Figure 4.

Resistance to SO₃²⁻ toxicity of leaf discs of transgenic plants. A, Photographs of the leaf discs cultivated on A1 medium with 20 mm sodium sulfite (bottom layer) and on A1 medium (top layer) for 54 h at 25°C under light (25 μE m⁻² s⁻¹). SR1, Non-transformed tobacco (cv SR1). B, Resistance is shown as a percentage of remaining chlorophyll content in a leaf disc after the cultivation in the presence of 20 mm sodium sulfite. The differences in the remaining chlorophyll content among control and transgenic plants were statistically significant by Student's t test (****, P < 0.005). Data are the means of analyses of 10 leaf discs ± sd.