Water use of apple trees on three rootstocks measured with heat pulse technique

Crop water use (sap flow) was measured with heat pulse techniqu e.Three apple orchards (M9,MM106 and Hashabi,rootstock is M9,MM106 and Hashabi,respectively) with different canopy structure were chosen for the study.The results showed that water use of the M9 orchard is much less than that of MM106 and Hashabi orchards,and measured water use is not well correlated with orchards water application according to the Class A Pan for the three orchards.The dwarfing rootstock,M9 orchard,having the lowest canopy conductance,was found to have lower sunlit leaf conductance in the porometer measurements,so it is in a condition of water stress.However,M9 orchard received enough irrigation,therefore,any water stress in M9 orchard was probably not caused by insufficient irrigation,but by high resistance to water transport in the stem or root.