Plant Growth Analysis: The Use of the Richards Function as an Alternative to Polynomial Exponentials

Abstract

The derived quantities in plant growth analysis, obtained by fitting the Richards function on the one hand and polynomial exponential functions on the other hand, are compared, using two sets of experimental data. Results show that, although there is rarely a statistical difference between the quantities derived from the two types of function, the time trends are often more biologically meaningful when derived from Richards function fittings. Further, use of the Richards function does not entail a problem of choice, as occurs in the use of polynomial exponentials when particular members of the family must be selected for given data sets; on the other hand, the Richards function will not fit those few sets of growth data which show insufficient curvature towards an upper asymptote. It is recommended that, whenever possible, the Richards function be used in plant growth analysis instead of polynomial exponentials.