Figure: Potassium concentration in root cells (cytosol) immediately after the onset of potassium deficiency (time series, from left). Representation in false colors; red (highest concentration) > yellow > green > blue. Photo Source: WWU - AG Kudla

A team of German and Chinese researchers has shown, for the first time, where and how plants detect potassium deficiency in their roots, and which signaling pathways coordinate the adaptation of root growth and potassium absorption to uphold potassium supply.

The absorption and transportation of potassium at the level of individual cells have been well characterized, but it was unknown how plants detect potassium availability in the soil. The researchers looked at Arabidopsis thaliana plants which were transformed with the newly developed potassium reporter protein GEPII. This reporter protein enables the microscopic detection of the concentration and distribution of potassium ions in cells and tissues. The research team found that the concentration of potassium in the cytoplasm of the cells increased with each cell layer within the root, from the outside to the inside.

They also found that in plants subjected to potassium deficiency, the concentration of potassium is reduced only within certain cells in the root tip. These cells in the root tip react extremely rapidly to potassium deficiency and the concentration of potassium inside the cell (in the cytoplasm) decreases within seconds. It had not previously been known that a certain group of cells located centrally inside the root tip reacts to a potassium deficiency in its surroundings. The researchers named this group of cells "potassium-sensitive niche". They have also visualized the path of potassium in a living organism.

For more details, read the article in the University of Münster website.