Hormone transport equation

A majority of the studies on transport of auxin (and other plant hormones) published during the years of research since the first papers of the Utrecht School (Went 1928, van der Weij 1932, 1934, Dolk 1930, 1936) have been designed to estimate the parameters in the transport equation. Using varying experimental conditions and many kinds of plant parts, and presupposing a uniform auxin stream, usually only two parameters, intensity and velocity, were determined in order to calculate the third, density, of the equation. Whether such calculations are justified, will be critically discussed in Section 3.3.3. 

When a constant delivery of auxin to the receivers is reached, the export curve becomes linear, which is a prerequisite for the equations and calculations outlined above. Linearity of the export curve usually lasts only for a few hours after donor application. The onset of the decline in rate varies with the type and length of the transport section, with the concentration and nature of the hormone applied, and with experimental conditions. 

Compartmental models are a class of dynamic, that is, differential equation, models derived from mass balance considerations, which are widely used for quantitatively studying the kinetics of materials in physiologic systems. Materials can be either exogenous, such as a drug or a tracer, or endogenous, such as a substrate or a hormone, and kinetics include processes such as production, distribution, transport, utilization, and substrate-hormone control interactions. 

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