Study On The Regulation Of Endogenous And Exogenous Hormones In The Formation And Development Of Adventitious Roots Derived From Stems In Vitro Of Plumbago Auriculata

To solve the shortage of seedling resources of Plumbago auriculata,we have established a tissue culture aseptic rapid propagation system after three years research.In the further research on the key technology of industrialized nursery,some problems were found,such as the instability of stem cutting rooting,and the specific manifestations are that the speed and type of adventitious roots under different hormonal conditions are very different,and after continuous culture rooting and growth effects are uneven.Rooting is the key to sterile cuttings,and plant growth regulators are often used not only to improve tissue culture conditions but also to enhance rooting ability.Based on the key technology of stem segment rooting,this study selected two IBA and NAA exogenous plant growth regulators,studied its effect on rooting and growth of stem explants,and responded to five endogenous hormones in stem segments,and the effect of plumbagin accumulation in rooting seedlings.The result is as follows:（1）The rooting type of the Plumbago auriculata sterilized cuttings belongs to the rooting type of the dermis,and the rooted stems do not contain latent primordial.According to morphological changes and histological observation,the three stages of adventitious root formation in the stem of blue flowering buds were:adventitious root induction period（0 to 6days）,adventitious root expression period（6 to 8 days）,and adventitious root elongation period（8 days later）.The differentiation of the root primordium requires high concentrations of endogenous IAA,IAA/CTK,IAA/ABA,and IAA/GA₃.Before the formation of the root primordium,the parenchyma cells divide into the primary cells of the root primordium,which requires lower IAA/CTK.A higher concentration of endogenous GA₃ is required throughout the induction and formation of adventitious roots.The change of endogenous NAA is not related to the induction and expression of adventitious roots.（2）Under the effect of exogenous NAA,the callus was formed in the underground part of the stem,and there were occasionally short adventitious roots;aerial adventitious roots or white callus were formed in the aerial part of the leaf,and many petioles to the leaf veins have white callus and some adventitious roots are formed on some stems.The increase of NAA concentration exacerbated the formation of callus.When the concentration was too high（1.5mg/L）,the formation of underground callus was inhibited,and the later mortality was high,and the fresh weight was weak.Under the effect of exogenous IBA,adventitious roots were also formed in the underground part of stems.With the growth of adventitious roots,the roots gradually developed and began to transport nutrients upwards,which promoted the growth of some aboveground leaves and leaf buds.Exogenous IBA had a certain inhibitory effect on the induction and expression of adventitious roots,but it promoted the growth of adventitious roots in the middle and late stages of adventitious root elongation.Comprehensive rooting index and adventitious root fresh weight,adding 1.0 mg/L IBA in MS medium is the best choice for obtaining strong root tissue culture seedlings.（3）In the process of callus induction and growth,IAA,CTK,GA₃ and ABA and NAA in the ground were increased under the action of exogenous NAA.In the underground part,IAA,CTK and ABA were increased relative to the aboveground part;IAA/CTK and IAA/ABA were decreased in the induction stage of callus and growth stage,while IAA/GA₃ decreased in the growth stage of callus.Under the effect of exogenous IBA,adventitious root induction and expression were inhibited,and IAA,CTK,ABA and IAA/GA₃ were increased;IAA/CTK,IAA/ABA,and GA₃ were decreased.However,exogenous IBA promoted the formation of developed roots in the extended period of adventitious roots,and made the underground IAA,CTK,GA₃ over the ground,the relative content of ABA and NAA on the ground increased,and ABA,IAA/CTK,IAA/ABA and IAA/GA₃ increased.（4）The optimal rooting exogenous hormone（1.0 mg/L IBA）increased the content of leucostatin in in vitro seedlings treated with adventitious roots relative to that treated with no hormones.Therefore,1.0 mg/L IBA was also the best MS medium formula for obtaining leucostatin.In addition,the spatial distribution relationship of the content of leucostantin in tissue culture seedlings in this study was as follows:leaf>stem>root.In this study,the type of root cuttings in the aseptic cuttings was determined,and the stages of formation of adventitious roots were divided,and the changes of endogenous hormones during induction and expression of adventitious roots were analyzed in detail.After using auxin analogs IBA and NAA,the best adventitious roots were obtained.Two different organs regeneration and growth direction were observed,and the regulation and interaction of endogenous hormones and exogenous hormones were analyzed.Finally,we compared the accumulation of plumbagin in the best hormone treatment and hormone-free treatment and studied the spatial distribution of aseptic plantlets.In conclusion,it is feasible and effective to use plant regulators to improve the quality of adventitious roots and the production of plumbagin in sterile cuttings.