Uptake and partitioning of zinc in Lemnaceae
Macrophytes provide food and shelter for aquatic invertebrates and fish, while also acting as reservoirs for nutrients and trace elements. Zinc accumulation has been reported for various Lemnaceae species. However, comparative accumulation across species and the link between zinc accumulation and toxicity are poorly understood. Morphological distribution and cellular storage, in either bound or soluble form, are important for zinc tolerance. This study shows differences in the uptake and accumulation of zinc by three duckweed species. Landoltia punctata and Lemna minor generally accumulated more zinc than Lemna gibba. L. minor, but not L. gibba or L. punctata, accumulated greater concentrations of zinc in roots compared to fronds when exposed to high levels of zinc. The proportion of zinc stored in the bound form relative to the soluble-form was higher in L. minor. L. punctata accumulated greater concentrations of zinc in fronds compared to roots and increased the proportion of zinc it stored in the soluble form, when exposed to high zinc levels. L. gibba is the only species that significantly accumulated zinc at low concentrations, and was zinc-sensitive. Overall, internal zinc concentrations showed no consistent correlation with toxic effect. We conclude that relationships between zinc toxicity and uptake and accumulation are species specific reflecting, among others, zinc distribution and storage. Differences in zinc distribution and storage are also likely to have implications for zinc bioavailability and trophic mobility.
KeywordsZinc Duckweed Lemnaceae Toxicity Bioavailability
This work was funded by IRCSET (Irish Research Council for Science, Engineering and Technology). The authors gratefully acknowledge Mr. David White for his expert work in maintaining the Lemnaceae collection at University College Cork. We also appreciate the assistance and guidance of Ms. Noreen Casey and Dr. Patrick Kiely of the Department of Biochemistry, University College Cork, in the maintaining and use of the liquid scintillation counter.
- Davies KL, Davies MS, Francis D (1992) Zinc-induced vacuolation in root meristematic cells of cereals. Ann Bot 69(1):21–24Google Scholar
- Eide DJ (2006) Zinc transporters and the cellular trafficking of zinc. BBA Mol Cell Res 1763(7):711–722Google Scholar
- Eisler R (1993) Zinc hazards to fish, wildlife, and invertebrates: a synoptic review. US Department of the Interior. Fish and Wildlife Service, WashingtonGoogle Scholar
- OECD (2002) OECD Guidelines for the testing of chemicals: Revised proposal for a new guideline 221. Lemna sp. growth inhibition test. OECD, ParisGoogle Scholar
- Pandit A (1984) Role of macrophytes in aquatic ecosystems and management of freshwater resources. J Environ Manag 18(7):73–88Google Scholar
- USEPA (1996) Aquatic plant toxicity test using Lemna spp., Tiers I and II “Public Draft”. EPA 712-C-96–156. United States Environmental Protection Agency, WashingtonGoogle Scholar
- WHO (1996) Guidelines for drinking water quality, vol 2. Health criteria and other supporting information, 2nd edn. World Health Organisation, GenevaGoogle Scholar