| The effects of molybdenum (Mo) on the absorption, transformation, distribution and utilization of nitrate-nitrogen, as well as root activity, nitrate reductase(NR) activity of leaves and roots in seedlings were investigated in the study using complete nitrate-nitrogen Hoagland’s solution and the5N-labeled tracer method. The main results were as follows:1. Mo could enhance root activity of Malus hupehensis Rehd. seedlings and the treatment with0.5μmol/L Mo in solution gave the highest activity. NR activity of Malus hupehensis Rehd. leaves reached the maximum on the4d and then decreased. The NR activity in Malus hupehensis Rehd. roots of the treatment with0.5μmol/L Mo was higher than that of the other treatments on the8d, and there was significant difference between the treatment with0.5μmol/L Mo and CK. The root activity of the treatment with0.5μmol/L Mo in Malus micromalus Makino seedlings were higher than that of CK. Mo could enhance biomass of seedlings, contents of chlorophyll and soluble sugar, and the treatments with0.5μmol/L Mo gave the best results.2. The15N utilization ratios of the Mo treatments in Malus hupehensis Rehd. were higher than that of CK, and the ratio of the treatment with0.5μmol/L Mo was the highest. Mo also had obvious effect on the15N distribution ratios. The ratios in stems and leaves of the treatments with0.5μmol/L Mo and spraying with0.04%molybdic acid were siginificantly higher than that of CK, while the highest15N distribution ratio in roots was found in the control. The Ndff value of leaves, stems and roots in Malus hupehensis Rehd. seedlings were the highest among all the treatments. Mo could enhance the5N utilization ratios, Ndff value of different organs, the total N and the15N absorption of Malus micromalus Makino seedlings. In short, the treatment with0.5μmol/L Mo was regarded as the most significant of all on growth, absorption, transformation, distribution and utilization of nitrate-nitrogen in Malus hupehensis Rehd. seedlings. |
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