Introduction Environmental Relevance of Cadmium Toxicity in Plants

1 Introduction Environmental Relevance of Cadmium Toxicity in Plants 

Cadmium has been found to be a micronutrient for an ecotype of Thalassiosira weissflogii, a marine alga [1] and many other heavy metals such as copper, nickel and zinc are well-known for a long time already as essential trace elements for plants. While general aspects of the entry of Cd into the environment are dealt with in detail in Chapter 2 of this book [2], we will summarize here in Sections 1.1 and 1.2 a few plant-specific aspects before discussing mechanisms of Cd toxicity in plants. 

Toxic heavy metal concentrations can have natural reasons naturally heavy metal-rich soils are found in various locations around the world where metal ores come to the surface and decay due to weathering. A few examples of such locations are the Katangan copper belt in Kongo and Zaire [3,4], nickel-rich serpentine soils in Cuba [5], North America [6] as well as Sulawesi and New Caledonia [7] and some zinc and cadmium sites in Europe [8]. While these locations are usually not regarded as agriculturally relevant, and usually no attempts are made to detoxify them (as it would be futile), the plants growing on them still have to detoxify the stream of nutrients they take up from such soils. 

While all these are examples of severe enviromnental pollution, comparing the Cd concentrations occurring under such conditions with those used in published articles about Cd toxicity reveals that in most laboratory studies far too high, enviroimientally irrelevant, Cd levels were used. Unfortunately, this is common practice for several technical reasons  

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