Histology And Hormones In Situ Of Adventitious Root In Platycladus Orientalis

Platycladus orientalis is one of the important greening tree species and afforestation tree species in China,Asexual reproduction and clonal breeding are important pathways for genetic improvement of Platycladus orientalis.Cutting is the key technology for asexual reproduction of plants,but the cuttings of Platycladus orientalis are unstable and the technical system is not perfect.There is still a lack of understanding about the origin of adventitious roots of it and the in situ distribution of phytohormones during adventitious root formation.In this study,the semi-lignified cuttings of Platycladus orientalis ' Liye ',Platycladrs orientalis 'Dieye' and Platycladus,Orientalis var.Nemperourescens(Variety of Platycladus orientalis)independently cultivated by Beijing Academy of Forestry and Pomology Sciences were used as experimental materials.The best incision-inducing factor was screened by the optimal combination of different growth regulators,different concentrations and different treatment times.Revealing the origin of adventitious roots through morphological observation and histological studies.The relationship between endogenous and exogenous hormones and adventitious roots was explored by immunohistochemistry and quantitative analysis of plant hormones.The main findings are as follows:1.The technical system of cutting the rooting of Platycladus orientalis was optimized.The highest rooting rates of 'Liye' and 'Dieye' treated with 2000mg/L IBA for 10s were 92.22%and 56.67%,respectively.The best Membership function value of 'Liye'is soaked in 800mg/L IBA for 4 hours,rooting rate is 71.11%.The best Membership function value of 'Dieye' is soaked in 4500mg/L Genwang for 4 hours,rooting rate is 41.11%.Growth adjustment treatment and variety interaction have a significant effect on cutting rooting rate.2.Through rooting process cutting and anatomical study,the rooting process of Platycladus orientalis was divided into four consecutive periods of callus formation(0?20d),induction(21?40d),expression(41?70d)and elongation(71?90d);There are no latent roots and inhibition of the structure of adventitious roots in the cuttings before cuttings.The adventitious root primordium originated from the intersection of the callus and the myelin rays with the formation layer,It must be induced to form callus before rooting,and belongs to callus induction type.3.Using immu no gold-sliver taining(IGSS)IAA and ABA signals mainly appeared in the cuttings cortex when the adventitious roots formed.The signal near the root primordia was stronger.After the adventitious root formation,the IAA signal was mainly distributed in the vascular tube sheath and endothelial layer of the adventitious roots;ABA signal Mainly distributed in the adventitious root marrow and endothelial layer.4.There were differences in endogenous hormone content during the rooting process of different varieties of the same treatment and the same species.The content of IAA,JA and GA3increased in different degrees,while BAB and ZT decreased in short time after treatment with growth regulators.The contents of IAA and ZT decreased and JA and GA3 increased during callus formation;The changes of IAA,ABA,JA and ZT in root primordium induction period tend to be within a certain range,and solid endogenous hormones promote root primordium formation within a certain range.