ORIGINAL PAPER Effects of NaCl or Na 2 SO 4 salinity on plant growth, ion content and photosynthetic activity in Ocimum basilicum L. Imen Tarchoune • Elena Degl’Innocenti • Rym Kaddour • Lucia Guidi • Mokhtar Lachaa ˆl • Flavia Navari-Izzo • Zeineb Ouerghi Received: 21 April 2011 / Revised: 1 September 2011 / Accepted: 3 October 2011 / Published online: 13 October 2011 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2011 Abstract Basil (Ocimum basilicum L., cultivar Genovese) plants were grown in Hoagland solution with or without 50 mM NaCl or 25 mM Na 2 SO 4 . After 15 days of treat- ment, Na 2 SO 4 slowed growth of plants as indicated by root, stem and leaf dry weight, root length, shoot height and leaf area, and the effects were major of those induced by NaCl. Photosynthetic response was decreased more by chloride salinity than by sulphate. No effects in both treatments on leaf chlorophyll content, maximal efficiency of PSII pho- tochemistry (F v /F m ) and electron transport rate (ETR) were recorded. Therefore, an excess of energy following the limitation to CO 2 photoassimilation and a down regulation of PSII photochemistry was monitored under NaCl, which displays mechanisms that play a role in avoiding PSII photodamage able to dissipate this excess energy. Ionic composition (Na ? ,K ? , Ca 2? , and Mg 2? ) was affected to the same extent under both types of salinity, thus together with an increase in leaves Cl - , and roots SO 4 2- in NaCl and Na 2 SO 4 -treated plants, respectively, may have resulted in the observed growth retardation (for Na 2 SO 4 treatment) and photosynthesis activity inhibition (for NaCl treatment), suggesting that those effects seem to have been due to the anionic component of the salts. Keywords Basil  Chlorophyll fluorescence  Gas exchange  Growth  Mineral composition  Salt stress Abbreviations U exc Quantum efficiency of open PSII reaction centres U PSII Quantum efficiency of PSII photochemistry A sat CO 2 assimilation rate at light saturation level Chl a Chlorophyll a Chl b Chlorophyll b C i Intercellular CO 2 concentration DW Dry weight ETR Electron transport rate F 0 Minimal fluorescence in dark-adapted state F 0 0 Minimal fluorescence in light adapted state F m Maximal fluorescence in dark adapted state F m 0 Maximal fluorescence in light adapted state F s Fluorescence yield in steady state conditions F v /F m Maximal photochemical efficiency G w Stomatal conductance to water vapor E Transpiration rate WUE Water use efficiency q NP Non-photochemical quenching coefficient q P Photochemical quenching coefficient Rubisco Ribulose-1,5-biphosphate carboxylase/ oxygenase Introduction Medicinal and aromatic plants are economically important because of the continuous and increasing demand for their products by local and foreign markets. O. basilicum L. (Lamiaceae) is one of the most important plants in this Communicated by G. Klobus. I. Tarchoune (&)  R. Kaddour  M. Lachaa ˆl  Z. Ouerghi Physiologie et Biochimie de la Tole ´rance au Sel des Plantes, Faculte ´ des Sciences de Tunis, Campus Universitaire, 2092 Tunis, Tunisia e-mail: imen_tarchoune@yahoo.fr E. Degl’Innocenti  L. Guidi  F. Navari-Izzo Dipartimento di Biologia delle Piante Agrarie, Universita ` di Pisa, Via del Borghetto 80, 56124 Pisa, Italy 123 Acta Physiol Plant (2012) 34:607–615 DOI 10.1007/s11738-011-0861-2