Effects Of Molybdenum On Ascorbic Acid Metabolism And Qualities In Chinese Cabbage

Based on the reviews of plant molybdenum (Mo) nutrition, a hydroponic trial and apot trial were conducted to investigate the effects of Mo on compounds concentrationsand enzymes activies in ascorbic acid metabolism and the qualities of Chinese cabbage(Brassica campestris L. ssp. pekinensis). The main results are as follows.1. Applying Mo at appropriate rates (0-0.15 mg/L or 0-0.30 mg/kg) would enhancethe growth of Chinese cabbage. In both hydroponic and pot trials, Mo applicationsincreased Mo concentrations in Chinese cabbage and enhanced plant biomass. Freshweight of Chinese cabbage increased as Mo application rates increased up to 0.15 mg/L inhydroponic trial and 0.30 mg/kg in pot trial. However, high level of Mo applaction (1.50mg/L) reduced the biomass of Chinese cabbage in the hydroponic trial.2. Mo application would enhance the redox cycle and regeneration of ascorbate(AsA), and result in the increase of total ascorbate and reduced ascorbate concentrations.In both hydroponic and pot trials, Mo application elevated concentrations of totalascorbate and reduced ascorbate in Chinese cabbage. On one hand, Mo applicationreduced the activity of ascorbate oxidase (AAO) but increased the activity of ascorbateperoxidase (APX), suggesting that Mo application enhanced the redox cycle of AsA. Onthe other hand, activities of monodehydroascorbate reductase (MDHAR) anddehydroascorbate reductase (DHAR) increased due to Mo addition, which implied thatthe presence of Mo could ficiliate the regeneration of AsA.3. Mo appliaction promoted the ability of Chinese cabbage to resist oxidative stress.In both hydroponic and pot trials, Mo application increased AsA concentrations andactivities of APX, MDHAR, DHAR and glutathione reductase (GR). The hydroponic trialexhibited a decreasing trend of malondialdehyde (MDA) concentration in Chinesecabbage.4. Application of Mo could improve the appearance quality of Chinese cabbage. Inboth hydroponic and pot trials, Mo application increased chlorophyll concentrations(SPAD). The pot trail showed the chlorophyll concentration was significantly correlatedwith either AsA concentration or the yield of Chinese cabbage.5. Mo application increased contents of vitamin c, soluble sugar and some essentialand non-essential free amino acids in Chinese cabbage; we conclude that Mo is beneficialto nutritious qualities of vegetables. The application of Mo elevated soluble sugarconcentration of Chinese cabbage in pot trial. Soluble suger concentration was found tobe significantly correlated to AsA content. Mo application also affected the amounts andcomponents of free amino acids in Chinese cabbage. Responding to the application of Mo,concentrations of both essential amino acid (Thr, Val, Ile, Leu and Lys) and non-essentialamino acid (Asp, Ser, Glu, Gly and Ala) increased in Chinese cabbage. In pot trial, Moapplication induced the decrease of nitrate contents in Chinese cabbage, and improved itssafe quality in a certain extent.