Chloride ( Cl − ) Uptake, Transport, and Regulation in Plant Salt Tolerance

Chloride (Cl−) plays an important micronutrient role in plants, but at high levels, it can act as a stress molecule and thus can hamper agriculture on saline lands. Thus far, most of the salt stress research has centered on sodium (Na+) ions, as they are most toxic to plants. However, in certain crops like Citrus, soybean, and grapes, Cl− toxicity is more severe. Studies have also shown that Na+ and Cl− can impose differential stress effects on plant growth and development. Na+ ion uptake, transport and homeostasis are well understood, but there is little information about Cl− ions and their dynamics in plants exposed to salt stress. A major Cl− transport process, the symplastic pathway of transport and candidate genes for anion transport, has been identified. In this article, we present an overview of the effects of Cl− ions, and aspects of their uptake, influx and efflux in roots, toxicity, homeostasis and mechanism of tolerance.