IN DEFENSE OF RADIATION USE EFFICIENCY - A RESPONSE

Radiation use efficiency (RUE) is the conversion factor between the am ount of radiation intercepted or absorbed by a plant canopy and the co rresponding amount of carbon dioxide fixed or biomass produced. This f actor has been applied to the study of the growth and the analysis of a wide variety of plant species, in diverse environments, for many yea rs. Criticism has recently arisen regarding the utility of RUE in fost ering increased understanding of plant growth. Specifically, critics p ropose that the variability in reported RUE values is a symptom of the inherent inadequacies of this concept. We argue that this criticism a rises from both an inconsistent definition of RUE and a lack of consid eration of the physiological basis of RUE. The RUE concept represents a fundamental description of plant growth which has enhanced understan ding of both potential growth rates and reductions in these potentials owing to stressful conditions. Variability in RUE values can be under stood in terms of the physical and biological processes which determin e the state of the plant canopy. Furthermore, the use of RUE has advan ced the development of robust plant growth models.