Table III.

Sulfate uptake and xylem loading of sulfate in excised roots from wild-type and transgenic poplar exposed to H₂S

	Wild Type	Wild Type	Transgenic	Transgenic
	0 μL L−1 H2S	0.25 μL L−1 H2S	0 μL L−1 H2S	0.25 μL L−1 H2S
Sulfate uptake (nmol g fresh wt−1 h−1)	129  ± 45a,A	118  ± 37a,A	152  ± 43a,B	164  ± 35a,B
Xylem loading (nmol g fresh wt−1 h−1)	8.5  ± 4.2b	4.1  ± 1.1a	10.0  ± 4.3b	8.1  ± 2.9b
Xylem loading (% of total uptake)	6.4  ± 2.5b	3.6  ± 0.9a	6.5  ± 1.7b	5.0  ± 1.6a

Excised poplar roots were pre-incubated in the incubation chamber described by Herschbach and Rennenberg (1991) with 0.1 mm sulfate for 2 h and subsequently exposed to 0.1 mm [³⁵S]sulfate. After 4 h of incubation radioactivity in root segments and in the solution of the exudation compartment were measured by liquid scintillation counting. The data shown are means ± sd with seven poplar plants of each poplar line and each treatment. Significant differences between treatments at P < 0.05 are indicated with different small letters; differences between poplar lines are indicated with capital letters.