Sulfur Dioxide Flux into Leaves of Geranium carolinianum L. : Evidence for a Nonstomatal or Residual Resistance

The concurrent exchange of SO₂ and H₂O vapor between the atmosphere and foliage of Geranium carolinianum was investigated using a whole-plant gas exchange chamber. Total leaf flux of SO₂ was partitioned into leaf surface and internal fractions. The emission rate of SO₂-induced H₂S was measured to develop a net leaf budget for atmospherically derived sulfur. Stomatal resistance to SO₂ flux was estimated by two techniques: (a) R_s^SO₂′ from SO₂ data using analog modeling techniques and (b) R_s^SO₂ from analogy to H₂O (i.e. 1.89 R_s^H₂o).