Abstract: Two-year-old SH6 dwarfing interstock apple trees（Kudowu/SH6/Malus hupehensis）and
vigorous rootstock apple trees（Kudowu/Malus hupehensis）were used in the present study to explore the
effect of SH6 dwarfing interstock on N absorption，distribution and storage in apple sapling. The results
were as follows：The net growth of vigorous rootstock tree was larger than that of SH6 dwarfing interstock.
During the same period，Ndff value of same organs vigorous rootstock was higher than that of the SH6
dwarf. Meanwhile，the 15N allocation rate of two kinds rootstock trees had a consistent pattern：Leaf was the highest，followed by new shoots and thick roots，while the center stem was the lowest，and
40%–70% of nitrogen was assigned to the new organs（new shoots and leaves）. The above part of N
fertilizer allocation in vigorous rootstock（63.66%）was higher than that of the SH6 interstock（57.68%）
in autumn shoot growth arrest stage，nitrogen use efficiency of vigorous rootstock young trees（14.32%）
was higher than that of SH6 interstock apple trees（8.55%）. After leaves fell in autum，33.11% of the
nitrogen in the vigorous rootstock leaves retreated into trees，while about 36.92% retreated into the
interstock trees. All organs except the fine root in the tree had 15N storage，and thick roots and phloems
were the main storage parts in apple trees. The increment of nitrogen in vigorous rootstock underground
part was 8.34%，while SH6 interstock apple tree was only 6.85%. SH6 interstocks had a certain block
effect on N absorption and backflow.

Key words: apple, SH6 dwarfing interstock, nitrogen, absorption, distribution, storage, retardant