Solos ricos em Ni, niquelíeros, são invadidos predominantemente por membros de Brassicaceae, Cyperaceae, Cunoniaceae, Caryophyllaceae, Fabaceae, Flacourtiaceae, Euphorbiaceous, Lamiaceae, Poaceae e Violaceae, e muitas dessas plantas são tolerantes e metais. Aproximadamente 300 plantas que superacumulam Ni (hiperacumuladoras) já foram identificadas. Estas plantas apresentam capacidade não usual de acumular metais tóxicos e defesa contra eles. O acúmulo excessivo de metais fornece proteção contra o ataque de insetos e fungos. Investigações sugerem que a hiperacumulação de Ni tem como função a proteção contra fungos e bactérias patogênicos em Streptanthus polygaloides e Thlaspi montanum. A importância de plantas niquelíferas e a sua significância em fitotecnologias são discutidas nesta revisão.

Nickeliferous soils are invaded predominantly by members of the Brassicaceae, Cyperaceae, Cunoniaceae, Caryophyllaceae, Fabaceae, Flacourtiaceae, Euphorbiaceous, Lamiaceae, Poaceae and Violaceae, and many of these plants are metal tolerant. About 300 Ni hyperaccumulating plants been identified. These members exhibit unusual appetite for toxic metals and elemental defense. Hyperaccumulators provide protection against fungal and insect attack. Investigations suggested that Ni-hyperaccumulation has a protective function against fungal and bacterial pathogens in Streptanthus polygaloides and Thlaspi montanum. Significance of nickelophilous plants and their significance in phytotechnologies are discussed in this paper.

A contaminação do ambiente por metais tóxicos torna-se uma ameaça tanto para o homem quanto para a biosfera, impedindo o desenvolvimento da agricultura e prejudicando os ecossistemas. Em nações desenvolvidas, esse problema está sendo direcionado e resolvido, consideravelmente, com o uso de plantas tolerantes especializadas na limpeza de substratos contaminados e poluídos com metais. O uso de plantas que naturalmente acumulam metais e a aplicação da engenharia genética acelerariam o processo de transferência de toda essa tecnologia do laboratório ao campo. É essencial, portanto, investigar e entender como essas plantas funcionam e quais os caminhos metabólicos e genes envolvidos no processo. A combinação das tecnologias das "ômicas" tem um prodigioso potencial no desenvolvimento dessa tecnologia verde. Entretanto, estratégias para produzir plantas geneticamente alteradas para remoção, destruição ou seqüestro de substâncias tóxicas do ambiente e suas implicações devem ser cuidadosamente investigadas.

The contamination of the environment by toxic metals poses a threat for "Man and biosphere", reducing agricultural productivity and damaging the health of the ecosystem. In developed nations, this problem is being addressed and solved to some extent by using "green technology" involving metal tolerant plants, to clean up the polluted soils. The use of naturally occurring metal tolerant plants and the application of genetic manipulation, should hasten the process of transferring this technology from laboratory to field. Therefore, it is essential to investigate and understand how plants are able to tolerate toxic metals and to identify which metabolic pathways and genes are involved in such a process. Recent advances in knowledge derived from the "omics", have considerable potential in developing this green technology. However, strategies to produce genetically altered plants to remove, destroy or sequester toxic metals from the environment and the long-term implications, must be investigated carefully.

Reclamation of metalliferous areas is a priority field of biogeochemistry of trace elements. Ultramafic outcrops rich in heavy metals have been mapped in different parts of the world. Heavy metals are potentially cytotoxic, caricinogenic and mutagenic. Environment protection agencies and legislations insisting the mine operators to restore the mine spoils and tailings since the metal leachates have serious implications in production of healthy agricultural products. Hence, restoration of mine spoils, tailings and metalliferous soils is a challenging task for the well being of Humans. Synthetic and natural zeolites have been used as chelators for rapid mobility and uptake of metals from contaminated soils by plants. Use of synthetic chelators significantly increased Pb and Cd uptake and translocation from roots to shoots facilitating phytoextraction of the metals from low grade ores. Contrastingly, synthetic cross linked polyacrylates, hydrogels have protected plant roots from heavy metals toxicity and prevented the entry of metals into roots. However, application of these synthetics on large scale may not be a practical solution due to exorbitant costs. Therefore, introduction of metal tolerant wild plants to metalliferous soils, genetic engineering of plants for enhanced synthesis and exudation of natural chelators into the rhizosphere, improvement of the rhizosphere with the help of mycorrhiza and integrated management of the metalliferous ecosystem following the principles of phytoremediation are discussed in this paper.