TY - JOUR AU - Briggs, Winslow R. AB - Abstract The nonphotochemical reactions of phytochrome in the coleoptiles of dark-grown corn seedlings were studied at 3 temperatures: 14°, 24°, and 34°. The data obtained show that the destruction of P fr is the only measurable reaction occurring; reversion of P fr to P r was not found. The Q10's (2.7 and 3.5) and zero order kinetics found for the destruction reaction are consistent with the hypothesis that the reaction is enzyme-mediated. In vivo action spectra for phytochrome transformation in the coleoptiles of darkgrown corn seedlings were obtained which agree qualitatively with those obtained by other workers for phytochrome-mediated physiological responses and in vitro action spectra. In vivo conversion of phytochrome by blue light, as determined from spectrophotometric measurements of phytochrome itself, is reported. Action peaks for P r were found at 667 mμ and in the blue in the region of 400 mμ, with a broad shoulder from 590 mμ to 640 mμ. Action peaks for P fr were found at 725 mμ and in the blue in the region of 400 mμ with a minor peak at 670 mμ, and a broad shoulder from 590 mμ to 640 mμ. The ratio of the quantum efficiencies of P r at 667 mμ and P fr at 725 mμ (Φr667/Φfr725) was estimated to be 1.0. 2 Present address: Botany Department, Oregon State University, Corvallis, Oregon. 1 This work was supported by Grants G-21530 and GB-2846 from the National Science Foundation. This content is only available as a PDF. © 1966 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) TI - Photochemical and Nonphotochemical Reactions of Phytochrome in vivo JF - Plant Physiology DO - 10.1104/pp.41.3.467 DA - 1966-03-01 UR - https://www.deepdyve.com/lp/oxford-university-press/photochemical-and-nonphotochemical-reactions-of-phytochrome-in-vivo-NE3Cuu6kx9 SP - 467 EP - 474 VL - 41 IS - 3 DP - DeepDyve ER -