Studies On Waterlogging And Saline Tolerance In Fraxinus Clones At Nursery Stage

Fraxinus is the generic name of Oleaceae Fraxinus L.,which is widely distributed in various provinces and regions of China.It is a precious afforestation and landscaping tree species in China.At present,the research on fraxinus mainly focuses on biological characteristics,germplasm resources,reproduction and afforestation technology,and has carried out systematic research and preliminary results.There are few reports on salt tolerance of clones.In this paper,the growth and physiological characteristics of fraxinus clones under water and salt stress were studied.Waterlogging stress is the physiological characteristics of wax clones after flooding in the field.Pot experiments were conducted to determine the growth indices of wax clones under five NaCl stress gradients(0,2,4,6,8),and to evaluate the waterlogging and salt tolerance of wax clones comprehensively by various resistance indices.The following results are obtained:1.Under flooding conditions,there was a significant difference in cell membrane permeability between different clones.Under the condition of impaired cell membrane structure and function,a large amount of electrolyte extravasation was caused,and the permeability of plasma membrane increased,resulting in a large amount of membrane lipid peroxidation product MDA,MDA levels are also lower in less sexual clones.Only Y3 clone had the lowest relative conductivity among 11 clones,and had significant difference with other clones.Meanwhile,the content of MDA in the clone was low,the damage degree of cell membrane was low,and the waterlogging resistance was strong.When cell membranes are damaged,plants will activate self-regulating system to resist adverse environment.SOD activity in clones is enhanced and excessive free radicals are eliminated.Different clones have different enzymes activities due to different physiological characteristics.JZ,YL and Y3clones with strong resistance have higher SOD activity and higher peroxidase activity.POD is mainly clear in plants.In addition to the hydrogen peroxide produced by SOD scavenging reactive oxygen species,the clones with poor resistance had lower enzyme activity.2.Under salt stress,the growth indexes such as seedling height increment,ground diameter increment and biomass of all clones showed a downward trend on the salinity gradient,and the growth of clones was severely inhibited,especially because of the increase of salt concentration.Salt-tolerant YL clones were the least affected by salt stress,with the highest growth rate during the stress period,followed by Y3 clones,and salt-tolerant ability was better than other clones.Roots play an important role in plant growth,absorbing inorganic ions and nutrients and transferring them to the aboveground parts for plant growth and development.When the fraxinus clone was under low salt stress,the root system also increased its quality to resist the damage caused by salt stress.The root-shoot ratio increased with the increase of salinity gradient,while the root-shoot ratio was severely damaged by salt stress at higher concentration,resulting in a decrease of root-shoot ratio,and the root-shoot ratio still showed salt tolerance.The root-shoot ratio of strong YL and Y3 clones was higher.3.During salt stress,the chlorophyll content of the nine clones showed a decreasing trend in both time gradient and salt gradient.The plasma membrane permeability of each waxy clone increased with the stress time and the salt gradient.In the early stage of salt stress,the relative conductivity of YL and QB clones with high salt tolerance did not increase obviously,and the other clones increased slightly Plants sense the damage of cell membrane system and activate antioxidant enzyme activity to reduce the damage of active oxygen to cell membrane system.MDA is closely related to cell membrane,and its content also reflects the damage degree of Cell Membrane under SALT STRESS The contents of Malondialdehyde in y 3,YL and QB clones were lower.The salt-tolerant clones also reduced the damage caused by adversity by increasing the osmotic adjustment substances such as proline,soluble sugar and inorganic ions.The Na~+/K~+value showed an upward trend on the salinity gradient Proline and soluble sugar of 5 clones increased at first and then decreased,and the synthesis of soluble sugar was inhibited when salt stress time and concentration exceeded a certain range.4.Comprehensive analysis showed that growth,root-shoot ratio,relative conductivity,malondialdehyde content,osmotic adjustment substance content,antioxidant enzyme activity and so on could be used as effective indicators for evaluating wax clones.Under waterlogging stress,the waterlogging resistance of 11 clones was ranked by principal component analysis.The preliminary results showed that the waterlogging resistance of 11 clones were JZ,OB,YL,L5,Y3,J10,HX,QB,JJ,JN11 and J5,respectively.At low salt concentration,the growth and physiological indices of the fraxinus clones were affected to a low degree.Therefore,it was considered that the fraxinus clones had salt tolerance.The salt tolerance of nine fraxinus clones was ranked by principal component analysis,from strong to weak in order of QB,YL,L5,J10,Y3,L2,JN11,HX and JJ.