Effect of metallic stress on seed emergence and early seedling development of Cistus monspeliensis (L.): Involvement in restoration of the Mediterranean contaminated soils

Cistus monspeliensis is one of the common plants found on heavy metal (HM) contaminated lands of the Mediterranean region. However, information about the effects of HMs on seed germination and early seedling growth of this shrub is not fully known. This study thus examined the effects of various concentrations (i.e. 0, 200, 400, 600 mg/dm³) of Pb, Cr, Zn, Cd, and Ni on seed germination and early seedling growth of this plant. Seeds germinated maximally in absence of HMs and increases in HM levels led to a decline in the germination. However, seeds could germinate in up to 600 mg/dm³. Generally, Cd was the most and Zn the least inhibitory to germination. Apparent inhibition of seedling growth occurred from the level of 400 mg/dm³ for Ni and Cd. At the higher concentrations (400 and 600 mg/dm³), Pb, Cr and Zn were generally less inhibitory to hypocotyl length than Cd and Ni. This study shows that the tested species is tolerant to increasing concentrations (200–600 mg/dm³) of all HMs, especially Zn, at both seed germination and seedling growth stages. Hence, this species could be considered an excellent candidate for the restoration/rehabilitation of HM-polluted sites under Mediterranean bioclimatic conditions.