[Objective] To study the relationships between water-consumption characteristics and stem xylem anatomical structures of Zizyphus jujuba and Vitex negundo var. heterophylla

in order to provide technical support for the selection of afforestation species in arid regions of North China.[Methods] The water consumption characteristics of Z. jujubavar and V. negundo. var. heterophylla were studied with the thermal dissipation probe (TDP)

and then the xylem anatomical structures of their stem were observed with slicing method.[Results] (1) The water consumption characteristics were different for the two trees in different seasons. In dry season

there were more fluctuating changes both for the two trees as compared with the ones in wet season

and the averages of daily sap flow velocity and daily water consumption were lower. In dry season

the max of sap flow velocity and the average of daily sap flow velocity

and daily water consumption of Z. jujuba were all higher than the ones of V. negundo var. heterophylla. In wet season

these were vice versa. (2) As for xylem anatomical structure of stem

compared with the ones of V. negundo var. heterophylla

the shape and size of Z. jujuba vessel were more uniform. And the average of vessel diameter

vessel length

vessel area and the sapwood relative cross-sectional area of Z. jujuba were all lower than the ones of V. negundo var. heterophylla. Only the vessel density of Z. jujuba var. spinosa was higher than that of V. negundo var. heterophylla. (3) The relative conductivity and the vulnerability indexes of Z. jujuba were lower than the ones of V. negundo var. heterophylla. It showed that the water conduction efficacy of Z. jujuba was lower than that of V. negundo var. heterophylla

and the safety and drought resistance of Z. jujuba were all higher than those of V. negundo var. heterophylla. In wet season

their water-consumption characteristics were mainly determined by the efficacy of water conduction. In dry season

however

their water-consumption characteristics were mainly determined by the safety and drought resistance. These might be the reason that the difference of their water-consumption in different seasons.[Conclusion] Compared with V. negundo var. heterophylla

stem xylem anatomical structure of Z. jujubavar was more capable to transport sap as high as possible

which can made it grow normally. So Z. jujuba was more suitable for the afforestation in arid regions.