Effects Of Saline Alkali Stress On Physiological Growth Of Four Perennial Flowers Of Compositae

In today’s world,soil salinization is one of the key factors restricting the development of agriculture and forestry and environmental protection.Excessive salinity will cause irreversible damage to plant morphology and physiology,affecting crop yields and other hazards.Therefore,the study of salinity tolerance of plants has always been one of the key contents of experts and scholars.In our daily life,the root flowers have the characteristics of high ornamental value,strong ecological adaptability and low maintenance costs and extensive management.They play an important role in the construction of garden landscapes.In order to determine the salt and alkali tolerance of the four Asteraceae flowers Chrysanthemum morifolium,Gaillardia aristata Pursh,Achillea millefolium and Dendranthema indicum,two treatment methods were set up,includeing neutral salt NACL and alkaline salt NA₂CO₃,Four stress concentration gradients per treatment,namely:T0=0g/L（control）,T1=3g/L,T2=6g/L,T3=9g/L,their morphological changes were observed and physiological indicators were measured.The fuzzy membership function method was used to analyze and compare the salinity tolerance of four plants,and the principal component analysis method was used to compare the strength and weakness of the salinity resistance of each index reaction,and the conclusions are as follows:1.Under NACL stress,The morphological characteristics of the four plants all appeared curled,shrunken,and the leaves lost green and turned yellow with the prolongation of stress concentration and time,of which the other three species died except for the Gaillardia aristata.The content of malondialdehyde in the four species of perennial flowers was consistent:all of them continued to rise with the prolongation of stress time and the increase of stress concentration.The activity of SOD in the four species of perennial flowers was same:increased first and then decreased.The Pod activity of Gaillardia aristata continued to increase.The Pod activity of the other three species showed a same trend,which increased first and then decreased.The soluble protein content showed a trend of first rising and then decreasing,and the free proline content showed a continuous upward trend.Chlorophyll content first increased slightly and then decreased sharply.2.Under NA₂CO₃stress,The morphological characteristics of the four plants all appeared curled,shrunken,and the leaves lost green and turned yellow with the prolongation of stress concentration and time,of which four species all died.the mda content of the four species of perennial flowers showed a continuous upward trend with the prolongation of the stress time and the increase of the stress concentration.SOD activity increased first and then decreased with the increase of stress days.In addition to the continuous increase in POD activity,the other three species showed a trend of first rising and then declining.The soluble protein content showed a trend of first rising and then decreasing,and the free proline content showed a continuous upward trend.Chlorophyll content first rose slightly and then decreased sharply.3.According to the value of the membership function,the four species of perennial flowers’NACL stress resistance ability can be obtained as follows:Gaillardia aristata>Achillea millefolium>Dendranthema indicum>Chrysanthemum morifolium.According to the value of the membership function,the NA₂CO₃stress tolerance of the four perennial flowers is as follows:Achillea millefolium>Gaillardia aristata>Chrysanthemum morifolium>Dendranthema indicu.4.According to the comprehensive analysis of the ranking situation,the four species of perennial flowers’salt and alkali stress resistance ability can be obtained as follows:The ability of Gaillardia aristata and Achillea millefolium tolerate both neutral salts（NACL）and alkaline salts（NA2CO3）is stronger,while the other two are relatively weak.