Effect of dithiothreitol (DTT) on root sap flow rate of SGE and SGECd^t plants exposed for 1 h to mercury (Hg) and/or DTT in hydroponics. A -– total root sap flow; B – specific root sap flow expressed per µm of xylem area. Pea genotypes: □ – SGE, ■ – SGECd^t. Treatments: Control –untreated control, Hg – 50 µM HgCl₂, DTT – 1 mM dithiothreitol, Hg+DTT – 50 µM HgCl₂ and 1 mM dithiothreitol. Different letters show significant differences between treatments (Fisher’s LSD test; P < 0.05). Data are means of 2 experiments with 5 replicates each.