Mechanisms contributing to differential sensitivities of plants to SO 2 .

SO ₂ -fumigation experiments were conducted with plants of pea (Pisum sativum) and corn (Zea mays) recognized to be, respectively, sensitive and tolerant to the gas. Accumulation of inorganic sulfur in the tissues revealed that the pea takes up considerably greater amounts of SO ₂ than corn. Porometer measurements and transpiration coefficients show that this greater SO ₂ uptake is partly related to the lower leaf diffusion resistance of peas. Additional internal sinks for SO ₂ uptake are discussed in order to give a complete explanation of the differential SO ₂ uptake of the two species.