Leaf cells accumulate solutes differently depending on their cell type. The accumulation profiles of inorganic ions have been well documented for the mesophyll and epidermis, particularly in cereals. These cell types accumulate ions such as phosphate and calcium to strikingly different extents. Understanding the processes that control ion accumulation could reveal how plants respond to either a limiting supply of important micro- and macronutrient ions or to potentially toxic loads of salts or heavy metal ions. Research has recently begun to reveal the processes that underlie this remarkable sorting of nutrient ions within the leaf.