Figure 4.

SO₄²⁻ uptake, SO₄²⁻ contents, and ATP sulfurylase activity in tobacco cells grown in different S conditions. Nontransformed tobacco cells (BY2) and transgenic tobacco cells overexpressing the APS2 cDNA (APS2) were grown on 1.5 mm SO₄²⁻ (+SO₄) or 0.75 mm S₂O₃²⁻ (+S₂O₃) for 6 d, or without S (−S) for 24 h. Asterisk (*) indicates that SO₄²⁻ was not detectable. ATP sulfurylase activities and SO₄²⁻ contents are the means of three extractions from the same culture. [³⁵S]SO₄²⁻-uptake results are the means of five extractions from the same culture. Bars are se at P = 0.05. Similar results were obtained from three independent experiments. DW, Dry weight.