Analysis of surface growth in shoot apices.

A salient feature of shoot meristem growth is the maintenance of distinct anatomical and morphological features despite a continuous flux of cells. To investigate how meristem organization is self-perpetuated, we developed a protocol for the analysis of meristem growth in 3-D. Our protocol uses a non-destructive replica method to follow the pattern of cell expansion and cell divisions on the meristem surface over several days. Algorithms to reconstruct the meristem surface and compute its curvature and rate of extension were implemented. We applied this approach to the shoot apical meristem of Anagallis arvensis and showed that a subcellular resolution of extension rates can be achieved. This is the first detailed quantitative analysis of meristem geometry and surface expansion in 3-D. This new approach will be useful to connect cellular activities such as cell expansion, cell division, and differential gene expression with overall meristem morphogenesis.