**6. Emergence of** *Arabidopsis* **as a good model system to study the vascular tissue formation and regeneration processes**

For a long time, the herbaceous plant *Arabidopsis* was postulated as a major model system for developmental plant biology due to its some important features, such as a short generation time and relatively small size of fully sequenced genome [52]. It was used as a modern research tool for different molecular studies, especially thanks to large mutant and transgenic line collections. Finally, in many studies *Arabidopsis* was also postulated as a perfect plant for secondary growth analysis [37–39, 44, 45, 50, 102, 103].

Although the vascularization and regeneration in *Arabidopsis* have been previously analyzed [3, 81], the role of vascular cambium in these processes has never been addressed. Only just modified and established method to obtain stems with closed vascular cambium rings and some typical features mimicking vascular tissue in trees [7, 51], such as secondary rays and intrusively growing cambial cells or tracheids—unusual example of tracheary elements found in woody plants—gives infinite possibilities to analyze secondary vascular tissue development and provides decisive advantage over previous approaches with the use of *Arabidopsis* stems. This strategy is particularly suited to elucidate different molecular mechanisms and other molecular components involved in auxin-mediated responses, canalization of auxin flow, and cellular polarity, underlying determination of plant developmental plasticity.

The availability of numerous genetic and molecular tools in *Arabidopsis* will provide clarifying picture of the process of vasculature formation as well as reconstruction after wounding and decisively extend the knowledge on molecular control of spatiotemporal vasculature patterning and regeneration both in vivo and in vitro. Resolving the involvement, the mechanism of canalization process will contribute to explain molecular mechanisms involved in vasculature regeneration and provide a useful model for further studies.
