Shoots and Buds in Arabidopsis

Abstract

The shoot is the above‐ground part of higher plants. To produce new shoot tissue, repetitive organ formation takes place at the tip of shoots and in floral buds by the activity of stem cell systems, called shoot and flower meristems. The shoot meristem is set up during embryogenesis and, after seedling germination, produces leaves, stems and eventually flowers. One of the key issues of the shoot meristem is to maintain a balance between cell proliferation and differentiation. A complex set of genetic and hormonal regulation ensures the maintenance of undifferentiated cells in the centre of the shoot meristem and the initiation of organ primordia at its flanks. While shoot meristems are indeterminate structures, in flower meristems stem cell maintenance ceases once the floral organs have been generated. Key Concepts: The shoot apical meristem produces the above‐ground organs of plants. Stem cells located in the centre of the shoot meristem are maintained by a self‐regulatory gene expression network involving the WUSCHEL and CLAVATA genes. Cytokinins play a role in meristem cell proliferation and in stem cell positioning. Auxin is essential for organ primordia formation. The shoot meristem is established during plant embryogenesis. In floral meristems, stem cells are only maintained for a limited time.