however some of heavy metals such as zn, are essential for plant growth, their elevated concentrations have toxic effects and may inhibit plant growth. in this study, plant tolerance and zn uptake and accumulation potential of some weed plant species from western azerbaijan region were studied in a soil spiked with 0, 1000, 3000 and 6000 mgzn kgsoil-1. seed of heliotrope (heliotropium europaeum...