Effects on antioxidant enzyme activities and osmolytes in Halocnemum strobilaceum under salt stress

The seedlings of Halocnermum strobilaceum were cultivated in 0.5% hoagland nutrient solution containing 0.0%, 0.9%, 2.7% and 5.4% of NaCl as well as composite salt (Na+, Ca2+, K+, Si4+) for 20 days; all the contents are in weight ratio. Succulent level, inorganic ions (Na+, K+), organics such as betaine, proline, malondialdehyde, and antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), betaine aldehyde dehydrogenase (BADH) were measured to reveal its salt tolerance mechanism. When the composite salt concentration reaches 5.4%, SOD activity level, and MDA content is five times the control group; when it reaches 2.7%, the succulent level of seedlings, and the content of K+ in roots is nearly two times the NaCl treatment; the dry weight is more than three times the control group; with the NaCl treatment, MDA is three times the contrast; when the salt concentration is 2.7%, POD reaches the maximum. Results indicate that Si4+, K+, and Ca2+ from composite salt in the roots of H. strobilaceum improved the water-holding capacity. The activities of antioxidant enzyme were raised by the accumulation of proline and betaine, which increased the salt tolerance. The absorption of K+ promoted the high ratio of K+/Na+ and alleviated the damage of cell membranes of H. strobilaceum, which is associated with osmotic contents such as betaine and proline.