Effects Of Low Temperature And Drought Stress On Physiological And Biochemical Indexes Of Celtis Bungeana Seedling

Celtisbungeana,Ulmaceae,Celtis.Deciduous trees,as high as 10 m,have large leaves,thick green color,neat crown,good shade,excellent germplasm resources,wide application prospects and high economic and ecological value.Therefore,it is of great significance to study the stress resistance of Celtis bungeana.Cold resistance and drought resistance are two important aspects in the study of stress resistance.In this experiment,the seedlings of annual Celtis bungeana were used as materials.A total of 4 drought stress treatments:W1,80% of soil field water holding capacity(CK),60% of field water holding capacity(mild stress),40% soil water holding capacity(moderate stress),W4,20% soil water holding capacity(Severe stress),and 1year old leaves of isolated branches of Celtis bungeana were selected.The photosynthetic characteristics and physiological and biochemical indexes of Celtis bungeanawere studied under different temperature ang drought stress treatments.The results were as follows:1.With the increase of low temperature,the SOD activity of isolated leaves of Celtis bungeana showed a trend of first increasing and then decreasing,reaching the highest value at-10 ?,and the relative conductivity and MDA content showed an increasing trend.The content of proline and soluble sugar increased first and then decreased,and reached the highest value at-10 ?.The results showed that low temperature stress had a certain effect on the physiologicaland biochemical indexes of isolated leaves of Celtis bungeana:the low temperature stress caused damage to the cell membrane of the leaves,and increased the resistance to low temperature by increasing the osmotic regulator substance and the protective enzyme activity when the temperature was under-10 ?,but the osmotic regulator substance and the protective enzyme activity also decreased when the temperature was lower than-10 ?.In the later introduction work,some degree of resistance exercise can be carried out in advance when the lowest temperature is tolerated,and the adaptability to low temperature can be improved better.2.With the increase of drought,net photosynthetic rate(PN)and stomatal conductance(Gs)increased firstand then decreased,intercellular carbon dioxide concentration(Ci)decreased first and then increased,transpiration rate(Tr)decreased significantly.The chlorophyll fluorescence parameter Fo increased with the severity of drought stress.Under drought stress,the relative water content of leaves decreased gradually,and the soluble protein decreased first and then increased,with the increase of drought degree,the decrease was gradually increased.All groups reache the lowest value at 21d;the content of malondialdehyde(MDA)increased gradually,and the change trend of superoxide dismutase(SOD)and peroxidase(POD)activity was basically the same with the tendency to rise first and then decline.According to the comprehensive evaluation results,the drought resistance ability of Celtis bungeana was relatively strong.Under mild stress,the indexes were not different from the control,Celtis bungeana had strong drought resistance.Under moderate and severe stress,the drought stress was more obvious.It was the most affected under severe stress.In the future production and life,the moderate and severe drought should be irrigated at the right time.