Selenium alleviated chromium stress in Chinese cabbage (Brassica campestris L. ssp. Pekinensis) by regulating root morphology and metal element uptake.

Excessive chromium (Cr) causes toxicity to plants, while the beneficial effects of selenium (Se) have been verified in plants under various adverse conditions. Under Cr stress, the impacts of exogenous Se on root morphology and metal element uptake were investigated in root of Chinese cabbage by cellular and biochemical approaches. Exogenous Se alleviated Cr-induced irreversible damage to root morphology, plasma membrane integrity and ultrastructure of root tip cells. Compared with Cr treatment alone, exogenous Se reduced root Cr content by 17%. Se supply changed the subcellular distribution of Cr in root, and the concentration of Cr was reduced in the fractions of plastids and mitochondria, while increased in soluble fraction. Besides, exogenous Se counteracted the nutrient elements (Na, Ca, Fe, Mn, Cu and Zn) loss induced by Cr. For plant with Se pretreatment, the increase rate of Cr influx was lower than that of plant without Se pretreatment, particularly in solution containing high concentration (100-400 µmol L-1) of Cr. In addition, higher Km value was observed in plant with Se pretreatment, which indicated a lower Cr affinity than that of plant without Se pretreatment. The results suggest that Se modified root morphology and regulated nutrient elements uptake by root, which might play a combined role in reducing Cr uptake by root, consequently alleviating Cr stress and maintaining plant growth.

Selenium alleviates chromium toxicity by preventing oxidative stress in cabbage (Brassica campestris L. ssp. Pekinensis) leaves.

The beneficial role of selenium (Se) in alleviation of chromium (Cr)-induced oxidative stress is well established. However, little is known about the underlying mechanism. The impacts of exogenous Se (0.1mg/L) on Cr(1mg/L)-induced oxidative stress and antioxidant systems in leaves of cabbage (Brassica campestris L. ssp. Pekinensis) were investigated by using cellular and biochemical approaches. The results showed that supplementation of the medium with Se was effective in reducing Cr-induced increased levels of lipid peroxides and superoxide free radicals (O(-)2(·)), as well as increasing activities of superoxide dismutase (SOD) and peroxidase (POD). Meanwhile, 1mg/L Cr induced loss of plasma membrane integrity, growth inhibition, as well as ultrastructural changes of leaves were significantly reversed due to Se supplementation in the medium. In addition, Se application significantly altered the subcellular distribution of Cr which transported from mitochondria, nucleus and the cell-wall material to the soluble fraction and chloroplasts. However, Se application did no significant alteration of Cr effects on osmotic adjustment accumulating products. The study suggested that Se is able to protect leaves of cabbage against Cr toxicity by alleviation of Cr induced oxidative stress, and re-distribution of Cr in the subcellular of the leaf. Furthermore, free radicals, lipid peroxides, activity of SOD and POD, and subcellular distribution of Cr can be considered the efficient biomarkers to indicate the efficiency of Se to detoxification Cr.