Phenomenology of Photomorphogenesis; the Goals of Photomorphogenic Research; the Operational Criteria for the Involvement of Phytochrome

Abstract

All living systems on this planet depend on a narrow band in the electromagnetic spectrum which we call “light”. By the term “light” we designate that range of the electromagnetic spectrum which causes the sensation of light in man. Physically this range can be located between about 390 and 760 nm. When we deal with plants we will also use the term “light” in the sense of “visible radiation” but we usually include the near ultraviolet down to about 320 nm and the very near infrared up to about 800 nm.