Effect of low-temperature stress on the physiological responses of six gramineous forages in alpine regions and evaluation of their cold resistance

To screen gramineous forage varieties with strong cold resistance, the physiological responses of Elymus sibiricus ‘Qingmu No. 1’, E. sibiricus ‘Tongde’, E. breviaristatus ‘Tongde’, Poa crymophila ‘Qinghai’, P. pratensis var. anceps Gaud ‘Qinghai’, and Festuca sinensis ‘Qinghai’ seedlings to low-temperature stress were studied, and a comprehensive evaluation of the cold resistance of the six grasses was conducted based on subordinate function values analysis. The results showed that low-temperature stress inhibited the growth of the six grasses to different extents. The decrease rate in the fresh weight of P. crymophila ‘Qinghai’ was the lowest, whereas the rate of decrease in the dry weight of E. sibiricus ‘Qingmu No. 1’ was the lowest. Under low-temperature stress, the chlorophyll content of the six grasses decreased to different degrees, whereas the malondialdehyde content, superoxide dismutase activity, soluble sugar content, and proline content increased to different extents. Based on the comprehensive evaluation using subordinate function values analysis, the order of cold resistance of the six grasses was as follows: E. sibiricus ‘Qingmu No. 1’ > F. sinensis ‘Qinghai’ > P. crymophila ‘Qinghai’ > P. pratensis var. anceps Gaud ‘Qinghai’ > E. breviaristatus ‘Tongde’ > E. sibiricus ‘Tongde’. Therefore, E. sibiricus ‘Qingmu No. 1’ has the strongest cold resistance among the six gramineous forages.