Measurement of Potassium Content in Arabidopsis Potassium is an essential element in plant growth and has an important role in regulating cell water potential and turgor in osmotic regulation. Potassium content in plants is high compared to trace elements, however, it is difficult to measure a relatively small change of potassium content in the large total. Here, we describe a procedure for measuring potassium in Arabidopsis that is easy to handle in preparative scale and avoids contamination.