Effects Of Saline Alkali Stress On Growth Physiology Of Switchgrass(Panicum Virgatum L.)

With the rapid development of society,the salinization degree of a large number of land in China increases.Switchgrass is widely planted in the northwest and other marginal areas due to its strongadaptability and high biological yield.In order to clarify the influence of salt alkali stress on the germination,seedling and maturity of switchgrass,Three parts are used in this experiment:1)Germination:two ecotypes,lowland（Alamo,Kanlow,New York）and highland（Blackwell-1,Forestburg,Trailblazer,Cave-in-Rock,Ansai）;2)Seedling stage:according to the emergence of seeds,Alamo,Blackwell-1,Forestburg,Trailblazer,Cave-in-Rock and Ansai;3)Maturity stage:two varieties,Alamo and Blackwell-1.They were selected to determine the physiological indexes of growth in three stages.Two kinds of salt(0 mmol·L^-1and 60 mmol·L^-1Na₂CO₃)and three kinds of Na OH solutionswith different alkalinity were designed in a completely randomized block design.The results are as follows:1.Under saline alkali stress,the germination potential,germination rate and germination index of switchgrass increased first and then decreased with the increase of stress degree.Under 60 mmol·L^-1+p H=8 saline alkali stress,Alamo had the highest germination potential,germination rate and germination index,which were 6.7,6.7 and 6.4 times of New York,respectively;Among the highland varieties under the same stress,Trailblazer had the highest germination potential,germination rate and germination index,which were 8.0,5.3 and 5.7 times higher than Ansai,respectively.At this time,the germination potential,germination rate and germination index of lowland Alamo were lower than that of upland Trailblazer,which may indicate that switchgrass varieties can adapt to light saline alkali environment better,and upland switchgrass varieties germinate better.2.The seedling height of Alamo under 60 mmol·L^-1+p H=8 stress was significantly higher than that of other varieties（P<0.05）,which was 2.66 times of Ansai.At the same concentration,the root length of highland Forestburg was 2.57 cm,which was significantly higher than that of Blackwell-1 and Cave-in-Rock（P<0.05）,leaf length was significantly higher than that of Blackwell-1（P<0.05）,leaf width was significantly lower than that of Forestburg,and was significantly higher than that ofBlackwell-1 and Ansai（P<0.05）.3.Effects of saline alkali stress on photosynthetic pigments and membrane permeability of switchgrass at maturityUnder saline alkali stress,the photosynthetic pigment content of switchgrass decreased,but it was still higher than that of the control group.The results showed that under 60 mmol·L^-1+p H=8 stress,the chlorophyll-a content of Alamo sampled on September 27 was 1.21 times of Blackwell-1,and the relative water content,electrical conductivity and malondialdehyde content of Alamo sampled on October 4 were 2.32,1.06 and 1.62 times of 0 mmol·L^-1+p H=8 alkali stress.Under the same treatment,the MDA content of Blackwell-1 was 2.45 times that of Alamo,which indicated that the two switchgrass had different salt tolerance.The results showed that Alamo was more suitable for 60 mmol·L^-1+p H=9 environment than Blackwell-1.4.Effects of saline alkali stress on antioxidant enzymes and osmotic substances of switchgrass at mature stageThe results showed that the content of antioxidant enzymes in switchgrass increased with the increase of saline alkali stress.On September 27,the contents of soluble protein,soluble sugar and proline of switchgrass increased significantly under single salt stress and saline alkali stress.Blackwell-1 was 2.7,3.3 and 2.0 times higher than Alamo.These results indicated that osmoregulants played an important role in maintaining the normal growth of switchgrass under salt stress.In conclusion,switchgrass can maintain a certain normal growth under 60 mmol·L^-1+p H=8saline alkali stress,and Alamo and Trailblazer have higher germination and plant height growth indicators than other varieties under higher saline alkali stress.The content of photosynthetic pigment and membrane permeability were damaged at maturity,but the damage of switchgrass under saline alkali stress could be alleviated through the regulation of antioxidant and osmotic substances.