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REGULATION OF PROTOCHLOROPHYLL(IDE) LEVELS IN DARK‐GROWN NON‐DIVIDING Euglena —I. CONTROL BY LIGHT *
Author(s) -
Alhadeff Myriam,
Coronado Roberto,
Figueroa Nara,
Schiff Jerome A.
Publication year - 1983
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.1751-1097.1983.tb03600.x
Subject(s) - euglena gracilis , darkness , blue light , biophysics , chemistry , biology , botany , materials science , chloroplast , biochemistry , optoelectronics , gene
— Dark‐grown cells of Euglena gracilis var. bacillaris contain low levels of protochlorophyll(ide) [Pchl(ide)] which absorbs at 635 nm in vivo. When growing cells are placed on a resting medium, cell division ceases after 3 days and the levels of total extractable and phototransformable Pchl(ide) decrease, reaching a new plateau at one‐half the original concentration by 7 days of resting. Phototransformable Pchl(ide) can be induced to regenerate to the original levels found in dark‐grown cells by treatment with light. The optimum conditions are 40 min of white light (0.2–0.3 W/m 2 ) followed by 1 h of darkness. Although reciprocity between fluence rate and duration of illumination was not observed in this system, it was possible to determine the effectiveness of various spectral regions for the regeneration of phototransformable Pchl(ide) as a function of fluence rate. Blue light (400–510 nm) was most effective followed closely by green (490–590 nm); red light (610–720 nm) was relatively ineffective. The results suggest that phototransformable Pchl(ide) is regulated to achieve the levels ordinarily found in dark‐grown cells and that the blue photoreceptor system, rather than Pchl(ide) itself, is probably the light receptor for Pchl(ide) regeneration.