Abstract: Fuji apple tree grafted on four types of interstocks[seedling Malus robusta（Carr.）Rehd.，
dwarfing M9，semi-dwarfing M26 and SH6] with seedling Malus robusta（Carr.）Rehd. were used to study
the response of hydraulics characteristic to drought stress. The results showed that the leaf specific
conductivity（Kl）of total plant，canopy，stem and root decreased with increasing drought stress，the trend
of leaf specific conductivity（Kl）of each organ decreased in the order of seedling，semi-dwarfing and
dwarfing，in which the range of change of dwarfing M9 was largest，and seedling was smallest. Hydraulics
resistance of interstock graft union varied as follows：dwarfing trees > semi-dwarfing trees > seedling. The
ratio of hydraulic conductance resistance of dwarfing rootstock graft union to plant in seedling，interstockM9，M26 and SH6 were 4.07%，6.60%，4.97% and 5.11% respectively under well-watered conditions，and
decreased under increasing levels of drought stress. Dwarfing rootstock may block transportition of water
to the canopy and limit vegetative growth，thus creating the dwarfing effect.

Key words: apple, graft, drought stress, rootstock, hydraulics characteristics