Testing differences in relative growth rate: a method avoiding curve fitting and pairing

Abstract

Poorter, H. and Lewis, C. 1986. Testing differences in relative growth rate: A method avoiding curve fitting and pairing.- Physiol. Plant. 67: 223-226. A method is discussed to test differences in relative growth rates. This method is based on an analysis of variance, with ln-transformed plant weight as dependent vari-able. A significant Group × Time interaction indicates differences in relative growth rates between groups. The advantages over the "classical " and "functional " growth analyses are: (1) No pairing procedure is required. (2) More than two groups may be evaluated in one analysis. (3) No decision is required about the polynomial used to fit the data. (4) By partitioning the interaction effect using orthogonal polynomials in-sight is gained into the nature of differences in relative growth rate. (5) By concen-trating attention on the lower order terms of the polynomials, the influence of extra-neous variation on conclusions may be minimized. Additional key word- Growth analysis