| The trial for the effects of the soil moisture on the overwintering survival rates of winter wheat was carried out in Harbin,Heilongjiang prvince,China,which located in the frigid region from 2009 to 2010.Two winter wheat cultivars different in the cold hardiness were used in this trial.Different soil water content gradients were set up based on the relation between the soil water contents and the overwinter survival rate of winter wheat.The photosynthetic preperties,physiological and biochemical indices and proteomics and so on in winter wheat plants during winter season were studied,and furthermore,the optical soil water content for the safe overwintering of winter wheat was definited,the indices and methods in the identification for the cold tolerance of wheat were explored and the mechanism in the safe overwintering of winter wheat in frigid region was revealed through the influence of proteins expression,and the theoretic fundation was provided for the production of winter wheat in the frigid area.The main conclusions were as follows:1.On the overwintering cases none of Jimai 22 but all of Dongnongdongmai 1 was able to be overwinterin in the all water treatments.It was very significant in the difference in the overwinter survival rate of Dongnongdongmai 1 among the soil water treatments,appearing CK(normal soil water management)>30%±2%>45%±2%>15%±2% in the soil moisture,and was 83.3%,49.2%,23.3%,2.5%,in the survival rate respectively.The ratio of the dead cells in the leaf and leaf sheath of the two cultivars was gradually enhanced with the delay of the sampling date.And the obvious difference in the cell vigor between cultivars occurred at the 20th day after frozen date in winter and the injury in Dongnongdongmai 1 was less than that in Jimai 22.The damage of plants under CK (normal soil water management) in soil water content were slightest.The extent of damage in the leaf was more serious than that in the leaf sheath.The change of the development status of the stem apical point was very slow and less affected by the soil water content after entering the frozen period and the profile of the apical point almost was in the elongation stage.On the contrary/the transition of the apical point in Jimai 22 was fast and quicker in the soil water treatment of 45%±2% and the form of the part was in the elongation and single ridge.2.The water content in the leaf and leaf sheath of the 2 cultivars performed downward and then upward as the sampling dates increased and lower in 15%±2% of soil water treatment. This trait in Jimai 22 was higher than that in Dongnongdongmai 1 and the one in leaf sheath higher than that in leaf.The free water content in samples was lower in 15%±2% and higher in 45%±2% in the soil water content treatment.The bound water content in the leaf sheath of Dongnongdongmai 1 remained higher and that of Jimai22 performed bimodal curve in the whole sampling period.3.The soluble protein content of the 2 cultivars increased in all soil water theatments and would be facilited to a higher level both under drought and hyperhydration condition during the sampling period.No significant difference between the 2 cultivars was observed in this trait.4.The relative electric conductivity in the leafs and leaf sheaths of the 2 cultivars elevated gradually during the sampling period and quickly in the early days and smoothly in the late days and lowest in CK (normal soil water management) and highest in 15%±2% of soil water treatment.The conductivity of Dongnongdongmai 1 was lower than that of Jimai22 and one in the leaf sheath higher than that in leaf.MDA of both cultivars appeared downward in the early days and upward in the late days in the sampling period.The content of MDA in the cultivars was higher relatively in 15%±2% and lower in CK(normal soil water management) and media both in 30%±2% and 45%±2% in the soil water treatment.The level of membrane lipid overoxidation was found to be worsened both in dought and overmoisture.5.The SOD activity of cultivars behaved in fluctuation during the sampling period.The order in the trait of Dongnongdongmai 1 among the soil water treatments showed as 15%±2%>30%±2%>45%±2%>CK (normal soil water management) and of Jimai 22 the highest in 15%±2%.And the POD activity appeared enhancing trands during the same period and higher in Dongnongdongmai 1 than in Jimai 22.The higher POD activity of Dongnongdongmai 1 presented in 15%±2% of soil water content in cold acclimation (?) in 45%±2% after frozen date and of Jimai 22 in 15%±2% covering winter,respectively.The GSH contents of 2 cultivars were downward during the sampling period and higher in Dongnongdongmai 1 than in Jimai 22 and of Dongnongdongmai 1 in 30%±2% while of Jimai 22 in 45%±2%..The As A contents of 2 cultivars showed upward in the early stage of the sampling period and then downward in the late stage.The lower value of As A was in CK(normal soil water management) of soil water content during cold acclimation phase. After entering frozen period the higher content of AsA was found in CK of soil water content in Dongnongdongmai 1,but the values of AsA in Jimai 22 waved remarkably in all soil water treatments.6.The change of the initial fluorescence values (Fo) of both cultivars in the soil water treatments presented the bimodal curv in the whole sampling period.The Fo value would increase under