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In Vivo Measurements of the Photo‐Oxidation of Chlorophyll Pigments in Dark Grown Wheat Leaves after Treatment with δ‐Aminolevulinic Acid
Author(s) -
AXELSSON LENNART
Publication year - 1974
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1974.tb03108.x
Subject(s) - protochlorophyllide , singlet oxygen , absorbance , pigment , chlorophyll , chemistry , photochemistry , light intensity , decomposition , reaction rate constant , chlorophyll a , oxygen , biochemistry , kinetics , chromatography , biosynthesis , optics , organic chemistry , enzyme , physics , quantum mechanics
Dark‐grown leaves of wheat fed with δ‐aminolevulinic acid accumulate protochlorophyllide 636 in excess. After the leaves had been illuminated with high intensity red light (154 W × m −2 ) for half a minute, a treatment which blocks the phototrans‐formation protochlorophyllide chlorophyllide, the sensitivity of chlorophyllide and protochlorophyllide to light was examined. The decrease in pigment content, caused by photo‐oxidation was found to be very close to a second order reaction. The second order “rate constant” for decrease in absorbance was found to be eight times greater for the formed chlorophyllide than for protochlorophyllide. The light intensity dependence of the decomposition was found to be linear within the intensity range used ( E = 25 – 154 W × m −2 ). In samples in which the pigments had been heat denatured, it was possible to photodecompose the chlorophyllide without affecting the protochlorophyllide. The results are discussed in connection with the theory of a photodynamic action involving oxygen in the singlet state ( 1 ΔO 2 ).