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Chloride nutrition increases mesophyll diffusion conductance to CO2 in tobacco plants

AuthorsFranco-Navarro, Juan D. ; Rosales Villegas, Miguel Á. ; Díaz-Espejo, Antonio ; Colmenero Flores, José M.
Issue Date25-Sep-2016
PublisherSociedad Española de Fisiología Vegetal
Sociedade Portuguesa de Fisiologia Vegetal
CitationXVI Simposio Hispano-Luso de Nutrición Mineral de las Plantas. San Pedro del Pinatar, Murcia, 25-28 de Septiembre de 2016
Abstract1. Background and Objectives: Chloride (Cl-) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a supposedly unspecific role as cell osmoticum, no clear biological roles had been explicitly associated with Cl- when accumulated to macronutrient concentrations until our group published a novel perspective on the matter, in which we proposed Cl- to be both a micronutrient and a beneficial macronutrient in higher plants (Franco-Navarro et al. 2016). We showed that Cl- specifically stimulated higher leaf cell size and led to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. When applied in the 1-5 mM range, Cl- played specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl- also altered water relations at the whole plant level through reduction of plant transpiration. This was a consequence of a lower stomatal conductance, which resulted in lower water loss and greater photosynthetic and integrated water-use efficiency. It was unclear however how the Cl-dependent reduction of stomatal conductance did not result in reduction of the plant photosynthetic efficiency. Our working hypothesis and the objective of this work was to verify whether the reduction in stomatal conductance is compensated by an increase in mesophyll diffusion conductance to CO2. 2. Material and Methods: Tobacco (Nicotiana tabacum L. var. Habana) plants were alternatively treated with a basal nutrient solution supplemented with three salt combinations containing the same cationic balance: 5 mM Cl-based (CL), 5 mM nitrate-based (N) and sulphate + phosphate-based (SP) treatments. Experimental design, greenhouse conditions, nutrient list of the irrigation treatments, harvesting procedures, leaf gas-exchange measurements and statistical analyses are described in Franco-Navarro et al. (2016). Mesophyll conductance (gm) was estimated from simultaneous measurements of A/Ci response curves and chlorophyll fluorescence measurements by the variable j method (Ethier & Livingston, 2004). 3. Results: Stomatal aperture size and density as well as mesophyll diffusion conductance parameters have been quantified. 4. Conclusions: The more efficient water-use efficiency and mesophyll diffusion conductance resulting from leaf anatomical ad subcellular modifications give light to a brand-new interpretation of Cl- properties as a beneficial macronutrient in higher plants. Franco-Navarro et al. (2016). J. Exp. Bot., 67. Pages 873-891 Ethier & Livingston (2004) Plant Cell Environ., 27. Pages 137¿153
Appears in Collections:(IRNAS) Comunicaciones congresos
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