Critical review of the science and options for reducing cadmium in tobacco (Nicotiana tabacum L.) and other plants

Cadmium (Cd) accumulation in crop plants such as tobacco can lead to human exposure to this carcinogenic metal. Therefore, efforts should be made to minimize the Cd content of soils and crops. We review the options for reducing Cd content of plants, with emphasis on tobacco, a plant that can accumulate relatively high levels of this metal in its leaves. Many studies aimed at understanding Cd biology in plants do not reflect field conditions, because, often of necessity, non-field-like conditions were used. Thus, further study is needed to understand which processes govern Cd uptake, accumulation, etc., under field conditions. Numerous factors, such as soil characteristics, agronomic practices, and environmental conditions, impact the uptake of Cd by plants, including tobacco. Identifying anthropogenic sources of Cd and controlling application may limit Cd accumulation in agricultural fields. Soil remediation strategies may be envisaged to reduce Cd availability to the plant (e.g., soil amendments) or to extract Cd from the soil (e.g., phytoextraction). Another approach for reducing Cd in crops involves genetic modification of the plant to reduce Cd uptake or to change its partitioning in the plant. Indeed, more knowledge has been gained in recent decades regarding the mechanisms governing the transport, accumulation, and compartmentalization of Cd by tobacco and other plants. Several types of genes can be considered for genetic engineering to affect these processes. Although no single remedy appears to exist that might drastically reduce the Cd content of crops, including tobacco, an integrated approach may prove useful. (C) 2004 Elsevier Inc.