Résumé
This chapter focuses on the analysis of inherent differences in relative growth rate (RGR). It uses the comparative approach to analyze the characteristics and distribution of species varying in the maximum RGR they can achieve. A simple framework to factorize RGR was developed at the beginning of the twentieth century. Originally, V. H. Blackman thought of RGR as a physiological constant, which would be characteristic for a given species under given conditions. A simple framework to factorize RGR was developed at the beginning of the twentieth century. RGR can then be expressed as the product of the root mass fraction and the nitrogen uptake rate divided by the mean plant nitrogen concentration. Shoot respiration and root respiration are positively associated with RGR. A positive relation between RGRmax and nutrient availability is also likely for woody species. RGR was factorized into components based on the assumption that leaf area is the important plant variable driving photosynthesis, and thus growth.