Effect Of Molybdenum On Absorption And Utilization Of Nitrate-Nitrogen In Malus Hupehensis Rehd. And Malus Robusta Rehd. Seedlings Under Different Nitrate Levels

From 2014 to 2015, the study was carried out at the horticultural experiment station of Shandong Agricultural University in Tai'an city, Shandong Province. Malus hupenensis Rhed. and Malus robusta Rehd. were taken as the test material. The influence of molybdenum on nitrate nitrogen absorption, utilization features were studied by adopting of the nitrate nitrogen in Hoagland solution with the ¹⁵N-labeled tracer method. Molybdenum content, root activity, NR activities of root and leaves, XDH activity of the leaves and other physiological indicators were analysed, ¹⁵N-nitrate absorption and utilization conditions was combined to study the effect of molybdenum on absorption and utilization under different nitrate levels. The main results were as follows:1?Root activity, NR activity and chlorophyll content of Malus hupenensis Rhed. were improved in varying degrees under different Mo levels, and the treatment with 0.7 ?mol/L molybdic acid had the highest effect in the study. The nitrogen metabolism and carbon metabolism of seedlings were improved with root activity, NR activity and chlorophyll content increasing, adequate carbohydrate was provided for the growth of seedings, thereby the biomass of seedings was affected. ¹⁵N distribution ratios and ¹⁵N use efficiency of Malus hupenensis Rhed. seedings were significantly different under different concentrations of Mo. ¹⁵N of absorbed by seedings was mainly distributed in the leaves, while stems was least. ¹⁵N distribution ratios of shoots were significantly improved under different Mo levels, and ¹⁵N distribution ratios of shoots in 0.7 ?mol/L molybdic acid treatment were highest. ¹⁵N use efficiency of Malus hupenensis Rhed. seedings in the treatment with 0.7?mol/L molybdic acid was the highest, it was 19.45%, and increased 54.98% compared with the control treatment.2?Effect of Mo on nitrogen absorption and utilization of Malus hupenensis Rhed. and Malus robusta Rehd. seedlings were significantly different. At low levels of nitrogen, root activity of Malus hupenensis Rhed. seedlings has no significant influence by Mo, but root activity of Malus robusta Rehd. seedlings was significantly improved, as well as the NR and XDH activity, and biomass of both seedings were significantly improved. ¹⁵N use efficiency was also improved by Mo. At normal levels of nitrogen, the root activity, NR and XDH activity of Malus hupenensis Rhed. and Malus robusta Rehd. seedlings were increased by Mo, the biomass of Malus hupenensis Rhed. seedlings was significantly influenced, while the biomass of Malus robusta Rehd. seedlings had no significant difference. ¹⁵N use efficiency of Malus hupenensis Rhed. seedlings was increased by 30.71%, and Malus robusta Rehd. seedlings was increased by 25.64%. At high nitrogen level, NR and XDH activity were improved, but root activity and biomass of Malus hupenensis Rhed. seedlings with Mo was significantly decreased, and the ¹⁵N use efficiency was reduced by 47.17%, while the root activity and biomass of Malus robusta Rehd. seedlings were improved and ¹⁵N use efficiency was increased by 67.25%.