Which layer is the most active in dicot roots?

The pericycle is the most active layer in dicot roots. This single layer of parenchymatous cells lies just inside the endodermis and surrounds the vascular tissue. The pericycle retains its meristematic potential throughout the life of the root, making it highly active. Its primary functions include: initiating lateral root formation (branch roots originate from pericycle cells), contributing to secondary growth by forming part of the vascular cambium in roots that undergo secondary thickening, and sometimes producing additional cork cambium. During lateral root development, pericycle cells divide actively to form root primordia that eventually break through the cortex. This perpetual ability to divide and differentiate makes the pericycle essential for root branching and the establishment of an extensive root system.