Wave length dependence of photomorphogenesis in plants

Light of various spectral regions (at low or high intensities) supplemented a short day (SD) in white light, or was used alone at high intensity. Two types of relation of wave length to photoperiodic reaction were found: Crucifers were sensitive to blue and infrared (even SD exposure promoted elongation and flowering) and did not respond to 520-700 mμ(so this region inhibited flowering in white light despite its blue component); other plants, e.g. Cosmos bipinnatus and Spinacia oleracea were sensitive to 520-700 mμand showed little or no response to blue and infrared. Flowering of day-neutral plants was not affected by wave length of supplementary light.All species showed strong response to supplementary blue and infrared radiation, by excessive elongation of a part such as internodes, leaves or petioles. The rate depended on light intensity and the process was inhibited by red or green. Light of restricted spectral regions also induced strong formative and biochemical effects. Infrared counteracted red light. 'Monochromatic' light of high intensity perhaps regulated auxin level, whereas the supplementary light might effect its activity or sensitivity to auxin.<p/