RESPONSES TO DROUGHT STRESS IN GERMINATING SEEDS OF AGRIOPHYLLUM SQUARROSUM (L.) AND SETARIA VIRIDIS (L.)

To understand how germinating psammophytc seeds adapt to drought stress in China's Horqin Sandy Land; we examined how the seedling growth and physiological properties of Agriophyllum squarrosum (L.) and Setaria viridis (L.) respond to drought. Results showed that Agriophylhtm squarrosum had stronger drought stress resistance compared with Setaria viridis. The seed germination rate, plumule length, single-seed fresh weight, and seed water content of both species decreased under drought. At a water potential of -0.30 MPa. seed germination of A. squarrosum was 15.7% and that of S. viridis was only 2.7%. Mild and moderate drought increased radicle length and superoxide dismutase (SOD) activity of A. squarrosum and S. viridis, the soluble proteins and soluble sugars contents of A. squarrosum and catalase (CAT) activity of S. viridis, but severe drought decreased these values. The radicle length of A. squarrosum was highest at -0.09 MPa (at 45.8% greater than in the control), and was significantly larger than in other treatments. With prolonged drought stress, the SOD and CAT activities and the soluble sugars and proteins contents of A. squarrosum were higher than those of S. viridis. However, the free proline content of A. squarrosum was lower than that of S. viridis when the water potential was higher than -0.30 MPa. Our results demonstrate different physiological adaptability to drought for the two species, and will support more effective vegetation restoration in the Horqin Sandy Land.