ORIGINAL PAPER Salicylic acid-mediated changes in photosynthesis, nutrients content and antioxidant metabolism in two mustard (Brassica juncea L.) cultivars differing in salt tolerance Shabina Syeed • Naser A. Anjum • Rahat Nazar • Noushina Iqbal • Asim Masood • Nafees A. Khan Received: 26 November 2008 / Revised: 12 September 2010 / Accepted: 14 September 2010 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2010 Abstract Mustard (Brassica juncea L.) cultivars Alankar (salt-tolerant) and PBM16 (salt-sensitive) plants were grown with 50 mM NaCl and were sprayed with 0.1, 0.5, and 1.0 mM salicylic acid (SA) to study the physiological processes determining salt tolerance and to observe the influence of SA application on the alleviation of NaCl- induced adverse effects. The content of leaf Na ? , Cl - , H 2 O 2 , TBARS, and electrolyte leakage and the activity of SOD were higher in PBM16 than Alankar. In contrast, nutrients content, activity of APX and GR, glutathione content, photosynthetic and growth characteristics were higher in Alankar. Treatment of 50 mM NaCl resulted in increase of Na ? and Cl - , oxidative stress, activity of antioxidant enzymes and glutathione content, while nutri- ents content, photosynthetic, and growth characteristics decreased in both the cultivars. Application of 0.5 mM SA alleviated the negative effects of 50 mM NaCl maximally, but 1.0 mM SA proved inhibitory. The effect of SA was more conspicuous in Alankar than PBM16. It is concluded that the higher tolerance of Alankar was due to its lower leaf Na ? and Cl - content, higher nutrients content, and efficient antioxidant metabolism. The application of 0.5 mM SA substantially alleviated salt-induced adverse effects in Alankar. Keywords Antioxidant enzymes Á Carbonic anhydrase Á Mustard Á Salicylic acid Á Salinity Abbreviations APX Ascorbate peroxidase CA Carbonic anhydrase CAT Catalase DAS Days after sowing GR Glutathione reductase C i Intercellular CO 2 concentration P N Net photosynthetic rate NBT Nitroblue tetrazolium GSSG Oxidized glutathione ROS Reactive oxygen species GSH Reduced glutathione SA Salicylic acid g s Stomatal conductance SOD Superoxide dismutase TBARS Thiobarbituric acid reactive substances Introduction Salinity is one of the major abiotic stress factors that adversely affects plant processes at physiological, bio- chemical, and molecular level (Munns 2002; Tester and Devenport 2003) and strongly reduces plant productivity (Bohnert et al. 1995; Munns 2002). It has been shown that salt stress negatively affects plant growth and development, and various cellular functions by disturbing the homeo- stasis of Na ? and Cl - ions, disturbance in the uptake of major nutrients such as, nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca), and impairment in pho- tosynthetic process (Munns 2002; Ashraf 2004; Munns and Tester 2008; Khan et al. 2009). The negative effects of salt stress on plants are also associated with the productions of Communicated by H. Gabrys. S. Syeed Á N. A. Anjum Á R. Nazar Á N. Iqbal Á A. Masood Á N. A. Khan (&) Plant Physiology and Biochemistry Division, Department of Botany, Aligarh Muslim University, Aligarh 202 002, India e-mail: naf9@lycos.com 123 DOI 10.1007/s11738-010-0614-7 Acta Physiol Plant (2011) 33: – 877 886 / Published online: 26 September 2010