLC). A shrunken-2 hybrid (cv . Illini Gold), was monitored from mid-whorl to fresh-market maturity (R3). Internodes near the base of the stalk, just below the ear, and b etween an ear and the tassel were sampled at each developmental stage. Chemical shifts in C-nmr spectra were measured in parts per million h ertz (ppm) down-field relative to tetramethyl silane. Through silk eme rgence (R1) C-nmr spectra were similar regardless of internode, having line positions between 60 and 105 ppm. Unique lines for glucose, fruc tose, and sucrose were at 96, 98, and 104 ppm, respectively, and mole fractions were similar to those determined by HPLC. The highest concen trations were recorded at R1 for sucrose (26.1 mg.mL(-1)), from tassel ing (VT) through R3 for fructose (avg. 30.4 mg.mL(-1)), and from VT to R1 for glucose (alg. 32 mg.mL(-1)). Carbon-13 nuclear magnetic resona nce spectroscopy can be used, with minimal sample handling, to monitor sugar concentrations in sweet corn.