Roles Of The Cambial GA Concentration On Tobacco Development

GA is one of the important hormones in plants, which can promote the growth of plant organs. As a plant growth regulator, GA has been widely used in agricultural production.Recently, Studies on GA is getting more and more people’s attention,The GA level is reduced in the stem xylem of tobacco in this study,which is based on the transgenic technology. In this study,we made a detailed record of different transgenic lines and studied them with cut section method and microscopic observation. And we also analyze the dffects of active GA in plant growth and xylem formation by comparing with related research of other scholars. The main contents and results are as follows:1) RNA was extracted from mature leaves of Populus tomentosa, and a key gene PtGA2oxl in GA metabolism were cloned from cDNA of Populus tomentosa.Get the transgenic plants of LMX5::PtGA2ox2 by using the transgenic technology. Measuring the growth indexes lines of LMX5::PtGA2ox1,wild-type and transgenic plants of 35S::PtGA20ox (35:G20) and 35S::PtGA2ox1 (35:G2) those kept in laboratory.Compare and analysis the plant height,leaves,ground stems and othe traits in their growth of different genotypes. The study found LMX5::PtGA2ox1 (L:G2) which reduced the GA level of the plant cambium significantly inhibited the growth of the various parts of the plant height, stem and other organs.2) The bioactive GA level and gene expression were all changed in transgenic lines. Detect the expression of PtGA2oxl gene by using qPCR technology. The results show that the gene PtGA2oxl is overexpressing in the stem of transgenic plants,but not in the leaves or roots.Several main categories of GA levels in roots, stems and leaves of transgenic lines were detected by LC-MS instruments.The results indicate that bioactive GA level in L:G2 was significantly reduced,but the inactive GA level was significantly increased.3) Check the bioactive GA transport mechanism in tobacco by using the micrografting techniques. The results demonstrated that endogenous bioactive GA can not be transported in tobacco plants,but exogenous GA4+7 can be transported in the plant and promote the growth of organizations of tobacco.And this suggests that bioactive GA in other organizations can not be freely transferred to the cambium of L:G2 transgenic line.4) Reducing bioactive GA in cambium of tobacco has a great impact on its leaf expansion and adventitious roots.Increase in the endogenous bioactive GA level of plant can promote the maturation of xylem and improve the degree of xylem;While reducing the bioactive GA levels can delayed xylem development.This suggests that bioactive GA regulation has played a positive role in the formation of xylem and development.The development of xylem in L:G2 and 35:G2 are almost at the same level.The result may suggest that the bioactive GA in cambium palys an important role in regulating xylem. In addition, the study found that reducing the bioactive GA level also had great affects on leaves and adventitious root development.