Physiological Effects Of Alkaline Salt Stress And Cutting Disturbance On Secale Cereale L. Seedlings In Freeze-thaw Environment

In northern China,the temperature difference between day and night is large at the end of autumn,crops will grow in a freezing and thawing environment,and they are vulnerable to freeze-thaw stress.At the same time,the northwestern part of the region is severely salinized,and plants are also subject to alkaline stress.Generally,overwintering pastures are mowed and harvested before winter and retain a certain stubble height and resume growth.For plants,mowing is a disturbance to plants,and freeze-thaw and alkaline salt stress will affect the physiological characteristics of plants.1.In order to investigate the physiological effects of freeze-thaw condition with different stubble height.In this study,Secale cereale L.used to the material of experimental,Through the hydroponic experiment,the seedlings were cut to 2,6 and 10 cm stubble height,and the simulated freeze–thaw(FT)stress(10/–5?)was carried out after 6 days regrowth.The plants were subjected to freeze-thaw stress,and the freeze-thaw treatment time was 14 hours.Decrease the temperature from 14.5 ° C.The rate of temperature change during the freezing phase is-0.5 ? / 12 min,and the rate of temperature change during the melting phase is 0.5 ? / 12 min.Samples are taken every 2h for a total of seven samples.The corresponding sampling temperatures are: 10,5,0,-5,0,5.10 ° C.The physiological effects of FT with different stubble height were revealed by analyzing the relative water content(RWC),osmotic adjustment substance concentration(soluble sugar and protein),membrane peroxidation(MDA)and catalase(CAT)activity.The results showed that under freeze stress(–5?),the soluble protein and MDA content decreased and the seedlings of 2 cm treatment kept a higher level,while the RWC,soluble sugar content,and CAT activity in 6 and 10 cm treatments kept higher level of.After FT stress,the content of soluble sugar and protein,RWC in the 6 cm treatment were higher than other cut treatments,and the CAT activity in 10 cm treatment was the highest while the MDA content is lower.These data suggest that keeping high stubble height is more adaptive for short–term freeze-thaw stress.2.In order to investigate the physiological effects of alkaline salt stress and cut disturbance on ryegrass in freeze-thaw environment,Secale cereale L.(rye)as the test material,was treated with alkaline salt stress,and castration was performed after 7 days of growth.And freeze-thaw(FT)stress was applied for 14 hours(10/-5?)after 6 d regrowth.The rate of change of temperature was 5 ° C / h.A total of three samplings were performed,which were 2h,8h,and 14 h after freeze-thaw stress,and the corresponding sampling temperatures were 10,5,and 10 ° C.The changes of soluble protein(SP),malondialdehyde(MDA),relative water content(RWC),catalase(CAT)and superoxide dismutase(SOD)activities in seedlings were studied to analyze.The results indicated,under the combined stress,the enzyme activity and RWC decreased but the content of soluble protein and MDA were increased.The MDA content in CT treatments were accumulated as the enzyme activity increase but the of RWC in seedlings was decrease.The finding from the study indicates that the CT could aggravate the membrane peroxidation under the combined stress of FT and AS and enhance the osmotic adjustment ability of rye and activated the antioxidant enzyme system.The rye having been cut is more sensitive to the compound stress.