Effect of heavy metals on seed germination and seedling development of Nama aff. stenophylla collected on the slope of a mine tailing dump

Abstract

Nama aff. stenophylla plants grow on mining waste abandoned 100 years ago, exposed to high concentrations of heavy metals. Accumulation of heavy metals in plant biomass has been related to the phyto-accessible fractions of these, so we assessed the effect of those heavy metals in different concentrations on the germination and development of seedlings. The seed traits were characterized with optical and scanning electron microscope. The seeds were assessed for dormancy by pre-germinative treatments, germination percentage, tolerance index regarding heavy metals, and the elongation of seedlings under three concentrations of arsenic (As), cadmium (Cd), Iron (Fe), lead (Pb), and zinc (Zn) (phyto-accessible [Ph], five times higher [Hi] and lower [Lo]). The seeds have no dormancy, and the heavy metals did not affect the embryo. Pb, Cd, and As, affected the germination percentage more (p < 0.005). The treatments that most affected seedling elongation were Zn [Hi], Cd [Hi], Pb [Lo], Zn [Ph], Pb [Hi], Zn [Lo] (p < 0.005). The seedlings cells alterations were associated with the reduction in length, although larger cortical cells may be due to heavy metal compartmentalization in vacuoles. The seeds and seedlings showed tolerance to high concentrations of Fe and As, and to phyto-accessible of As, Cd, Pb, and Fe.