  This work examines the relevance of the one-dimensional models used to study
the influx and the cumulative uptake of nutrient by roots. The physical models
studied are the fixed boundary model (Barber and Cushman 1981) and an improved
version of our moving boundary model (Reginato et al. 2000). A weight averaged
expression to compute influx on root surface and a generalized formula to
estimate the cumulative nutrient uptake are used. The moving boundary model
problem is solved by the adaptive finite element method. For comparison of
simulations of influx and cumulative uptake versus observed results six set of
data extracted from literature are used. For ions without limitations of
availability fixed and moving boundary models produces similar results with
small errors. Instead, to low concentrations, the fixed boundary model over
predicts while the moving boundary model always produces better results mainly
for K. For the P uptake the moving boundary model produces better results only
when the concentrations are very low and their predictions are comparable to
the obtained by a 3D-architectural model. The obtained improvements would
explain any failures of previous models for ions of low availability.
Therefore, our model could be a simpler alternative due to its low
computational burden.
