Physiological Response To Cold Stress In Wild Tibetan Elymus Nutans

Low temperature is one of the important limiting factors to affect plant growth. Highaltitude climate conditions restrict many plant growths, but Elymus nutans Grisb. grows wellhere and is considered as good herbages due to its high yield and good quality. In this study,we studied effects of cold stress on wild E. nutans seed germination and their seedling growthand physiological changes in sand culture. We hope the study could provide an evidence forTibet alpine grassland improvement and selection of cold-resistant variety or species forartificial grass establishment. The results included:(1) To investigate physiological response of wild E. nutans from Tibet under cold stress.Nine sources of wild E. nutans were selected in the preliminary experiment. The resultsshowed that Diangxiong (DX) was higher cold-tolerence, but Nanmulin (NML), Dazi (DZ),Mozhugongga (MZG) were cold-sensitive. Kangma (KM), Baqing (BQ) and Ali (AL) rowedbehind DX, Shenzha (SZ), Langkazi (LKZ) were middle in nine sources of wild E. nutans.(2) Experiments were conducted in order to investigate germination behaviour of DXand gannan (GN) seeds subjected to different temperature (5oC,10oC,15oC,20oC,25oC and30oC). The experiment revealed that DX and GN could germinate with a range from5oC to30oC. The highest germination percentage of DX and GN were obtained at25oC with91%and75%. Temperature of5oC and30oC decreased germination percentage of two kinds of E.nutans.(3) Plants of cold-tolerant DX and cold-sensitive GN were exposed to control conditionsin growth chambers for21d and then transferred to cold stress for5d. The result showed thatDX exhibited significantly higher chlorophyll (Chl), carotenoids (Car), glutathione (GSH),ascorbate (AsA) concentrations and the higher ratio of GSH: GSSG and AsA: DHA, lowerelectrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H2O2) contents andsuperoxide radical (O2) and maintained significantly higher activities of peroxidase (POD),superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathionereductase (GR), which increased80.3%,27.3%,65.9%,75%and66.7%, respectively. After5d of cold stress, DX showd a62.2%increase in PM-H+-ATPase activity compared withcontrol, while a28.3%decrease observed in GN. It can be concluded that GN is moresusceptible to cold stress than DX due to more severe oxidative damage resulting fromreactive oxygen species (ROS), as well as lower GSH, AsA concentrations, antioxidant enzyme activities and PM-H+-ATPase activity.