Fig. 2.

Sulphur metabolite contents and ³⁵S flux into different metabolite pools of fine roots excised from poplar plants pre-treated with Cd. Fine roots were excised from poplar trees watered without (A, n=10) or with 0.5 mM Cd (B, n=10) in the nutrient solution for 4 weeks. The excised fine roots were pre-incubated for 2 h and subsequently exposed to [³⁵S]sulphate for 4 h to measure sulphate uptake and ³⁵S flux into different metabolite pools. Sulphate (μmol g⁻¹ FW), GSH (nmol g⁻¹ FW), and protein (mg g⁻¹ FW) contents were determined (pink squares). ³⁵S flux into internal sulphate, GSH, and protein is given as pmol ³⁵S g⁻¹ FW h⁻¹ (light blue squares). APR activity is indicated in a green square as nmol mg⁻¹ protein min⁻¹. Significant differences at P <0.05 from control roots without Cd pre-treatment are indicated by asterisks.