
%0 Journal Article
%A Küpper, Hendrik 
%A &#x0160;etlík, Ivan 
%A &#x0160;etliková, Eva 
%A Ferimazova, Naila 
%A Spiller, Martin 
%A Küpper, Frithjof C. 
%T Copper-induced inhibition of photosynthesis: limiting steps of <emph type="2">in vivo</emph> copper chlorophyll formation in <emph type="2">Scenedesmus quadricauda</emph>
%J Functional Plant Biology
%D 2003/12/12
%V 30
%N 12
%P 1187-1196
%K adaptation, algae, cell cycle, chlorophyll fluorescence kinetics, Cu transport, epifluorescence microscopy, metal resistance, thermoluminescence.
%R https://doi.org/10.1071/FP03129
%U https://www.publish.csiro.au/paper/FP03129 
%X The in vivo substitution of Mg2+ in chlorophyll by heavy metals is an important damage mechanism in heavy metal-stressed plants that leads to an inhibition of photosynthesis. In photosynthetic organisms with LHC II antennae, the in vivo substitution of Mg2+ by Cu2+ occurs particularly readily under low irradiance with a dark phase &#8212; a phenomenon referred to as &#39;shade reaction&#39;. In the present study the limiting steps of the shade reaction were investigated with synchronised cultures of the chlorococcal green alga Scenedesmus quadricauda (Turp.) Br&#233;b. The rate of copper chlorophyll formation during shade reaction was shown to be controlled by several factors; firstly, in some phases of the cell cycle, especially at the end of the light period, Mg2+ in chlorophyll was not accessible to substitution. This pattern is likely to be caused by cell cycle-dependent changes in photosynthesis and thylakoid ultrastructure, which were published earlier and are reconsidered in the discussion of the present work. Secondly, prolonged culture in a medium containing 3 &#956;M Cu2+ reversibly increased the resistance of the strain to Cu2+. Culturing without added Cu2+ lowered the threshold concentrations of various deleterious effects more than 10-fold within 8 months of de-adaptation. Adaptation to high Cu2+ levels is discussed in the context of studies of the regulation of metal transporter proteins. In addition, it was also observed that toxic Cu2+ levels impaired photosynthesis sooner than cell division. 
