AOBPreview originally published online on August 30, 2008
Annals of Botany 2008 102(5):771-782; doi:10.1093/aob/mcn160
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Impact of Iron Supply on the Kinetics of Recovery of Photosynthesis in Cd-stressed Poplar (Populus glauca)
1 Department of Plant Physiology and Molecular Plant Biology, Eötvös University, Pázmány P. sétány 1/C Budapest, 1117 Hungary
2 Agricultural Research Institute of the Hungarian Academy of Sciences, PO Box: 19, Martonvásár, 2462 Hungary
3 Department of Botany, Debrecen University, PO Box: 14 Debrecen, 4010 Hungary
4 Department of Agricultural Botany and Crop Physiology, Debrecen University, Egyetem tér 1. Debrecen, 4032 Hungary
* For correspondence. E-mail: sadambio{at}elte.hu
Received: 17 April 2008 Returned for revision: 22 May 2008 Accepted: 9 July 2008 Published electronically: 30 August 2008
Background and Aims: Cadmium (Cd) causes Fe-deficiency-like symptoms in plants, and strongly inhibits photosynthesis. To clarify the importance of Cd-induced Fe deficiency in Cd effects on photosynthesis, the recovery processes were studied by supplying excess Fe after the Cd symptoms had developed.
Methods: Fe-citrate at 10 µM or 50 µM was given with or without 10 µM Cd(NO3)2 to hydroponically cultured poplars (Populus glauca ‘Kopeczkii’) with characteristic Cd symptoms. Ion, chlorophyll and pigment contents, amount of photosynthetic pigment–protein complexes, chlorophyll fluorescence and carbon assimilation were measured together with the mapping of healing processes by fluorescence imaging.
Key Results: In regenerated leaves, the iron content increased significantly, while the Cd content did not decrease. As a result, the structural (increase in the amount of photosynthetic pigments and pigment–protein complexes, decrease in the F690/F740 ratio) and functional (elevation of CO2 fixation activity and 
F/Fm') recovery of the photosynthetic machinery was detected. Cd-induced, light-stress-related changes in non-photochemical quenching, activity of the xanthophyll cycle, and the F440?/F520 ratio were also normalized. Imaging the changes in chlorophyll fluorescence, the recovery started from the parts adjacent to the veins and gradually extended to the interveinal parts. Kinetically, the rate of recovery depended greatly on the extent of the Fe supply, and chlorophyll a/b ratio and F/Fm' proved to be the most-rapidly reacting parameters.
Conclusions: Iron deficiency is a key factor in Cd-induced inhibition of photosynthesis.
Key words: Cadmium, chlorophyll–protein, iron deficiency, poplar, Populus glauca Haines 1906 var. Kopeczkii, fluorescence imaging, chlorophyll fluorescence induction
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