Stem cells located in the shoot apical meristem

On the left, an Arabidopsis plant is shown, with the growing shoot tip indicated by the orange line. The orange box shows a top view of the shoot tip at higher magnification, with the shoot meristem in the center (indicated by the yellow line), surrounded by flower buds of increasing age. The yellow box shows a virtual section through a three-dimensional reconstruction of the shoot meristem, based on microscopy images. The cells marked in red are the shoot stem cells; the cells in blue express the WUS gene and are required to maintain the stem cells; descendants of the stem cells are displaced to the periphery of the meristem, where they are periodically recruited to form a new organ (in this case, a new floral bud).