IN DEFENSE OF RADIATION USE EFFICIENCY - A RESPONSE

Radiation use efficiency (RUE) is the conversion factor between the amount of radiation intercepted or absorbed by a plant canopy and the corresponding amount of carbon dioxide fixed or biomass produced. This factor has been applied to the study of the growth and the analysis of a wide variety of plant species, in diverse environments, for many years. Criticism has recently arisen regarding the utility of RUE in fostering increased understanding of plant growth. Specifically, critics propose that the variability in reported RUE values is a symptom of the inherent inadequacies of this concept. We argue that this criticism arises from both an inconsistent definition of RUE and a lack of consideration of the physiological basis of RUE. The RUE concept represents a fundamental description of plant growth which has enhanced understanding of both potential growth rates and reductions in these potentials owing to stressful conditions. Variability in RUE values can be understood in terms of the physical and biological processes which determine the state of the plant canopy. Furthermore, the use of RUE has advanced the development of robust plant growth models.