Study On Rooting Mechanism And Metabolite Differences At Different Cutting Times Of Cutting Of Michelia Martinii

Michelia martinii,a type genus of Michlia L.in the family Magnoliaceae,is an evergreen tree plant.It has a straight trunk,compact and plump tree shape,and shiny leaves and light yellow color.It has high material value,spice value and ornamental value,and has a good prospect for development and utilization.In this study,M.martinii was used as cutting material and developed in five aspects:different cutting bases,types of growth regulator,concentration of growth regulator,the combination of growth regulator and cutting period.The stem structure of cuttings was observed by paraffin section,the relationship between nutrient content,antioxidants and enzyme activity during rooting and metabonomics during callus formation were compared and analyzed.The rooting mechanism and the changes of metabolites in cutting propagation were discussed,The aim is to provide theoretical guidance and technical support for the suitable cutting propagation of the M.martinii.The main results were as follows:（1）The cutting base had a significant effect on the rooting rate and rooting index of the M.martinii:The most suitable cutting base for M.martinii was perlite+peat soil（3:1）.The rooting rate of each cutting base from low to high was yellow soil<river sand<perlite+peat soil（3:1）.The results of different growth regulators on rooting effect of cutting showed that:In the single growth regulator experiment,the rooting rate and rooting index of K-IBA were the highest.In the experiment of different concentrations of three kinds of growth regulators,the rooting efficiency of cutting treated with 400 mg/L K-IBA or 8000 mg/L K-IBA was better,followed by 100 mg/L ABT or 8000 mg/L ABT,K-NAA treatment was the worst.The results of the combined growth regulator test study show that:K-IBA 400 mg/L+ABT 100mg/L is the most favorable method for cutting propagation,and the rooting rate was as high as 55.57%.Different cutting periods also had significant influence on the rooting rate of cutting.It found that September was more suitable for cutting,and the rooting rate can reach 47.23%.（2）Most of the rooting of M.martinii cuttings grows through calluses,a very small number of cuttings rooting through the skin,observation of many paraffin section showed that there was no latent root base in M.martinii cuttings,and adventitious roots were formed from induced root base,which belonged to plants difficult to root in cuttings.Physiological changes of cuttings can affect rooting.During the rooting process of M.martinii cutting,the contents of soluble sugar and soluble protein in the treatment group（K-IBA 400 mg/L+ABT 100 mg/L）and the control group（CK group）showed similar trends of"up-down-up"and"slowly up-down",respectively.The starch content showed a decreasing trend.In addition,the activities of POD（peroxidase）,PPO（polyphenol oxidase）and SOD（superoxide dismutase）at the base of cuttings in treatment group were higher than those in CK group,the content of MDA（malondialdehyde）was lower than that in CK group,and the rate of decline of CAT（catalase）activity and H₂O₂（hydrogen peroxide）content was faster than that in CK group.These results indicated that the use of growth regulators not only accelerated the hydrolysis and transformation of starch,promoted the accumulation of soluble sugar and soluble protein,but also affected the cutting healing,callus and adventitious root formation by regulating the changes of antioxidant content and related enzyme activities in the rooting process of M.martinii.（3）The changes of differential metabolites were associated with the formation of callus.The contents of differential metabolites from S0（normal stage）to S2（callus enlargement stage）were the largest,with 375 differential metabolites,143up-regulated and 231 down-regulated,and 76 differential metabolites enriched to 107 metabolic pathways.From S0 to S1（callus formation stage）,315 differential metabolites were detected,202 were down-regulated,113 were up-regulated,and67 differential metabolites were enriched to 103 metabolic pathways.The metabolite components from S1 to S2 were relatively stable,with only 27 differential metabolites,4up-regulated and 23 down-regulated,and 9 differential metabolites enriched to 52 metabolic pathways.There were 11and 3 different metabolites in the biosynthetic pathways of ABC transporters and Choline metabolism in cance,respectively.Therefore,it was speculated that there might be significant differences in the key enzyme genes of these two metabolic pathways in the callus formation process of cuttings.There were metabolic differences in callus formation of M.martinii:Alkaloids,phenylpropanes,insecticides,vitamins and cofactors,and organic acid metabolites were expressed in all three stages;while terpenoids,lipids,and flavonoids were expressed in callus induction stage,but not in expansion stage.It is hypothesized thatduring the process of healing tissue induction in Michelia martinii cuttings,a large amount of aminoacids and their derivatives accumulate to provide energy and substrate for healing tissueformation,while interacting with flavonoids and their derivatives,lipids,etc.to promotehealing tissue formation.