Seed germination is very sensitive to unfavourable environmental conditions. An important factor of the environment, which inhibits most metabolic processes and, consequently, limits the growth and productivity of plants, is the presence of heavy metals. This study was conducted to determine the effects of the following heavy metals Cd, Cu, Ni, Pb, Co and Zn on germination and later, the growth of lettuce (Lactuca sativa L.) and spinach (Spinacia oleracea L.) seedlings. The experiment was performed using soluble salts of the metals mentioned above, that dissociate in water (Cd(NO3)2•4H2O, Cu(NO3)2•3H2O, Ni(NO3)2•6H2O, Pb(CH3COO)2•3H2O, Co(NO3)2•6H2O, Zn(CH3COO)2•2H2O). Five solutions with different concentrations were tested. Distilled water was used as control variant. The experimental variants consist on mixtures of the six metals in quantities ranging from reference values to values that exceeds intervention threshold for sensitive soils. Concentrations ranges as follows: Cd (3 to 20 ppm), Cu (20 to 200 ppm), Ni (25 to 200 ppm), Pb (30 to 150ppm), Co (20 to 100 ppm) and Zn (100 to 700 ppm). The abundance of this elements was chosen according to the values for trace chemical elements in soil (Order 756/1997). For conducting the study, 20 cm outer diameter Petri dishes were used, with 2 filter paper disks soaked in heavy metal solutions. Each repetition had a total of 25 seeds, that was replicated 4 times, in the pot resulting in a total of 100 seeds per plant species. A total of 1200 seeds were used. Seed germination tests were performed in accordance to ISTA - International Seed Testing Association (1999). A series of physiological indicators associated with germination and seedling vigour were calculated. The dynamics of the germination was followed for 6 days for Lactuca sativa L. and 10 days for Spinacia oleracea L., starting from the first day of germination. It has been observed that the influence of heavy metals on the germination and early development of the seedlings is very complex and determines a multitude of effects on many parameters, which in most situations do not have a standard or predictable distribution.

germination, Lactuca sativa L., Spinacia oleracea L., toxicity, heavy metals

environmental engineering

Presentation: poster