Cadmium uptake in Elodea canadensis leaves and its interference with extra‐ and intra‐cellular pH |
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Authors: | M T Javed S Lindberg M Greger |
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Institution: | 1. Department of Ecology, Environment and Plant Sciences, Stockholm University, , Stockholm, Sweden;2. Department of Botany, Government College University, , Faisalabad, Pakistan |
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Abstract: | This study investigated cadmium (Cd) uptake in Elodea canadensis shoots under different photosynthetic conditions, and its effects on internal (cytosolic) and external pH. The plants were grown under photosynthetic (light) or non‐photosynthetic (dark or in the presence of a photosynthetic inhibitor) conditions in the presence or absence of CdCl2 (0.5 μm ) in a medium with a starting pH of 5.0. The pH‐sensitive dye BCECF‐AM was used to monitor cytosolic pH changes in the leaves. Cadmium uptake in protoplasts and leaves was detected with a Cd‐specific fluorescent dye, Leadmium Green AM, and with atomic absorption spectrophotometry. During cultivation for 3 days without Cd, shoots of E. canadensis increased the pH of the surrounding water, irrespective of the photosynthetic conditions. This medium alkalisation was higher in the presence of CdCl2. Moreover, the presence of Cd also increased the cation exchange capacity of the shoots. The total Cd uptake by E. canadensis shoots was independent of photosynthetic conditions. Protoplasts from plants exposed to 0.5 μm CdCl2 for 3 days did not exhibit significant change in cytosolic Cd2+] or pH. However, exposure to CdCl2 for 7 days resulted in increased cytosolic Cd2+] as well as pH. The results suggest that E. canadensis subjected to a low CdCl2 concentration initially sequesters Cd into the apoplasm, but under prolonged exposure, Cd is transported into the cytosol and subsequently alters cytosolic pH. In contrast, addition of 10–50 μm CdCl2 directly to protoplasts resulted in immediate uptake of Cd into the cytosol. |
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Keywords: | Cadmium uptake cytosol
Elodea canadensis
pH
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