Cadmium-mediated oxidative stress and ultrastructural changes in root cells of poplar cultivars

Abstract

To understand the phytoremediation capability of poplar 107 (Populus×euramericana cv. ‘Neva’) and poplar 118 (Populus nigra×Populus ussuriensis) stressed by cadmium (Cd), a hydroponic culture was performed. Cd accumulation and translocation were evaluated, activities of antioxidant enzymes and lipid peroxidation were assessed and ultrastructural alterations in root tip cells were investigated. The superoxide dismutase (SOD) activity in the leaves of the two cultivars exposed to 50μM and 100μM Cd was significantly higher (P<0.05) than that of the control and SOD activity in the roots was low. The levels of peroxisome (POD) and catalase (CAT) were significantly higher (P<0.05) than those of the control. The content of malondialdehyde (MDA) increased during the treatment. The morphological alterations in plasma membrane, dictyosomes and ER reflect the features of detoxification and tolerance under Cd stress. Reduction in number of ER, mitochondria and dictyosomes, swelling of rER and significant expansion of mitochondrial cristae were observed. The plasma membrane was damaged and cytoplasmic electron density increased, revealing a pool-like structure. Some electronic-dense granules occurred in the cytoplasm or cell wall. Plasmolysis occurred in some cells. The poplar cultivars used in the present study could be efficient phytoextraction plants as they have considerable ability to accumulate Cd (Cd concentration in shoot exceeding 0.01% (w/w)). The alterations of antioxidant enzymes and MDA content and ultrastructural changes in the poplar cultivars can serve as useful biomarkers in ecotoxicological tests with Cd.