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

Cadmium (Cd), known as a non-essential heavy metal, can cause oxidative stress in plants. In this study, an attempt was carried out to find out whether Cd-induced oxidative and microscopic changes could be observed in the early stage of seedling growth. Seeds of Brassica napus (cvs. Zheda ۶۱۹ and ZS ۷۵۸) were germinated in vitro at ۰, ۱۰۰, ۲۰۰, ۳۰۰, and ۵۰۰ μM Cd concentrations in dark for ۴۸ hours. Results showed that the higher concentration of Cd (۵۰۰ μM) significantly reduced plant growth in both cultivars. However, Cd concentration in both cultivars increased linearly with the Cd concentration, but was more pronounced in ZS ۷۵۸ than the other cultivar. Moreover, Cd caused oxidative stress in germinated seeds by increasing reactive oxygen species, however, no relationship was found between antioxidative defense capacity including catalase, peroxidase, superoxide dismutase and glutathione reductase activities and Cd tolerance in the two cultivars. Cd toxicity showed significant ultrastructural changes in germinated seed cells, but cell structure in Zheda ۶۱۹ did not show any difference, while cell structure in ZS ۷۵۸ was totally damaged under higher concentration of Cd (۵۰۰ μM). Based on the present findings, it can be concluded that cultivar Zheda ۶۱۹ showed comparatively higher tolerance and integrity of cell organelles under Cd stress.