Abstract: Five kinds of one-year-old apple rootstocks［Malus hupehensis Rehd.，M. micromalus Makino，M. prunifolia（Willd）Borkh.，M. sievesii（Ledeb.）Roemer and M. baccata Borkh.］were used to study the growth characteristics and the characteristics of absorption，distribution and utilization of labeled ¹⁵NH₄NO₃ and NH₄¹⁵NO₃. The results were as follows：The biomass of five rootstocks from high to low were M. prunifolia（Willd）Borkh. > M. hupehensis Rehd. > M. micromalus Makino > M. sievesii（Ledeb.）Roemer > M. baccata Borkh. The root surface area，total root length and root tips of M. prunifolia（Willd）Borkh. were the largest of the five，while M. baccata Borkh. were the least. The ¹⁵NO₃^--N and ¹⁵NH₄⁺-N utilization ratio of five rootstocks from high to low were M. prunifolia（Willd）Borkh. > M. sievesii（Ledeb.）Roemer > M. hupehensis Rehd. > M. micromalus Makino > M. baccata Borkh. The ¹⁵NO₃^--N utilization ratio of the five kinds of rootstocks were higher than that of ¹⁵NH₄⁺-N，and the ¹⁵NO₃^--N utilization ratio of the five kinds of rootstocks were significantly correlated with root tips. Ndff value of ¹⁵NO₃^--N of the five kinds of rootstocks were higher than that of ¹⁵NH₄⁺-N，and the value of leaves，shoots and roots of M. prunifolia（Willd）Borkh. with ¹⁵NO₃^--N treatment was the highest，meanwhile value of M. hupehensis Rehd. with ¹⁵NO₃^--N treatment was the lowest. The Ndff value of leaves，shoots and roots of M. baccata Borkh. with ¹⁵NH₄⁺-N treatment was the highest. The leaves of M. sievesii（Ledeb.）Roemer，the shoots of M. prunifolia（Willd）Borkh.，the roots of M. hupehensis Rehd.with ¹⁵NH₄⁺-N treatments were the lowest. The two kinds of ¹⁵N distribution ratio of leaves were the highest，while the shoots were the lowest.

Key words: apple, rootstock, absorption, distribution, utilization