Chloride: From Nutrient to Toxicant

Abstract

In salinized soils in which chloride (Cl') is the dominant salt anion, growth of plants that tolerate only low concentrations of salt (glycophytes) is disturbed by Cl' toxicity. Chlorotic discolorations precede necrotic lesions, causing yield reductions. Little is known about the effects of Cl' toxicity on these dysfunctions. A lack of understanding exists regarding (i) the molecular and physiological mechanisms that lead to Cl' -induced damage and (ii) the adaptive aspects of induced tolerance to Cl' salinity. Here, mechanistic explanations for the Cl' -induced stress responses are proposed and novel ideas and strategies by which glycophytic plants avoid the excessive accumulation of Cl' are reviewed. New experiments are suggested to test the proposed hypotheses. Cl' salinity constrains global food security and thus we urgently need more research into the causes and consequences of Cl' salinity.