A cellular growth model for root tips.

Growth of the root tip is modeled using a one-dimensional string of cells. Each cell is characterized by three distinct phases, division, elongation-only or maturity. In this model two hypothetical phytohormones, one produced at the root tip and the other at the shoot, determine the behavior of the cell, and therefore the growth of the entire tip. While the division rate is taken to be a step function of the string coordinate, the growth rate of each cell is assumed to be piecewise linear and composed of linear functions of cell length. Thereafter, suitable operators for the calculation of the velocity and relative growth rate distributions are given. The results of the model are finally compared to measurements of Arabidopsis thaliana, Nicotiana tabacum and Pisum sativum roots.