Physiological Responses of Highland Barley Seedlings to NaCl, Drought, and Freeze-Thaw Stress

Qinghai-Tibet plateau as an alpine and high-altitude area is frequently confronted with freeze-thaw stress. Recently, due to the change of global climate, the drought and salinization of soil in this area have become increasingly serious, together with low temperature, and constitute the main limiting factors for crop growth in this area. Physiological responses of blue barley to salinization (S), drought (D), and freeze-thaw (F) stress were studied. Through applying 100 mmol/L NaCl, 15% drought and freeze-thaw cycle (10, - 5, 10 degrees C) stress, the changes of relative water content (RWC), soluble protein, malondialdehyde (MDA), superoxide dismutase (SOD), and peroxidase (POD) in seedling leaves of 8 treatment groups (CK, S, D, DS, F, FD, FS, and FDS) were analyzed. The results showed that single stress, either NaCl, drought, or freeze-thaw, could lead to the decrease of RWC and the increase of not only the soluble protein and MDA content, but also the SOD and POD activity in leaves. During the freeze-thaw cycle, the soluble protein, MDA content, SOD, and POD activity of seedlings increased at first and gradually decreased, while RWC gradually decreased with the change of temperature. The research indicated that there were synergistic effects among the stresses of drought, NaCl, and freeze-thaw on the plant, and the compound stress could cause more serious effect on the plant compared with the single one.