Physiological responses of the halophyte Sesuvium portulacastrum to salt stress and their relevance for saline soil bio-reclamation

• Morphological and physiological responses of Sesuvium portulacastrum under NaCl stress.
• Sesuvium adapts to salinity with increased growth, photosynthesis, antioxidant defense and osmolytes synthesis.
• Sesuvium is promising for the desalination of saline soil.

Sesuvium portulacastrum is a facultative halophyte growing in coastal salt marshes. The aim of this study was to determine growth, physiological and biochemical traits of Sesuvium portulacastrum when subjecting pot-grown plants to different concentrations of NaCl supplemented with half strength Hoagland’s nutrient solution to get the desired soil electrical conductivity (EC) of 0.3 (control), 4, 8, 12, 16, 20 dS m−1. Enhancing salinity levels to 12 dS m−1 resulted in concomitant increase in plant height, number of shoots per plant, number of leaves per plant and leaf area. Plants grown up to EC of 12 dS m−1 exhibited higher net CO2 assimilation rate (PN), transpiration rate (E), and water use efficiency (WUE). Significant increases in electrolyte leakage and lipid peroxidation were observed in plants grown at EC 16 and 20 dS m−1. Chlorophyll a and carotenoid pigment contents were significantly increased under high salt treatment (up to EC 16 dS m−1) and chl a content was higher than chl b. Osmolyte accumulation as a function of osmotic adjustment and antioxidant enzyme activity (CAT, GR, SOD, APX and GPX) were maintained under salinity whereas significant Na+ sequestration and Na+/K+ ratio were evident with increase in salinity stress. A preliminary field experiment was conducted by using plants of S. portulacastrum grown for 90 days in control and saline soil of a field plot. The results showed that the desalination potential of the target species was reflected in the reduction of the soil electric conductivity in the salinized plots in addition to significant increases in the Na+ contents in the leaves of the salinity treated plants. To summarize, our results suggest that S. portulacastrum adapts to high salinity with better growth, photosynthesis, antioxidant defense and can be used in the desalination of saline lands.