Chloride as a macronutrient increases water-use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO2

17 págins.- 8 figuras.- 113 referencias.- Additional Supporting Information may be found in the online version of this articlen https://doi.org/10.1111/tpj.14423

Chloride (Cl−) has been recently described as a beneficial macronutrient, playing specific roles in promoting plant growth and water-use efficiency (WUE). However, it is still unclear how Cl− could be beneficial, especially in comparison with nitrate (NO3−), an essential source of nitrogen that shares with Cl− similar physical and osmotic properties, as well as common transport mechanisms. In tobacco plants, macronutrient levels of Cl− specifically reduce stomatal conductance (gs) without a concomitant reduction in the net photosynthesis rate (AN). As stomata-mediated water loss through transpiration is inherent in the need of C3 plants to capture CO2, simultaneous increase in photosynthesis and WUE is of great relevance to achieve a sustainable increase in C3 crop productivity. Our results showed that Cl−-mediated stimulation of larger leaf cells leads to a reduction in stomatal density, which in turn reduces gs and water consumption. Conversely, Cl− improves mesophyll diffusion conductance to CO2 (gm) and photosynthetic performance due to a higher surface area of chloroplasts exposed to the intercellular airspace of mesophyll cells, possibly as a consequence of the stimulation of chloroplast biogenesis. A key finding of this study is the simultaneous improvement of AN and WUE due to macronutrient Cl− nutrition. This work identifies relevant and specific functions in which Cl− participates as a beneficial macronutrient for higher plants, uncovering a sustainable approach to improve crop yield. © 2019 The Authors The Plant Journal © 2019 John Wiley & Sons Ltd

This work was supported by the Spanish Ministry of Science Innovation and Universities-FEDER grants AGL2015-71386-R and RTI2018-094460-B-I00 and by the Spanish National Research Council grants CSIC-201540E108 and CSIC-201740E08

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