Effects of Si+, K+, and Ca2+ on Antioxidant Enzyme Activities and Osmolytes in Halocnemum strobilaceum under Salt Stress

We evaluated the effects of silicon, potassium, and calcium on the salt-tolerant plant Halocnemum strobilaceum (Pal.l) Bie under salt stress. The experimental treatments consisted of a NaCl-only treatment (150, 450, or 900 mmol/l NaCl), a complex salts treatment (NaCl with K+, Ca2+,andSi(+) at total concentrations of 150, 450, or 900 mmol/l;(Na+:K+:Ca2+:Si+=1:0.03:0.14:0.004), and a control with no complex ions or NaCl. After 20 and 60 days of treatments, we investigated activities of the major antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as succulence and the contents of malondialdehyde (MDA), proline(Pro) and glycine betain (GB). We found that additions of K+, Ca2+, and Si+ partially alleviated the negative effects of salinity stress by increasing the salt tolerance of the plant. The improved salt tolerance was associated with increased Pro, GB,and increased activities of SOD, CAT, and POD,and decrease MDA. In contrast, the NaCl-only treatments caused marked decreases in succulence and soluble protein contents. The results of these experiments suggest that K+, Ca2+, and Si+ can alleviate the damaging effects of salt on H. strobilaceum by preventing oxidative membrane and oxidant enzyme activities damage, and that they may be associated with osmotic adjustment.