**7. Conclusions**

Specifically manipulated *Arabidopsis* represents a good system for the analysis of vascularization machinery that typically occurs in trees. Obtained results revealed that this process is accompanied with cellular events following cambium ontogenesis, xylem formation, and regeneration: (1) elevated auxin concentration in tissues, (2) new polarity establishment, (3) reposition of PIN1 proteins at plasma membranes of differentiating cells, (4) cellular divisions, and finally (5) cambium and vascular tissue development or regeneration.

Knowledge about the molecular mechanisms regulating vascular tissue development in trees is incomplete, and such studies can take full practical advantages from a recently proposed new approach. Temporal analysis and experiments in trees are hampered mainly because of variability in environmental conditions, their long life cycle, and restricted amount of transgenic lines and mutants available.

Currently, new insights into the vascular tissue formation problematics can be obtained by using *Arabidopsis thaliana* (L.) Heynh. This modest plant commonly used as a genetic model can be also modified to become a perfect experimental "tree-like" model, with a closed ring of functional cambium and secondary vascular tissues with complexity of phenotype features fully comparable to woody plants. This new approach promises to identify additional genetic and molecular components involved in vascular tissue functioning, including the insights into the role of cambial cells in this process in woody plants. Extensive studies with the use of *Arabidopsis* model system allow obtaining a more complete data about vasculature development and regeneration under more controlled experimental conditions.

Interdisciplinary scientific approach with the use of *Arabidopsis* as the "tree-like" model promises to pioneer new, original, and valuable information about the mechanisms regulating vascularization and allows defining molecular factors of the auxin-dependent machinery involved in this process. This creates a unique opportunity to compare the processes in *Arabidopsis* with analogical situation found in trees. There is a hope that the obtained knowledge could be applied practically. Plant life conditions are closely related to dynamic environmental and climate changes, which is a global problem of the last decades. Among the most endangered ecosystems are forests, which are shrinking very fast not only because of environmental changes but mostly because of the non-sustainable economic exploitation. Thus obtaining additional options to study typical tree features including their regenerative abilities is important to design efficient strategies for sustainable wood production.
