Abstract
Abstract— Accumulation of weakly absorbing phytochrome intermediates has been demonstrated in Pisum epicotyl tissue under conditions of pigment cycling using a quasi‐continuous measuring spectrophotometer. An action spectrum shows 690–700 nm to be the most efficient wavelength range in this process. Difference spectra for the decay of intermediates maintained by 690 nm light show that, if the experiment is done at 0°C, only Pfr is formed. At – 11°C, intermediates decaying to Pr can also be observed. At – 20°C, Pr is produced as well as a pigment with peak absorption at 710nm. Kinetic analysis of intermediate decay at – 11°C reveals that at least two intermediates are maintained by 690 nm light. The level of intermediate maintained by incandescent light at 0°C was 25% higher in air than in nitrogen.