text: Sulfate transported through the roots and SO diffusing into leaves becomes the pool for plants to assimilate sulfur throughout their tissues. Though there is minimal fractionation from the source sulfur of the total plant organic matter, in wheat, roots and stems are depleted from soil by 2‰ and leaves and grain are 2‰ enriched. The S enrichment in leaf whole matter is not caused by S-enriched sulfate present in the leaf, but is the result of the S-enrichment arriving at sink organs causing proteins in the leaves to be S-enriched. In rice, translocation from root to shoot does not discriminate S isotopes, however, the sulfate pools of the shoot are significantly S-enriched with respect to the sulfate pools of both root and sap. As sulfate moves through the plant system and is incorporated into biomass, the pool becomes enriched, giving organs such as leaves and grains higher δS values than earlier tissues.