Analysis of root meristem size development.

Plant post-embryonic development takes place in the meristems. In the root of the model plant Arabidopsis thaliana, stem cells organized in a stem-cell niche in the apex of the root meristem generate transit-amplifying cells, which undergo additional division in the proximal meristem and differentiate in the elongation/differentiation zone. For meristem maintenance, and therefore continuous root growth, the rate of cell differentiation must equal the rate of generation of new cells: how this balance is achieved is a central question in plant development. We have shown that maintenance of the Arabidopsis root meristem size is established by a balance between the antagonistic effects of cytokinin, which promotes cell differentiation, and auxin, which promotes cell division. Cytokinin antagonizes auxin in a specific developmental domain (the vascular tissue transition zone) from where it controls the differentiation rate of all the other root tissues. Here, we describe protocols to analyze development of root meristems.