Root Apical Meristems

Abstract

Abstract Apical root growth requires iterative processes of cell division, elongation and differentiation. Root apical meristem localised at the root tip harbours stem cells that divide asymmetrically and generate initial cells for all the cell types in the root. Fates of these initial cells are determined by positional signals that integrate both intrinsic and extrinsic cues. The quiescent centre maintains the stem cells and thereby sustains a constant supply of cells for root growth. Another important aspect of root growth regulation is to balance the rate of cell division and differentiation. The crosstalks between plant hormones auxin and cytokinins help to establish this balance. Gene regulatory networks that govern root meristem activities and growth have been discovered over the years in the model plant Arabidopsis thaliana . This introductory article provides an overview of the organisation of the root meristem and the underlying regulatory mechanisms. Key Concepts: Roots support the areal parts of plants and absorb water and nutrients that are essential for plant growth and survival. Roots, which made their first appearance in vascular plants, have evolved into a multitude of sizes and shapes. A root is composed of the outermost epidermis, ground tissue and the innermost stele as well as the quiescent centre and root cap. Root apical meristem serves as the source of new cells for root growth. In the root apical meristem, the stem cell niche sustains pluripotent stems cells to ensure a constant supply of cells for continuous root growth. Two transcription factor pathways led by the SHORTROOT–SCARECROW and the Auxin–PLETHORA play a central role in maintaining the root stem cell niche. Crosstalks between auxins and cytokinins establish a balance between cell proliferation and cell differentiation in the root meristem. In the root meristem, cell fate decisions are made based on positional information and various intrinsic and extrinsic signals. Cell‐to‐cell communications mediated by mobile transcription factors, peptides and small RNAs play critical roles in the root cell type patterning. Owing to the vital importance of roots in overall plant health and survival, study of roots and root meristem poses utmost significance in plant biology.