Inter-population differences tolerance to Cu excess during the initials phases of Juncus acutus life cycle: implications for the design of metal restoration strategies

The research on the plant population metal intra-specific tolerance variability is of paramount importance for the design of phytoremediation restoration. The aim of this study was to asses if any variability exists in the copper stress response during seed germination and seedling development in Juncus acutus depending on provenance habitat. Our results showed that J. acutus were able to germinate until Cu concentration of 23 mM Cu, but at 15 and 23 mM Cu, the final percentage of germination were 100 and 68% for seeds derived from polluted area and were 86 and 40% for those collected in non-polluted one, respectively. Moreover, the germination kinetic was more impaired by Cu concentration in those no historically exposed to metal excess. Provenance effect was also reflected in seedlings survival and development; thus at 9 mM Cu higher survival percentage, total height and dry mass were recorded in seedlings derived from no polluted area compared with their historically exposed counterparts. Therefore, we can conclude that the variability of Cu tolerance in J. acutus should be considered for the design of restoration projects, since it allows use of provenances with greater potential as a source of propagules highly adapted to metal excess.