Initiation of lateral (branch) roots

Three diagrams based on carrot (Daucus carota) which show the early pattern of endogenous lateral root formation.

A & B = initiation of lateral root through repeated local periclinal cell divisions in pericycle. The first stage of the lateral root initiation is the start of meristematic activity and the enlargement of a few initial pericyclic cells ("founder cells").

C = enlargement of the lateral root primordium.

Endodermal and cortical cells are pushed outward for a distance before being torn apart.

Illustration from: Weier, Stocking & Barbour, 1974, Botany: An Introduction to Plant Biology, 5th Ed. This material is used by permission of a subsidiary of John Wiley & Sons, Inc.