Multicompartment analysis of the response of lupin hypocotyl segments to the addition and removal of indolyl-3-acetic acid

Abstract

The typical growth rate curve of the response of lupin hypocotyl to auxin is discussed and explanations suggested for the different parts of the curve. Two alternatives are shown to be able to account for the latent period after auxin addition. One is a linear series of compartments with the transport between compartments similar to allosteric activation in enzyme kinetics and the other alternative is an unmixed compartment (transport delay). Computer simulation is used to test different models to determine whether any model quantitatively predicts the observed results. An example (and variations) of a model is given that predicts much of the experimental results. The model is tested under different conditions such as the addition of different concentrations of auxin, and different times of cycloheximide pretreatment, and on removal from different auxin concentrations. The results of the computer simulations are then compared with experimental results and the model improved to overcome discrepancies. The usefulness of computer simulation in an experimental study is discussed.