Optical properties of phytochrome in the blue-spectral region as measured in vivo and in vitro

Bernard Lewis Epel, B. A. Horwuz, Orna Baron

Research output: Contribution to journalArticlepeer-review


In the blue spectral region, the phototransformation difference spectrum of oat phytochrome extracted as Pfr differs from that of phytochrome extracted as Pr. The difference absorbance maximum for phytochrome extracted as Pfr is at 420 nm, while that extracted as Pr is at 412 nm. The phototransformation difference spectrum measured in the blue in oat coleoptile tips without inner leaves, corresponds very well with that of phytochrome as extracted in its Pfr form. There is, however, a slight apparent attenuation of the blue difference band relative to those in the red-far-red. In coleoptile tissue containing inner leaves, the blue difference band is relatively even more highly attenuated. A similar attenuation is observed in the blue, in the protochlorophyllide to chlorophyllide phototransformation difference spectrum. In the spectrum measured with excised coleoptile without inner leaves, there is a small attenuation, while in coleptile tissue with inner leaves the attentuation is nearly 9-fold. These data suggest that the observed attenuation is probably artifactual. Neither instrumental non-linearity nor fluorescence induced by the measuring beam could explain the observed attenuation. It is suggested that the observed attenuation is probably mainly the result of wavelength dependent scatter amplification, the amplification in the blue being attenuated by the high background absorption of other pigments in this region.
Original languageEnglish
Pages (from-to)229-232
Number of pages4
JournalPhotochemistry and Photobiology
Issue number2
StatePublished - Feb 1983
Externally publishedYes

ASJC Scopus subject areas

  • Radiation
  • Biochemistry
  • Physical and Theoretical Chemistry


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