Deteriorative Effects of Cadmium Stress on Antioxid ant System and Cellular Structure in Germinating Seeds of Brassica napus L.

Abstract

Cadmium (Cd), known as a non-essential heavy metal, can cause oxidative stress in plants. In this study, an attempt was carried out t o find out whether Cd-induced oxidative and microscopic changes could be observed in the ea rly stage of seedling growth. Seeds of Brassica napus (cvs. Zheda 619 and ZS 758) were germinated in vitro at 0, 100, 200, 300, and 500 μ M Cd concentrations in dark for 48 hours. Results s howed that the higher concentration of Cd (500 μ M) significantly reduced plant growth in both culti vars. However, Cd concentration in both cultivars increas ed linearly with the Cd concentration, but was more pronounced in ZS 758 th an the other cultivar. Moreover, Cd caused oxidative stress in germinated seeds by incr easing reactive oxygen species, however, no relationship was found between antioxid ative defense capacity including catalase, peroxidase, superoxide dismutase and glut athione reductase activities and Cd tolerance in the two cultivars. Cd toxicity showed significant ultrastructural changes in germinated seed cells, but cell structure in Zheda 619 did not show any difference, while cell structure in ZS 758 was totally damaged under higher concentration of Cd (500 μ M). Based on the present findings, it can be concluded that cultivar Zheda 619 showed comparatively higher tolerance and integrity of cel l organelles under Cd stress. Keywords: Defense system, Malondialdehyde, Microscopic analy sis, Oilseed rape, Phytoremediation.