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Metal fate and sensitivity in the aquatic tropical vegetable Ipomoea aquatica
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aquatic plant Ipomoea aquatica is a popular vegetable in Southeast Asia, often cultivated in nutrient rich and polluted waters. The overall aim of this thesis was to estimate potential risks for human health and reduced plant growth due to accumulation and toxicity of total-Hg, methyl-Hg, Cd and Pb.

In plants from cultivations in Thailand, the concentrations of Cd and Pb in the shoots were well beneath recommended maximum values for human consumption, but at some sites the Hg concentrations were high. It was demonstrated that I. aquatica has the capacity to accumulate much higher Cd and Pb concentrations in the shoots than found in field-cultivations, before exhibiting toxic symptoms. The Hg concentrations, however, occasionally reached levels that are toxic for the plant. Up to11% of total-Hg was methyl-Hg, the most toxic Hg species, though at one site it was 50-100%. To study if methyl-Hg is formed in I. aquatica, plants were exposed to inorganic Hg through the roots. Of the Hg that reached the young, metabolically active parts of the shoots, a part was transformed to methyl-Hg. A major proportion of absorbed metals was retained in the roots, which had a high tolerance for high internal metal concentrations.

The nutrient level did influence accumulation and effects of Hg, Cd and Pb in I. aquatica. Low external nutrient levels resulted in increased metal accumulation in the shoots and in metal-induced toxic effects in the plant at low external metal levels. A generous supply of sulphur or nitrogen induced formation of thiol-rich peptides in I. aquatica, compounds that have a metal detoxifying effect in plants.

To conclude, the levels of Cd and Pb in field cultivated I. aquatica do not pose any apparent threat to human health or risk for reduced plant growth. The levels of Hg however, were high at some sites and could be a health threat, for children and foetuses in particular, and especially considering the presence of methyl-Hg. The use of fertilizers is favourable as it reduces the risk for increased metal concentrations in I. aquatica and for reduced crop yields.

Place, publisher, year, edition, pages
Stockholm: Institutionen för tillämpad miljövetenskap (ITM) , 2008. , 39 p.
Keyword [en]
aquatic plants, vegetables, methyl mercury, metal accumulation, metal effects, thiol-rich peptides, Ipomoea aquatica
National Category
Botany
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-7625ISBN: 978-91-7155-653-0 (print)OAI: oai:DiVA.org:su-7625DiVA: diva2:198712
Public defence
2008-05-29, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 13:00
Opponent
Supervisors
Available from: 2008-05-05 Created: 2008-05-05Bibliographically approved
List of papers
1. Accumulation of heavy metals in water spinach (Ipomoea aquatica) cultivated in the Bangkok region, Thailand
Open this publication in new window or tab >>Accumulation of heavy metals in water spinach (Ipomoea aquatica) cultivated in the Bangkok region, Thailand
2002 In: Environmental Toxicology and Chemistry, ISSN 0730-7268, Vol. 21, no 9, 1934-1939 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25004 (URN)
Note
Part of urn:nbn:se:su:diva-7625Available from: 2008-05-05 Created: 2008-05-05Bibliographically approved
2. Influence of nutrient levels on uptake and effects of mercury, cadmium and lead in water spinach
Open this publication in new window or tab >>Influence of nutrient levels on uptake and effects of mercury, cadmium and lead in water spinach
2004 In: Journal of Environmental Quality, ISSN 0047-2425, Vol. 33, 1247-1255 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25005 (URN)
Note
Part of urn:nbn:se:su:diva-7625Available from: 2008-05-05 Created: 2008-05-05Bibliographically approved
3. Formation of methyl mercury in an aquatic macrophyte
Open this publication in new window or tab >>Formation of methyl mercury in an aquatic macrophyte
2006 In: Chemosphere, ISSN 0045-6535, Vol. 65, 2096-2105 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25006 (URN)
Note
Part of urn:nbn:se:su:diva-7625Available from: 2008-05-05 Created: 2008-05-05Bibliographically approved
4. Formation of thiol-rich peptides in water spinach at exposure to metals and nutrients
Open this publication in new window or tab >>Formation of thiol-rich peptides in water spinach at exposure to metals and nutrients
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25007 (URN)
Note
Part of urn:nbn:se:su:diva-7625Available from: 2008-05-05 Created: 2008-05-05 Last updated: 2010-01-13Bibliographically approved

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