The effects of lead toxicity on various physiological, biochemical and genotoxic parameters in Brassica rapa L. var. rapa

In this study, various physiological, biochemical and genotoxic effects of lead [as Pb(NO3)2] on forage turnip (Brassica rapa L. var. rapa) were investigated. Germination percentages, root and shoot lengths in forage turnip were significantly decreased (P<0.05) by increasing Pb concentrations (0-12 mM Pb). 14 days-old forage turnip seedlings cultured in ¼ MS liquid media were treated with different concentrations of lead (0, 0.5, 1, 3 and 5 mM ) for 6 days. The results of inductively coupled plasma optical emission spectrometry (ICP-OES) analysis indicated that accumulation of lead in root and aerial tissues of forage turnip seedlings was dose-dependent. The content of photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) and the activity of ?-aminolevulinic acid dehydratase (ALAD) in the leaves of treated seedlings were significantly decreased (P<0.05) at higher concentrations of lead compared to the control group, whereas an increase in the level of ?-aminolevulinic acid (ALA) was determined. The genomic DNA extracted from the leaves of control and treated seedlings were used in random amplified polymorphic DNA (RAPD) analyses. A total of 126 RAPD fragments in the range of 2928-189 bp in RAPD profiles were obtained by using 11 random primers. The changes occurring in RAPD profiles of leaf tissues following Pb treatment included variations in band intensity, loss of normal bands and appearing of new bands compared with normal seedlings. Additionally, these variations in RAPD profiles were dose-dependent. As compared to control seedlings, genomic template stability compares favourably with the traditional indices such as photosynthetic pigment content, ALAD activity and ALA level. The DNA polymorphisms detected by RAPD analysis can be applied as a suitable biomarker assay for the detection genotoxic effects of Pb contamination in plants.