| In this study,seed germination experiment and alfalfa growth experiment were designed from two aspects of seed germination and growth of alfalfa.The germination ability of three alfalfa seeds under soil water stress was explored by measuring the germination index of Alfalfa under water stress,the water content of leaves in the early stage of germination and the activity of some protective enzymes in the early germination,and the drought resistance of three alfalfa in the germination period was studied by fuzzy mathematics.Through comprehensive evaluation,the drought resistance of three alfalfa varieties at germination stage was obtained,which provided a theoretical basis for the screening,cultivation and extension of Alfalfa Germplasm in Northwest China.The alfalfa growth experiment is the best alfalfa species obtained from the comprehensive evaluation of the drought resistance during the germination period of the seed germination experiment.By measuring the physiological and biochemical indexes of different growth periods under different soil water stress,the response of the physiological and biochemical characteristics of alfalfa and branching stage to soil water stress is analyzed.[Objective] to understand the physiological and biochemical adaptability of Alfalfa under drought stress,and to provide a theoretical basis for further study on the drought resistance mechanism of alfalfa.Seed germination test: using polyethylene glycol(PEG-6000)to simulate drought,this paper simulated the germination of Medicago sativa widely cultivated in three northwest regions: Medicago Varia.cv.GanNongNO.1,Medicago sativa L.cv.AmeriGraze40,and Medicago.sativa L in Xinjiang.And some protective enzyme activities and leaf water content.Set 6 solution osmotic potential gradients of 0,-0.539,-1.767,-3.926,-7.345,-12.489 MPa and so on,weighing the culture dish with electronic balance and recording.Petri dish(diameter 90 mm,bottom with two layers of filter paper),3 replicates per treatment,100 seeds per iteration.The total average germination rate of all three alfalfa treatments was 86.11%,and the average value of germination rate between ganong No.1,pastoral song and Xinjiang large leaf water treatment was 88.17%,88.22% and 89.44% respectively.The germination percentage of the control group was 97.33%,98.00% and 96.00% respectively,with an average of 97.11%,which was 112.77% of the total average.The germination rate of 25%PEG stress was the lowest,which was 67.67%,74.33% and 72.67% respectively,with an average value of 71.56%,which was 83.10% of the total average value.The number of budding fingers of ganong No.1,pastoral song and Xinjiang large leaf was 158.00,162.00 and 160.00 respectively under the treatment of zero concentration.The germination index reached the minimum of 7.30,24.20 and 15.60 respectively under the concentration of 25%PEG,respectively,and the difference values were 150.70,137.80 and 145.40 respectively.The average values of three alfalfa treatments were about 82.03,94.88 and 88.61 respectively,with a mean value of 88.51.The maximum values of the vitality index of ganong No.1,pastoral song and Xinjiang large leaf were 0.2370,0.2754 and 0.2432 respectively,and the minimum values were 0.0073,0.0460 and 0.0265 respectively.The difference between the maximum and the minimum were 0.2297,0.2294 and 0.2167,respectively.The average vigor index of different alfalfa was about 0.1510,0.1241 and 0.1264,the total mean value was about 0.1338.The difference between the total mean value of the vigor index and the mean value of the three species were 0.0172,-0.0097 and-0.0074 respectively.The average germination potential of three alfalfa were 79.30%,83.60%,Xinjiang big leaf: 82.40%,three alfalfa germination potential of 81.77%,three kinds of Alfalfa germination average and the total mean value of the difference was-2.47%,1.23%,0.63%,the difference between the illumination and the minimum were 59.00%,28.50% and 44.50% respectively.When PEG concentration was 5%,the SOD enzyme activities of Alfalfa treated by Gong Nong I and alfalfa were all the highest,which were 7.30 U/g FW and 9.34 U/g FW,respectively.When the PEG concentration was 15%,the activity of CAT enzyme reached the peak value of 156.80U/g*min.However,the Nong Nong I and Xinjiang leaves reached