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CHANGES IN ENDOGENOUS CYTOKININ CONCENTRATIONS IN CHLORELLA (CHLOROPHYCEAE) IN RELATION TO LIGHT AND THE CELL CYCLE

Authors

  • Wendy A. Stirk,

    1. Research Centre for Plant Growth and Development, University of KwaZulu-Natal Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa
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  • Johannes van Staden,

    1. Research Centre for Plant Growth and Development, University of KwaZulu-Natal Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa
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  • Ondřej Novák,

    1. Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany AS CR, Slechtitelů 11, CZ-783 71 Olomouc, Czech Republic
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  • Karel Doležal,

    1. Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany AS CR, Slechtitelů 11, CZ-783 71 Olomouc, Czech Republic
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  • Miroslav Strnad,

    1. Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany AS CR, Slechtitelů 11, CZ-783 71 Olomouc, Czech Republic
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  • Petre I. Dobrev,

    1. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojová 263, CZ-16502, Praha 6, Czech Republic
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  • György Sipos,

    1. Institute of Plant Biology, Faculty of Agricultural and Food Sciences, University of West Hungary, H-9200 Mosonmagyaróvár, Hungary
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  • Vince Ördög,

    1. Institute of Plant Biology, Faculty of Agricultural and Food Sciences, University of West Hungary, H-9200 Mosonmagyaróvár, Hungary
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  • Péter Bálint

    1. Institute of Plant Biology, Faculty of Agricultural and Food Sciences, University of West Hungary, H-9200 Mosonmagyaróvár, Hungary
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  • Received 15 October 2009. Accepted 26 July 2010.

Abstract

Endogenous cytokinins were quantified in synchronized Chlorella minutissima Fott et Novákova (MACC 361) and Chlorella sp. (MACC 458) grown in a 14:10 light:dark (L:D) photoperiod. In 24 h experiments, cell division occurred during the dark period, and cells increased in size during the light period. Cytokinin profiles were similar in both strains, consisting of five cis-zeatin (cZ) and three N6-(2-isopentenyl)adenine (iP) derivatives. Cytokinin concentrations were low during the dark period and increased during the light period. In 48 h experiments using synchronized C. minutissima (MACC 361), half the cultures were maintained in continuous dark conditions for the second photoperiod. Cell division occurred during both dark periods, and cells increased in size during the light periods. Cultures kept in continuous dark did not increase in size following cell division. DNA analysis confirmed these results, with cultures grown in light having increased DNA concentrations prior to cell division, while cultures maintained in continuous dark had less DNA. Cytokinins (cZ and iP derivatives) were detected in all samples with concentrations increasing over the first 24 h. This increase was followed by a large increase, especially during the second light period where cytokinin concentrations increased 4-fold. Cytokinin concentrations did not increase in cultures maintained in continuous dark conditions. In vivo deuterium-labeling technology was used to measure cytokinin biosynthetic rates during the dark and light periods in C. minutissima with highest biosynthetic rates measured during the light period. These results show that there is a relationship between light, cell division, and cytokinins.

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