Molybdenum improves antioxidant and osmotic-adjustment ability against salt stress in Chinese cabbage (Brassica campestris L. ssp. Pekinensis)

A pot experiment was conducted to determine the effects of molybdenum on antioxidative defense and osmotic-adjustment systems of Chinese cabbage under salt stress. Molybdenum fertilizer was applied at three levels (0, 0.15, 0.3 mg kg(-1)). Ten days after sowing, 500 ml 136.8 mM of NaCl solution was added to half of the plants for each treatment every 10th day for three consecutive times. The results revealed that with the application of molybdenum in Chinese cabbage under salt stress the fresh weight significantly increased; activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were dramatically improved; the contents of non-enzymatic antioxidants such as glutathione (GSH), carotenoid (CAR) and ascorbic acid (ASA) were significantly increased. There was also an significant increase in low molecular osmotic-adjustment products such as soluble sugar, soluble protein and proline. Moreover, molybdenum significantly increased potassium ion (K+) content and reduced sodium ion (Na+) contents, which eventually improved the K+/Na+ ratios. The present study suggests that the application of molybdenum enhances the salt stress tolerance in Chinese cabbage by increasing the capacity to eliminate active oxygen and the ability of osmotic-adjustment.