Root architecture: Influence of metameric organization and emission of lateral roots

It has yet to be established whether or not root architecture results from a metameric organization similar to that recognizable in the stem. To address this question, we have reviewed the data on the major cytological, histological and anatomical events underlying root development and on the intrinsic factors controlling these events. The evidence emerging from this review indicates that root architecture has a metameric organization that can be ‘deranged’ when environmental factors interfere with the intrinsic factors rhythmically controlling lateral root development. Metameric patterning occurs in the primary body of a root, but not in the secondary body. This difference can be attributed to the fact that primary and secondary body roots arise from completely different tissues. The root system of a woody plant is very complex, and its architecture is largely governed by roots with a secondary body organization that lack metameric patterning. The architectural contribution of the portion of roots with a primary body organization, where metameric patterning could be present, is negligible. This explains why it is difficult to recognize metameric patterning in the root architecture of these plants.