Identifying the physiological traits associated with salt tolerance is important in optimal management of biosaline systems and optimum utilization of saline water resources in dry and saline areas. Therefore, some indices of photosynthetic activity, dry matter production and accumulation of sodium and potassium ions in Blue panicgrass (Panicum antidotale Retz) were evaluated in five levels of salinity treatment (0, 70, 140, 210 and 280 mM NaCl solution) under greenhouse conditions. The results showed that at 28 and 35 days after salt stress, plant leaf area reduced in the highest salinity treatment, 93 and 96% respectively, compared with control. Leaf stomatal conductance, CO2 fixation and quantum efficiency of photosystem II were decreased by increasing salinity. It caused also a reduction in chlorophyll content (Chl a, Chl b) in leaves of Blue panicgrass. Content of carotenoids showed binary patterns to different salinity levels, slightly increased in 70-140 mM NaCl and decreased again in 210-280 mM, respectively. Increasing levels of salinity, increased sodium content in both roots and shoots but the shoots potassium content decreased. Decline in photosynthesis indices caused the reduction of root and shoot dry weight. This decrease resulted from lower leaf area (r=0.91**), lower stomatal conductance (r=0.78**), lower CO2 fixed in photosynthesis (r=0.63**), lower quantum efficiency of photosystem II (r=0.54**) and lower Chl a (r=0.45**), respectively. Data analysis base on using stepwise regression introduced leaf area (β=0.560), chlorophyll a content (β=0.245) and shoot potassium content (β= 0.264) as main effective components of salinity tolerance in Blue panicgrass.

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