Action Spectrum for the Photoperiodic Control of Floral Initiation in Biloxi Soybean

Abstract

A study of the effect of various wave-lengths of visible light on the dark period interruption for Biloxi soybean was made with a spectrograph having a spectrum wide enough to irradiate fully expanded leaflets while maintaining spectral purity at high intensity. Most expts. included 5 treatments differing in energy of irradiation. The energy was varied by varying exposure time at const. intensity. Floral irradiation was detd. by dissection several days later. This initiation was suppressed by interrupting the dark period with any visible light of sufficient energy but there were 2 regions of max. efficiency, one in the yellow, orange and red, and the other in the violet. The general response curve was very similar to that for photosynthetic utilization of CO2. It indicated that the chloroplast pigments of the leaf are associated with the dark periods of interruption reaction. The action spectrum may be due to a porphyrin-like material which is probably chlorophyll.