the dought and water logging conditions.The Maximum fluorescence value (Fm) of the 2 cultivars enhanced rapidly in all soil water treatments before the frozen date and decreased fast after the stage.After 20 days entering the frozen stage the change of Fm was smooth while showed highest in CK (normal soil water management).The maximal quantum yield (Fv/Fm) and the actual quantum yield (Yield) of Dongnongdongmai 1 appeared to be smooth or a slightly increasing trend in all soil water treatments from the cold acclimation period to the frozen stage and of Jimai 22 downward.The Fv/Fm and Yield of the cultivars reduced gradually and those values in CK (normal soil water management) treatment were higher obviously than those in other soil water contents after entering into the frozen stage.The photochemical quenching parameter (qP) of Dongnongdongmai 1 in all soil water treatments dropped gradually during the sampling period and of Jiami 22 fluctuated downward.The non-photochemical quenching parameter (qN) of both cultivars appeared to be fluctuating upward.The difference in the actual fluorescence yield (Ft) of both cultivars was very significant among the sampling dates.The value of Ft could be induced to incease in the cold acclimation period but to reduce in the early stage of frozen perion by slightly drought.The photosynthetic electron transfering rate (ETR) of both cultivars decreased gradually in the whole sampling period and sharply in the frozen period and was higher under the optical and some more soil water contents than that under drought condition. The photoinhibition in Dongnongdongmai 1 was heavier than that in Jiami 22 in the cold acclimation period and more seriously in Jimai 22 in the frozen period.The transient maximal quantum yield (Fm) of Dongnongdongmai 1 was higher than that of Jimai 22 and the significant difference in Fm between cultivars was observed in all actinic light treatments.The Fm in CK (normal soil water management) was lower in the early stage of the frozen period and became higher after the date of Dec 2.The change of Fm with the actinic light intensives of the cultivars was fluctuating in the cold acclimation period and the early stage of the frozen period and became smooth in the whole frozen period.7.The number of the different protein spots was found to be 32 in the early and late stages of the frozen period in the soil water contents of 15%±2%,30%±2% and 45%±2% in both cultivars.Of which 26 spots matched highly with proteins found in wheat and 3 with in rice,1 with in maize,1 with in barley and 1 with in cucumber.12.5% of the protein spots participated in the process of energy metablism,and 25% of material synthesis,9.3% belonged to molecular chapron,31.25% to resistant proteins,6.25% of photosynthetic reaction and 15.62% to other proteins.There were 9 protein spots appearing both in the cold tolerant cultivar and cold sensitive cultivar in the early stage of the frozen period and all participated in the process of the osmotic matters synthesis,scavenging of the active matters damaging cell.stress resistance and photosynthesis.The different protein spots participating energy metablism in the cold tolerant cultivar were more than that in the cold sensitive cultivar. There were no different protein spots both expressing in the cold-tolerant and -sensitive cultivars in the late stage of the frozen period.The different expressing protein spots jioned thicking cell wall,energy metablism and stress resistance in the cold tolerant cultivar and in the cold sensitive cultivar participated dissolving cell membrane and photosynthesis.The more of the different expression protein spots occurred in the soil water treatments of dought (15%±2%) and more moisture (45%±2%) and less of slight drought (30%±2%).8.The strong cold resistant cultivar has characterestics as follows:slight damage of tissues in the frozen period,more alive cells,low progress of apical point development,low level of water content in leaf sheathes in the overwinter period,high activity of SOD,POD in the cold acclimation period and the early stage of the frozen period,high content of GSH in the overwinter period,high in qP,qN in the cold acclimation period,high in Fv/Fm,Yield after the date of frozen,low in Fo after 20 days entering into the frozen period,high in Fm in the whole frozen period.The evaluation for the cold tolerance of winter wheat in the frigid region could be carried into execution by the indices of paints vigor,apical point status,relative conductivity,MDA,chlorophyll fluorescence parameters (Fo,Fm,Fv/Fm,Yield,qP,qN),activity of SOD,POD and GSH content.9.The close relationship was found between the cold tolerance of winter wheat and the indices of the overwinter survival rate in spring,plant vigor,conductivity and MDAin winter,the maximal fluorescence and transient maximal quantum yield after 20 days entering into the frozen period,maximal quantum yield and actual quantum yield in the frozen period,ETR in winter. All of the indices were affected obviously by the soil water content.The soil water content of 35%-40% before winter season was in favor of the safe overwintering of winter wheat according to the relationship between the indices and the cold tolerance of winter wheat and its changes with the soil water content levels. |
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