Nutrient uptake and use efficiencies in Medicago ciliaris under salinity Siwar Ferchichi, Amine El Khouni, Walid Zorrig, Abdallah Atia, Mokded Rabhi, Mohamed Gharsalli, and Chedly Abdelly Laboratory of Extremophile Plants (LPE), Biotechnology Centre of Borj Cedria (CBBC), Hammam-Lif, Tunisia ARTICLE HISTORY Received 4 September 2013 Accepted 18 May 2015 ABSTRACT Salt-induced responses of Medicago ciliaris was studied under controlled conditions. Twenty-two-day old seedlings were cultivated for one month in a nutrient medium added or not with 75 mM sodium chloride (NaCl). Our results showed that this species is relatively salt-tolerant since the whole biomass production of salt-treated plants was affected a little (¡30%) as compared to the control. The slight salt effect was mainly nutritional and concerned both macro potassium, calcium and magnesium (K, Ca, and Mg) and micro-nutrients iron (Fe). K and Fe uptake efficiencies were more affected than those of Ca and Mg. Nevertheless, M. ciliaris was able to counterbalance this impact by increasing both K and Fe use efficiencies. The enhancement of K use efficiency could be due in part to the plant aptitude to accumulate sodium (Na C ) ions within its shoot tissues and to use them for osmotic adjustment. This “includer” behavior allowed M. ciliaris to maintain an adequate water status under saline conditions. KEYWORDS Glycophyte; includer; nutrient uptake efficiency; nutrient use efficiency; salinity Introduction Soil salinity is responsible for a reduction in plant growth and performance (Adams, 1991). In addition, shoots are generally more affected by high salinity than roots (Marcelis and Van Hooijdonk, 1999). Actually, high salt concentrations decrease leaf expansion (Wang and Nil, 2000), which affects growth of both shoots and whole plant (Hernandez et al., 1995; AliDinar et al., 1999; Chartzoulakis and Kla- paki, 2000). Moreover, salt stress induces water stress by decreasing water potential of the soil solution. It may also reduce plant growth by increasing the internal concentration of certain ions such as sodium, chloride and sulfate (Na C , Cl ¡ and SO 4 2¡ ) (Greenway and Munns, 1980). In some cases, reduced growth by salinity resulted from a non-specific effect of salt, depending more on the total con- centration of soluble salts than on specific ions (Adams, 1991). Plant mineral nutrition is complex even in the absence of salt stress. Under saline conditions, Na C and/or Cl ¡ concentrations are often much higher in the soil solution than those of nutrients, mainly micronutrients (Grattan and Grieve, 1992). High sodium chloride (NaCl) concentrations in the soil solution induce Cl ¡ and/or Na C specific ion effects as well as their respective antagonisms. Indeed, Cl ¡ exerts an antagonist effect against nitrate (NO 3 ¡ ) and SO 4 2¡ and generally opposes anion absorption by roots.. Another antagonist effect has also been described between Na C on the one side and potassium (K C ) (Cramer et al., 1997; Shiyab et al., 2003) and calcium (Ca 2C ) (Grattan and Grieve, 1992) on the other side. In addition, plants differ not only by their rates to absorb an CONTACT Walid Zorrig zorrigwalid@yahoo.fr Laboratory of Extremophile Plants (LPE), Biotechnology Centre of Borj Cedria (CBBC), P.O. Box 901, Hammam-Lif 2050, Tunisia. © 2016 Taylor & Francis Group, LLC JOURNAL OF PLANT NUTRITION 2016, VOL. 39, NO. 7, 932–941 http://dx.doi.org/10.1080/01904167.2015.1087567