Overlapping toxic effect of long term thallium exposure on white mustard (Sinapis alba L.) photosynthetic activity

BMC Plant Biology

Research Article

Maciej Garstka¹  Radosław Mazur¹  Agnieszka Mostowska²  Łucja Kowalewska²  Hazem M. Kalaji³  Monika Sadowska⁴  Beata Krasnodębska-Ostręga⁴  Agnieszka Abratowska⁵ 

[1] Department of Metabolic Regulation, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warsaw, Poland;Department of Plant Anatomy and Cytology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warsaw, Poland;Department of Plant Physiology, Warsaw University of Life Sciences SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland;Laboratory of Chromatography and Environmental Analysis, Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warsaw, Poland;Laboratory of Ecotoxicology, Institute of Botany, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096, Warsaw, Poland;

关键词: Thallium;    Heavy metal toxicity;    Sinapis alba;    Mustard plant;    Chlorophyll fluorescence imaging;    Photosynthetic complexes;    Chemical speciation;    Tolerance index;   

DOI  :  10.1186/s12870-016-0883-4

 received in 2016-07-05, accepted in 2016-08-25,  发布年份 2016

来源: Springer

【 摘 要 】

BackgroundHeavy metal exposure affect plant productivity by interfering, directly and indirectly, with photosynthetic reactions. The toxic effect of heavy metals on photosynthetic reactions has been reported in wide-ranging studies, however there is paucity of data in the literature concerning thallium (Tl) toxicity. Thallium is ubiquitous natural trace element and is considered the most toxic of heavy metals; however, some plant species, such as white mustard (Sinapis alba L.) are able to accumulate thallium at very high concentrations. In this study we identified the main sites of the photosynthetic process inhibited either directly or indirectly by thallium, and elucidated possible detoxification mechanisms in S. alba.ResultsWe studied the toxicity of thallium in white mustard (S. alba) growing plants and demonstrated that tolerance of plants to thallium (the root test) decreased with the increasing Tl(I) ions concentration in culture media. The root growth of plants exposed to Tl at 100 μg L−1 for 4 weeks was similar to that in control plants, while in plants grown with Tl at 1,000 μg L−1 root growth was strongly inhibited. In leaves, toxic effect became gradually visible in response to increasing concentration of Tl (100 − 1,000 μg L−1) with discoloration spreading around main vascular bundles of the leaf blade; whereas leaf margins remained green. Subsequent structural analyses using chlorophyll fluorescence, microscopy, and pigment and protein analysis have revealed different effects of varying Tl concentrations on leaf tissue. At lower concentration partial rearrangement of the photosynthetic complexes was observed without significant changes in the chloroplast structure and the pigment and protein levels. At higher concentrations, the decrease of PSI and PSII quantum yields and massive oxidation of pigments was observed in discolored leaf areas, which contained high amount of Tl. Substantial decline of the photosystem core proteins and disorder of the photosynthetic complexes were responsible for disappearance of the chloroplast grana.ConclusionsBased on the presented results we postulate two phases of thallium toxicity on photosynthesis: the non-destructive phase at early stages of toxicant accumulation and the destructive phase that is restricted to the discolored leaf areas containing high toxicant content. There was no distinct border between the two phases of thallium toxicity in leaves and the degree of toxicity was proportional to the migration rate of the toxicant outside the vascular bundles. The three-fold (nearly linear) increase of Tl(I) concentration was observed in damaged tissue and the damage appears to be associated with the presence of the oxidized form of thallium − Tl(III).

【 授权许可】

CC BY   
© The Author(s). 2016