Main content area

Phototransformation of the red-light-absorbing form of undegraded pea phytochrome by laser flash excitation

Shimazaki, Yukio, Inoue, Yasunori, Yamamoto, Kotaro T., Furuya, Masaki
Plant & cell physiology 1980 v.21 no.8 pp. 1619-1625
absorbance, peas, photochemistry, phytochrome
The phototransformation of undegraded pea phytochrome, which was estimated to be about 30 to 40% pure, from its red-light-absorbing form to its far-red-light-absorbing form was examined at 2–4°C after laser flash excitation at 655 nm using a custom-designed multichannel transient spactra analyzer. A difference spectrum measured 10 μsec after the flash showed an absorbance increase at 692 nm, a decrease at 660 nm and a slight decrease at 604 nm. With time in darkness, the peak at 692 nm gradually decreased in magnitude and shifted to 695 nm. A decay curve of absorbance at 692 nm between 10 and 500 μsec after the flash could be resolved into two reaction components, one proceeding with a rate constant of 46,000 sec ⁻¹ and the other with one of 2,500 sec ⁻¹. The faster component has not been reported previously. Difference spectra also indicated that a small but significant increase in absorbance between 400 and 410 nm and decrease around 360 nm took place 10–260 μsec after the flash.