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Cytosolic uptake of cadmium causes an extra- and intra-cellular basification in Elodea canadensis
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The current study was aimed to investigate the pH changes by Elodea canadensis shoots under different photosynthetic conditions in the presence and absence of cadmium (Cd) and its influence on Cd uptake. Plants were grown under light, dark and in the presence of the photosynthetic inhibitor (3-(3,4-dichlorophenyl)-1,1-dimethylurea) with and without 0.5 µM Cd in the solution at a starting pH of 5.0. The Cd uptake into the cytosol of leaf protoplasts was investigated by using a Cd-specific fluorescent dye, LeadmiumTM Green AM. Cadmium and proton dynamics were monitored in leaf protoplasts after plant exposure to 0.5 µM CdCl2 for 3 and 7 d, respectively. The pH sensitive dye BCECF-AM was used to detect cytosolic pH changes. The shoots increased the surrounding water pH, which enhanced Cd uptake. Beside pH increase by photosynthetic activity, E. canadensis possessed additional mechanisms to raise the surrounding water pH in the presence of Cd. The cytosolic cadmium (Cd2+cyt) fluorescence of leaf protoplasts increased upon addition of CdCl2 to the external medium, reflecting (Cd2+cyt) uptake. Plant exposure to 0.5 µM CdCl2 for 3 d did not induce significant changes in (Cd2+cyt)and [pH]cyt. However, the (Cd2+cyt) and pHcyt were significantly increased after plant exposure to 0.5 µM CdCl2 for 7d. This suggests that E. canadensis initially sequester Cd in its apoplasmic region depending upon the presence of acidic polysaccharides in its cell wall and external medium basification. With time Cd translocates into the cytosol and subsequently causes its basification.

Keyword [en]
Elodea canadensis, cadmium uptake, pH increase, photosynthesis, protoplast, cytosolic Cd2+/H+ dynamics, fluorescence microscopy
National Category
Botany
Research subject
Plant Physiology
Identifiers
URN: urn:nbn:se:su:diva-64328OAI: oai:DiVA.org:su-64328DiVA: diva2:457096
Note
In thesis, Mechanisms behind pH changes by plant roots and shoots caused by elevated concentration of toxic elementsAvailable from: 2011-11-16 Created: 2011-11-16 Last updated: 2011-11-17Bibliographically approved
In thesis
1. Mechanisms behind pH changes by plant roots and shoots caused by elevated concentration of toxic elements
Open this publication in new window or tab >>Mechanisms behind pH changes by plant roots and shoots caused by elevated concentration of toxic elements
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Toxic elements are present in polluted water from mines, industrial outlets, storm water etc. Wetland plants take up toxic elements and increase the pH of the medium. In this thesis was investigated how the shoots of submerged plants and roots of emergent plants affected the pH of the surrounding water in the presence of free toxic ions. The aim was to clarify the mechanisms by which these plants change the surrounding water pH in the presence of toxic ions.

The influence of Elodea canadensis shoots on the pH of the surrounding water was studied in the presence of cadmium (Cd) at low initial pH (4-5). The involvement of photosynthetic activity in the pH changes was investigated in the presence and absence of Cd. The cytosolic, vacuolar and apoplasmic pH changes as well as cytosolic Cd changes in E. canadensis were monitored. The influence of Eriophorum angustifolium roots on the pH of the surrounding water was investigated in the presence of a combination of Cd, copper, lead, zinc and arsenic at low initial pH (3.5). Eriophorum angustifolium root exudates were analyzed for organic acids.

Elodea canadensis shoots increased the pH of the surrounding water, an effect more pronounced with increasing Cd levels and/or increasing plant biomass and increased plant Cd uptake. The pH increase in the presence of free Cd ions was not due to photosynthesis or proton uptake across the plasmalemma or tonoplast. Cadmium was initially sequestered in the apoplasm of E. canadensis and caused its acidosis. Eriophorum angustifolium roots increased the surrounding water pH and this effect was enhanced in the presence of arsenic and metals. This pH increase was found to depend partly on the release of oxalic acid, formic acid and succinic acid by the plants.

In conclusion, E. canadensis shoots and E. angustifolium roots were found to increase the low initial pH of the surrounding water. The pH modulation by these species was enhanced by low levels of free toxic ions in the surrounding water.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2011. 40 p.
Keyword
Elodea canadensis, Eriophorum angustifolium, fluorescence microscopy, mechanisms, metals and metalloid, pH changes, protoplasts, phytofiltration, phytostabilization, root exudates
National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-64324 (URN)978-91-7447-413-8 (ISBN)
Public defence
2011-12-20, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.Available from: 2011-11-28 Created: 2011-11-16 Last updated: 2011-11-28Bibliographically approved

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