Study On Physiological Responses Of Different Strains Of Sweet Sorghum To Salinity Stress And Drought Stress

In recent years,drought disasters and the salinization of land have become increasingly serious,which has had a great impact on the development of agriculture and economy.Due to the dry climate in Ningxia Hui Autonomous Region and unreasonable irrigation in the Yellow River irrigation area,the salinization in the north and the crop output in the central arid zone are low and unstable.Screening and planting drought-and salt-tolerant crop varieties can effectively solve the above problems.Sweet sorghum has strong stress resistance,the study of the response of sweet sorghum to physiological changes under salt and drought stress has revealed the physiological mechanism of drought resistance and salt tolerance of sweet sorghum,at the same time,it provides a theoretical basis for screening and cultivation of drought-resistant and salt-tolerant sweet sorghum lines suitable for salinization and drought land cultivation in Ningxia.It is of great significance to promote the development of regional agriculture and animal husbandry.In this study,5 sweet sorghum varieties(lines)were selected as test materials,the experiment was conducted in Gaozhuang Township,Pingluo County,Shizuishan City,which is heavily polluted in the northern part of Ningxia,and in Wangcun Town,Tongxin County,Wuzhong City,which is central arid zone in Ningxia,measured agronomic indicators such as plant height and yield,photosynthetic gas exchange parameters,antioxidant enzyme activity,osmotic adjustment substances,and other physiological indicators,using variance analysis and principal component analysis to analyze changes in various indicators of different growth stages,and the interactions between different genotypes and environments of sweet sorghum were analyzed,in order to reveal the drought resistance and salt-tolerance mechanism of sweet sorghum,further provide theoretical basis for the selection of sweet sorghum lines with strong drought resistance and salt tolerance.The main research results obtained are as follows:1.Chlorophyll content increased at the early growth stage,but decreased at the later stage of the growth period.Under drought stress,the chlorophyll content decreased under severe drought stress.Photosynthesis was affected under salt stress and drought stress,both of which showed stoma limitation during short-term stress and non-stomatal limitation after long-term stress.2.Under salt stress and drought stress,cell membrane permeability,MDA,SOD,POD,CAT content increased to varying degrees.Soluble sugar and soluble protein were the main osmotic regulators under salt stress.Proline and soluble protein were the main osmotic regulators under drought stress.Superoxide dismutase(SOD)is the main antioxidant enzyme during jointing stage under salt stress.Peroxidase(POD)and catalase(CAT)play a major role in booting stage and maturation stage,and POD and peroxidase(POD)under drought stress.Hydrogenase CAT is the main antioxidant enzyme.3.After analysis of principal components of different traits under different salt stress and drought stress,the indicators of factor loading greater than 0.9 for each main component under salt stress were transpiration rate,SPAD value,Fv/Fo at the jointing stage,and booting period was Fv/Fm,cell membrane permeability,stomatal conductance,and mature period was plant height,Plabs,cell membrane permeability;the indicators of factor loading greater than 0.9 for each main component under drought stress were cell membrane permeability,Plabs,and booting period was Fv/Fm,plant height,Plabs,and mature period was protein soluble,cell membrane permeability,SPAD value.4.The interactions of chlorophyll content,net photosynthetic rate,stomatal conductance,Plabs,cell membrane permeability,soluble sugar,soluble protein,SOD,POD,CAT,and plant height in GxS,GxT,and GxTxS(F value)reached extremely significant difference(P<0.05),which can be used as indicators for identifying the mechanism of drought resistance and salt tolerance of sweet sorghum;Intercellular C02 concentration,Fv/Fo,transpiration rate,malondialdehyde and other indicators of GxS and GxT interaction(F value)did not reach significant levels(P<0.05),and it can be used as an index for screening strains/species with strong drought resistance and salt tolerance.5.Both salt stress and drought stress led to a decrease in plant height of sweet sorghum,and the biomass yield decreased by 16.57%to 57.17%.With the increase of the stress level,the decline rate was greater and greater,and there was good repeatability in 2016 and 2017.Based on the two-year biomass production and intercellular CO2 concentration,Fv/Fo,transpiration rate,malondialdehyde and other indicators,the strains that performed better under salt stress were F373,A60 and A47 which were poor in salt tolerance.The strains that performed well under drought stress were F373,Hercules and A60 had poor drought resistance.