Heavy Metal Adaptation


Fifty‐three chemical elements, those with densities higher than 5 g cm−3, are categorized as heavy metals. Ecologically speaking, any element that is not used in basic metabolism or biodegradable should be regarded as a heavy metal. Heavy metals are natural components of the biosphere and as such are part of biogeochemical cycles; however, as a consequence of human activities, heavy metal concentrations have reached toxic levels in the soils and water bodies of many ecosystems around the world. Actually, using multidisciplinary approaches, including ‘omics’ strategies, several factors involved in heavy metal adaptation have been identified. In the coming years, the detailed study of the contribution of these factors to the heavy metal tolerance mechanism, as well as the crosstalk between them, should produce the necessary knowledge for the development of heavy metal‐tolerant crops that would improve agricultural productivity to meet growing food demand.

Key Concepts

  • Heavy metals are the group of chemical elements with densities higher than 5 g cm−3.
  • Any chemical element that causes environmental pollution could be considered as heavy metal.
  • Heavy metal concentrations increase to toxic levels through human activities.
  • Biogeochemical cycles are considered to have an important role in maintaining environmental equilibrium of heavy metals.
  • All heavy metals reaching a concentration higher than 0.1% generate a polluted and toxic environment.
  • Metallophytes can be used as biomarkers of heavy metal‐polluted soils.
  • Hyperaccumulator plants are those that actively take up and translocate heavy metals from the soil, accumulating them in aboveground organs.
  • Some plant exudates (named phytosiderophores) are known to take part in the uptake and mobilisation of heavy metals.

Keywords: heavy metals; heavy metal tolerance; biochemical cycles; metallophytes; hyperaccumulator plants; phytosiderophores

Figure 1. Plant heavy metal hyperaccumulators and metallophytes growing in pullulated soils (a) Polygonum aviculare (mercury‐accumulator); (b) Minuartia verna (zinc‐metallophyte); (c) Viola lutea ssp calaminaria zinc‐metallophyte); (d) Armeria maritina spp. halleri (zinc‐metallophyte); (e) Thlaspi goesingenseas (Pb‐accumulator); (f) Viola lutea ssp westfalica (lead‐accumulator); (g) Cardiminopsis halleri (heavy metal‐accumulator); (h) Thlaspi caerulescens (cadmio‐accumulator); (i) Silene vulgaris (heavy metal‐accumulator) (j) Alyssum wulfenianum (heavy metal‐accumulator); (k) Thlaspi cepaifolium (heavy metal‐accumulator); (l) Viola tricolor (metallophyte facultative). Images taken from http://images.google.com.


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Further Reading

Emamverdian A, Ding Y, Mokhberdoran F and Xie Y (2015) Heavy metal stress and some mechanisms of plant defense response. Scientific World Journal 2015: 18 pp.

Gall JE, Boyd RS and Rajakaruna N (2015) Transfer of heavy metals through terrestrial food webs: a review. Environmental Monitoring and Assessment 187: 201 (21 pp).

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Sade H, Meriga B, Surapu V, et al. (2016) Toxicity and tolerance of aluminum in plants: tailoring plants to suit to acid soils. Biometals 29: 187–210.

Singh S, Parihar P, Singh R, Singh VP and Prasad SM (2016) Heavy metal tolerance in plants: role of transcriptomics, proteomics, metabolomics, and ionomics. Frontiers in Plant Science 6: 1143(36pp).

Thakur S, Singh L, Wahid ZA, et al. (2016) Plant‐driven removal of heavy metals from soil: uptake, translocation, tolerance mechanism, challenges, and future perspectives. Environmental Monitoring and Assessment 188: 206 (11pp).

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Guevara‐García, Ángel A, Lara F, Paloma, Juárez L, Katy, and Herrera‐Estrella, Luis R(Jan 2017) Heavy Metal Adaptation. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001318.pub3]