Effects of 3,4-benzopyrene on the course of cell cycle events in the chlorococcal alga Scenedesmus quadricauda

Synchronous cultures of the chlorococcal alga Scenedesmus quadricauda were grown under optimal growth conditions. The mean length of their cell cycle was approximately 20 h. The cultures were treated at the start, at the 4th, and 8th hour of the cell cycle with 3,4-benzo(a)pyrene (BP) in the range o...

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Bibliographic Details
Published in:Planta 1983-04, Vol.157 (5), p.432-440
Main Authors: Zachleder, V, Abarzua, S, Wittenburg, E
Format: Article
Language:English
Subjects:
Algae
aquatic organisms
Cell cycle
Chlorophylls
Daughter cells
DNA
DNA replication
environmental degradation
Freshwater
Irradiance
Mother cells
plant biochemistry
plant physiology
pollution
RNA
Scenedesmus quadricauda
Starches
waste management
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Summary:Synchronous cultures of the chlorococcal alga Scenedesmus quadricauda were grown under optimal growth conditions. The mean length of their cell cycle was approximately 20 h. The cultures were treated at the start, at the 4th, and 8th hour of the cell cycle with 3,4-benzo(a)pyrene (BP) in the range of 0.1—0.5 μg ml-1 of final concentration. A period about 4 h was found within which no inhibitory effects could be detected even at the highest BP concentrations used. In presence of BP the rates of RNA and protein syntheses gradually decreased until complete inhibition of net syntheses occurred. In a similar way chlorophyll synthesis was inhibited, and this was followed by gradual degradation of the chlorophyll. The higher the concentration of BP the more rapid the decrease of the rates of syntheses and the earlier their complete inhibition. At low BP concentrations while DNA replications were initiated, the number of replications was lowered. At higher concentrations the initiations of DNA replications were delayed or completely suppressed. Syntheses of saccharides were the least inhibited processes in presence of BP. Starch synthesis was slowed down at the end of the cell cycle and fructose synthesis (free and sucrose bound) was even stimulated later in the cell cycle. The release of daughter coenobia, and protoplast fissions were most susceptible to BP treatment, being affected at concentrations which produced no measurable disturbances of macromolecular syntheses. At BP concentrations at which the inhibition of macromolecular syntheses occurred, the delay or suppression of mitoses was observed.
ISSN:0032-0935
1432-2048
DOI:10.1007/BF00397200