Halophytes have potential as heavy metal phytoremediators: A comprehensive review

•Halophytes are able to cope with stress due to heavy metals.•Halophytes can be classified as phytoextractors or phytostabilizers.•Halophytes seem to be feasible for immobilizing heavy metals in the root system.•Halophytes could help to clean up heavy metal-polluted marginal areas that are at high risk. Halophytes are widely distributed worldwide and thrive in a wide range of environments such as coastal salt marshes, dunes, saline depressions, and inland deserts. They are also able to cope with heavy metal stress due to their developed morphological and physiological traits such as restricted entry of heavy metals through the root system, synthesis and storage of osmolytes such as proline, and intracellular complexation/chelation/compartmentalization of metal ions. Heavy metal-polluted areas result in yield losses of crops, higher environmental risks for the population, and a severe reduction in biodiversity of these areas. This review highlights studies on the heavy metal phytoremediation capacity of halophytic species from different plant families. An attempt has been made to include the pertinent information regarding heavy metal phytoremediation together with the most important characteristics of halophytes, followed by information on different studies conducted under controlled conditions or in natural environments related to heavy metal phytoremediation of different halophyte taxa from different families. The most promising species have been classified as phytoextractors or phytostabilizers together with recommendations for future research prospects in this topic.