茎部形成层赤霉素在植物生长发育中的调控作用

目的赤霉素(GAs)是一种重要的植物激素，对植物生长发育具有广泛的调控作用。本文通过对茎部形成层赤霉素在植物生长发育中的调控作用进行研究，为阐明植物体内源活性GAs的运输及其调控作用提供参考。方法本研究通过转基因方法特异下调烟草茎部形成层活性GAs含量，探究其对植株茎部、叶片、根生长发育的调控作用；在此基础上，利用35S:: PtGA20ox、35S:: PtGA2ox1转基因烟草株系分别作接穗和砧木进行微嫁接和施加外源GAs，探究内源与外源活性GAs在烟草体内的运输特性。结果结果表明，茎部形成层特异启动子LMX5介导的PtGA2ox1转基因烟草植株茎部GAs含量与野生型相比显著降低，而叶与根中含量无明显变化；通过石蜡切片观察发现茎部形成层GAs含量降低明显延缓了茎部木质部的发育，同时对植物的叶片、侧根的生长也有抑制作用；对不同转基因株系微嫁接分析发现，外源施加的GAs可以恢复茎部形成层GAs缺乏引起的表型，而内源活性GAs却不能自由运输，也不能恢复表型；结论茎部形成层GAs含量不仅对茎部木质部的发育有重要作用，并且对叶片的生长及不定根的发育也有调控作用，利用微嫁接的方法验证了活性GAs在烟草中的运输机制，明确了GAs在调控植物组织发育中的重要意义，为今后GAs在林木中的应用奠定了理论基础。 

Regulatory effect of stem cambium gibberellin on plant growth and development

Objective Gibberellin (GAs) is an important plant hormone, which has a wide range of regulatory effects on plant growth and development. In this paper, the regulatory role of gibberellin in stem cambium in plant growth and development was studied, providing reference for elucidation of the transport and regulatory role of source active GAs in plants. Method In this study, the content of active GAs in stem cambium was specifically down-regulated by transgenic method to explore its regulatory effect on the growth and development of plant stems, leaves and roots. On this basis, 35S:: PtGA20ox and 35S:: PtGA2ox1 transgenic tobacco strains were used as scions and rootstocks respectively for micrografting and application of external GAs, to explore the transport characteristics of endogenous and exogenous active GAs in tobacco. Result The results showed that the content of GAs in the stem of PtGA2ox1 transgenic plants mediated by the specific promoter LMX5 in the stem cambium was significantly lower than that in the wild type, while there was no significant change in the content of GAs in the leaves and roots. By observing paraffin sections, we found that the decrease of GAs content in stem cambium significantly delayed the development of stem xylem and inhibited the growth of leaf and lateral root. The analysis of micrografting of different transgenic lines shows that the exogenous GAs can restore the phenotype caused by the lack of stem cambium GAs, while the endogenous active GAs cannot be transported freely or restore the phenotype. Conclusion Stem cambium GAs content is not only an important role in the development of stem xylem, and development of the growth of leaves and adventitious roots also have regulation function, the method of using micro grafting reactive GAs is verified in transport mechanism in the tobacco, it has been clear about the GAs in the regulating plant tissue development, for the future GAs thus lay a foundation for the application in the trees.