their respective peaks at PEG concentration of 10%,190.12 U/g*min and 176.40 U/g*min respectively.When the concentration of PEG is 5%,ganong 1 and Xinjiang big leaf have higher CAT enzyme activity compared with the Xinjiang large leaf.The activity values of the three groups are 186.20 U/g*min,107.80 U/g*min and 13.72 U/g*min.The total water content of leaves was 0.94.In addition to 0.81 of the water content of Gant No.1 leaves under the treatment of 20%PEG concentration,the water content of the leaves of Alfalfa under other treatments were more than 0.90.The drought resistance of three alfalfa seeds in the germination period was analyzed by the membership function method.The average value D of the comprehensive evaluation of ganong No.1,pastoral song and Xinjiang large leaf was 0.4221,0.3997 and 0.4187 in turn.According to the comprehensive evaluation,the order of drought resistance of three alfalfa species is: Gong Nong 1 > Xinjiang leaf > pastoral song.Alfalfa growth experiment: the experiment set up a 3 level soil moisture,that is to treat 1,2,3(:85%,65%,45%)for the full water supply of the soil moisture content to maintain the maximum field capacity of 85%,65%,45%.Treatment 1(:85%)was mild water stress,soil moisture content was 85% of maximum water holding capacity,treatment 2(:65%)was moderate water stress,soil moisture content was 65% of maximum water holding capacity,treatment 3(:45%)was severe water stress,soil moisture content remained the maximum water holding capacity of 45%.The highest value of Alfalfa under 85% water treatment in seedling and branching period is 18.883 cm,33.392 cm,and the highest value of Alfalfa under 45% water treatment is 14.267 cm,21.658 cm,and the difference of maximum and minimum of height and minimum of seedling and branching period is 4.616 cm and 11.734 cm respectively.Under different water stress,the root length of Alfalfa at seedling stage had no obvious difference.The average value of the treatment was 8.735 cm,the maximum and the minimum value were 9.563 cm and 8.692 cm respectively.The mean of the branching period was 15.286 cm,and the maximum and the minimum were 18.692 cm and 11.850 cm respectively.The leaf area values of 85%,65% and 45% under water treatment were 9.433 cm2,5.125 cm2 and 3.867 cm2 respectively.The fresh weight of alfalfa stems and leaves accounted for a larger proportion of plant fresh weight biomass under different water treatments.The proportion of the two species was greater than that of the root.And under 65% water treatment,the ratio of leaves was 0.515.When water stress was 85%,the amount of root dry matter accumulation in alfalfa was the largest,and the proportion was 0.411.Under 65% water treatment,the root and stem were predominant.Under 45% water treatment,dry matter accumulation was more uniform.Under the water stress of 85% and 45% water stress,the water content of the leaves of alfalfa was 0.786 and 0.790 respectively,and the water content of Alfalfa Seedlings in the seedling stage of alfalfa were higher than the water content of the alfalfa branch period under the same water stress.The water content of alfalfa roots was the highest at 65% water treatment at seedling stage,followed by 45% water treatment and 85% at the lowest moisture content,and their values were 0.687,0.539 and 0.469 respectively.The content of soluble sugar in seedling stage was significantly higher than that of soluble sugar in branching period.The mean value of soluble sugar was 52.35 mg/g and 10.41 mg/g respectively.The lowest soluble sugar content of Alfalfa under 65% water treatment was 49.25mg/g.The average activity of superoxide dismutase(SOD)in leaves at seedling and branching stages was 299.68U/gFW and 204.40 U/gFW,respectively,and the difference was 95.28 U/gFW,85%,65% and alfalfa seedlings in each water treatment.The mean value of proline content was higher than that of Alfalfa in the branch water.It was 85.89ug/g.56.23ug/g.The proline content of alfalfa leaves increased with the increase of water stress.Under the treatment of 45% water stress,the value reached the maximum value of 112.03ug/g.65% and 45%.The proline content of alfalfa leaves was increased by 6.10ug/g and 42.26ug/g respectively under the water stress of 85%. |
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