Sulfur-dioxide fluxes into different cellular compartments of leaves photosynthesizing in a polluted atmosphere : I....

Using experimental information obtained in earlier studies on cellular buffering and SO2 uptake into leaves (Pfanz and Heber, 1986, Plant Physiol. 81, 597-602; Pfanz et al., 1987 a, b, Plant Physiol.), a mathematical model is presented which permits computer analysis of the transport of SO2 from the atmosphere into the mesophyll of leaves and describes the intracellular distribution of hydration products of SO2. Oxidation of sulfite and metabolization of sulfate can also be included. Although the model does not attempt to incorporate all available information on the intracellular transport of sulfur species, it permits general conclusions in regard to cellular responses to SO2. The model can be extended and modified for gases other than SO2. Examples are presented to illustrate the information the model is able to give. Times required for SO2 equilibration are long. Equilibrium relationships between SO2 in the atmosphere and cellular SO2 show that in order to survive in even slightly contaminated air, leaves must prevent equilibration between external and internal SO2.