Pedro José Aphalo, Titta K Kotilainen

The concept of ``wasted illumination'' and its application to the design of light sources for plant cultivation is a good example of misuse of reductionism. Equating instantaneous rate of photosynthesis to crop yield is a prevailing but nonsensical idea, and in the case of the design of red plus blue light sources an extreme case of ignoring the multiple regulatory mechanisms and interactions present in individual plants and crop canopies. The misconception about red plus blue LED growth lights has been challenged already, but in this article we describe in detail several of the mechanisms that have been ignored in early attempts to optimize the spectrum of light sources for plant cultivation. They exemplify very well the dangers of a purely reductionist approach to scientific research that ignores the complexity inherent in biological systems, their multiple feedback loops and hierarchical organization. Translation of basic research results into applications that benefit growers is a complex up-scaling problem not amenable to easy short-cuts.