Chloride Nutrition: Novel Functions in Water Relations

Abstract

Although Cl- has been characterized as a micronutrient, we have observed that when available in the millimolar range (e.g. 1-5 mM), higher plants accumulate Cl- to levels that are typical of the content of a macronutrient (Plant Cell Env. 2010, 33: 2012-27). Since this requires a considerable cost of energy, we speculate whether Cl- might play a poorly understood function in plants when accumulated to macronutrient levels. Given that Cl- is a major osmotically active solute in the plant vacuole, we propose that this element alter plant water relation mechanisms. Besides promoting plant growth and dry weight, we observed that chloride nutrition in the millimolar range improved water parameters like the relative water content, leaf succulence and water use efficiency. Under conditions of water deficit chloride-treated plants exhibited an improved regulation of the water balance and drought-tolerance. According to the data obtained, we propose that critical factors behind these phenomena are an improved osmotic regulation, a reduced transpiration and developmental alterations.