Physiological responses to low temperature stress and cold tolerance evaluation in three Elymus species

In order to screencold tolerant Elymus germplasm, the 21 days aged seedlings of three Elymus species from Tibet were used to investigate the physiological, biochemical responses and resistanceunder different low temperature treatments(18, 10, 5, 0 ℃) with 18 ℃ as check.With the increase of low temperature stress Elymus sibiricus cv. Tongde had maximum relative membrane permeability, but Baqing (E. nutans) is the minimum. The contents of chlorophyll in Baqing showed a trend of rising first then falling, but the content of Chlorophyll in Tongde and Naqu (E. nutans) increased significantly (P<0.05). The soluble protein content in Baqing had the smallest increase and it only increased 2.59 times when compared with control; The soluble protein content in Tongde and Naqu increased significantly (P<0.05), and they increased 5.31 times than the control. The soluble sugar content in Baqing and Tongde showed a trend of rising first and then falling, but the soluble sugar content in Naqu increased significantly (P<0.05) and it is 2.14 times of the control. The MDA content in Tongde had the biggest increase; the MDA content in Baqing decreased significantly at 0 ℃ when compared with that at 5 ℃(P<0.05). The free proline in all materials tested increased.Tongde had the maximum Pro content, and it increased 2.58 times when compared with control; Baqing had the minimum Pro content, it only increased 1.44 times when compared with control. The superoxide dismutase activities of Baqing showed a trend of rising first then falling. But the superoxide dismutase activities of Naqu increased significantly (P<0.05) and it is 1.65 times of control. The peroxidase activities in Naqu is the maximum and it increased 4.13 times when compared with control; The peroxidase activities in Tongde is the maximum and it is 2.19 times of control. Membership function analysis showed the order of cold resistance of three Elymus species: Baqing>Tongde>Naqu.