Effects of sand burial on the survival and physiology of three psammophytes of Northern China
Corispermum macrocarpum, Setaria viridis and Agriophyllum squarrosum are dominant psammophytes with strong environmental adaptability in Horqin Sandy Land, a typical agro-pastoral ecotone with frequent and intense sand activity in Northern China. We studied the survival rates, activity of antioxidant enzyme (superoxide dismutase, peroxidase and catalase), content of osmotic substances (soluble sugar, soluble protein and proline), and extent of lipid peroxidation and membrane permeability of the three psammophytes under ten treatments of sand burial with different depths to understand the effects of burial stress on survival and physiology of these species. The results show that A. squarrosum had the strongest adaptability to sand burial with the highest survival rate in all treatments except treatment C (buried to 3/4 of seedling height), compared to the other two species. The role of different enzymes varied among the three psammophytes. Peroxidase plays a protective role in scavenging reactive oxygen species of all three psammophytes. Superoxide dismutase and catalase are effective in A. squarrosum and S. viridis, C. macrocarpum and S. viridis, respectively. The osmotic substances also increased to keep Malondialdehydeand Relative electrolyte leakage at a low level (except the soluble protein content of A. squarrosum and S. viridis). However, because stress increased consistently in this study due to the enhanced level of sand burial depth, the antioxidant enzyme system and osmotic substances were not able to repair the damage leading to death of the plants.
Key words: Sand burial, psammophytes, survival rate, lipid peroxidation, membrane permeability, antioxidant enzyme activity, osmotic substances.