Fluorescence and Photochemical Investigations of Phytochrome in Higher Plants
Figure 4
The low-temperature fluorescence method of phytochrome in situ assay. To characterize the pigment, three fluorescence spectra (corrected for background emission of the sample) of phytochrome were measured at 85 K: 1 in etiolated tissues (of wheat in this figure) when all phytochrome is in its Pr form, 2 in the same sample after saturating red illumination at 85 K partially converting Pr into lumi-R, the first stable photoproduct, and 3 in the same sample after thawing at 273 K, saturating red illumination converting Pr into Pfr, and freezing again at 85 K. Four major parameters were obtained from these spectra: position of the emission spectrum (), total phytochrome content proportional to the fluorescence intensity (), extent of the Prlumi-R photoconversion, equal to the relative fluorescence decline () and characterizing the initial photoreaction, and the extent of the PrPfr photoconversion (), characterizing the whole phytochrome cycle. (From [26]).
