Genotypic variation of the responses to chromium toxicity in four oilseed rape cultivars

Abstract

Heavy metal toxicity in soils has been considered as major constraints for oilseed rape (Brassica napus L.) production. In the present study, toxic effects of chromium (Cr) were studied in 6-d-old seedlings of four different cultivars of B. napus (ZS 758, Zheda 619, ZY 50, and Zheda 622). The elevated content of Cr inhibited seedling growth, decreased the content of photosynthetic pigments, and activities of antioxidant enzymes, as well as increased the content of malondialdehyde and reactive oxygen species in all the cultivars. The Cr content in different parts of plants was higher in Zheda 622 than in other cultivars. The electron microscopic study showed changes in ultrastructure of leaf mesophyll and root tip cells at 400 μmol Cr, and these changes were more prominent in Zheda 622. An increased size and number of starch grains and number of plastoglobuli, damaged thylakoid membranes, and immature nucleoli and mitochondria were observed in leaves. In roots, enlarged vacuoles, disrupted cell walls and cell membranes, an increased number of mitochondria and a size of nucleolus, as well as plasmolysis (in Zheda 622) were observed. On the basis of these findings, it can be concluded that cv. Zheda 622 was more sensitive to Cr as compared to other three cultivars.