Effects Of PBZ And TIBA On Nutrient Uptake Of Euonymus Japonicus Seedlings

Hedge trees pruning and geometric shape maintaining of arbor tree have been the important practice activities in urban forest management.To maintain hedge tree in desired shape in low cost way,PBZ and TIBA were widely applied in E.japonicus.Overall,It is important to reveal the nutrient uptake mechanism of E.japonicus to PBZ and TIBA,which is of great significance to provide theoretical guidance for the rational cultivation and management of hedge tree in the future and understand the effects of plant growth retardants.With E.japonicus 3-year-old and 1-year-old seedlings as the study materials,split-plot design was adopted in the experiment.Four types PBZ concentrations with 0 mg/L,20 mg/L,50 mg/L and 80 mg/L,and 3 types of TIBA concentration,and 12 treatment combinations were formed.The root morphology traits,root biomass,root nutrient content and leaf nutrient content were measured and analyzed to study the effect law of different concentrations of PBZ and TIBA on nutrient uptake by E.japonicus.And the experiment of nutrient depletion was conducted to study the effects of PBZ and TIBA on NO3-uptake by E.japonicus seedlings as well as its funtion pathway.We have gotten the following five main conclusions.1.The nutrient uptake capability of E.japonicus root was promoted significantly by treated with PBZ,TIBA individually and interactively in different levels,and the total-N,nitrate-N,total-P and free amino acid contents of fine roots were improved significantly mostly.They were all promoted as the concentration of PBZ increased.By contrast,they were promoted at first and then inhibited as the TIBA concentration increased.The content of root nutrients were improved by 9.28%-144.82%under P4 treatment,and were improved by 4.92%-76.81%under T2 treatment.2.The total root morphological traits,fine roots morphological traits,total uptake area and active uptake area of E.japonicus were showed significant plasticity to PBZ and TIBA,and the total root volume and morphological traits of fine roots were showed significant plasticity to interactive effects of PBZ and TIBA.The contents of total-N,soluble protein and photosynthetic pigments in leaves of E.japonicus were promoted significantly by main effects of PBZ and TIBA as well as their interactive effect.The content of free amino acid in leaf was promoted by treating with PBZ individually and the content of nitrate-N was only promoted by TIBA at high concentration level.3.There were extremely significant positive correlations between the contents of root nutrient and root economic traits.The contents of nutrient in fine roots and medium roots were extremely positively correlated with contents of leaf nutrient.The contents of total-P in fine and medium roots were positively correlated with total-P in lea-ves.The main two factors influencing the uptake capability strengthening of root of E.japonicus by plant growth retardants were that root uptake morphology was showed significant plasticity to PBZ and TIBA,and then the nutrient metabolism in E.japonicus leaf had been strengthened by PBZ and TIBA.4.In the study of kinetics of nutrient uptake,Cmm,Km were inhibited significantly by PBZ(by 9.81%and 7.95%,respectively)but Imax,?,?,root surface area,root tissue density,specific root length,specific root surface area,total uptake area,active uptake area,total specific surface area and active specific surface area were all promoted significantly by PBZ(by 54.6%-86.27%).While Cmm,Km were inhibited at first,then promoted with the increasing concentration of TIBA(by 8.87%and 6.46%,respectively).Differently,Imax,?,?,root surface area,total uptake area,active uptake area,active specific surface area were increased at low concentration level of TIBA,then decreased at high concentration level(by 36.30%-54.96%).The inhibiting effects on Cmm,Km,and promoting effects on Imax,?,? and morphological traits related to root uptake were the most significant when seedlings applied with PBZ at 80 mg/L combined with TIBA at 50 mg/L or 100 mg/L,Results indicate the uptake capacity and rate of NO3-by roots of E.japonicus seedlings could be affected significantly by PBZ,TIBA and their interaction and it was through altering root uptake morphology that PBZ and TIBA enhance the root uptake traits of E.japonicus.