ABSTRACT
Roots have the ability to induce pH changes at the root-soil interface, thereby lowering or raising the pH of alkaline or acidic surroundings, respectively. Consequently, the soil pH at the root surface may differ considerably from that in the soil a few millimeters away from the root surface. Because pH governs many of the parameters involved in plant metabolism and mineral nutrition (i.e., ion uptake), the root’s ability to interact and actively modify its immediate surroundings (i.e., rhizosphere) has a direct effect on the uptake of both mineral nutrients and phytotoxic metals. For example, root-induced acidification of the rhizosphere mobilizes limiting macro-and micronutrients such as phosphorus, zinc, and iron. Consequently, plant nutrition relies on the plant’s ability to interact with the surrounding soil medium, recognizing, binding, and transporting an array of substances into the root.
