Fig. 3. Concentrations of (a) glutathione and (b) phytochelatin in new leaves, old leaves, and roots of lettuce exposed to a range of free Cd concentrations after at least 14 d in the flow-through hydroponic (FTH) system. Phytochelatin is reported as –glu–cys = 2(n = 2) + 3(n = 3). Error bars represent the standard deviation of the mean (number of plants, x = 2 to 4, generally with duplicate samples analyzed from individual plants).