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Yasunori Inoue, Masaki Furuya, Phototransformation of the Red-Light-Absorbing Form to the Far-Red-Light-Absorbing Form of Phytochrome in Pea Epicotyl Tissue Measured by a Multichannel Transient Spectrum Analyser, Plant and Cell Physiology, Volume 26, Issue 5, July 1985, Pages 813–819, https://doi.org/10.1093/oxfordjournals.pcp.a076975
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Abstract
Phototransformation of the red-light-absorbing form (PR) to the far-red-light-absorbing form (PFR) of phytochrome in 7-day-old etiolated pea epicotyl hook segments was examined at 0.5°C after a red laser flash excitation using a multichannel transient spectra analyser with electrically gated photomultiplier. Effects of a red laser pulse on the induction of phototransformation from PR to PFR were saturated at Ca. 15 mJ for flash wavelengths of both 640 and 655 nm. The amount of PFR induced by a saturating laser pulse was ca. 50% of that obtained at the photostationary equilibrium. A difference spectrum measured 15 μs after the flash showed an absorbance increase at 697 nm and a decrease at 663 nm. A difference spectrum determined 200 ms after the flash showed no such major absorbance increase. Kinetic analysis of the rapid absorbance decrease at 700 and 710 nm gave one simple first-order reaction component having a rate constant of 2,500 s−1. Kinetics of PFR appearance measured by absorbance increase at 750 nm was resolved into three first-order reactions having rate constants of 5, 1.8 and 0.4 s−1. The second flash light of 710 nm given 2 μs and 2 ms after the first red flash irradiation on PR resulted in the formation of PR rather than PFR.
