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TWO SPECTROSCOPICALLY AND PHOTOCHEMICALLY DISTINGUISHABLE PHYTOCHROMES IN ETIOLATED SEEDLINGS OF MONOCOTS AND DICOTS *
Author(s) -
Sineshchekov Vitally
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb05004.x
Subject(s) - etiolation , phytochrome , fluorescence , wavelength , chemistry , analytical chemistry (journal) , emission spectrum , spectral line , photochemistry , red light , botany , materials science , biology , physics , biochemistry , optics , chromatography , astronomy , optoelectronics , enzyme
Fluorescence (F) emission spectra of the red‐absorbing phytochrome form (Pr) at 85 K, temperature dependence of the F intensity and the extent of the Pr F changes in the phototransformation of Pr into the first stable photoproduct (lumi‐R) at 85 K (γ 1 ,) and into the far‐red‐absorbing form (Pfr) at 267 K (γ 2 ) were investigated in etiolated shoots and roots of monocots (oat, maize, rice) and dicots (pea, cress). These characteristics monotonously changed as a function of the phytochrome content, [Ptot]: with its decrease to 3‐5% of the maximal values, the F spectrum shifts from 686 nm to 682 nm, its half‐band width rises from 22 nm to ca 25 nm, temperature dependence of Pr F changes its character, γ 1 , drops down from ca > 0.45 to ca 0.05‐0.10 and γ 2 from 0.80–0.82 to ≤0.70. These data were interpreted in terms of two different phytochromes whose relative concentration varies with [Ptot]: (1) a longer wavelength type with the F maximum at 686 nm, low activation energy of the photoreaction (Ea ≤ 3–4 kj/ mol) and high extent of the phototransformation at 85 K (0.49 ± 0.03) and at 267 K ( ca 0.85) (Pra); (2) a shorter wavelength type practically inactive at 85 K with F maximum at 682 nm, higher Ea ( ca 35 kj/mol) and lower extent of the Pr & Pfr phototransformation (≤0.70) (Pri). [Pra] widely varies in different parts of the seedlings (up to 100 times) and Pra dominates when [Ptot] is high. The [Pri] is much more constant (variations, <10 times), and it becomes the major one when [Ptot] drops down. The two species are likely to belong to the labile (type 1) and stable pools of pigment and not to be connected with the localization of the pigment in the cell since red‐far‐red preillu‐mination, which is believed to bring about sequestering of the pigment, does not change their relative concentration and properties.