plants Review Zinc Hyperaccumulation in Plants: A Review Habiba Balafrej 1,* , Didier Bogusz 2, Zine-El Abidine Triqui 1, Abdelkarim Guedira 1, Najib Bendaou 1, Abdelaziz Smouni 1 and Mouna Fahr 1,* 1 Laboratoire de Biotechnologie et Physiologie Végétales, Centre de biotechnologie végétale et microbienne biodiversité et environnement, Faculté des Sciences, Université Mohammed V de Rabat, 10000 Rabat, Maroc;
[email protected] (Z.-E.A.T.);
[email protected] (A.G.);
[email protected] (N.B.);
[email protected] (A.S.) 2 Equipe Rhizogenèse, Institut de Recherche pour le Développement, Unité Mixte de Recherche Diversité Adaptation et développement des Plantes, Université Montpellier 2, 34394 Montpellier, France;
[email protected] * Correspondence:
[email protected] (H.B.);
[email protected] (M.F.); Tel.: +21-2537775461 (H.B. & M.F.) Received: 2 March 2020; Accepted: 14 April 2020; Published: 29 April 2020 Abstract: Zinc is an essential microelement involved in many aspects of plant growth and development. Abnormal zinc amounts, mostly due to human activities, can be toxic to flora, fauna, and humans. In plants, excess zinc causes morphological, biochemical, and physiological disorders. Some plants have the ability to resist and even accumulate zinc in their tissues. To date, 28 plant species have been described as zinc hyperaccumulators. These plants display several morphological, physiological, and biochemical adaptations resulting from the activation of molecular Zn hyperaccumulation mechanisms. These adaptations can be varied between species and within populations. In this review, we describe the physiological and biochemical as well as molecular mechanisms involved in zinc hyperaccumulation in plants.