Review on controlling the ratio of red light to far-red light in protected environment

Researches on the effects of the ratio of red light to far-red light(R/FR) on the morphology, growth of plants in protected horticulture were reviewed to give an overview on the subject researched in recent years. Methods for controling R/FR ratio were mentioned, and the R/FR characteristics of photoselective plastic film and several artificial lights were introduced too, and some suggestions were presented to conduct investigations in this area in the future.