Effect of variety and stage of growth on potential allelochemic compounds in soybean roots.

HPLC was used to obtain fingerprint patterns of organic compounds extracted from roots of five soybean varieties at seven stages of growth. Fifteen major peaks were observed in all varieties at most growth stages. With increasing stage of growth, the less polar compounds accounted for a greater relative percentage of total peak area. Concentration of compounds extracted from roots increased dramatically as plants approached nodulation and flowering and then decreased to initial levels as plants matured.