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PHYTOCHROME PHOTOCONVERSION in vivo . EFFECT OF THE INITIAL Pfr/Ptot RATIO
Author(s) -
Mancinelli Alberto L.,
Rossr Federica,
Moroni Anna
Publication year - 1992
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.1751-1097.1992.tb02207.x
Subject(s) - phytochrome , kinetics , cucurbita pepo , in vivo , biophysics , chemistry , red light , biochemistry , photochemistry , biology , botany , physics , microbiology and biotechnology , quantum mechanics
— The equation for phytochrome photoconversion, derived from photoconversion kinetics of purified phytochrome, predicts that the rates of photoconversions starting from low and high Pfr/Ptot (0) , (initial Pfr/Ptot) should be the same for light of the same quality and fluence rate. The situation might be different in vivo . Phytochrome photoconversion rates were measured in excised cotyledons of Cucurbita pepo L. exposed to BL (blue; ϕ BL = 0.39; ϕ, Pfr/Ptot at photoequilibrium) and RI (mixture of red and far red; ϕ RI = 0.46) after saturating preirradiations with red and far‐red to establish high (0.78) and low (0.02) Pfr/Ptot (0) , respectively. Under BL, the rate of photoconversion is faster when starting from a high than a low Pfr/Ptot (0) ; under RI, the rate of photoconversion is faster when starting from a low than a high Pfr/Ptot (0) ., No effects of Pfr/Ptot (0) , on photoconversion rates were found in phytochrome solutions exposed to BL and RI. These data provide another indication of the discrepancies between phytochrome photconversion kinetics in vivo and in vitro .