Abstract: Malus xiaojinemis seedlings grew normally without any iron ehlorosis symptom at soil pH 7.8 and its leaf chlorophyll content was much higher than that of control species M.rockii. which showed severe ehlorosis under the same pH conditions．Mild but typical iron ehlorosis symptom was observed in scion leaves of M.xiaojinemis grafted on M.rockii rootstock in the field with pH 7.8. Conversely，when M .rockii was exploited the scion and grafted on M.xiaojinenesis rootstock, its iron ehlorosis symptom disappeared．The rate of root H⁺ excretion and ferric-chelate reduetase activity inereased in M.xiaojinemis and were substantially higher than that of M．rockii under iron deficiency．The part of root H⁺ excretion overlapped with the functioning region of root FCR, It is hypothesized that the high root H⁺ excretion in the absorptive parts in the roots of M.xiaojinemis provided an optimum pH environment for root FCR.

Key words: Malus, Malus xiaojinemis, Malus rockii, Resistance to iron chlorosis