Research On Dormancy Regulation And Cold Resistance Characteristics Of Sedum Aizoon L. Seedling With Sprout

Sedum aizoon L.is a perennial facultative crassulacean acid metabolism herb of Crassulaceae with strong cold resistance and bud dormancy in winter.It is distributed in the Yangtze River Basin,the Yellow River Basin and even the Northeast China.At present,the research on Sedum aizoon L.is mainly focused on the pharmacognosy and the direction of salt,heavy metals,soil acidification and drought stress.There are few reports on dormancy regulation and cold resistance characteristics of Sedum aizoon L.seedling with sprout.Through the study of cold resistance characteristics and dormancy regulation of Sedum aizoon L.seedling with sprout,the purpose of this test was to provide reference for reducing its production cost,realizing its annual supply,and revealing its unique cold resistance mechanism deeply.The main results are as follows:1.The effects of dormancy releasing were compared by measuring the growth,photosynthetic characteristics and glycometabolism when Sedum aizoon L.seedling with sprout were treated at 5 degrees Celsius for 1,3,5 and 7 days in darkness respectively,restoring growth at 25 degrees Celsius.The results showed that Sedum aizoon L.seedling with sprout were physiological dormancy,which realized recovery growth after 5 days of darkness treatment at 5 degree Celsius.The plant height,stem diameter,aboveground fresh weight all were the largest,quantum yield of PSII,electron transport rate,photochemical quenching,contents of reducing sugar,fructose and sucrose,activities of total amylase,soluble acid invertase,cell wall bound invertase and neutral invertase all came to complete dormancy-released state state after 5 days treatment.2.The effects of recovery growth were compared by measuring the biomass and quality indices when dormancy-released Sedum aizoon L.seedling with sprout were treated at 25,20 and 15 degree Celsius respectively.The results showed that the more suitable recovery growth temperature for dormancy-released Sedum aizoon L.seedling with sprout was 20 degree Celsius.With the increasing temperature,the plant height and aboveground fresh weight all showed an upward first and then downward trend.The contents of chlorophyll,carotenoids,calcium and zinc all showed an upward trend,while magnesium and iron all showed a downward first and then upward trend in fresh food part.The contents of soluble protein,vitamin C,free amino acid and flavonoids all showed a downward trend,while total soluble sugar,caffeine and oleanolic acid all showed an upward first and then downward trend.Under 20 degree Celsius,the plant height,aboveground fresh weight,the total chlorophyll to carotenoid ratio,the contents of total soluble sugar,caffeine and oleanolic acid were all the highest,while the contents of mineral elements,soluble protein,vitamin C,free amino acids and flavonoids were the best with a comprehensive evaluation.3.The difference of cold resistance between aboveground and underground parts was compared by measuring the growth,microscopic structure and cold-resistance physiology of dormancy-released Sedum aizoon L.seedling with sprout at-5,0 and 5 degrees Celsius respectively.The results showed that the cold resistance of the underground part was stronger than aboveground part in Sedum aizoon L.seedling with sprout.The aboveground part survived at-5 degrees Celsius for 30 days without chilling symptoms.With the decreasing temperature,the plant height,root length and root vigor all showed a downward trend,and the plant height decreased more than root length.The aboveground and the underground fresh weight all showed a downward first and then upward trend.The cross-sectional microstructures of leaves and roots showed that the number of mucilage cells all showed a downward trend,which in leaves decreased more than roots.Mucilage cells were only distributed around vascular bundles,upper and lower epidermis cells in leaves,and pith to epidermis in roots.The relative conductivity,tissue water content,total soluble sugar and free proline content all showed an upward trend,while malondialdehyde showed a downward trend in leaves.The content of soluble protein showed a downward first and then upward trend in leaves.The changing trend of roots was the same as leaves in relative conductivity,total soluble sugar and soluble protein content,but the relative conductivity of roots increased less than leaves.There was no significant change in tissue water content,free proline and malondialdehyde content in roots.At the same low temperature,roots were all higher than leaves in the content of total soluble sugar and soluble protein,while the tissue water content and malondialdehyde content were the contrary.