Fig. 2. Total quaternary ammonium compound (QAC) levels ( ± SE mean) in betaine fraction of young expanding leaves of sorghum genotypes IS2319 (open bars) and P932296 (solid bars). Plants were grown for a total of 21, 28, 35, 42, or 49 d (bottom row, x axis) and were salinized with 100 mM NaCl for 0, 7, or 14 d (top row, x axis) before leaves were harvested for QAC isolation and quantification. Total QAC levels were determined in three individual plants by the colorimetric periodide assay after purification of the betaine fraction from plants.