Influence of medium frequency light/dark cycles of equal duration on the photosynthesis and respiration of Chlorella pyrenoidosa |
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Authors: | Johan U Grobbelaar Bernd M A Kroon Tineke Burger-Wiersma Luuc R Mur |
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Institution: | (1) Department of Botany and Genetics, University of the OFS, 9300 Bloemfontein, South Africa;(2) Laboratory of Microbiology, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands |
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Abstract: | Chlorella pyrenoidosa was grown in three continuous cultures each receiving a different light regime during the light period of a diurnal cycle. Hourly samples taken during the light period were subjected to medium frequency light/dark oscillations of equal duration, ranging from 3 to 240 seconds. The oxygen consumption and production of each sample were measured with an oxygen electrode in a small oxygen chamber. Although the light/dark cycles had little overall influence on photosynthetic activity, the microalgae appeared to adapt to the light regime to which they were subjected. Large differences were found between the maximum chlorophyll-specific production rates (P
infmax
supB
), the chlorophyll-specific production rates (PB) and the respiration rates between the cultures and treated subsamples. Respiration rates increased during the light period, whilst PB either increased, or had a mid light period minimum or maximum. The culture which received an hourly light oscillation during the light period had the highest P
infmax
supB
and lowest respiration rates, and it is suggested that these algae react as in nature, whereas either a sinusoidal or a block light pattern is unnatural. The latter light regime is commonly used in laboratory studies. |
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Keywords: | light/dark cycles photosynthesis Chlorella diurnal variations respiration |
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