Research Team Explains How Plants Can Grow on Saline Soils

Scientists from the University of Würzburg in Germany have examined how plants regulate their salt intake. Salt consists of the cation sodium and the anion chloride. Higher doses of chloride in saline soils have toxic effects on plant development. However, plants need the anion nitrate as a nitrogen source to build proteins and multiply their DNA. Würzburg plant scientists Dietmar Geiger and Rainer Hedrich studied whether and how plants are capable of distinguishing between the nutrient nitrate and the harmful chloride.

The researchers identified the two anion channels SLAH1 and SLAH3 found in plant cells, which are responsible for regulating the passage of nitrate and chloride. Working with a Spanish group, the scientists studied genetically modified plants in which SLAH1 or SLAH3 is missing. The sap of these plants ascending to the shoot only contained half the amount of chloride ions. The nitrate content, however, remained unchanged, giving the conclusion that both anion channels regulate the entry of chloride into the shoot.

The researchers found SLAH1 incapable of conducting anions, and SLAH3 mainly conducts nitrate. The contradiction between the nitrate and chloride contents in the sample plants and in the genetically modified plants was resolved when the two anion channels were brought together, forming a functional complex. Each time SLAH1 enters the complex, the anion filter in SLAH3 will switch from nitrate to chloride and vice versa. The role of this switch was determined by the Spanish team. They observed that the higher the salt load the roots of the sample plants were exposed to, the more SLAH1 was withdrawn from the anion channel complex. In the process, the chloride-conducting complex gradually evolves into a nitrate-conducting status, allowing the plant to maintain its nitrate intake as a vital source of nitrogen without taking damage by the salinization-related increase in chloride concentration.

For more details, read the news release at the University of Würzburg website.