Effect of Some Heavy Metals on Seed Germination of Medicago arborea L. (Fabaceae)

The present work deals with the effect of three heavy metals (zinc, copper and lead) on germination of Medicago arborea seeds. Solutions of four concentrations (25, 50, 75 and 100 ppm) of each heavy metal were tested separately, and deionised water was used as a control treatment. The experiments were conducted during 14 days, under strictly controlled laboratory conditions according to a completely random design with three replicates of 20 seeds/Petri dish, for each treatment. The following germination indices: Final germination percentage (FGP), Mean daily germination (MDG), Mean germination time (MGT), Germination index (GI) and Germination value (GV) were estimated. The results showed that FGP, MDG, GI and GV were significantly affected by heavy metal stress. In contrast, the increase of applied heavy metal dose resulted in prolongation of MGT, and therefore, in significant increase of its value. It should be noted that M. arborea seeds were able to germinate even at 100 ppm, which is a concentration higher than critical limits for agricultural soils and irrigation water. This suggests that M. arborea could be considered as a moderately tolerant species, at least during the germination phase, to metal stress and as a candidate with acceptable potential for phytoremediation. AR-SA