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DIURNAL VARIATIONS IN LUMINESCENCE IN Scenedesmus obtusiusculus (CHLOROPHYCEAE) INDUCED BY 3‐(3,4‐DICHLOROPHENYL)‐1,1‐DIMETHYLUREA
Author(s) -
Mellvig Staffan,
Tillberg JanEric
Publication year - 1984
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.1751-1097.1984.tb08865.x
Subject(s) - dcmu , luminescence , photochemistry , scenedesmus , chlorophyceae , chemistry , photosynthesis , photosystem ii , optics , physics , algae , biology , botany , chlorophyta , biochemistry
— Luminescence from synchronously cultured Scenedesmus obtusiusculus cells was measured with a high sensitivity photon counter. Recording of light emission was initiated 0.2 s after switching off actinic light. Luminescence decay was separated into two phases: one for decay to 10 4 pulses s ‐1 , the other for decay from 10 4 to 10 3 pulses s ‐1 . Most photons are emitted during the rapid decay to 10 4 pulses s ‐l . Only small diurnal variations of the two phases could be observed in controls. Treatment with 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) decreased both the total number of photons emitted and the time required to reach the 10 4 pulses s ‐1 level. No diurnal rhythmicity was induced by DCMU in the first phase but DCMU induced a pronounced diurnal variation in decay time in the second phase of luminescence parallelled by a periodicity in the number of photons emitted. The results indicate that DCMU interferes with the participation of PS I in luminescence. The chlorophyll alb ratio was constant during the life cycle of the cells. No relation could be observed between luminescence and the diurnal rhythmicity in photosynthesis that is characteristic for synchronized unicellular algae.