Influence of copper and lead on germination of three Mimosoideae plant species

Contamination with heavy metals is a critical problem facing large areas of agricultural soils. Seed, a developmental stage, is considered highly protective against environmental stresses. This study aimed to examine the influence of two heavy metals; copper and lead, on the germination of Acacia tortilis, A. raddiana, and Prosopis juliflora. Seeds were exposed to different concentrations of copper and lead including control, low (1000 ppm) and high (2000 ppm) copper or lead, low mix (500 ppm of copper andlead), or high mix (1000 ppm of copper and lead). High copper and high mix had highly negative effects on germination of A. tortilis. Germination of A. raddianawas slightly affected under stress. While all stress treatment showed significantly negative effects on germination rate of Prosopis juliflora. Both Acacia species were not significantly affected after recovery, while the germination of stressed seeds of Prosopis juliflora has been induced after recovery. The 1st germination day was greatly affected with treatments, especially for Prosopis juliflora, where 1st germination day delayed about eight days under high mix treatment compared to control. The results suggested that heavy metals had negative impacts on germination rate. Prosopis juliflorawas more sensitive to heavy metal stress compared to Acacia species.