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Salinity and heavy metal contaminations of the soil are the major environmental factors deleteriously affecting the agricultural yield. Suaeda maritima (L.) Dumort is a halophytic species that grows proficiently in high saline coastal areas. In the present study, individual effects of various levels of salinity (0, 200 and 600 mM NaCl) and arsenic (0, 200 and 400 μM As), as well as combined effects of As and salinity (200 μM As + 200 mM NaCl and 400 μM As + 200 mM NaCl) on growth, water status, mineral ion homeostasis, photosynthetic pigments, lipid peroxidation, phytochelatin levels and antioxidative components were investigated in the halophyte S. maritima to get an insight into salinity and arsenic tolerance mechanisms. The seedlings of S. maritima survived under prolonged exposure to high dosage of As (400 μM As). The oxidative stress indicators such as H 2 O 2, O 2 − and MDA remained at a low level in both NaCl and As treated seedlings. The levels of GSSG, GSH, total glutathione and TAST increased in seedlings treated with As alone whereas it declined under combined treatments of As with NaCl. The antioxidative response showed a decreased activity of SOD and increased activity of CAT both in NaCl and As treated seedlings as compared to control. In contrasts, the activities of other antioxidative enzymes such as APX, POX, and GR consistently decreased in NaCl-treated seedlings and increased in As-treated seedlings. The ratios of AsA/DHA and GSH/GSSG (indicators of cellular redox potential) were either elevated or remained unchanged in S. maritima seedlings subjected to salinity and As treatments. Our results suggest that the halophyte, S. maritima can withstand high salinity and As by regulating antioxidative enzymes and maintaining cellular redox level. Moreover, the salinity and arsenic tolerance index (T i ) of S. maritima was at par to the control or more than the control value in all the treatments. The arsenic bio-concentration factor (BCF) and translocation factor (T f ) values of S. maritima were all greater than 1.0 which clearly indicates that this plant has the basic characteristics of As-hyperaccumulator. Taken together, our results suggest that S. maritima plants can be utilized for phytoremediation/phytostabilization of saline soils contaminated with high arsenic. [ABSTRACT FROM AUTHOR]

• Growth reduction under high salinity is an energy conservation strategy in H. salicornicum. • Downregulation of stomata is a water conservation strategy in H. salicornicum. • Na+, total soluble sugars, and total free amino acids are major contributors for osmotic adjustment. • Coordination of enzymatic and non-enzymatic antioxidative components play vital role in salt tolerance of H. salicornicum. • Structural integrity of photosystems is maintained by efficient sequestration of ROS. Salinity is a foremost environmental threat that challenges agriculture and food security worldwide. In the present work, physiological, biochemical and anatomical strategies adopted by the xero-halophyte Haloxylon salicornicum in response to salinity was investigated. H. salicornicum plant withstands a prolong treatment of salinity, even under high dose of NaCl (400 mM). Our results showed that both fresh and dry biomass of shoot, plant height, and shoot area increased under low salinity (100–200 mM NaCl), whereas these parameters remained unaffected under high salinity (300–400 mM NaCl). In H. salicornicum , shoot water content (SWC%) was maintained at all levels of salinity. Salt tolerance index of H. salicornicum did not decline with increasing doses of salinity indicating salt tolerance capability of the plant. Although, salinity caused an increase in Na+ content of shoot, but K+ content of shoot remained steady at all levels of salinity. The rate of photosynthesis (P N), stomatal conductance (g s), rate of transpiration (E), water use efficiency (WUE), quantum yield of PSII (Φ PSII), photochemical quenching (qP), and electron transport rate (ETR) remained at par to the control level under low salinity (100–200 mM NaCl) and then reduced significantly under high salinity (300–400 mM NaCl). Salinity had no significant impacts on maximum quantum efficiency of PSII (F v /F m) and non-photochemical quenching (NPQ) which implies that PS II remained unaffected by sanity-induced oxidative damage. The levels of H 2 O 2 and NO increased significantly under salinity, whereas the level of O 2 •− remained unaffected under various levels of salinity. Higher level of H 2 O 2 and NO indicates the signaling role of these molecules. Lipid peroxidation level remained unchanged under low salinity (0–300 mM NaCl), but increased significantly under extreme salinity (400 mM NaCl). Ratio of AsA/DHA (indicator of cellular redox potential) elevated under high salinity (300–400 mM NaCl). The activities of various enzymatic antioxidants like SOD, APX, POX, GR and CAT showed differential responses under salinity. The results propose that coordination between enzymatic and non-enzymatic antioxidative components regulates ROS levels in H. salicornicum and contribute in salt tolerance by maintaining water status, ion homeostasis, redox status of the cells, and efficient protection of PSII form salinity induced oxidative damage. Higher tolerance index, optimal growth and competent antioxidative system make this xero-halophyte a suitable candidate for reclamation of salt degraded agricultural lands and can be a potent genetic resource for the development of salinity tolerant crops. [ABSTRACT FROM AUTHOR]