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Sunflowers that love heavy metal

Sunflowers take up uranium twice or even three times better than their maize and soybean counterparts, making them a top 'clean crop' for removing toxic metals from the environment.

Scientists at the Centre for Pesticides and Environmental Research, Yugoslavia, studied growth and uranium uptake in sunflower, soybean and maize crops. Sunflowers were found to have the fastest growth rate and highest concentration of uranium, making them an excellent fast-cleaning crop. Dr Ljubinko Jovanovic will present the study's findings at the Society for Experimental Biology Meeting in Canterbury on 2 April.

The Yugoslavian scientists are just one of many groups studying bioremediation to find plants and bacteria suitable for treating soils contaminated with heavy metals (such as mercury, lead, cadmium and nickel) or radioactive isotopes (such as caesium-134) from chemical, nuclear or mining industries.

Further speakers will present work on other systems. Dr Mark Macnair in Exeter has studied wild plants that have evolved to resist toxic metals. These plants grow in polluted areas such as mine sites, accumulating high levels of nickel and zinc. Dr Macnair will cast doubt on the prevailing explanation behind accumulation in plants, where high metal content is thought to discourage predators. His study found no evidence of snails avoiding plants based on the amount of zinc they contain.

But what do you do with the plants and bacteria after cleaning the soil? "Removing these toxic metals from the food chain is the most immediate concern", says Dr Phil White of Horticulture Research International, "but disposing of the contaminated material must also be considered. At least the metal will be in a less poisonous and more manageable form in the plant than in the environment."