Length of the apical unbranched zone of maize axile roots: Its relationship to root elongation rate

Abstract

The length of the apical unbranched zone was studied in maize axile roots. Plants were grown in an aeroponic growth chamber allowing direct measurements on individual axile roots. The total length of the roots and the length of the apical unbranched zone were measured regularly. A commonly accepted hypothesis, according to which laterals emerge at a constant distance behind the root tip, was refuted. Conversely, a linear relationship was found between the length of the apical unbranched zone and the root elongation rate. This suggests that laterals emerge on a root segment at a constant time interval after lateral primordia are differentiated.