The effects of lead on growth characteristic and some physiological traits of garden cress (Lepidium sativum) under in vitro conditions

Heavy metal over-dosage is a predominant concern in soil pollution worldwide due to high stability of these elements as well as their their health side-effects on many organisms including humans. Experiments were conducted to study the effects of lead on growth characteristics (germination rate, plant fresh and dry weight, leaf number, leaf length and width) and some physiological traits (leaf and root lead concentration, relative water content and malondialdehyde, hydrogen peroxide, protein, bio-concentration factor and chlorophyll content) of Lepidium sativum as CRD in three replications. Different lead concentrations (0, 1, 2, 3, 4 and 5 mgL-1) were included in MS medium upon which seeds were cultured. The results revealed that lead concentrations from 3-5 mgL-1, led to significant increases in malondialdehyde and hydrogen peroxide contents. The highest lead concentration was recorded at 5 mgL-1of lead in leaves and roots. The highest amount of Bio-Concentration Factor was recorded at 1 and 3 mgL-1 Pb. The greatest amount of chlorophull a, leaf number and protein content was found in control plants and plants subjected to 1 mgL-1 lead treatment. For chlorophyll b, the lowest content was recorded in 5 mgL-1 lead. Pb concentration up to 2 mgL-1 had no significant effects on germination rate and the length and width of leaves, but any Pb increment from 3 mgL-1 upward, significantly affected the above-mentioned traits. Our studies make it evident that growing cress in Pb-polluted soil should be avoided if the plant is to be used as food. However, if the idea is to take advantage of the hyper-accumulation capacity of a plant in a soil decontamination program, cress would be an excellent candidate.