| Due to the periodic water level fluctuation of hydro-fluctuation belt,which formates water logging stress and then drought stress.The distribution of water and nutrients are nonuniform,which makes the ecosystem stability and ecological restoration difficult during the stress.Mulberry has high economic,ecological value and strong adaptability in extreme environment.AM fungi is widely distributed in the soil,and can form mutualistic symbiosis with most of the vascular bundle plants,which improve the ability of absorbing water and mineral nutrition from soil and is important for the growth and health of plants and soil.Studies showed that AM fungi have high mycorrhizal dependency for mulberry,mycorrhizal mulberry had great potential for ecological restoration under waterlogging and drought stress and improve the survival rate of mulberry in waterlogging and drought environment.In order to explore the resistance of mycorrhizal mulberry after persistent waterlogging and drought stress,using two years of inoculated and uninoculated mulberry in a dormant state as potted materials,carried out waterlogging in winter in November 2015,meanwhile set the not waterlogging(contrast I),half waterlogging,all waterlogging.After stable growth of one month,we put the materials in the Houyi park of southwest university to simulate waterlogging stress test for 4 months,and stopped waterlogging stress in April 2016.After restoring growth for 20 days,we measured the physiological and biochemical indexes of half of mulberry.The rest kept growing for 3 months,and carried out drought stress experiment in July 2016 for 15 days,meanwhile set the not waterlogging and drought(contrast II),waterlogging contrast(contrast I)to drought,half waterlogging to drought,all waterlogging to drought.We measured the physiological and biochemical indexes of mycorrhizal mulberry and uninoculated mulberry after restoring growth for 20 days.The research results of the full text are as follows: 1.The exploration of physiological resistance of mycorrhizal mulberry after waterlogging stress of winter dormancy periodThe colonization rate of inoculated mulberry was as high as 87.78 ± 11.11%,while the control group did not observed mycorrhizal colonization phenomenon;regardless of mulberry were inoculated or not,the chlorophyll and net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)were reduced with the deepening of waterlogging stress,and the content of these indexes were significantly higher in inoculated mulberry than uninoculated one,but intercellular CO2 concentration(Ci)showed the contrast.After waterlogging stress for 4 months and restoring growth for 20 days,oxygen levels in root of mulberry did not reach the control level so that the leaf photosynthesis abated and synthesis of carbohydrate decreased,while inoculation of AMF improved the inoculation rate of mycorrhiza,root activity and the content of osmotic regulation substances,decreased MDA content and promoted the growth of the mulberry.Enzyme system(SOD,POD,CAT,APX)in the leaves enhanced with the increase of waterlogging stress degree,but in the same treatment,the enzyme activity in mycorrhizal mulberry were significantly higher than uninoculated mulberry.We proposed the physical resistance of mycorrhizal mulberry resistanting to waterlogging stress.AMF and root system of mulberry formatted mycorrhizal symbiosis,which improved the root activity of mulberry and absorbed water and nutrients from the soil(nitrogen,phosphorus and potassium,etc.),then passed to host plants through the roots,which helping host plants compound more organic matter(such as chlorophyll,enzymes,proline,soluble protein,etc.),adjust the contents of osmotic regulation substances,enhance photosynthesis,and promote vegetative growth of host plants.Hypoxia under waterlogging stress made oxidation system weak in mulberry cells,which harmed the plants and affected the normal physiological process of plants,while mulberry inoculated with AMF increased leaf protective enzyme activity and decreased the cell membrane lipid peroxidation,thus raised the waterlogging resistance of mulberry.2.The exploration of physiological resistance of mycorrhizal mulberry after drought stressAfter drought stress and restoring growth for 20 days,tissue water content of mulberry decreased compared with the contrast,leaf blade saturated loss and MDA content improved,and water requirement degree increased;root activity,Pn,Gs,Tr,chlorophyll a and b,total chlorophyll,the osmotic regulation substances content(soluble sugar,soluble protein,proline),the protective enzymes(SOD,POD,CAT,APX)were reduced,and the tredency increased along with the deepening of early waterlogging degree,but these indicators were significantly higher in inoculated mulberry than uninoculated one,and MDA content also decreased significantly in inoculated mulberry.We proposed the physical resistance of mycorrhizal mulberry resistanting to drought stress.Mycorrhizal increased root absorption area through a lot of external mycorrhizal hyphae,and helped mulberry absorb more moisture and nutrients,increased the tissue water content,reduced the leaf saturated losses,which improved the water retention capacity and root activity,then promoted root system to absorb and transport moisture and nutrient elements,thus produced more chlorophyll to provide the need of carbon source of mulberry growth,increased osmotic regulation substances content and cell osmotic pressure,which kept certain moisture in mulberry,improved the activity of protective enzyme,and reduced the damage degree of cell membrane,while it enhanced the drought resistance of mulberry.And at the same drought stress treatment,regardeless of the mulberry were inoculated,various physiological indicators showed some regularity with early waterlogging stress degree,which showed that early waterlogging influenced the physiological and biochemical response under drought stress. |
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