Heavy Metal Uptake and Detoxification Mechanisms in Plants

摘要

Plants take up heavy metals from their surroundings via a number of different plasma membrane localized transporters. Inside the plant system toxicity of heavy metals is manifested by an array of physiological and metabolic disturbances if metal detoxification processes are delayed or not efficient. Immobilization of heavy metals by root exudates and in some cases mycorrhizal association constitute the extracellular mode of detoxification whereas chelation of heavy metals by phytochelatins, metallothioneins, organic acids and amino acids, induced synthesis of proline and synthesis of stress proteins are implicated in preventing metal accumulation in fully reactive form in the cytosol. Plant cells have developed sophisticated toxic metal sensing proteins that transmit signals to activate expression of metal detoxification and homeostasis genes in order to cope with the elevated heavy metal concentrations. In transducing signals of heavy metal origin involvement of second messengers viz., Ca~(2+), jasmonic acid and H_2O_2 as well as participation of ethylene and salicyhc acid are likely. This review aims to give succinct overview of plant metal uptake and detoxification mechanisms.