Nickel uptake mechanisms in two Iranian nickel hyperaccumulators, Odontarrhena bracteata and Odontarrhena inflata
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Background and aims
Mechanisms and transporters responsible for Ni uptake in plants are largely unknown. To characterize Ni uptake mechanisms in Ni hyperaccumulators, we compared the effects of channel blockers, high Ca, high Fe, Zn, Mn, Cu, or Co, and low temperature on Ni uptake in two Iranian serpentine endemics, Odontarrhena bracteata and (two populations of) O. inflata.
Ni uptake was measured in the presence and absence of the K and Ca channel blockers, tetraethylammonium (TEA) and verapamil, respectively, at high and low Ca, and with and without (additional) Fe, Zn, Cu, Mn or Co (100 μM) in the nutrient solution. To estimate the potential contribution of passive uptake, Ni uptake was also measured at low and high temperature (4 and 25 °C).
Verapamil inhibited Ni uptake by 65, 72, and 91% in O. bracteata, O. inflata from Baneh, and O. inflata from Marivan, respectively, but TEA was without effect. High Ca inhibited Ni uptake by 30 to 40%. Mn inhibited Ni uptake by about 40% in all species/populations. Fe inhibited Ni uptake, by about 30%, in O. bracteata, but not at all in O. inflata. Other metals had no effect. Low temperature decreased Ni uptake by ±70% in both species/populations.
In Odontarrhena Ni hyperaccumulators Ni is predominantly taken up via Ca channels. A Fe-deficiency inducible transporter contributes to Ni uptake in O. bracteata, but not in O. inflata. A relative small part of the Ni uptake in O. inflata (10–30%) remains unexplained. In any case, it is most probably neither mediated by apoplastic transport, nor by more or less specific transporters of Zn, Fe, Mn, or Co.
KeywordsHyperaccumulation Nickel uptake Ca channels Serpentine soil Odontarrhena
We would like to thank the Graduate School of University of Isfahan for providing research facilities.
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