Effect of Pb contaminated soil on germination and development of Sinapis alba sps

The mineral component of the soil fixes the lead especially on clay minerals, and the organic component of the soil fixes the lead on humic acids. Consequently, over 80% of the lead from soil is bound, and only a small part remains bioavailable to the plants. This explains why in lead-polluted soils the toxicity on plants is not proportional to the total lead content. The study of Sinapis alba (SIA, MicroBiotests Belgium) grown on a rich organic matter soil (12% humus), at two levels of contamination with Pb, confirms at the end of experimental tests that the added Pb content remains in proportion of 96% in sol. The concentrations of 40 mg/kg Pb (Pb I), respectively 80 mg/kg Pb (Pb II) were tested, the last one being a value located above the alert threshold for agricultural soils according to the Romanian legislation. Excessive concentrations of lead in the soil led to a decreased germination process [2], a fact confirmed also by the results of this study. Germination in the Pb I test was 10% lower than in the control test, respectively 30% lower in the case of the Pb II experiment compared to the control test, where 85% of seed were germinated. Both experiments show that mustard plants do not bioaccumulate lead at this level of concentration, recording values of transfer, and bioaccumulation indices lower than 1 or zero. Thus, lead is mainly found in the root, the plants do not accumulate lead either in the stem or in the leaves. The plants from the contaminated experiments showed more intense pigment, the chlorophyll content for each experiment being higher than the value of the chlorophyll concentration in the control sample.