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The most famous of zinc and cadmium hyperaccumulating Thlaspi caerulescens are J. & C. Presl and Arabidopsis halleri (L.) O'Kane & Al- Shehbaz . They are characterized by an increased collection of these metals from the substrate , higher transport to the shoots and resistance to high concentrations of metals in the tissues compared to non-hyperaccumulating species . In T. caerulescens was shown that Zn is done by the media ZNT1 with high affinity to the metal. The increased uptake of Zn in hyperakumulatora decides increased expression of the gene responsible for synthesis of media ZNT1 in roots and shoots. Presumably, a similar mechanism operates in A. halleri . Transport Cd T. caerulescens cells can be performed via the carrier ZNT1 which has low affinity for Cd or through IRT1 ( iron -specific carrier ) , which has high affinity for Cd. So far there was no evidence or other transport systems cadmium into plant cells in hyperaccumulators ( LCT1, members of the Nramp family ) , which have low affinity for Cd, are involved in the uptake of cadmium hyperaccumulator . The place of deposition of zinc in T. caerulescens J. & C. Presl are vacuoles of epidermal cells of leaves, with the exception of stomata cells , which are found in very low concentrations of this metal. In the case of A. halleri highest concentrations of Cd and Zn was observed in leaf trichomes , while other cells in the epidermis of both metals concentration was lower in the mesophyll cells . This is probably related to the small size , and thus weak vacuolisation epidermal cells in this species . This fact indicates that in A. halleri , in contrast to T. caerulescens , a fundamental role in the accumulation of zinc and cadmium play mesophyll cells in the leaves. In both species Zn and Cd accumulated in the shoots are mainly found in soluble forms . The deposition of both metals in the vacuoles of leaf cells and trichomes is likely to decide on hyperaccumulation and tolerance T. caerulescens and A. halleri to the toxic effects of Zn and Cd. A recent study showed that in T. caerulescens , unlike non -hyperaccumulating species , Cd resistance is not related to the synthesis and concentration of phytochelatins .

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The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

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