Phenolic compounds level and localization in chilled roots of soybean [Glycine max (L.) Merr.] KATARZYNA SZAFRANΪSKA1*, JOANNA KALWINEK2, BARBARA GABARA2 and KRYSTYNA M. JANAS1 1 Department of Ecophysiology and Plant Development, University of ϋoΪdzΪ, Banacha 12/16, 90-237 Lodz, Poland 2 Department of Plant Cytology and Cytochemistry, University of ϋoΪdzΪ, Banacha 12/16, 90-237 Lodz, Poland Abstract The changes in L-phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity, soluble phenolic compounds and isoflavonoid content in soybean [Glycine max (L.) Merr.] roots grown 1-4 days at 5°C were investigated. Moreover, the localization of intracellular phenolic compounds after 24 h of chilling stress was ultrastructurally determined. The activity of PAL and the levels of soluble phenolic compounds were higher in the chilling-treated roots than in the controls. PAL activity did not correlate with the amount of soluble phenolic compounds in the roots. Enhanced content of isoflavonoids (daidzein, genistein and genistin) in 24 h chilling-stressed roots diminished after 4 days of chilling. At the ultrastructural level, the phenolic compounds in the form of dark deposits varying in shape and size, were visible in the cytoplasm and the vacuoles of both control and chilled roots. A higher frequency of cells with dark deposits in the cytoplasm was noticed in the controls, while vacuoles with tonoplast partly or almost completely covered with these deposits were more characteristic of the cells of chilled roots. In the roots chilling-treated in caffeine presence, deposits disappeared from the cytoplasm, and the vacuoles with clear tonoplast dominated over the vacuoles of the second and third type. The obtained results favour the suggestion that at least part of the dark material in the cytoplasm and in the first type of vacuoles (with clear tonoplast) represented epicatechine-like phenols. The differences between chilled and control roots are discussed.   < back .